1 Laws of Motion

CONCEPT MAP

Motion

Related to

Law of Motion Displacement, Speed,

Velocity, Acceleration

Newton’s Newton’s Newton’s

First Law Second Law Third Law Uniform Motion Non Uniform Motion
of Motion of Motion of Motion
Relation can be
describes explains
between
Rate of Action and
Inertia change of Reaction Uniform Non Uniform
Acceleration Acceleration
momentum force
Calculated
Law of using
corollary
conservation Newton's Equation of Motion
of momentum

I II II
v = u + at 1 v = u2 + 2 as
2
s = ut + at2
2

(4) is the length of the actual path

MASTER KEY QUESTION SET - 1 travelled by an object in motion while going
from one point to another.
Q.1. Fill in the blanks and rewrite the complete
statements: (5) The distance covered by a body in unit time is
called its .
(1) is a relative concept.
(6) S.I. unit of speed is and C.G.S unit is
(2) A body is said to be in motion if it changes its
.
with respect to its surroundings.
(7) The distance travelled in a particular direction
(3) A body is said to be at if it does
by an object in unit time is called its .
not change its position with respect to its
surroundings. (8) Unit of speed and velocity are the .
(9) is related to distance, while
is related to displacement.
(5)
6 Master Key Science & Technology (Term - I) (Std. IX)

(10) If an object covers equal distances in equal decreases (16) deceleration, retardation (17) uniform,
time intervals, it is said to be moving with distances (18) Newton (19) uniform circular
speed. (20) tangential (21) straight line (22) velocity
(11) If an object covers unequal distances in equal (23) velocity (24) inertia (25) unbalanced
time intervals, it is said to be moving with forces (26) mass, velocity (27) Momentum
speed. (28) unbalanced force (29) kg m/s (30) Total
(12) The rate of change of velocity is called . momentum (31) recoil (32) dyne
(13) Speed of light in dry air is m/s. Q.2. Rewrite the following statements by
(14) When velocity of a body increases its selecting correct options given below:
is positive. (1) Even if the displacement of an object is zero,
(15) When velocity of a body , its the actual distance traversed by it
acceleration is negative . (a) may not be zero. (b) will be zero
(16) Negative acceleration is also called (c) will be constant (d) will be infinity
or . (2) The displacement that occurs in unit time is
(17) In case of motion, object travels called .
equal in equal intervals of time. (a) displacement (b) distance
(18) Motion of an object was studied by . (c) velocity (d) acceleration
(19) When an object moves in a circular path with (3) If the velocity changes by equal amounts in
uniform speed, its motion is motion. equal time intervals, the object is said to be in
(20) When a coin moves along a circular path, .
the direction of its motion at every point is (a) uniform acceleration
.
(b) uniform velocity
(21) For all uniformly accelerated motions, the
(c) non-uniform acceleration
velocity-time graph is a .
(d) non-uniform motion
(22) In the distance-time graph, the slope of the
straight line indicates . (4) The unit of velocity in the SI system is .
(23) The first equation of motion gives relation (a) cm / s (b) m / s2 (c) cm / s2 (d) m / s
2 2
between and time. (5) v = u + 2as is the relation between
(24) Newton’s first law explains the phenomenon and .
of . (a) speed and velocity
(25) causes a change in the state of an (b) distance and acceleration
object at rest or in uniform motion. (c) displacement and velocity
(26) To describe momentum we must specify its (d) speed and distance
and .
(6) If an object is moving with a uniform velocity
(27) is the product of mass and velocity .
of an object.
(a) its speed remains the same, but direction
(28) The rate of change of momentum is of motion changes
proportional to the applied .
(b) its speed changes but direction of motion
(29) S.I. unit of momentum is . is same
(30) is always conserved in a collision. (c) its speed and direction both change
(31) When a bullet is fired from the gun, the gun (d) its speed and direction both remain the
moves in backward direction. This motion is same
called as .
(7) is the relation between displacement
(32) In CGS, the unit of force is .
and time.
Ans. (1) Motion (2) position (3) rest (4) distance
(a) v = u + at (b) v2 = u2 + 2as
(5) speed (6) m/s , cm/s (7) velocity (8) same 1
(9) speed, velocity (10) uniform (11) non-uniform (c) s = ut + at2 (d) v = u + 2as
2
(12) acceleration (13) 3 × 108 (14) acceleration (15)
Laws of Motion 7

(8) is an example of positive acceleration. (3) Uniform acceleration means that the body is
(a) A stone is thrown vertically upwards moving with a uniform velocity.
(b) A stone falls freely towards the earth Ans. False, In uniform acceleration, velocity changes
(c) Brakes are applied by the truck driver by equal amounts in equal time interval.
(d) The train arriving at the station (4) The direction of acceleration can be opposite
(9) An object continues to remain at rest or in a to that of velocity.
state of uniform motion along a straight line Ans. True
unless an acts on it. (5) Work is a vector quantity.
(a) internal unbalanced force
Ans. False, work is a scalar quantity as it doesn’t
(b) external unbalanced force depend upon direction.
(c) internal balanced force
(6) Displacement is always greater than distance.
(d) external balanced force
Ans. False, dispalcement is equal to or less than
(10) The is proportional to the applied
distance covered.
force and it occurs in the direction of the force.
(7) The distance and displacement are equal only
(a) change of momentum
if motion is along a straight path.
(b) rate of change of velocity
Ans. True
(c) change of velocity
(d) rate of change of momentum (8) If an object experiences acceleration, a force is
acting on it.
(11) The force necessary to cause an acceleration
of 1 m/s2 in an object of mass 1 kg is called Ans. True
. (9) A train pulling out from a station is in uniform
(a) 1 dyne (b) 1 m/s (c) 1 newton (d) 1 cm/s motion.
Ans. (1 ) may not be zero (2) velocity (3) uniform acceleration Ans. False, A train pulling out from station is in
(4) m/s (5) displacement and velocity (6) its speed non- uniform motion.
1 (10) If a bus in motion is suddenly stopped, the
and direction both remain the same (7) s = ut + at2 passengers fall backwards.
2
(8) A stone falls freely towards the earth
Ans. False, If bus is stopped , passengers will fall in
(9) external unbalanced force (10) rate of change of the front.
momentum (11) 1 newton.
(11) If a single force is acting on an object, it will
Q.3. State whether the following statements are always accelerate.
true or false and if false, write the correct Ans. True
statement:
(12) In circular motion, direction of motion is
(1) The velocity of a body is given by the distance tangential.
covered by it in unit time in a given direction.
Ans. True
Ans. True
(13) The inertia of a body is measured in terms of
(2) Displacement is a scalar quantity. its mass.
Ans. False, Displacement is a vector quantity as it Ans. True
has both magnitude and direction.
*Q.4. (A) Match the first column with appropriate entries in the second and third columns and remake the
table:
Column ‘I’ Column ‘II’ Column ‘III’
(1) Negative acceleration The velocity of the object remains A car, initially at rest reaches a velocity of
constant 50 km/hr in 10 seconds.
(2) Positive acceleration The velocity of the object decreases A vehicle is moving with a velocity of 25 m/s.
(3) Zero acceleration The velocity of the object increases A vehicle moving with the velocity of 10
m/s, stops after 5 seconds.
8 Master Key Science & Technology (Term - I) (Std. IX)

Ans.
Column ‘I’ Column ‘II’ Column ‘III’
(1) Negative acceleration The velocity of the object decreases A vehicle moving with the velocity
of 10 m/s, stops after 5 seconds.
(2) Positive acceleration The velocity of the object increases A car, initially at rest reaches a
velocity of 50 km/hr in 10 seconds.
(3) Zero acceleration The velocity of the object remains A vehicle is moving with a velocity
constant of 25 m/s.
(B) Complete the following table:
Column ‘I’ Column ‘II’ Column ‘III’
(1) Newton's first law of Describes the relationship between In a high jump athletic event, the athletes are
motion the forces on two interacting object. made to fall on a sand bed.
(2) Newton's second law Gives an idea of effects of force Motion of rocket
of motion
(3) Newton's third law of Also called as law of inertia Only the carrom coin at the bottom of a pile is
motion removed when a fast moving stricker hits it.
Ans.
Column ‘I’ Column ‘II’ Column ‘III’
(1) Newton's first law of Also called as law of inertia Only the carrom coin at the bottom of a pile is
motion removed when a fast moving striker hits it.
(2) Newton's second law Gives an idea of effects of force In a high jump athletic event, the athletes are
of motion made to fall on a sand bed.
(3) Newton's third law of Describes the relationship between Motion of rocket
motion the forces on two interacting object.

(C) Match the following:

(3) Column ‘A’ Column ‘B’
(1) Column ‘A’ Column ‘B’
(1) Inertia (a) Newton's second law
(1) Speed zero (a) Distance
(2) Rate of change of (b) Body at rest
(2) Negative acceleration (b) Body at rest momentum
(3) Displacement (c) Retardation (3) Balanced force (c) Newton's first law
(4) Always positive (d) vector quantity
(4) Force equation (d) Mass × velocity
Ans. (1-b), (2-c), (3-d), (4-a)
(e) Mass × acceleration
(2) Column ‘A’ Column ‘B’
(1) When body comes to (a) Acceleration is zero Ans. (1-c), (2-a), (3-b), (4-e)
rest at the end of the
motion
(2) When body is at rest at (b) Initial velocity is
the starting of motion zero
(3) Uniform circular (c) Final velocity is zero
motion
(4) Uniform velocity (d) Electrons revolve
around the nucleus
Ans. (1-c), (2-b), (3-d), (4-a)
Laws of Motion 9

*(D) Complete the following table: Ans. Displacement: The minimum distance
between the start and finish points of the
u(m/s) a(m/s2) t(sec) v = u + at (m/s)
motion of an object is called the Displacement
2 4 3 -
of the object.
- 5 2 20
*(2) Deceleration is acceleration.
u(m/s) a(m/s2) t(sec) 1
s = ut + at2 (m) Ans. Negative : In deceleration the velocity of the
2
body goes on decreasing, hence it is called as
5 12 3 - negative acceleration.
7 - 4 92
*(3) When an object is in uniform circular motion,
u(m/s) a(m/s2) s(m) v = u2 + 2as
2
its changes at every point.
(m/s)2
Ans. Direction : In uniform circular motion the
4 3 - 8 speed is constant along the circumference but
- 5 8.4 10 its direction at every point is tangential.
Ans. *(4) During collision remains constant.
u(m/s) a(m/s2) t(sec) v = u + at (m/s) Ans. Total momentum : Law of conservation of
2 4 3 14 momentum : Total final momentum is equal
to total initial momentum.
10 5 2 20
*(5) The working of a rocket depends on Newton’s
1 law of motion.
u(m/s) a(m/s2) t(sec) s = ut + at2 (m)
2
Ans. Third : The escaping gases exerts an equal and
5 12 3 69 opposite reaction on the rocket so that it gets
7 8 4 92 propelled in the forward direction.
2
u(m/s) a(m/s ) s(m) v = u + 2as (m/s)2
2 2
Q.7. Answer the following in one or two sentences:
4 3 8 8 (1) When is acceleration said to be positive?
4 5 8.4 10 Ans. When the velocity of a body increases, the
acceleration is in direction of velocity and
Q.5. Name the following: hence acceleration is said to be positive.
(1) The scientist who summarized motion in a (2) What is negative acceleration?
set of equations of motion. Ans. When the velocity of a body decreases, the
Ans. Isaac Newton acceleration is in opposite direction of velocity
(2) Motion of an object along a circular path and hence acceleration is said to be negative
with uniform speed. acceleration.
Ans. Uniform circular motion (3) What is the direction of velocity of an object
(3) What is the backward motion of the gun called? performing uniform circular motion?
Ans. Recoil Ans. The direction of velocity of an object
performing uniform circular motion is along
(4) The motion in which the object covers equal
the tangential direction to its position.
distance in equal intervals of time.
(4) Give the mathematical expression used to
Ans. Uniform motion
determine velocity of an object moving with
(5) S. I. unit of acceleration. uniform circular motion.
Ans. m/s2 circumference
Ans. Velocity =
(6) CGS unit of momentum time
Ans. g cm/s  v = 2pr is the expression used to determine
t
*Q.6. Complete the sentences and explain them: velocity of a body moving with uniform
*(1) The minimum distance between the start and circular motion.
finish points of the motion of an object is called (5) What kind of force keeps the body at rest?
the of the object. Ans. Balanced force keeps the body at rest.
10 Master Key Science & Technology (Term - I) (Std. IX)

(6) Which law of motion gives the measure of Q.9. Distinguish between:
force? * (1) Distance and Displacement:
Ans. Newton’s second law of motion gives the
Distance Displacement
measure of force.
(1) Distance is the (1) Displacement is the
Q.8. Define the following / state the laws:
length of the actual minimum distance
(1) Displacement: path travelled by between the starting
Ans. Displacement is the minimum distance an object in motion and finishing points.
between the starting and finishing points. while going from
(2) Velocity: one point to another.
Ans. The displacement that occurs in unit time is (2) It is a scalar quantity. (2) It is a vector quantity.
called velocity.
(3) It is either equal (3) It is either equal to
(3) Acceleration:
to or greater than or less than distance.
Ans. The rate of change of velocity is called displacement.
acceleration.
(4) Retardation: (4) Distance travelled is (4) Displacement
Ans. When velocity of a body decreases, acceleration always positive. may be positive or
negative or zero.
is negative. Negative acceleration is called
deceleration or retardation.
* (2) Uniform motion and non-uniform motion.
(5) Newton’s first law of motion:
Ans. ‘An object continues to remain at rest or in a Uniform motion Non-uniform motion
state of uniform motion along a straight line (1) If an object covers (1) If an object moves
unless an external unbalanced force acts on it.’ equal distances in unequal distances
equal intervals of in equal intervals
(6) Newton’s second law of motion:
time it is said to be of time, its motion
Ans. ‘The rate of change of momentum of a body in uniform motion. is said to be non-
is proportional to the applied force and this uniform.
change in momentum occurs in the direction
of the applied force.’ (2) Distance - time (2) Distance - time graph
(7) Newton’s third law of motion: graph for uniform for uniform motion
motion is a straight is not a straight line.
Ans. ‘Every action force has an equal and opposite
line.
reaction force which acts simultaneously.’
(3) In uniform motion, (3) In non-uniform
(8) Momentum:
acceleration is zero. motion, acceleration
Ans. It is the product of mass and velocity of an is non zero.
object.
(9) Law of conservation of momentum: (3) Speed and velocity.
Ans. ‘When two objects collide, the total momentum Speed Velocity
before collision is equal to the total momentum (1) Speed is the distance (1) The displacement that
after collision.’ covered by a body occurs in unit time is
(10) 1 newton: per unit time. called velocity.
Ans. The force necessary to cause an acceleration (2) It is a scalar (2) It is a vector quantity.
of 1 m/s2 in an object of mass 1 kg is called quantity.
1 newton. 1 N = 1 kg × 1 m/s2
(3) Speed is always (3) Velocity can be
(11) 1 dyne: positive. positive or negative.
Ans. The force necessary to cause an acceleration
distance displacement
of 1 cm/s2 in an object of mass 1 gm is called (4) Speed = (4) Velocity =
time time
1 dyne. 1 dyne = 1 g × 1 cm/s2
Laws of Motion 11

(4) Balanced force and Unbalanced force. time 't'. Form the graph the distance covered
by the object during time 't' is given by the
Balanced force Unbalanced force area of quadrangle DOEB.
(1) Two equal forces (1) Two unequal forces  s = area of quadrangle DOEB
applied on a body applied on a body. = area (rectangle DOEA) + area of triangle
in the opposite (DAB)
direction. 1
 = (AE × OE) + ( × [AB × DA])
(2) This force does not (2) This force can change 2
change the state of the state of rest or But, AE = u, OE = t and (OE = DA = t)
rest or the state of the state of uniform AB = at ...(AB = CD) ..... from (CD = at)
uniform motion motion of a body in a 1
straight line.  s = u × t + × at × t
2
Q.10. Obtain the equations of motion by graphical  Newton's second equation of motion is
method: 1
(a) Equation for velocity-time relation. s = ut + at2.
2
Ans. (c) Equation for displacement-velocity relation.
Velocity-time graph: shows the change in
Ans.
velocity with time of a uniformly accelerated
object. The object starts from the point D in We can determine the distance covered by the
the graph with velocity v. Its velocity keeps object time t from the area of the quadrangle
increasing and after time t. It reaches the point DOEB. DOEB is a trapezium. So we can use
B on the graph. the formula for its area.
The initial velocity of the object = u = OD  s = area of trapezium DOEB
The final velocity of the object = v = OC 1
Time = t = OE  s = × sum of lengths of parallel sides
2
× distance between the parallel sides
B
v 1
C  s = × (OD + BE) × OE
2
But, OD = u, BE = v, and OE = t
Velocity

1
 s= × (u + v) × t ...(ii)
A 2
u
D (v – u)
But, a =
t t
O Time E (v – u)
 t= ...(iii)
Change in velocity a
Acceleration (a) = Time 1 (v – u)
 s = × (u + v) ×
(Final velocity – Initial velocity) 2 a
= Time (u + v) (v – u)
(OC – OD)  s=
= 2a
t
 CD = at ...(i) (OC – OD = CD)  2as = (u + v) (v – u) = v2 – u2
From the graph ... BE = AB + AE  v2 = u2 + 2as
 v = CD + OD ...(AB = CD and AE = OD) this is Newton's third equation of motion.
 v = at + u ... (from i)
Q.11. Give scientific reasons:
 v = u + at
* (1) When an object falls freely to the ground, its
This is the first equation of motion.
acceleration is uniform.
(b) Equation for displacement-time relation.
Ans.
Ans.
(i) When the body falls freely on the ground,
Suppose that on object in uniform acceleration
there are equal changes in velocity of body in
'a' and it has covered the distance 's' within
equal intervals of time.
12 Master Key Science & Technology (Term - I) (Std. IX)

(ii) Thus the acceleration of the body is constant. need to exert more force to push a heavier body.
(iii) Hence, it possesses uniform acceleration. (ii) Inertia is related to the mass of the object.
* (2) Even though the magnitudes of action (iii) Hence heavier objects offer more inertia.
force and reaction force are equal and their
(iv) As the same property is described by Newton’s
directions are opposite, their effects do not
first law of motion, so it is called as law of inertia.
get cancelled.
Ans. (7) The launching of a rocket is based on
(i) Action and reaction forces act on different Newton’s third law of motion.
bodies. Ans.
(ii) They don’t act on the same body, hence they (i) Newton’s third law of motion states that
cannot cancel each other’s effect. ‘Every action force has an equal and opposite
(iii) Hence, even though the magnitudes of action reaction force which acts simultaneously.’
force and reaction force are equal, they do not (ii) When the fuel in a rocket is ignited, it burns as
cancel each other. a result of chemical reaction.
* (3) It is easier to stop a tennis ball as compared (iii) The exhaust gases escape with a great force
to a cricket ball, when both are travelling
through a small opening at the tail end of the
with the same velocity.
rocket.
Ans.
(i) Momentum of an object depends on its mass (iv) It exerts an equal and opposite reaction force
as well as its velocity. on the rocket, due to which the rocket moves
(ii) Cricket ball is heavier than a tennis ball. in the forward direction. Thus, the principle
Although they are thrown with the same of launching of rocket is based on Newton’s
velocity, cricket ball has more momentum third law of motion.
than a tennis ball. Q.12. Answer in short:
(iii) Hence, force required to stop a cricket ball is (1) Explain the three different ways to change
more than a tennis ball.
the velocity.
(iv) Hence, it is easier to stop a tennis ball than a
cricket ball moving with same velocity. Ans. As velocity is related to speed and direction, it
can be changed by :
* (4) The velocity of an object at rest is considered
to be uniform. (i) changing the speed while keeping the
Ans. direction constant.
(i) When a body is in a state of rest, it attains a (ii) changing direction while keeping speed constant.
constant velocity.
(iii) changing both speed as well as direction of motion.
(ii) A body with constant velocity is said to be in
uniform motion. (2) Explain what is positive, negative and zero
(iii) Hence, the state of rest is an example of acceleration.
uniform motion. Ans.
(5) Motion is Relative. (i) Positive Acceleration: When the velocity of an
Ans. object increases, the acceleration is positive. In
(i) A body is said to be in motion if it changes its this case, the acceleration is in the direction of
position with respect to its surrounding. velocity.
(ii) Motion of an object depends on the observer, (ii) Negative Acceleration: When the velocity of
hence a body may appear moving for one an object decreases with time, it has negative
person and at the same time at rest for other. acceleration. Negative acceleration is also
(iii) Hence, motion is relative. called deceleration. Its direction is opposite to
(6) Newton’s first law of motion is called as law the direction of velocity.
of inertia. OR
(iii) Zero Acceleration: If the velocity of the
Heavier objects offer more inertia. object does not change with time, it has zero
Ans.
acceleration.
(i) As mass is the quantity of matter in a body, we
Laws of Motion 13

(3) What inference do we draw from the velocity- (iii) This backward motion of the gun is called its
time graph for a uniformly accelerated motion? recoil. The velocity of recoil, v2, is such that.,
–m1
Ans. m1v1 + m2v2 = 0 or v2 = × v1
m2
(i) From velocity-time graph we can infer
Q.13. Answer the following in detail:
whether velocity changes by equal amounts
in equal intervals of time or not. (1) What is speed? State its units and types.
Explain instantaneous speed and avg. speed.
(ii) Thus, for all uniformly accelerated motion,
Ans.
the velocity - time graph is a straight line and
slope of the line gives the acceleration. (i) The speed of a body is the distance travelled
in unit time. The units of speed in CGS systen
(iii) For non-uniformly accelerated motion,
is cm / s and in SI system is m / s.
velocity-time graph can have any shape
distance
according to variation in velocity with respect (ii) Speed =
time
to time. There are two types of speed :
(4) State the three equations of motion and give (a) Uniform speed : When a body moves
the relationship explained by them. equal distance in equal interval of time
Ans. throughout its motion, it is said to have
(i) v = u + at : This is the relation between velocity uniform speed.
and time. (b) Non-uniform or variable speed : A body
1 is said to move with variable speed if it
(ii) s = ut + at2 : This is the relation between covers unequal distances in equal intervals
2
displacement and time of time.
(iii) v2 = u2 + 2as : This is the relation between (iii) The speed of the body at any instant is called
displacement and velocity. instantaneous speed. Average speed is ratio of
total distance covered to total time taken.
(5) What are the implications of Newton’s Third
Law of motion? (2) What is velocity? State its units and types.
Ans. Ans.
(i) Action and reaction are terms that express force. (i) The velocity of a body is the distance travelled
(ii) These forces act in pairs. One force cannot by a body in a particular direction in unit time.
exist by itself. Thus, rate of change of displacement is called
(iii) Action and reaction forces act simultaneously. velocity.
s
(iv) Action and reaction forces act on different (ii) v=
t
objects. They do not act on the same object where : s = displacement; t = time taken;
and hence cannot cancel each other’s effect. v = velocity
(6) Explain recoil and recoil velocity and derive (MKS units : m/s CGS units : cm/s)
its expression. There are two types of velocities :
Ans. (a) Uniform velocity : If there is equal
(i) Let os consider the example of a bullet fired displacement taking place in equal interval
from a gun. When a bullet of mass m1 is fired of time, it is uniform velocity.
from a gun of mass m2, its velocity becomes (b) Non-uniform velocity or variable
v1, and its momentum becomes m1v1. Before velocity: If there is unequal displacement
firing the bullet both the gun and the bullet in equal intervals of time, it is non-uniform
are at rest. Hence, total initial momentum is velocity.
zero. (3) What is acceleration? State its units and types.
(ii) According to the above law, the total final Ans. Acceleration is a rate of change in velocity. It is
momentum also has to be zero. Thus, the a vector quantity.
forward moving bullet causes the gun to move v-u
a=
backward after firing. t
where : v = final velocity; u = initial velocity;
14 Master Key Science & Technology (Term - I) (Std. IX)

a = acceleration  F = kma (k = Constant of proportionality

2
Units of acceleration in SI system is m / s and and it's value is 1).
CGS system is cm / s2.  F = ma
Types of acceleration : (5) State the law of conservation of momentum
(i) Uniform acceleration : If the change in and derive the formula.
velocity is equal in equal interval of time, the Ans.
acceleration is uniform acceleration. (i) Let mass of objects A & B be m1 & m2
(ii) Non-uniform acceleration : If the change in Let their initial velocity be u1 & u2
velocity is unequal in equal intervals of time,
the acceleration is a non-uniform acceleration. Let their final velocity be v1 & v2
Kinds of acceleration: (ii) We know,
(a) Positive acceleration : When the velocity P = mv
of an object goes on increasing, it is said to
Let their initial momentum m1u1 and m2u2
have Positive acceleration.
(b) Negative acceleration : When the velocity Let their final momentum m1v1 and m2v2
of an object goes on decreasing, it is said to (iii) Total initial momentum = (m2u2 + m1u1)
have negative acceleration or retardation
Total final momentum = (m2v2 + m1v1)
or deceleration.
(c) zero acceleration : If the velocity of the (iv) If F2 is the force that acts on object B,
object does not change with time, it has F2 = – F1
zero acceleration.
 m2a2 = – m1a1 ..... F = ma
(4) Explain Newton’s second law of motion and
derive the formula . v2 − u2 v −u (v − u)
Ans. Newton’s second law explains about change in  m2 × = – m1 × 1 1 ..... a=
t t t
momentum. It states that ‘The rate of change
 m2 (v2 – u2) = – m1 (v1 – u1)
of momentum is proportional to the applied
force and the change of momentum occurs in  m2v2 – m2u2 = – m1v1 + m1u1
the direction of the force.’
(i) Suppose an object of mass ‘m’ has an initial  (m2v2 + m1v1) = (m2u2 + m1u1)
velocity ‘u’. When a force ‘F’ is applied in the
i.e. The magnitude of total final momentum =
direction of its velocity for time ’t’, its velocity
the magnitude of total initial momentum.
becomes ‘v’. Then, the total initial momentum
of the body = ‘mu’. Its final momentum after Q.14. Graph based questions:
time t = ‘mv’. * (1) Draw the distance-time graph from the table
(ii) So, the rate of change of momentum showing the distances covered by a car in
Change in momentum fixed time intervals taking ‘time’ along the
= X-axis and ‘distance‘ along the Y-axis.
time
mv – mu
= Time (seconds) Distance (metres)
t
m(v – u) 0 0
=
t
(v – u) 10 15
= ma a=
t
(iii) Hence by Newton’s second law of motion, the 20 30
rate of change of momentum is proportional
to the applied force. 30 45
 ma  F
40 60
 F  ma
Laws of Motion 15

Ans.
50 75
Y Scale : X axis 1 cm = 5 sec
60 90
Y axis 1 cm = 10 m
70 105 (35,58)
60
Ans. (30,50)
50
Y Scale : X axis 1 cm = 10 seconds (25,41)
Y axis 1 cm = 20 meters 40

Distance (metres)
(20,30)
120 30
(70,105) (15,20)
100 20
(60,90)
(10,12)
80 (50,75) 10 (5,7)
Distance (metres)

(0,0)
X
(40,60)
60 X´ O
(30,45) 5 10 15 20 25 30 35
40 Y´ Time (seconds)
(20,30)

20 (10,15)
No, the graph does not show a direct
(0,0)
X
proportionality between distance and time.
X´ O 10 20 30 40 50 60 70 Here, the distance changes non-uniformly
Time (seconds) with time. Thus the bus is having non-uniform
Y´ motion.
* (2) Draw the distance-time graph from the table * (3) A train is moving with a uniform velocity
showing the distances covered by a bus in of 60 km/hour for 5 hours. The velocity-time
fixed time intervals taking ‘time’ along the graph for this uniform motion is shown in
X-axis and ‘distance‘ along the Y-axis. figure.
Does the graph show a direct proportionality
(i) With the help of the graph, how will you
between distance and time?
determine the distance covered by the train
Time (seconds) Distance (metres) between 2 and 4 hours?
(ii) Is there a relation between the distance
0 0
covered by the train between 2 and 4 hours
5 7 and the area of a particular quadrangle in the
graph? What is the acceleration of the train?
10 12

15 20

20 30

25 41

30 50

35 58
16 Master Key Science & Technology (Term - I) (Std. IX)

Time (seconds) Distance (metres)

0 0
5 8
10 16
15 24
20 32
25 40
30 48
35 56
Ans.

Velocity - time graph

Ans.
(i) Distance covered = Velocity × time
= 60 × 2
= 120 km
Distance covered by the train between 2 and 4
hours is 120 km.
(ii) Yes, there is a relation between the distance
covered by the train between 2 and 4 hours
and the area of quadrangle in the graph.
Distance covered = Area of quadrangle (ABDC)
=l×b (a) The above graph represents which type of
motion?
= 60 × 2
Ans. In the above graph, the velocity changes by
= 120 km equal amounts in equal time intervals. Thus,
this is uniformly accelerated motion.
(Final velocity – Initial velocity)
Acceleration = (b) How much does the velocity change in every
time
5 minutes?
(60 – 60)
= Ans. The velocity changes by 8m/s in every 5
2
minutes.
0
= (c) For all uniformly accelerated motions, what
2
is the shape for velocity-time graph?
= 0 m/s2 Ans. For all uniformly accelerated motions, the
* (4) In the velocity-time graph for uniform velocity-time graph is a straight line.
acceleration. The changes in the velocity of a (d) For non-uniformly accelerated motions,
car in specific time intervals are given in the what is the shape for velocity-time graph?
following table. Ans. For non-uniformly accelerated motions, the
velocity-time graph may have any shape
Laws of Motion 17

depending on how the acceleration changes Average speed = ?

with time. Formula :
(e) Calculate the distance covered by the car (Total distance covered)
between the 10th and the 20th seconds. Average speed =
Total time taken
Ans. For all uniformly accelerated motions, the Solution :
velocity-time graph is a straight line. (Total distance covered)
Average speed =
Q.15. Solve the following: Total time taken

Type - A 225
=
100
Formulae :
(Total distance covered) = 2.25 m/s
(i) Average speed =
Total time taken Ans: The person swims with an average speed
(Total displacement) of 2.25 m/s.
(ii) Average velocity =
Total time taken *(3) An object moves 18 m in the first 3 sec, 22 m
*(1) An athlete is running on a circular track. in the next 3 sec and 14 m in the last 3 sec.
He runs a distance of 400m in 25 s before What is its average speed?
returning to his original position. What is Ans. Given :
his average speed and velocity? Total distance (d) = 18 + 22 + 14 = 54 m
Ans. Given : Total time taken (t) = 3 + 3 + 3 = 9 sec
Total distance travelled = 400 m
To find :
Total displacement = 0, as he returns to his
Average speed = ?
original position.
Formula :
Total time = 25 seconds.
(Total distance covered)
To find : Average speed =
Total time taken
Average speed = ?
Solution :
Average velocity = ? (Total distance covered)
Formula : Average speed =
Total time taken
Total distance covered 54
Average speed = =
Total time taken 9
Total displacement = 6 m/s
Average velocity = Ans: The object moves with an average speed of
Total time taken
6 m/s.
Solution :
Total distance covered (4) A person travels a distance of 72 km in 4
Average speed =
Total time taken hours. Calculate average speed in m/s.
400 Ans. Given :
= = 16 m/s
25 Total distance (d) = 72 km
Total displacement
Average velocity = = 72 × 1000
Total time taken
0 = 72000m
= = 0 m/s
25 Total time taken (t) = 4 hours
*(2) A person swims 100 m in the first 40 s, 80 m = 4 × 3600 ( 1hr = 3600 sec)
in the next 40 s and 45 m in the last 20 s. What
= 14400 s
is the average speed?
Ans. Given : To find :
Total distance (d) = 100 + 80 + 45 = 225 m Average speed = ?
Total time taken (t) = 40 + 40 + 20 = 100 sec Formula :
Total distance covered
To find : Average speed =
Total time taken
18 Master Key Science & Technology (Term - I) (Std. IX)

Solution : Ans. The distance covered on the runway is 1440 m.

Total distance covered
Average speed = *(2) Kangaroo can jump 2.5 m vertically. What
Total time taken
72000 must be the initial velocity of the kangaroo?
= Ans. Given :
14400
720 a = 9.8 m/s2, s = 2.5 m, v = 0,
= m/s
144 To find :
10 u=?
= m/s
2 Formula :
= 5 m/s v2 = u2 + 2as
Ans: The person travels with average speed of Solution :
5 m/s v2 = u2 + 2as
02 = u2 + 2 × (–9.8) (2.5) : (Negative sign
NUMERICAL FOR PRACTICE
is used as the acceleration is in the direction
(1) A person runs 100m in the first 50s. 80 m in opposite to that of velocity.)
the next 30 s and 45 m in the last 35 s. 0 = u2 – 49
What is the average speed? u2 = 49
Ans. 1.95 m/s u = 7 m/s
(2) An object moves 26 m in first 3 seconds and Ans: The initial velocity of the kangaroo must
16 m in the next 3 seconds while it travels be 7 m/s.
18 m in the last 3 seconds. Calculate average *(3) A motorboat starts from rest and moves with
speed. uniform acceleration. if it attains the velocity
Ans. 6.67 m/s of 15 m/s in 5s, calculate the acceleration and
Type - B the distance travelled in that time.
Ans. Given :
Formulae :
v–u Initial velocity, u = 0
(i) a =
t Final velocity, v = 15 m/s
1 time, t = 5 s.
(ii) s = ut + at2
2 To find :
(iii) v2 = u2 + 2as Acceleration (a) = ?
Distance (s) = ?
*(1) An aeroplane taxies on the runway for 30
s with an acceleration of 3.2 m/s2 before Solution:
taking off. How much distance would it have From the first equation of motion
v–u
covered on the runway? a=
t
Ans. Given : 15 – 0
=
a = 3.2 m/s2, t = 30 s, u = 0, 5
To find : a = 3 m/s2
s=? From the second equation of motion, the
Formula : distance covered will be
1 2 1
s = ut + at s = ut + at2
2 2
1
Solution : s= 0×5+ × 3 × 52
2
1 0 + 72
s = ut + at2 =
2 2
1 = 37.5 m
= 0 × 30 + × 3.2 × 302
2
Ans: The acceleration is 3 m/s2 and distance
= 1440m
travelled is 37.5 m.
Laws of Motion 19

NUMERICAL FOR PRACTICE with a velocity of 2.5 m/s. Calculate the

velocity of the other ball after collision.
(4) A car starting form rest acquires a speed of 20
Ans. Given :
m/s in covering a distance of 100m. Calculate
The mass of first ball (m1) = 50 g = 0.05kg,
the acceleration of the car.
The mass of second ball (m2) = 100 g = 0.1kg
Ans. 2 m/s2
Initial velocity of the first ball (u1) = 3 m/s,
(5) A train starting from a railway station attains
Initial velocity of the second ball (u2) = 1.5 m/s,
a speed of 40 km/hr in 10 min. Find its
Final velocity of the first ball (v1) = 2.5 m/s,
acceleration.
To find :
Ans. 0.018 m/s2
Final velocity of the second ball (v2) = ?
(6) A car acquires a velocity of 72 km/hr in
Formula :
10 seconds starting from rest. Find the
m1u1 + m2u2 = m1v1 + m2v2
acceleration, average velocity and distance
travelled in this time. Solution :
Ans. 2 m/s2 , 10 m/s, 100 m According to the law of conservation of
momentum, total initial momentum = Total
(7) A car starts from rest and moves with a
final momentum
uniform acceleration of 2 m/s2. How much
m1u1 + m2u2 = m1v1 + m2v2
time will it take to cover the distance of 49
m? (0.05 × 3) + (0.1 × 1.5) = (0.05 × 2.5) + (0.1 × v2)
Ans. 7 s (0.15) + (0.15) = 0.125 + 0.1v2
0.3 = 0.125 + 0.1v2
Type - C
0.1 v2 = 0.3 – 0.125
Formulae :
0.175
(i) F=m·a v2= = 1.75 m/s
0.1
(ii) P = m · v
*(3) An object of mass 16 kg is moving with an
(iii) m1u1 + m2u2 = m1v1 + m2v2
acceleration of 3 m/s2. Calculate the applied
force. If the same force is applied on an
*(1) The mass of a cannon is 500kg and it
object of mass 24 kg, how much will be the
recoils with a speed of 0.25 m/s. What is the
acceleration?
momentum of the cannon?
Ans. Given :
Ans. Given :
Mass of 1st body (m1) = 16 kg
mass of the cannon = 50 kg
Acceleration of 1st body (a1) = 3 m/s2
recoil speed = 0.25 m/s
Mass of 2nd body (m2) = 24 kg
To find : To find :
Momentum = ? Force on 1st body (F1) =?
Formula : Acceleration of 2nd body (a2) = ?
Momentum = m × v Formula :
Solution : F=m·a
Solution :
Momentum = m × v
F1 = m1 · a1
= 500 × 0.25
= 125 kg m/s F1 = 16 × 3
Ans: The momentum of cannon is 125 kg m/s F1 = 48 N

*(2) 2 balls have masses of 50 gm and 100 gm F2

a2 =
and they are moving along the same line in m2
the same direction with velocities of 3 m/s 48
respectively. They collide with each other a2 =
24
and after the collision, the first ball moves a2 = 2 m/s2
20 Master Key Science & Technology (Term - I) (Std. IX)

Ans: The force acting on the 1st body is 48 N (8) A body of mass 5 kg moves with an
and the acceleration of the 2nd body is 2 m/s2 acceleration of 4 m/s2. Calculate its change in
*(4) A bullet having a mass of 10 g and moving momentum in 3 seconds.
with a speed of 1.5 m/s, penetrates a thick Ans. 60 kg m/s
wooden plank of mass 90 g. The plank was
initially at rest. The bullet gets embedded in (9) A shell of mass 6 kg is fired from a gun of
the plank and both move together. Determine mass 600 kg. If the recoil velocity of the gun
their velocity. is 3 m/s. Find the muzzle velocity of the shell.
Ans. Given : Ans. 300 m/s
10
Mass of bullet (m1) = 10 g = kg = 0.010 kg (10) A body of mass 5 kg moves with an
1000
Mass of plank (m2) = 90 g = 0.090 kg acceleration of 2m/s2. Find the change in
Initial velocity of bullet (u1) = 1.5 m/s momentum of the body in 2 seconds.
Initial velocity of plank (u2) = 0 m/s Ans. 20 kg m/s
To find : *Q.16. Activity based question:
Common velocity (v) = ?
*(A)
Formula : A
m1u1 + m2u2 = m1v1 + m2v2
Solution : B
Let v1 and v2be the common velocities of the School
(a)
bullet and plank
v1 = v2 = v 1200

m
00
m

13
m1u1 + m2u2 = m1v1 + m2v2
Path B
(0.01 × 1.5) + (0.09 × 0) = (0.01 × v) + (0.09 × v)
0.015 + 0 = v (0.01 + 0.09)
500 m
0.015 = 0.1v Sheetal and
Path A
0.015 Prashant’s house
v= (b) Sangeeta’s house
0.1
v = 0.15 m/s Location of the school and houses
Ans: The plank moves with a velocity of 0.15 m/s. (1) Measure the distance between points A and
NUMERICAL FOR PRACTICE B in different ways as shown in figure (a).
Ans. Distances measured may be of different
(5) A bullet has a muzzle velocity of 300 m/s. The
lengths depending on the path taken.
gun of mass 3 kg has a recoil velocity of ‘v’.
Calculate ‘v’. Mass of the bullet is 30 grams. (2) Now measure the distance along the dotted
line. Which distance is correct according to
Ans. 3 m/s
you and why?
(6) A force of 10 N acts on a body of mass
Ans. Dotted line shows the shortest way of reaching
2 kg for 3s, initially at rest. Calculate :
(i)Velocity acquired by the body. (ii) Change from A to B.
in momentum of the body. (3) Sheetal first went to her friend Sangeeta’s
Ans. (i) 15 m/s (ii) 30 kg m/s house on her way to school (see figure (b).
Prashant went straight from home to school.
(7) If the momentum of a body of mass 10 kg is
Both are walking with the same speed. Who
20 kg m/s. Find its velocity.
will take less time to reach the school and
Ans. 2 m/s why?
Laws of Motion 21

Ans. Prashant will take less time as the path (1) What is the time interval between the
followed by him is the shortest. notings of distances made by Amar, Akbar
and Anthony?
(B) (a)
Ans. The time intervals are of 30 minutes.
(2) Who has covered equal distances in equal
A time intervals?
Distance and displacement Ans. Amar and Anthony have covered equal
distances in equal intervals of time.
(1) Every morning, Swaralee walks round the
(3) Are all the distances covered by Akbar in the
edge of a circular field having a radius of 100 m. fixed time intervals the same?
As shown in figure (a), if she starts from the point Ans. No, the distances covered by Akbar is not the
A and takes one round, how much distance same in the fixed time intervals.
has she walked and what is her displacement? (4) Considering the distances covered by Amar,
Ans. Radius (r) = 100m Akbar and Anthony in fixed time intervals,
Distance covered = Circumference of the circle what can you say about their speeds?
= 2 pr Ans. Amar and Anthony are travelling with
= 2 × 3.14 × 100 uniform speed while Akbar is travelling with
= 628 m non-uniform speed.
Displacement = 0 m (Shortest distance between (D) Observe the following figures. If you
initial and final position is zero) increase the number of sides of the polygon
(b) and make it infinite, how many times will
you have to change the direction? What will
be the shape of the path?
P 360 metres Q
(2) If a car, starting from point P, goes to point Q
(see figure b) and then returns to point P,
how much distance has it travelled and what
Changes in direction
is its displacement?
Ans. If we increase the number of sides of the
Ans. Distance covered = PQ + QP
polygon and make it infinite, then we will have
= 360 + 360
to change the direction an infinite number of
= 720 m
times. The shape of the path thus obtained
Displacement = 0 m (Shortest distance between
will be a circle.
initial and final position is zero )
(C) Amar, Akbar and Anthony are travelling in (E) Observe the velocity of the ball as it rolls
different cars with different velocities. The down along the channel. Is its velocity the
distances covered by them during different same at all points?
time intervals are given in the following table.
Time in Distance covered by
the clock Amar Akbar Anthony
in km in km in km
5.00 0 0 0
5.30 20 18 14
Channel
6.00 40 36 28
6.30 60 42 42 Ball
7.00 80 70 56
7.30 100 95 70
8.00 120 120 84 Change in velocity
22 Master Key Science & Technology (Term - I) (Std. IX)

Ans. No, its velocity is not the same at all the points. (ii) Hence, impact is less.
Its velocity increases as it rolls down.
(iii) The force experienced by the high jumper is
(F) In which of the following examples can less.
you sense motion? How will you explain
presence and absence of motion Brain Power
(i) The flight of a bird Q.1. An object travels from point A to point D
(ii) A stationary train along the path shown in the figure. What is
(iii) Leaves flying through air the distance and displacement of the object?.
(iv) A stone lying on a hill
Ans. In example 1 and 3 we can see motion. If the D
body is moving in a certain interval of time
then we can say that it is in motion. 2 cm
(G) You are travelling in a bus. Is the person
sitting next to you in motion? What do you B 3 cm
take into consideration to decide if an objects C
is moving or not?
2 cm
Ans. The person sitting in the bus is at rest if I am
the observer, and is in motion for an observer
outside the bus. The observer is considered to A
decide if an objects is moving or not Ans :
(H) When an object is at rest in the beginning of (i) Total distance = 2 + 3 + 2 = 7 cm
its motion, what is its initial velocity? (ii) Total displacement = shortest path between A
Ans. u = 0 and D
(I) When an object comes to rest at the end of its Redrawing the above figure, we get
motion, what is its final velocity?
D 3 cm D
Ans. v = 0 C
(J) Take 5 examples from your surrounding and
2 cm 2 cm
give explanation based on Newtons laws of
motion. 3 cm B
B C
Ans.
(i) An electric fan keeps on rotating for some 2 cm
2 cm
time after being switched off due to inertia
A
(Newton's 1st law) A
(ii) Fruits on a tree fall down when the branches
are shaken (Newtons 1st law). Length AD = Hypotenuse of  ACD
(iii) Athletes jump on a bed of sand during long Using Pythagoras theorem,
jump (Newtons 2nd law).
AD2 =AC2 +CD2
(iv) A fielder moves his hands backward while
catching a fast moving ball (Newtons 2nd = 42 + 32
law). = 16 +9
(v) While firing a gun, the gun recoils backwards
(Newtons 3rd law) AD2 = 25
(K) Why is there a thick bed of a sand for a high AD = √25
jumper to fall on after his jump?
AD = 5 cm
Ans.
(i) By using a sand bed, the rate of change of Hence, displacement = 5 cm
momentum is less.

vvv
Laws of Motion 23

ASSIGNMENT - 1
Time : 1 Hr Marks : 30

Q.1. (A) Choose the correct alternatives and rewrite the complete sentences: (4)
(1) Retardation means acceleration.
(a) zero (b) positive (c) uniform (d) negative
(2) When body is performing uniform circular motion, its changes at every point.
(a) speed (b) direction (c) velocity (d) acceleration
(3) The tendency of a body to resist acceleration is called .
(a) acceleration (b) position of rest (c) inertia (d) kilogram
(4) In a collision is always conserved.
(a) mass (b) momentum (c) inertia (d) acceleration
(B) Rewrite the Column II to match Column I and Column III: (3)
Column ‘I’ Column ‘II’ Column ‘III’
(1) Negative acceleration (a) Body has constant (a) A car initially at rest acquires
velocity velocity 50km/hr in 10 seconds

(2) Positive acceleration (b) Velocity of the body (b) A vehicle moving with a velocity
decreases of 25 m/s

(3) Zero acceleration (c) Velocity of the body (c) A vehicle moving with a speed of
increases 10 m/s stops after 5 seconds

(C) State whether the statements are True or False and if false write correct statement: (1)
(1) Displacement is a scalar quantity.
Q.2. (A) Answer the following: (6)
(1) Explain with proper examples : Motion is Relative.
(2) Give scientific reasons : Distance and displacements are different concepts.
(3) Give scientific reasons: Action and reaction forces do not cancel each other even though they have
equal magnitude and opposite direction.
(B) Answer in one sentence : (4)
(1) Define uniform motion.
(2) When is a body said to be in motion?
(3) The velocity with which a gun moves in the opposite direction of firing of bullet.
(4) What is momentum?
Q.3. Solve the following numerical: (4)
(1) An object moves 18 m in the first 3 seconds and 22 m in the next 3 seconds while it travels 14 m in
the last 3 seconds. Calculate average speed.
(2) Calculate momentum of a field gun of mass 500 kg when it recoils with velocity of 0.25 m/s after
firing a shell from it.
Q.4. Answer in brief: (8)
(1) State five examples of uniform circular motion.
(2) State the principle of conservation of momentum.
vvv
 2 Work and Energy
CONCEPT MAP

Positive
can be
Work Negative
Expressed by Zero
Force × Displacement
leads to
concept of

changes
illustrated by Law of
Energy Conservation Power
of Energy
given by

Work
time
Mechanical Different forms
types

Heat
Electrical
Kinetic Potential Solar
Energy Energy Chemical
Nuclear

1 P·E = mgh
K·E = mv2
2

(6) For a freely falling body, kinetic energy is

MASTER KEY QUESTION SET - 2 at the ground level.
Q.1. (A) Fill in the blanks and rewrite the complete (7) Energy can neither be nor .
statements: (8) Work and have the same unit.
(1) The energy stored in the dry cell is in the form (9) S.I. unit of energy is
of . Ans. (1) chemical energy (2) displacement (3) kinetic
(2) The work done is zero if there is no . (4) potential (5) newton (6) maximum (7) created,
(3) Flowing water has energy. destroyed (8) Energy (9) joule
(4) By stretching the rubber strings of a catapult, *(B) Choose one or more correct alternatives:
we store energy in it. (1) For work to be performed, energy must be
(5) is the unit of force. (a) transferred from one place to another.
(24)
Work and Energy 25

(b) concentrated (c) zero (d) none of these

(c) transferred from one type to another (4) is the capacity to do work
(d) destroyed (a) Energy (b) Force
(2) joule is the unit of (c) Power (d) Momentum
(a) force (b) work (5) Kinetic energy of a body (KE) = .
(c) power (d) energy 1
(a) mv2 (b) mv2
2
(3) Which of the forces are involved in dragging
(c) mgh (d) Fs
a heavy object on a smooth, horizontal surface
and have the same magnitude? (6) Potential energy of a body is given by (P.E) =
.
(a) the horizontal applied force
(a) Fs (b) mgh
(b) gravitational force
(c) ma (d) mv2
(c) reaction force in vertical direction
(7) When some unstable atoms break up they
(d) force of friction.
release tremendous amount of
(4) Power is the measure of the energy.
(a) rapidity with which work is done (a) chemical (b) potential
(b) amount of energy required to perform the (c) nuclear (d) mechanical
work
(8) 1 hp = .
(c) slowness with which work is performed
(a) 476 watts (b) 746 watts
(d) length of time.
(c) 674 watts (d) 764 watts
(5) While dragging or lifting an object, negative
(9) is the commercial unit of power.
work is done by
(a) kilowatt second (b) dyne
(a) the applied force (b) gravitational force
(c) kilowatt (d) erg
(c) frictional force (d) reaction force
(10) 1 kWh = joules.
Ans. (1) (a) transferred from one place to another. 3
(c) transferred from one type to another (2) (b) work (a) 3.6 × 10 J (b) 3.6 × 106J
(d) energy (3) (a) the horizontal applied force (c) 6.3 × 106J (d) 6.3 × 103J
(b) gravitational force (c) reaction force in vertical Ans. (1) force and displacement (2) newton-metre or
direction (d) force of friction (4) (a) rapidity with 1
joule (3) zero (4) Energy (5) mv2 (6) mgh
which work is done (c) the slowness with which 2
work is performed (5) (b) gravitational force (7) nuclear (8) 746 watts (9) kilowatt
(c) frictional force (10) 3.6 × 106J

(C) Rewrite the following statements by *(D) Rewrite the following statement using
selecting correct options given below: proper alternative.
(1) Work is the product of . (1) The potential energy of your body is least
(a) force and distance when you are

(b) displacement and velocity (a) sitting on a chair

(c) kinetic and potential energy (b) sitting on the ground

(d) force and displacement (c) sleeping on the ground

(2) SI unit of work is . (d) standing on the ground

(a) dyne (b) newton-metre or erg (2) The total energy of an object falling freely
towards the ground
(c) N/m2 or joule (d) newton-metre or joule
(i) decreases
(3) The work done by a force is said to be
(ii) remains unchanged
when the applied force does not produce
displacement. (iii) increases

(a) positive (b) negative (iv) increase in the beginning and then
decreases.
26 Master Key Science & Technology (Term - I) (Std. IX)

(3) If we increase the velocity of a car moving on (2)

a flat surface to 4 times its original speed, its
potential energy Column ‘I’ Column ‘II’ Column ‘III’
(a) will be twice its original energy (1) Positive work (a) θ = 180° (i) W = 0
(b) will not change (2) Negative work (b) θ = 90° (ii) W = Fs
(c) will be 4 times its original energy (3) Zero work (c) θ = 0° (iii) W = –Fs
(d) will be 16 times its original energy.
Ans. (1 - c - ii), (2 - a - iii), (3 - b - i)
(4) The work done on an object does not depend
on Q.4. Give two examples in each of the following
(a) displacement cases:
(b) applied force (1) Potential energy
(c) initial velocity of the object Ans.
(d) the angle between force and displacement. (i) water stored in a dam
Ans. (1) sleeping on the ground (2) increases (3) will not (ii) a compressed spring
change (4) initial velocity of the object (2) Kinetic energy
Q.2. State whether the following statements are Ans.
true or false and if false, write the correct (i) water flowing
statement: (ii) bullet fired from a gun
(1) The potential energy of a body of mass 1 kg (3) Zero work done
kept at height 1 m is 1 J. Ans.
Ans. False, potential energy is mgh = 1 × 9.8 × 1 (i) A stone tied to a string and whirled in a
= 9.8 J. circular path
(2) Water stored at some height has potential (ii) motion of the earth and other planets moving
energy. around the sun
Ans. True (4) Negative work done
(3) Unit of power is joule. Ans.
Ans. False, unit of power is watt. (i) A cyclist applies brakes to his bicycle, but the
(4) Mechanical energy can be converted into bicycle still covers some distance
electrical energy. (ii) When a body is made to slide on a rough
Ans. True surface, the work done by the frictional force.
(5) Work is a vector quantity. (5) Positive work done
Ans. False, work is a scalar quantity. Ans.
Q.3. (1) Match the column: (i) A boy moving from the ground floor to the
first floor
Column ‘I’ Column ‘II’ Column ‘III’
(ii) A fruit falling down from the tree
(1) Potential (a) can be positive, (i) 1 Q.5. Answer the following in one or two
mv2
Energy negative or zero 2 sentences:
(2) Power (b) energy possessed (ii) mgh (1) Name unit of energy used for commercial
by an athlete purpose.
Ans. kilowatt hour is the unit of energy used for
(3) Work (c) water raised at W commercial purpose.
(iii) P =
some height t
(2) Name unit used in industry to measure
(4) Kinetic (d) depends on work (iv) W = Fs power.
energy and time Ans. Horse power (hp) is the unit used in industry
to express power.
Ans. (1 - c - ii), (2 - d - iii), (3 - a - iv), (4 - b - i)
Work and Energy 27

(3) State the SI unit of energy. (8) Potential energy

Ans. joule is the SI unit of energy. Ans. The energy stored in an object because of its
(4) Name the two types of mechanical energy. specific state or position is called its potential
Ans. Potential energy and kinetic energy are the energy.
two types of mechanical energy. Q.7. Give reasons:
(5) Give an example where force acting on an (1) A moving ball hits a stationary ball and
object does not do any work. displaces it.
Ans. In a simple pendulum the gravitational force Ans.
acting on the bob does not do any work as
(i) The moving ball has certain energy.
there is no displacement.
(ii) When it hits the stationary ball the energy is
(6) Give the relationship between 1 joule and
transferred to the stationary ball.
1 erg.
(iii) Because of which it moves.
Ans. 1 joule = 107 erg.
(iv) Hence, a moving ball hits a stationary ball and
(7) What is free fall?
displaces it.
Ans. An object falling solely under the influence of
gravitational force is said to be in free fall or to (2) Flowing water from some height can rotate a
be falling freely. turbine.
(8) State the various forms of energy Ans.
Ans. The various forms of energy are mechanical, (i) Flowing water has certain energy.
heat, light, sound, electro-magnetic, chemical, (ii) When it hits the turbine, energy is transferred
nuclear and solar. to the turbine.
Q.6. Define the following: (iii) Because of which it rotates.
(1) Work (iv) Hence, flowing water from some height can
Ans. Work is said to be done on a body when a force rotate a turbine.
applied on an object causes displacement of (3) A stretched rubber band when released
the object. regains its original length.
(2) Energy Ans.
Ans. The capacity of a body to perform work is (i) When we stretch the rubber band we give
termed as energy. energy to it.
(3) Power (ii) This energy is which is stored in it.
Ans. Power is the rate at which work is done. (iii) Hence, when we release it, it regains its
(4) 1 joule original length.
Ans. If a force of 1 newton displaces an object (4) Wind can move the blades of a wind mill.
through 1 metre in the direction of the force, Ans.
the amount of work done on the object is 1 joule. (i) Wind has certain energy.
(5) 1 erg (ii) When it hits the wind mill energy is transferred
Ans. If a force of 1 dyne displaces an object through to the wind mill
1 centimetre in the direction of the force, the
(iii) Because of which it moves.
amount of work done on the object is 1 erg.
(iv) Hence, wind can move the blades of a wind
(6) Law of conservation
mill.
Ans. Energy can neither be created nor destroyed.
(5) An exploding firecracker lights as well as
It can be converted from one form to another.
make sound.
The total amount of energy in the universe
remains constant. Ans.
(7) Kinetic energy (i) The exploding firecracker convert the chemical
Ans. The energy which an object has because of its energy stored in it into light and sound
motion is called its kinetic energy. respectively.
28 Master Key Science & Technology (Term - I) (Std. IX)

(ii) Here energy is converted from one type to (3) Explain the relation between, the commercial
another. and SI unit of energy.
(iii) Hence, an exploding firecracker lights as well Ans. The commercial unit of energy is kilowatt-
as make sound. hour (kWh) while the SI unit of energy is
joule. Their relation is
(6) Work done on an artificial satellite by gravity
1 kWh = 1 kW × 1hr
is zero while moving around the earth.
= 1000 W × 3600 s
Ans.
= 3600000 J
(i) When the artificial satellite moves around the
1 kWh = 3.6 × 106 J.
earth in a circular orbit, gravitation force acts
* (4) If an object has 0 momentum, does it have
on it.
kinetic energy? Explain your answer.
(ii) The gravitational force acting on the satellite Ans. No, it does not have kinetic energy if it does
and its displacement are perpendicular to not have momentum.
each other. i.e. θ = 90° Momentum is the product of mass and
(iii) For θ = 90°, work done is zero. velocity. If it is zero, it implies that v = 0 (since
(iv) Hence, work done on an artificial satellite by mass can never be zero).
gravity is zero while moving around the earth. 1
Now K.E = mv2 So if v = 0 then K.E also will
2
Q.8. Answer in short: be zero.
(1) Derive the expression for potential energy. Thus, if an object has no momentum then it
Ans. To carry an object of mass ‘m’ to a height ‘h’ cannot possess kinetic energy.
above the earth’s surface, a force equal to ‘mg’ * (5) Why is the work done on an object moving
has to be used against the direction of the with uniform circular motion zero?
gravitational force. The amount of work done Ans.
can be calculated as follows.
(i) When a body performs uniform circular
Work = force × displacement motion, then the force acting on it is along the
 W = mg × h radius of the circle.
 W = mgh (ii) While its displacement is along the tangent
 The amount of potential energy stored in the to the circle. Thus, they are perpendicular to
object because of its displacement each other.
P.E = mgh (W = P.E) Hence θ = 90º and cos 90 = 0

 Displacement to height h causes energy equal  W = Fs cos θ = 0

to mgh to be stored in the object. * (6) Determine the amount of work done when
(2) When can you say that the work done is an object is displaced at an angle of 300 with
either positive, negative or zero? respect to the direction of the applied force.
Ans. Ans. When object is displaced by displacement 'S'
(i) When the force and the displacement are in and by applying force 'F' at an 'angle' 300.
the same direction, the work done by the force work done can be given as
is positive. W = Fs cos θ
∴
(ii) When the force and displacement are in the ∴ W = Fs cos 30 ( θ = 30°)
opposite directions, the work done by the   ∴  
∴ W = Fs  3  ( cos 30 = 3 )
force is negative.  2   2 
(iii) When the applied force does not cause any (7) How is work calculated if the direction of
displacement or when the force and the force and the displacement are inclined to
displacement are perpendicular to each other, each other?
the work done by the force is zero. Ans. If the direction of force and the displacement
are inclined to each other then, we must
Work and Energy 29

convert the applied force into the force acting velocity (here u = 0). Let the applied force be F.
along the direction of displacement. This generates an acceleration a in the object,
If θ is angle between force and displacement, and, after time t, the velocity of the object
then force (F1) in direction of displacement is becomes equal to v. The displacement during
F cos θ. this time is s. The work done on the object
∴ W = F1 × s W = Fs
W=F×s
∴ W = F cos θ × s
According to Newton’s second law of motion,
∴ W = Fs cos θ
F = ma (1)
Q.9. Answer in brief: Similarly, using Newton’s second equation of
(1) State the expression for work done when motion
displacement and force makes an angle θ 1
s = ut + at2
OR State the expression for work done when 2
force is applied making an angle θ with the However, as initial velocity is zero, u = 0
horizontal force. 1
F
 s = 0 + at2
2
1
 s = at2 (2)
2
1
 W = ma × at2 using equations (1) and (2)
2
θ 1
 W = m × (at)2 (3)
F1 2
Using Newton’s first equation of motion
Force used for the displacement v = u + at
Ans. Let F be the applied force and F1 be its  v = 0 + at
component in the direction of displacement.  v = at
Let s be the displacement.  v2 = a2t2 = (at)2 (4)
The amount of work done is given by 1
 W = mv2 using equations (3) and (4)
W = F1s (1) 2
The kinetic energy gained by an object is the
The force F is applied in the direction of the
amount of work done on the object.
string i. e. at an angle with the horizontal.
 K.E = W
Let θ be the angle that the string makes with the 1
horizontal. We can determine the component  K.E = mv2
2
F1, of this force F, which acts in the horizontal
(3) When a body is dropped on the ground from
direction by means of trigonometry.
some height its P.E is converted into K.E but
base
cos θ = when it strikes the ground and it stops, what
hypotenuse happens to the K.E?
F
∴ cos θ = 1 Ans. When a body is dropped on the ground, its
F K.E appears in the form of:
∴ F1 = F cos θ
(i) Heat (collision between the body and the
Substituting the value of F1 in equation 1
ground).
Thus, the work done by F1 is
(ii) Sound (collision of the body with the ground).
W = F cos θ s
(iii) Potential energy of configuration of the body
∴ W = F s cos θ and the ground.
* (2) Derive the formula for the kinetic energy of (iv) Kinetic energy is also utilized to do work i.e.
an object of mass m, moving with velocity v. the ball bounces to certain height and moves to
Ans. Suppose a stationary object of mass m moves a certain distance vertically and horizontally
because of an applied force. Let u be its initial till K.E becomes zero.
30 Master Key Science & Technology (Term - I) (Std. IX)

(v) The process in which the kinetic energy of a

∴ K.E = 1 mv2 = 1 m(2gx)
freely falling body is lost in an unproductive 2 2
chain of energy is called dissipation of energy. K.E = mgx
(4) Explain the statement “Potential Energy is Height of the object when at B = h-x
relative”.
∴ P.E = mg (h-x)
Ans.
P.E = mgh – mgx
(i) Potential energy of an object is determined
∴ Total Energy T.E. = K.E + P.E
and calculated according to height of the
object with respect to the observer. = mgx + mgh – mgx
(ii) So, the person staying on 6th floor will have ∴ T.E. = mgh ---------- (2)
more potential energy then those staying on (3) Let the velocity of the object be vC when it
3rd floor. reaches the ground, near point C.
(iii) But, if another observer staying on 8th floor U = 0, s = h, a = g
will have more potential energy then those v2 = u2 + 2as
on the 6th floor. Hence, potential energy is vC2 = 0 + 2gh
relative.
∴ K.E = 1 mvC2 = 1 m(2gh)
* (5) Prove that the kinetic energy of a freely 2 2
falling object on reaching the ground is K.E = mgh
nothing but the transformation of its initial
The height of the object from the ground
potential energy.
at point C is h = 0
Ans. Let us look at the kinetic and potential energies ∴ P.E = mgh = 0
of an object of mass, falling freely from height
∴ T.E. = K.E + P.E
h, when the object is at different heights.
T.E. = mgh ------ (3)
As shown in the figure, the point A is at a
height h from the ground. Let the point B be at From equations (1) and (3) we see that the
a distance x, vertically below A. Let the point total potential energy of the object at its initial
C be on the ground directly below A and B. position is the same as the kinetic energy at
Let us calculate the energies of the object at A, the ground.
B and C. Q.10. Difference between
A
(1) When the object is stationary * (1) Kinetic energy and Potential energy:
at A, its initial velocity is u = 0
x Kinetic Energy Potential Energy
∴ K.E = 1 mass × velocity2
2 (1) Kinetic energy is the (1) Potential energy
1 mu2 energy possessed by is the energy
= B h
2 the body due to its possessed by the
K.E = 0 motion. body because of its
shape or position.
P.E = mgh h–x
∴ Total energy = K.E + P.E (2) Kinetic energy (2) Potential energy
is given by the is given by the
= 0 + mgh
formula : formula :
Total Energy = mgh. - - - (1) C
K.E = 1 mv2 P.E = mgh
(2) Let the velocity of the object be vB when it 2
reaches point B, having fallen through a (3) e.g. flowing water, (3) e.g. water at the top
distance x. such as when falling of a waterfall, before
u = 0, s = x, a = g from a waterfall. the drop.
v2 = u2 + 2as
vB2 = 0 + 2gx
vB2 = 2gx
Work and Energy 31

(2) Work and Power: * (2) Ravi applied a force of 10 N and moved a
book 30 cm in the direction of the force. How
Work Power much was the work done by Ravi?
(1) Work is the product (1) Power is rate of Ans. Given :
of force and doing work.
Force (F) = 10 N
displacement.
θ = 0º, (Since force and displacement are in
(2) Work is given by the (2) Power is given by
same direction)
formula : the formula : 30
W = Fs Displacement (s) = 30 cm = m
W 100
P= To Find :
t
Work (W ) = ?
(3) MKS unit - joule (3) MKS unit - joule/sec
CGS unit - erg CGS unit - erg/sec Formula :
W = Fs cos θ
Q.11. Solve the following:
Solution :
TYPE – A
W = Fs cos θ
Formula : 30
= 10 × × cos 0
W = Fs cos θ 100
30
• If Force and displacement are in same = ×1 ..... (cos 0 = 1)
10
direction then 0º , and cos θ = 1
=3J
• If Force and displacement are in opposite
The work done by Ravi is 3 J
direction then θ = 180º , and cos θ = –1
• If Force and displacement are perpendicular
then θ = 90º , and cos θ = 0 NUMERICAL FOR PRACTICE
* (1) Pravin has applied a force of 100 N on an (3) A force of 50 N acts on an object and displaces
0
object, at an angle of 60 to the horizontal. it by 2 m. If the force acts at an angle of 60°
The object gets displaced in the horizontal to the direction of its displacement, find the
direction and 400 J work is done. What is the work done.
1
displacement of the object? (cos 600 = ) Ans. 50 J
2
Ans. Given : (4) Raj applied a force of 20 N and moved a
0
θ = 60 book 40 cm in the direction of the force. How
much was the work done by Raj?
Force (F) = 100 N
Ans. 8 J
Work (W) = 400 J
To Find : TYPE – B
Displacement (s) = ? Formulae :
1
Formula : 1) W = K.E = mv2
2
W = Fs cos θ 2) W = P.E = mgh
Solution : • W = P.E , W = K.E
W = Fs cos θ
*(1) A stone having a mass of 250 gm is falling
∴ 400 = 100 × s × 1 from a height. How much kinetic energy
2 does it have at the moment when its velocity
400 1
∴ = ×s is 2 m/s?
100 2
Ans. Given :
∴ 4×2=s
∴ s=8m Mass (m) = 250 g
250
The object will be displaced through 8 m. = kg
1000
Velocity (v) = 2 m/s
32 Master Key Science & Technology (Term - I) (Std. IX)

To Find : To Find :
Kinetic energy (K.E) = ? Work done to increase the velocity = ?
Formula :
Formula :
1 Work done to
K.E = mv2 = Change in K.E
2 increase velocity
Solution : 1 1
Change in K.E = mv2 – mu2
1 2 2
K.E = mv2
2 Solution :
1 250 1 1
= × × (2)2 Change in K.E = mv2 – mu2
2 1000 2 2
25 1
= ×2 = m (v2 – u2)
100 2
1
50 = × 1500 [(20)2 – (15)2]
= = 0.5 J 2
100
The kinetic energy of the stone is 0.5 J = 750 × [400 – 225]
= 750 × 175
*(2) 500 kg water is stored in the overhead tank of
a 10 m high building. Calculate the amount = 131250 J
of potential energy stored in the water. Work done to increase the velocity = 131250 J
Ans. Given : * (4) Calculate the work done to take an object of
Mass (m) = 500 kg mass 20 kg to a height of 10 m. (g = 9.8 m/s2)
Height (h) = 10 m Ans. Given :
Acceleration due to gravity (g) = 9.8 m/s2 Mass (m) = 20 kg
To Find : Acceleration due to gravity (g) = –9.8 m/s2
Potential energy (P.E) = ? Displacement (s) = (h) = 10 m.
Formula : To Find :
P.E = mgh Work done (W) = ?
Solution : Formula :
P.E = mgh (i) W = P.E = mgh
= 500 × 10 × 9.8 Solution :
= 500 × 98 W = mgh
= 49000 J = 20 × –9.8 × 10
The P.E of the stored water is 49000 J = –1960 J
The work done to take an object of mass 20 kg
* (3) The velocity of a car increases from 54 km/hr to a height of 10 m is –1960 J.
to 72 km/hr. If the mass of the car is 1500 kg,
(5) A body of 0.5 kg thrown upwards reaches a
find the work done to increase the velocity.
maximum height of 5 m. Calculate the work
Ans. Given : Mass (m) = 1500 kg done by the force of gravity during this
[1 km/hr = 1000
3600
m/sec =
5
18
m/sec]
vertical displacement.
Ans. Given :
Initial velocity (u) = 54 km/hr Mass (m) = 0.5 kg
5
= 54 × Acceleration due to gravity (g) = –9.8 m/s2
18
= 15 m/s Displacement (s) = 5 m.
Final velocity (v) = 72 km/hr To Find :
5 Work done (W) = ?
= 72 ×
18 Formula :
= 20m/s W= P.E = mgh
Work and Energy 33

Solution : * (8) If the energy of a ball falling from a height of

W = mgh 10 metres is reduced by 40%, how high will it
rebound?
= 0.5 × –9.8 × 5
Ans. Given : Initial height (h1) = 10 m
= –24.5 J
Initial P.E = P.E1
The work done by the force of gravity is
–24.5 joule. Final P.E = P.E2
P.E2 = 60% of P.E1 = 0.6 P.E1
(6) 1 kg mass has a kinetic energy of 2 joule.
Calculate its velocity. To Find :
Ans. Given : Final height (h2) = ?
Mass (m) = 1 kg Formula :
Kinetic Energy (K.E) = 2 J P.E = mgh
To Find : Solution :
Velocity (v) = ? P.E1 = mgh1 (i)
Formula : P.E2 = mgh2 (ii)
1 Dividing (ii) by (i)
K.E = mv2
2 P.E 2 mgh 2
Solution : =
1 P.E1 mgh1
K.E = mv2
2 0.6 P.E1 h 2
1 =
2 = × 1 × (v)2 P.E1 h1
2 h2
4 = (v)2 0.6 =
h1
(v)2 = 4
h2 = 0.6 × h1
v = 4
= 0.6 × 10
= 2 m/s
=6m
The velocity is 2 m/s The ball will rebound by 6 m.
(7) A rocket of mass 100 tonnes is propelled with
a vertical velocity 1 km/s. Calculate kinetic
NUMERICAL FOR PRACTICE
energy
Ans. Given : (9) 1 kg mass has a kinetic energy of 2 joule.
Calculate its velocity.
Mass (m) = 100 tonnes,
= (100 × 1000) kg Ans. 2 m/s
Velocity (v) = 1 km/s (10) A ball of mass 1 kg slows down from a speed
= 1000 m/s of 5 m/s to that of 3 m/s. Calculate the change
in kinetic energy of the ball.
To Find :
Kinetic Energy (K.E) = ? Ans. 8 joule
Formula : (11) An energy of 2J is used to lift a block of 0.5
1 kg. How high will it rise? (Take g = 10 m/s2)
K.E = mv2
2
Ans. 0.4 m
Solution :
1 (12) An object of mass 10 kg is lying 10 m above
K.E = mv2 the ground. Calculate the potential energy
2
1 possessed by the object. (Take g = 9.8 m/s2)
= × 100 × 1000 × (1000 × 1000)
2 Ans. 980 J
= 50 × 109 J
= 5 × 1010 J
The kinetic energy of the rocket is 5 × 1010 J
34 Master Key Science & Technology (Term - I) (Std. IX)

TYPE – C Pt
m=
gh
Formulae :
work mgh 2000 × 60
1) Power = = =
time t 9.8 × 10
Electric energy consumed
2) Electric power =
time 120000
=
• Power should be expressed in kW 98
• Time should be expressed in hours m = 1224.5 kg
• 1 kWh = 1 unit Water lifted by the pump is 1224.5 kg
*(1) Swaralee takes 20 s to carry a bag weighing * (3) If a 1200 W electric iron is used daily for
20 kg to a height of 5 m. How much power 30 minutes, how much total electricity is
has she used? consumed in the month of April?
Given : Ans. Given :

Mass (m) = 20 kg Power of electric iron (P) = 1200 W

1200
Height (h) = 5 m = kW = 1.2 kW
1000
Time (t) = 20 s Time (t) = 30 min × 30 days
= 0.5 hr × 30 days
Acceleration due to gravity (g) = 9.8 m/s2
= 15 hr
To Find :
To find :
Power (P)= ?
Energy consumed = ?
Formula : Formula :
mgh
P= Electric energy consumed
t Electric power =
time
Solution :
mgh Solution :
P= Electric energy consumed
t 5 Electric power =
= 20 × 9.8 × time
20
= 9.8 × 5 Electric energy
= Electric power × time
consumed
= 49 W
= 1.2 × 15
Power used by Swaralee is 49 W = 18 kWh
* (2) An electric pump has 2 kW power. How = 18 units
much water will the pump lift every minute
The units of energy consumed in the month of
to a height of 10 m?
April by the iron is 18 units.
Ans. Given :
*(4) A 25 W electric bulb is used for 10 hours
Power (P) = 2 kW = 2000 W
every day. How much electricity does it
Height (h) = 10 m
consume each day?
Time (t) = 1 min = 60 s
Given:
Acceleration due to gravity (g) = 9.8 m/s2
Power (P) = 25 W
To find :
25
Mass of water (m)= ? = kW
1000
Formula : = 0.025 kW
P = mgh To Find :
t
Solution : Electric energy consumed
mgh Formula :
P=
t Electric energy consumed = power × time
Work and Energy 35

Solution : (iii) Why do the balls cover the same distance on

Electric energy consumed = power × time rolling down?
= 0.025 × 10 (iv) What is the form of the eventual total energy
of the balls?
= 0.25 kWh
(v) Which law related to energy does the above
The electric bulb consumes 0.25 kWh of
activity demonstrate? Explain.
electricity each day.
Ans.
NUMERICAL FOR PRACTICE (i) At the moment of releasing the ball they
possess P.E as they are at a height above the
(5) If a 60 W electric bulb is lighted for 6 hours
ground.
how much electrical energy is consumed?
(ii) As the balls roll down, the P.E is converted
Ans. 0.36 kWh into K.E since they are now in motion.
(6) A man draws a bucket of water from a well (iii) Since they have been released from the same
which is 10 m deep in 20 secs. If the mass of height, they will cover the same distance.
the water drawn is 20 kg, find the power used (iv) The eventual form of the total energy of the
by the man. Can the power be calculated if balls is “Mechanical Energy” i.e a combination
mass of water is not known? (g = 9.8 m/s2) of P.E and K.E.
Ans. 98 W (v) The above activity demonstrates the “Law of
Conservation of Energy”
(7) An electric pump is used to lift water to a
height of 60 m in 2 minutes. If the mass of As the balls roll down, the value of ‘h’
the water raised is 800 kg, find the power of decreases due to which P.E also decreases as
pump. (g = 9.8 m/s2) P.E = mgh. At the same time, the velocity of
the balls increases as they roll down due to
Ans. 3920 W which
(8) An electric motor is used to lift the water 1
their K.E increases as K.E = mv2
stored in a tank at the ground level to an 2
overhead tank at a height of 20 m. If the Thus, we find that P.E decreases while K.E
power of the motor is 1 HP how much time increases. But energy can neither be created
will be required to pump 746 kg of water? nor destroyed. Thus, the P.E that decrease is
(Take g = 10 m/s2) in fact being converted to K.E.

Ans. 2000 sec * (2) Study the pictures given below and answer
the questions:
*Q.12. Activity based question:
* (1) Study the following activity and answer the
questions.
(i) Take two aluminium channels of different
lengths.
(ii) Place the lower ends of the channels on the floor
and hold their upper ends at the same height. Various activities

(iii) Now take two balls of the same size and (i) In which of the pictures above has work
weight and release them from the top end of been done?
the channels. They will roll down and cover (ii) From scientific point of view, when do we
the same distance. say that no work was done?
Questions Ans.
(i) At the moment of releasing the balls, which (i) Girl studying : No work done
energy do the balls have? Boy playing with ball : Work is done
(ii) As the balls roll down which energy is Girl watching T.V. : No work done
converted into which other form of energy? Person lifting sack of grains : Work is done
36 Master Key Science & Technology (Term - I) (Std. IX)

(ii) No work is said to be done when force is (ii) Force of friction has been overcome using the
applied but there is no displacement. energy
* (3) Discuss the directions of force and of * (5) You have learnt how to calculate the work
displacement in each of the following cases. done on an object when the displacement is
(i) Pushing a stalled vehicle in the direction of the applied force. But if
the displacement is not in the direction of
(ii) Catching the ball which your friend has
the applied force, how do we calculate the
thrown towards you.
amount of work done?
(iii) Tying a stone to one end of a string and
Ans.
swinging it round and round by the other end
of the string. (i) If the displacement is not in the direction of
the applied force,
(iv) Walking up and down a staircase; climbing a
tree. Then amount of work done can be calculated
as, W = Fs cos θ : θ = angle formed between
(v) Stopping a moving car by applying brakes.
force and displacement.
Ans.
(ii) Where θ = 180° or 90°
(i) Force and displacement are in the same
direction. * (6) Ajay and Atul have been asked to determine
(ii) Force and displacement are in the opposite the potential energy of a ball of mass m
direction. kept on a table as shown in the figure. What
answers will they get? Will they be different?
(iii) Force and displacement are perpendicular to
What do you conclude from this?
each other.
(iv) Force and displacement are in the same
direction.
(v) Force and displacement are in the opposite
direction.
* (4) Minakshee wants to displace a wooden block
from point A to point B along the surface of a
table as shown. She has used force F for the
purpose.

Ans.
(i) Potential energy is relative.
(ii) The heights of the ball with respect to Ajay
and Atul are different. So the potential energy
with respect to them will be different.
* (7) (i) An arrow is released from a stretched
bow.
(ii) Water kept at a high flows through a pipe
into the tap below.
(i) Has all the energy she spent been used to (iii) A compressed spring is released.
produce acceleration in the block?
(a) Which words describe the state of the object
(ii) Which forces have been overcome using that in the above examples?
energy?
(b) Where did the energy required to cause the
Ans. motion of the objects come from?
(i) Only part of the energy applied by Minakshee (c) If the objects were not brought in those
is used in accelerating the block states, would they have moved?
Work and Energy 37

Ans. each other while swinging. Now swing one

(a) Words such as stretched bow, water kept at a of the pendulums and observe. What do you
height and compressed spring describes the see?
state of the object. thread

(b) The energy required for the objects came thread thread
from its specific state or motion in the form of
potential energy. nut nut
(c) No, if the objects were not brought in those Ans.
states, they would have not moved.
You will see that as the speed of oscillation of
* (8) Study the activity and figure 2.4 on textbook the pendulum slowly decreases, the second
page 21 and answer the following questions. pendulum which was initially stationary,
(i) Figure A - Why does the cup get pulled? begins to swing. Thus, one pendulum transfers
its energy to the other.
(ii) Figure B - What is the relation between
the displacement of the cup and the force *(10) Mention the type of energy used in the
applied through the ruler? following examples.

(iii) In Figure C - Why doesn't the cup get (i) Stretched rubber string.
displaced? (ii) Fast moving car
(iv) What is the type of work done in figures A, B (iii) The whistling of a cooker due to steam
and C? (iv) A fan running on electricity
(v) In the three actions above, what is the (v) Drawing out pieces of iron from garbage,
relationship between the applied force and using a magnet.
the displacement? (vi) Breaking of a glass window pane because of a
Ans. loud noise.
(i) The cup get pulled as the force of the nut and (vii) The crackers exploded in Diwali
the displacement of the cup is in the same Ans.
direction. (i) Potential energy (ii) Kinetic energy
(ii) The displacement of the cup and the force (iii) Sound energy (iv) Electrical energy
applied through the ruler is in the opposite (v) Kinetic energy (vi) Mechanical energy
direction. (vii) Sound energy, light energy and heat energy
(iii) The cup does not get displaced as two equal
* (11) What are different types of forces? Give
forces are working in opposite direction.
examples.
(iv) The work done in figure A is positive, figure B
Ans. The different types of force are
is negative and in figure C is zero.
(a) Gravitational force e.g.: The force exerted by
(v) In figure A the applied force and the
the earth on all objects.
displacement is in the same direction, in figure
(b) Frictional force
B the applied force and the displacement
is in the opposite direction and in figure * (12) Why is the work done on an object moving
C the applied force and displacement is with uniform circular motion zero?
perpendicular to each other. Ans.
(a) In uniform circular motion, the direction of
* (9) Make two pendulums of the same length
the applied force and the also displacement
with the help of thread and two nuts. Tie
are perpendicular to each other.
another thread in the horizontal position.
(b) The work done by a force is given by W = Fs
Tie the two pendulums to the horizontal
cos θ. Since θ = 90°, cos 90° = 0 the work done
thread in such a way that they will not hit
is zero.
38 Master Key Science & Technology (Term - I) (Std. IX)

* (13) Form the following activities find out (b) On increasing the volume of a music system
whether work is positive, negative or zero. or TV beyond a limit, the vessels in the house
Give reasons for your answers. start vibrating.
(a) A boy is swimming in a pond. Ans. The magnitude of sound energy increases and
(b) A coolie is standing with a load on his head it gets transferred from place to another. since
energy can do work, on increasing the volume
(c) Stopping a moving car by applying brakes
of a music system or TV beyond a limit, the
(d) Catching the ball which you friend has vessels in the house start vibrating.
thrown towards you
(c) Collecting sunlight on a paper with the help
Ans. of a convex lens burns the paper.
(a) A boy is swimming in a pond : The work done
Ans.
is positive because the direction of applied
force and displacement are the same. (i) While collecting sunlight on a paper through
a convex lens, solar energy is converted into
(b) A coolie is standing with a load on his head:
heat energy.
The work done is zero because the applied
force does not cause any displacement. (ii) Hence, the paper burns converting heat
energy into light energy.
(c) Stopping a moving car by applying brakes:
The work done is negative because the fore * (16) What will happen in the following cases?
applied by the brakes acts in a direction (a) A fast cricket ball strikes the stumps.
opposite to the direction of motion of car. Ans. When a fast moving cricket ball strikes the
(d) Catching the ball which you friend has stationary stumps then the stumps move and
thrown towards you : Negative force because fall. Thus, the moving ball shares its kinetic
the force required to stop the ball, acts opposite energy with stumps thereby making the
the displacement of the ball. stumps to fall.
* (14) Find whether work is positive, negative or (b) The striker hits a coin on the carom board.
zero. Ans. When the striker hits the coin on the carom
(a) Person moving along circle from A to B. board then the coins move in thereby making
Ans. Work done is zero because the direction the coins to move.
of applied force and displacement are (c) One marble strikes another in a game of
perpendicular to each other. marbles.
(b) Person completing one circle and returns to Ans. When one marble strikes the other marbles
position A. then the kinetic energy of the marble makes
Ans. Work done is zero because there is no the other stationary marble to move.
displacement for the person. * (17) If the mass of a moving body is doubled, how
* (15) Why does it happen ? may times will the kinetic energy increase?

(a) If a pot having a plant is kept in the dark, the Ans. Mass is doubled without changing velocity.
plant languishes. If mass is doubled, kinetic energy will also be
Ans. doubled.

(i) During photosynthesis plants convert solar Since mass is directly proportional to kinetic
energy into chemical energy and use it for energy.
their growth. 1
K.E = mv2
(ii) Since the plant is kept in dark, photosynthesis 2
i.e. the energy production does not occur. K.E a m if v is constant.

(iii) Hence, plant grow feeble due to absence of

energy.
Work and Energy 39

Brain Power
(1) If a TV of rating 100W is operated for 6 hrs Solution :
per day, find the amount of energy consumed Electric energy consumed = power × time
in any leap year?
= 0.1 × 2196
Ans. Given :
= 219.6 kWh
Power (P) = 100 W
The amount of energy consumed is 219.6 kWh
100
= kW (2) A ball is thrown vertically upwards, what
1000
will be its velocity when it reaches the
= 0.1 kW
maximum height?
Time (t) = 6 × 366
Ans. The velocity of the ball when it reaches the
= 2196 hrs. maximum height will be zero.
To Find : (3) A girl is walking on a horizontal leveled
Electric energy consumed road, the work done by the gravitational
Formula : force on her will be?
Electric energy consumed = power × time Ans. Zero, since force and displacement are
perpendicular to each other.

vvv
40 Master Key Science & Technology (Term - I) (Std. IX)

ASSIGNMENT - 2
Time : 1 Hr. Marks : 30

Q.1. (A) Choose the correct alternatives and rewrite the complete sentences: (6)
(1) The work done is zero if there is no .
(a) displacement (b) change of state (c) acceleration (d) change in velocity
(2) By stretching the rubber strings of a catapult we store energy in it.
(a) kinetic (b) mechanical (c) chemical (d) potential
(3) A bullet fired from a gun possesses energy.
(a) potential (b) kinetic (c) power (d) mechanical
(4) S.I unit of work is .
(a) joule (b) newton (c) pascal (d) dyne
(5) 1 kWh = joules.
3
(a) 3.6 × 10 J (b) 3.6 × 106 J (c) 6.3 × 106 J (d) 6.3 × 103 J
(6) The work done by a force is said to be when the applied force does not produce
displacement.
(a) Positive (b) Negative (c) Zero (d) None of these
(B) Match the following: (2)
Column ‘A’ Column ‘B’
(1) Potential Energy (a) Can be positive, negative or zero
(2) Power (b) Energy possessed by an athlete
(3) Work (c) Water raised at some height
(4) Kinetic energy (d) Depends on work and time

Q.2. (A) Give scientific reasons: (6)

(1) Flowing water from some height can rotate a turbine.
(2) A stretched rubber band when released regains its original length.
(3) Work done on an artificial satellite by gravity is zero while moving around the earth.
(B) Define or state : (4)
(1) Energy (2) Potential energy.
(3) Law of conservation of energy. (4) Work.
Q.3. Solve the following numerical: (4)
(1) Calculate the potential energy acquired by a 10 kg hammer when it is raised to a height of 10 m.
(2) The velocity of a car increases from 54 km/hr to 72 km/hr. If the mass of the car is 1500 kg, find the
work done to increase the velocity.
Q.4. Answer in brief: (8)
(1) (i) Derive the expression for work done when the displacement is in the direction of the force.
(ii) Distinguish between Kinetic Energy and Potential Energy.
(2) Derive the expression for kinetic energy.

vvv
 3 Current Electricity
CONCEPT MAP

Electric Current

Domestic electric circuit Potential difference

Ohm’s Law

Earthing Fuse
can be connected V
Resistance R =
in 2 ways I

RA
Resistivity r =
Series Parallel L

RS = R1+R2+R3 1 1 1 1
= + +
Rp R1 R2 R3

Conductors Insulators

(5) In order to measure the electric current flowing

MASTER KEY QUESTION SET - 3 through a circuit, we connect with
the circuit.
Q.1. (A) Rewrite the following statements by
selecting the correct options given below: (a) a voltmeter in parallel
(b) a voltmeter in series
(1) 1 mA = A.
(c) an ammeter in parallel
3 –3
(a) 10 (b) 10 (c) 106 (d) 10–6 (d) an ammeter in series
(2) To increase the effective resistance in a circuit (6) P and Q are two wires of same length and
the resistors are connected in . different cross sectional areas and made of
(a) series (b) parallel same material. Name the property which is
(c) both ways (d) none of these same for both the wires.
(3) 1 kilowatt hr = joules. (a) Resistivity (b) Resistance
(a) 4.6 × 10 6
(b) 3.6 × 106 (c) current (d) Both (a) and (b)
(c) 30.6 × 106 (d) 3.6 × 105 (7) The voltage difference in India between the
(4) If a P.D. of 12 V is applied across a 3  resistor live and neutral wires is about .
then the current passing through it is . (a) 110 V (b) 220 V (c) 440 V (d) 60 V
(a) 36 A (b) 4 A (c) 0.25 A (d) 15 A (8) Following is true for identical bulbs connected
in parallel.

(41)
42 Master Key Science & Technology (Term - I) (Std. IX)

(a) All bulbs glow with unequal brightness (2) Voltmeter is always connected in series with
(b) If one bulb is non functional, all will stop the device.
working Ans. False, Voltmeter is always connected in
(c) All bulbs glow with equal brightness parallel with the device.
(d) Bulbs function for longer time
(3) The conventional direction of flow of current
(9) Resistivity is the specific property of a . is from positive terminal to negative terminal.
(a) Area of cross section (b) temperature Ans. True
(c) length (d) material
(4) Silver and copper are good conductors.
(10) The wire is either yellow or green in
colour. Ans. True

(a) live (b) neutral (c) earth (d) fuse (5) Resistivity of pure metals is more than alloys.
Ans. (1) 10–3 (2) series (3) 3.6 × 106 (4) 4 A. Ans. False, Resistivity of pure metals is less than
(5) an ammeter in series (6) Resistivity (7) 220 V alloys.
(8) All bulbs glow with equal brightness (9) material (6) Resistance in series arrangement is used to
(10) earth decrease resistance of circuit.
(B) Fill in the blanks and rewrite the Ans. False, Resistance in series arrangement is used
complete statements: to increase resistance of circuit.
(1) A current flows through a circuit due to the (7) A conducting wire offers less resistance to
difference in between two points in flow of electrons.
the conductor. Ans. True
(2) is the amount of charge flowing (8) Charges are measured in ampere.
through a particular cross sectional area in
unit time. Ans. False,Charges are measured in coulomb.
(3) The flow of constitutes the electric (9) The unit of potential difference is ampere.
current in a wire. Ans. False, The unit of potential difference is volt.
(4) The conventional direction of flow of current is (10) Resistance of a conductor is inversely
from terminal to terminal. proportional to the length of the conductor.
(5) Current stops flowing when potential Ans. False, Resistance of a conductor is directly
difference between two ends of a wire becomes proportional to the length of the conductor.
.
(11) Ammeter is connected in parallel to the cell to
(6) Resistances are connected in so as to measure current.
pass the same current through them.
Ans. False, Ammeter is connected in series to the
(7) To decrease effective resistance in circuit, the cell to measure current.
resistances are connected in .
(12) Fuse is made of wire having high melting
(8) 1V = V point.
(9) Good conductors contain a large number of . Ans. False,Fuse is made of wire having low melting
(10) Electrons flow from terminal to point.
terminal in a conductor when
Q.3. Match the columns:
potential difference is applied.
Ans. (1) potential (2) Electric current (3) electrons (A) Column ’A’ Column ’B’
(4) positive, negative (5) zero (6) series (7) parallel (1) Electric current (a) joule
(8) 10–6 (9) free electrons (10) negative, positive
(2) Electric charge (b) ampere
Q.2. State whether the following statements are (3) Electric resistance (c) ohm
true or false and if false, write the correct
(4) Potential difference (d) coulomb
statement:
(e) volt
(1) The SI unit of charge is volt.
Ans. False, The SI unit of charge is coulomb. Ans. (1 - b), (2 - d), (3 - c), (4 - e)
Current Electricity 43

upto a certain value close to 0 K. Such

(B) Column ’A’ Column ’B’
conductors are called superconductors.
(1) Electric current (a) It
Q.5. Define the following:
(2) Electric charge (b) Q/t
(1) Electric current
(3) Potential difference (c) mgh
Ans. An electric current is the flow of electrons
(4) Electric resistance (d) IR through a conductor. Quantitatively, current
(e) V/I (I) is defined as the charge passing through a
conductor in unit time.
Ans. (1 - b), (2 - a), (3 - d), (4 - e)
(2) 1 ampere
*(C) Column ’A’ Column ’B’ Ans. One ampere current is said to flow in a
conductor if one coulomb charge flows
(1) Free electrons (a) V/ R
through it every second.
(2) Current (b) Increases the resistance 1C
in the circuit 1A=
1s
(3) Resistivity (c) Weakly attached (3) 1 volt
(4) Resistances in series (d) VA/LI Ans. The potential difference between two points is
said to be 1 volt if 1 joule of work is done in
Ans. (1 - c), (2 - a), (3 - d), (4 - b) moving 1 coulomb of electric charge from one
Q.4. Answer the following in one or two sentences: point to another.
1J
(1) Which is the unit used to measure large 1V=
voltages? 1C
(4) Potential Difference
Ans. Kilovolts and Megavolts are the units used to
Ans. The amount of work done to carry a unit
measure large voltages.
positive charge from point A to point B is
(2) What is the SI unit of potential difference? called the electric potential difference between
Ans. The SI unit of Potential difference is volt (V). the two points.
(3) What is lightning? (5) Conductor
Ans. Lightning is the electric discharge travelling Ans. Those substances which have very low
from clouds at high potential to earth surface resistance are called conductors. Current can
which is at zero potential. flow easily through such materials.
(4) What is the unit of resistivity. (6) Insulators
Ans. The unit of resistivity is ohm metre (m). Ans. Those substances which have extremely high
(5) Which substances are called conductors of resistance and through which current cannot
flow are called insulators.
electricity?
(7) 1 ohm
Ans. Those substances which have very low
electrical resistance are called conductors of Ans. If one ampere current flows through a
electricity. conductor when one volt potential difference
is applied between its ends, then the resistance
(6) What is Earth wire?
of the conductor is one ohm.
Ans. Earth wire is generally yellow or green colour, 1 volt
it is connected to a metal plate buried deep = 1 ohm (W)
1 ampere
underground near the house and is for safety
(8) Potential
purpose.
Ans. The level of electric charge present is known
(7) What are Non-ohmic conductors?
as potential.
Ans. Conductors which do not obey Ohm’s Law are (9) Ohm’s Law
called non-ohmic conductors.
Ans. If the physical state of a conductor remains
(8) What are superconductors? constant, the current (I) flowing through
Ans. The resistance of some conductors becomes it is directly proportional to the potential
nearly zero if their temperature is decreased difference (V) between its two ends.
44 Master Key Science & Technology (Term - I) (Std. IX)

Q.6. Give scientific reasons: effective resistance of the resistors is equal

(1) Free electrons are required for conduction of to the sum of their individual resistances.
electricity. RS = R1 + R2 ...
Ans. (ii) The effective resistance is larger than each
(i) Every atom of a metallic conductor has one of the individual resistances. Hence, This
or more outermost electrons which are very arrangement is used to increase the resistance
in a circuit.
weakly bound to the nucleus.
(6) A parallel combination of resistances decreases
(ii) These are called free electrons. These electrons
the effective resistance of the circuit.
can easily move from one part of a conductor
to its other parts. The negative charge of the Ans.
electrons also gets transferred as a result of (i) In a parallel combination, the inverse of the
this motion. effective resistance is equal to the sum of
(iii) The free electrons in a conductor are the carriers 1 1 1
the inverses of individual = + resistances.
of negative charge. Hence free electrons are Rp R1 R2
required for conduction of electricity. (ii) The effective resistance of resistors connected
in parallel is less than the individual resistors.
(2) Wood and glass are good insulators.
(iii) Due to this, any addition of an individual
Ans.
resistance in parallel combination will
(i) Those substances which have infinitely high
decrease the overall resistance of the circuit.
electrical resistance are called insulators. Hence a parallel combination of resistance
(ii) Wood and rubber have high resistance and decreases the effective resistance of the circuit.
negligible free electrons for conduction of
(7) Lightning occurs from sky to earth.
electricity.
Ans.
(iii) Hence wood and rubber are good insulators.
(i) Lightning is the electric discharge travelling
(3) Connecting wires in a circuit are made of
from clouds at high potential to the earth
copper and aluminium.
surface, which is at zero potential.
Ans.
(ii) The earth is always at lower potential as
(i) Copper and aluminium are good conductors compared to the clouds.
of electricity.
(iii) Hence, lightning occurs from sky to earth.
(ii) They have low electrical resistance.
(8) In street lights bulbs are connected in parallel.
(iii) As they are malleable and ductile, they can be Ans .
drawn into thin wires. Hence connecting wires
in a circuit are made of copper or aluminium. (i) Even if any one of the several bulbs connected
in parallel becomes non-functional because of
(4) A thick wire has a low resistance.
some damage to its filament, the circuit does
Ans. not break as the current flows through the
(i) The resistance (R) of a wire is inversely other paths, and the rest of the bulbs light up.
proportional to the cross sectional area (A) of (ii) When several bulbs are connected in parallel,
a wire. i.e. .R 
1 they emit the same amount of light as when
A
they are connected individually in the circuit,
(ii) Thus, greater is the cross sectional area of a while bulbs connected in series emit less light
conductor (wire), lower is its resistance. Hence than when connected individually. Hence
a thick wire has a low resistance. street lights are connected in parallel.
(5) A series combination of resistances is used
Q.7. Answer in brief:
to increase the resistance of a circuit.
* (1) The following figure shows the symbols
Ans.
for components used in the accompanying
(i) When resistances are connected in series , the electrical circuit.
Current Electricity 45

V (volts) I (Amp)
+ – 4 9
+ A – 5 11.25
6 13.5
+ –
V (A) Find the average resistance.
(B) What will be the nature of the graph between
the current and potential difference? (Do not
draw a graph.)
(C) Which law will the graph prove? Explain the
law.
(A) Place them at proper places and complete the
Ans.
circuit.
(B) Which law can you prove with the help of the (A) V1= 4V, V2= 5V, V3= 6V
above circuit? I1= 9A, I2= 11.25A, I3=13.5A
V1 4
Ans. (A) R1 = = = 0.44 
I1 9
–
V
R2= 2 = 5 = 0.44 
I2 11.25
V
R3= 3 = 6 = 0.44 
I3 13.5
R1 + R2 + R3
Average resistance =
3
(0.44 + 0.44 + 0.44)
=
3
= 0.44 
(B) This circuit can be used to prove Ohm’s law. (B) Graph will be linear as current and potential
* (2) Umesh has two bulbs having resistances of difference are directly proportional.
15  and 30 . He wants to connect them (C) The graph proves Ohm’s Law. It states that
in a circuit, but if he connects them one at “If the physical state of a conductor remains
a time the filament gets burnt. Answer the constant, the current (I) flowing through
following. it is directly proportional to the potential
(A) Which method should he use to connect the difference (V) between its two ends”.
bulbs? * (4) The resistance of a conductor of length x is
(B) What are the characteristics of this way of r. If its area of cross-section is a, what is its
connecting the bulbs depending on the answer resistivity? What is its unit?
of A above? Ans. Resistance (R) = r Length (L) = x
(C) What will be the effective resistance in the
Area of cross section (A) = a Resistivity (r) = ?
above circuit?
Ans. We know that,
rL
(A) Umesh should connect the bulbs in series R= A
combination.
RA
(B) (i) Bulbs are connected in series. (ii) Overall \ r =
L
resistance will increase and hence current will ra
r = m
decrease. (iii) So the filament of the bulb will x
not get burnt. Its unit is ohm-metre ( m)
(C) The effective resistance in the circuit will be * (5) Resistances R1, R2, R3 and R4 are connected as
RS = R1 + R2 = 15 + 30 = 45 . shown in the figure. S1 and S2 are two keys.
* (3) The following table shows current in Discuss the current flowing in the circuit in
amperes and potential difference in volts. the following cases.
46 Master Key Science & Technology (Term - I) (Std. IX)

(B) As x is larger than x1, x2 and x3 , they are

R1
C A
D F H connected in series. As effective resistance in
series is greater than individual resistance.
S1
(C) As x is smaller than x1, x2 and x3, they are
B connected in parallel. As effective resistance in
E S2 R4
R2 parallel is smaller than individual resistance.
(D) As the potential difference across x1, x2 and x3
is the same, they are connected in parallel.
(E) x = x1 + x2 + x3 is the formula for effective
A + – G I resistance in the circuit when resistances are
R3
connected in series.
(A) Both S1 and S2 are closed.
(B) Both S1 and S2 are open. (F) x=
(C) S1 is closed but S2 is open.
Ans. This can also be expressed as,
(A) When both S1 and S2 are closed, the effective 1 1 1 1
x = x1 + x2 + x3
resistance of the circuit decreases and hence
current will increase. This is the formula for the effective resistance
(B) When both S1 and S2 are open, the effective of the circuit when resistors are connected in
resistance of the circuit increases and hence parallel.
current will decrease. (7) P and Q are the two wires of same length
(C) When S1 is closed and S2 is open, the effective and different cross sectional areas and made
resistance of the circuit decreases and hence of same metal. Name the property which is
current will increase. [current will be more same for both the wires and different for
than case (b) but less than in case (a)] both the wires.
Ans.
*(6) Three resistances x1, x2 and x3 are connected
in a circuit in different ways. x is the effective (i) Resistivity of the wire is dependent upon the
resistance. The properties observed for these material of the wire, hence, resistivity of both
different ways of connecting x1, x2 and x3 the wires is same.
are given below. Write the way in which (ii) Resistance is inversely proportional to the
they are connected in each case. (I-current, cross sectional area. As the cross sectional
V-potential difference, x-effective resistance) areas of the two wires are different, their
(A) Current I flows through x1, x2 and x3 resistances will be different.

(B) x is larger than x1, x2 and x3 (8) Resistivity of some materials is given below.
State which one will be the best conductor
(C) x is smaller than x1, x2 and x3
and the best insulator.
(D) The potential difference across x1, x2 and x3 is
the same Material Copper Nichrome Diamond
Resistivity 1.7 × 10 1.1 × 10  m 1.62 × 1013 to
–8 –6
(E) x = x1 + x2 + x3
m m 1.62 × 1018  m
1
(F) x= Ans.
1 1 1
+ +
x1 x2 x3 (i) Copper has the lowest resistivity i.e. 1.7 × 10–8
Ans.  m , hence it will be the best conductor.
(A) If I is total current and same current I flows (ii) Diamond has the highest resistivity i.e.
through x1, x2 and x3 , then the three resistors 1.62 × 1013 to 1.62 x1018  m , hence it will be
are connected in series combination. the best insulator.
Current Electricity 47

(9) Explain with the help of a diagram, what are free electrons and how they move through the conductor?
Nucleus Electrons
Weakly attached outermost electrons
Free electrons move freely
from atom to atom

Single atom Atoms in a conducting solid

Ans.
(i) Every atom of a metallic conductor has one or more outermost electrons which are very weakly bound to
nucleus.
(ii) These are called free electrons.
(iii) These electrons can easily move from one part of a conductor to its other parts.

(10) Explain the function and working of a fuse. (2) Conductors and Insulators
Ans.
Conductors Insulators
(i) Fuse wire is used to protect domestic
(1) Substances which (1) Substances which
appliances.
have very low have extremely high
(ii) It is made of a mixture of substances and has a
electrical resistances electrical resistances
specific melting point.
are called conductors. are called Insulators.
(iii) It is connected in series to the electric
appliances. If for some reason, the current in (2) They contain a large (2) They contain
the circuit increases excessively, the fuse wire number of free practically no free
gets heated up and melts. The circuit gets electrons. electrons.
broken and the flow of current stops, thus
protecting the appliance. (3) Conductors are (3) Insulators are
mostly metals. mostly non metals.
(iv) This wire is fitted in a groove in a body of
porcelain - like non-conducting material. For
domestic use, fuse wires with upper limits of (3) Resistance and Resistivity
1 A, 2 A, 3 A, 4 A, 5 A and 10 A are used.
Resistance Resistivity
Q.8. Distinguish between:
(1) The hindrance to the (1) Resistivity is the
(1) Voltmeter and Ammeter flow of electrons is specific property
Voltmeter Ammeter called resistance. of the material of a
conductor.
(1) It is an instrument (1) It is an instrument to
used to measure the measure the electric (2) The S.I unit of (2) The S.I unit of
potential difference current flowing resistance is ohm resistivity is ohm-
between the two through the circuit. (W). metre (W – m).
terminals of a cell.
(3) It depends on (3) It depends on
(2) It is connected in (2) It is connected in temperature, area material of the
parallel with the cell. series with the cell. of cross section, conductor.
length of conductor
(3) It has a very high (3) It has a very low and material of the
resistance. resistance. conductor.
48 Master Key Science & Technology (Term - I) (Std. IX)

(4) Resistance in Series and Resistance in V = V 1 + V2 + V3 .... (i)

Parallel By using Ohm’s law
Resistance in Series Resistance in Parallel V = IRS
\ V1 = IR1, V2 = IR2 and V3 = IR3
(1) Effective resistance (1) Inverse of the
of the resistors is effective resistances is Substituting these values in equation (i) we get
equal to the sum equal to the sum of the IRS = IR1 + IR2 + IR3
of their individual inverse of individual \ RS = R1 + R2 + R3
resistances. resistances. For ‘n’ number of resistors connected in series
(2) The same current (2) The total current we get
flows through each flowing through the RS = R1 + R2 + R3+ R4 + R5 + R6 + ........ + Rn
resistor. circuit is the sum of
(2) Find the expression (i.e., derive the expression)
the currents flowing
for the resistors connected in parallel.
through individual
resistors. Ans. Expression for the resistance connected in
parallel.
(3) The effective resistance (3) The effective resistance
(i) Let R1, R2 and R3 be the three resistances
is larger than each of resistors connected
connected in parallel combination between
of the individual in parallel is less than
points C and D and let Rp be their effective
resistances. the least resistance of
resistance.
individual resistors.
(ii) Let I1, I2 and I3 be the currents flowing through
(4) This arrangement (4) This arrangement resistances R1, R2 and R3 respectively.
is used to increase is used to decrease Let I be the current flowing through the circuit
the resistance in a the resistance in a and V be the potential difference of the cell.
circuit. circuit.

Q.9. Answer in detail: I1

(1) Find the expression (i.e., derive the expression) I2 R1
for the resistors connected in series.
C I3 R2 D
Ans. Expression for the resistance connected in
series: R3
(i) Let R1, R2 and R3 be three resistances connected
in series between C and D.
(ii) Let RS be the effective resistance in circuit and
V1, V2 and V3 be the potential difference
across R1, R2 and R3 respectively. K E
(iii) Let the potential difference across CD be V. Resistors in Parallel
(iii) For parallel combination of resistances,
I = I1 + I2 + I3 ...... (i)
According to Ohm’s law,
V
I=
Rp
Therefore,
V V V
I1 = , I2 = , I3 =
R1 R2 R3
(iv) Substituting the values of (I, I1, I2 and I3) in
equation (i) we get
Resistors in series V V V
V
(iv) In series combination. = + +
Rp R1 R2 R3
Current Electricity 49

(ii) In parallel combination the resistance of the

=V overall circuit decreases whereas in series it
increases, so the current flowing through the
bulbs in parallel circuit is more.
1 1 1 1
= + + (iii) Due to this intensity of light given out by
Rp R R R
1 2 3
bulbs in parallel combination is more than the
For ‘n’ number of resistances bulbs in series combination.
1 1 1 1 1 (5) State some of the safety precautions to be
= + + ..........
Rp R1 R2 R3 Rn taken while using electricity.
Ans:
(3) Find the expression for resistivity of a
material. (i) Electric switches and sockets should be fitted
at a height at which small children cannot
Ans.
reach and put pins or nails inside. Plug wires
(i) At a given temperature, the resistance (R) of
should not be pulled while removing a plug
a conductor depends on its length (L), area of
from its socket.
cross-section (A) and the material it is made
of. (ii) Before cleaning an electrical appliance it
should be switched off and its plug removed
If the resistance of a conductor is R, then
from the socket.
RL
(iii) One’s hands should be dry while handling an
Also, R 1 electrical appliance, and, as far as possible,
A one should use footwear with rubber soles. As
\ R L rubber is an insulator, it prevents the current
A from flowing through our body, thereby
\ R=rL protecting it.
A
(iv) If a person gets an electric shock, you should
(ii) r is the constant of proportionality and is
called the resistivity of the material. not touch that person. You should switch off
the main switch or remove the plug from the
(iii) The unit of resistivity in SI units is ohm metre
socket if possible. If not, then you should use
( m).
a wooden pole to push the person away from
(iv) Resistivity is a specific property of a material
the electric wire.
and different materials have different
resistivity. (6) How are Domestic electrical connections made ?
(4) In which arrangement will the bulbs be Ans.
brighter? Why? (i) The electricity in our homes is brought
through the main conducting cable either from
the electric pole or from underground cables.
(ii) Usually, there are three wires in the cable.
(a) Live wire which brings in the current. It
has a red or brown insulation.
(b) Neutral wire through which the current
returns. It is blue or black.

Series Parallel
(c) Earth wire is of yellow or green
colour. This is connected to a metal plate
Ans. buried deep underground near the house
(i) The amount of light given out by bulbs in and is for safety purposes.
parallel combination will be more than that in (iii) In India, the voltage difference between the
series combination. live and neutral wires is about 220 V.
50 Master Key Science & Technology (Term - I) (Std. IX)

(iv) Live and neutral wires are connected to the Variable To change the
electric meter through a fuse. resistance resistance as
(v) They are connected through a main switch, to required and
all the conducting wires inside the home so as thereby control the
to provide electricity to every room. current
(vi) In each separate circuit, various electrical Ammeter To measure the
appliances are connected between the live and current flowing in
neutral wires. the circuit
(vii) The different appliances are connected in Voltmeter To measure the
parallel and the potential difference across potential difference
every appliance is the same. between two points
in the circuit
Q.10. Draw a neat labelled diagram of the
following: (2) Random motion of free electrons in a metal
(1) Symbols for components of an electric circuit wire.
and their uses. Ans.
Ans. Metal wire Electrons
Component Symbol Use
Electric cell To apply a
potential difference
between two ends
of a conductor
Battery To apply a larger
(collection of potential difference (3) Motion of electrons after applying a potential
a number of between two ends difference to the two ends of a metal wire.
cells) of a conductor Ans.
Open top To stop the flow of Direction of flow of electrons
key or plug current in a circuit
key by disconnecting
two ends of a wire.
Direction of conventional electric current
Close top To start the flow of
key or plug current in a circuit Electric cell
key by connecting two
ends of a wire.
Connecting To connect various (4) Electrical circuit for experimental verification
(conducting) components in the of Ohm’s law.
wires circuit Ans.

Crossing To show wires

wires which cross but are
not connected a b c d
Light bulb To test the flow of
electricity; Lighted:
current is flowing; Plug key
Unlighted: current X Y
is not flowing R
Resistance To control the flow Ammeter
Ammeter
of current in the
R circuit Voltmeter a, b c, d - 4 cells
XY - nichrome wire
Current Electricity 51

Q.11. Numerical: NUMERICAL FOR PRACTICE

TYPE A (4) The potential difference between any two
Numericals based on the formulae: points in a circuit is 60 V. If a charge of 24 C is
(1) Q = It (2) W = VQ transferred between these two points, find the
work done in joules.
* (1) A current of 0.4 A flows through a conductor
Ans. 1440 joule
for 5 minutes. How much charge would have
passed through the conductor? (5) If 100 J of work is done in moving a charge of
5 C from one point to another, find the
Ans.
potential difference between the two points.
Given: Current (I) = 0.4 A
Ans. 20 volt
Time (t) = 5 min = 5 × 60 = 300 s
To find: Charge (Q) = ? TYPE B
Formula: Q = I × t Numericals based on the formulae:
Solution: Q = 0.4 × 300 (1) V = IR (2) R = rL/A
Q = 120 C. * (1) If the resistance of the filament of a bulb is
Charge passing through the conductor is 120 C. 1000 . It is drawing a current from a source
of 230 V. How much current is flowing
* (2) If a charge of 420 C flows through a conducting
through it?
wire in 5 minutes. What is the value of the
current? Ans.
Ans. Given : Resistance (R) = 1000 
Given : Electric charge (Q) = 420 C P. D. = (V) = 230 (V)
Time (t) = 5 min = 5 × 60 To find: Current (I) = ?
= 300 sec. V
Formula: = R
I
To find: Electric current (I) = ? V
Q Solution: = R
Formula: I = I
t V
Q I=
R
Solution: I = t
230
420 \ I = 1000
\ I = 300
\ I = 0.23 A
\ I = 1.4 A \ The current flowing through the filament
\ The current in the circuit is 1.4 A. of bulb is 0.23 A.
(3) Find the amount of work done if 3 C of charge * (2) The length of a conducting wire is 50 cm and
is moved through a potential difference of 9 V. its radius is 0.5 mm. If its resistance is 30 ,
Ans. what is the resistivity of its material?
Given : Electric charge (Q) = 3 C Ans.
P. D. = (V) = 9 (V) Given : L = 50 cm = 50 × 10–2m,
To find: Work done (W) = ? r = 0.5 mm = 0.5 × 10–3 m = 5 × 10–4m
W R = 30 
Formula: V =
Q
To find : Resistivity (r) of wire = ?
W
Solution: V = RA
Q Formula : r =
L
\ W = VQ RA
Solution : r = and A = pr2
\ W=9×3 L
\ W = 27 J R × pr2
= L
\ The work done is 27 joule.
52 Master Key Science & Technology (Term - I) (Std. IX)

(ii) V2 = IR2
\ r =
\ V2 = 0.3 × 500
\ V2 = 150 V
\ r =
\ The current is 0.3 A and potential
\ r = 47.1 × 10 m –6 difference to be applied is 150 V.
\ r = 4.71 × 10–5 m * (5) Determine the resistance of a copper wire
The resistivity of the wire is 4.71 × 10–5 m. having a length of 1 km and diameter of
* (3) A current of 0.24 A flows through a conductor 0.5 mm.
when a potential difference of 24 V is applied Ans. Given : Resistivity of copper (r)
between its two ends. What is its resistance? = 1.7 × 10-8 Ω m
Ans. Converting all measures into metres.
Given : Current (I) = 0.24 A Length of wire (L) = 1 km
P. D. (V) = 24 V = 1000 m = 103 m
To find: Resistance (R) = ? Diameter of wire (d) = 0.5 mm
Formula: V = IR = 0.5 x10–3m
Solution: V = IR To find: Resistance of wire (R) = ?

V Formula: R = r L
\ R = A
I If r is the radius of the wire then, its area of
24
\ R = cross-section
0.24
Solution:
\ R = 100 
A = π/4 ×(0.5 ×10–3)2 m2 = 0.2 × 10–6 m2
\ The resistance of conductor is 100 .
* (4) Determine the current that will flow when R=r L
A
a potential difference of 33 V is applied R = 1.7 × 10-8 Ω-m × (103m) / 0.2 × 10–6 m2 = 85 Ω
between two ends of an appliance having
Ans. Resistance of a copper wire is 85 Ω.
a resistance of 100. If the same current
is to flow through an appliance having a * (6) The resistance of a 1 m long nichrome wire
resistance of 500, how much potential is 6 . If we reduce the length of the wire to
difference should be applied across its two 70 cm, what will its resistance be?
ends?
Ans. Case - I Case - II
Ans.
R1 = 6  r = 6A ...(From (i))
Given : P. D. (V1) = 33V
L1 = 1 m L2 = 70 cm = 0.7 m
Resistance (R1) = 110 
r and A are the same in both cases.
Resistance (R2) = 500 

To find: (i) Current (I) = ? R1 = R2 =

(ii) P.D. (V2) for Resistance R2 =? r×1 6A × 0.7

6 = A R2 = A ..(From (i)
Formula: V = IR
r = 6A ..... (i) = 6 × 0.7
Solution:
= 4.2 
(i) V1 = IR1
V1 NUMERICAL FOR PRACTICE
\ I=
R1 (7) Calculate the potential difference across a 7 W
resistor carrying a current of 0.2 A.
33
\ I = 110 = 0.3 A Ans. 1.4 volt
Current Electricity 53

(8) A negligibly small current is passed through V = IRs

a wire of length 15 m and of uniform cross- V
\ I=
section 6.0 × 10–7 m² and its resistance is RS
measured to be 5.0 W. What is the resistivity of 18
the material? \ I = 30
Ans. 2.0 × 10–7 Wm \ I = 0.6 A
(9) A copper wire of length 2m and area of cross- Also, V1 = IR1
section 1.7 × 10–6 m2 has a resistance of 2 × 10–2 \ V1 = 0.6 × 16
ohms. Calculate the resistivity of copper.
\ V1 = 9.6 volt
Ans. 1.7 × 10–8 Wm
V2 = IR2
TYPE C \ V2 = 0.6 × 14
Numericals based on the formula: \ V2 = 8.4 volt
(1) RS= R1+R2+R3 (2)
1
=
1
+
1
+
1 The current in the circuit is 0.6 A and potential
Rp R1 R2 R3 across 16  resistor is 9.6 volt and 14  resistor
is 8.4 volt.
(1) If three resistors 15 Ω, 3 Ω and 4 Ω each are
connected in series, what is the effective * (3) Three resistances 15 , 20  and 10  are
resistance in the circuit? connected in parallel. Find the effective
Ans. resistance of the circuit.
Given: R1 =15 Ω Ans.
R2 = 3 Ω Given: R1 = 15
R3 = 4 Ω R2 = 20 
To find: Effective resistance in series (Rs) = ? R3 = 10 
Formula: Rs = R1 + R2 + R3 To find: Effective resistance in parallel (Rp) = ?
1 1 1 1
Solution: Rs = 15 + 3 + 4 Formula: = + +
Rp R1 R2 R3
\ Rs = 22 Ω
1 1 1 1
The effective resistance in the circuit is 22 Ω. Solution:
Rp
= + +
R1 R2 R3
* (2) Two resistors having resistance of 16 and
1 1 1 1
14 are connected in series. if a potential \ = 15 + 20 + 10
Rp
difference of 18 V is applied across them,
calculate the current flowing through the 1 (4 + 3 + 6 )
\ =
circuit and the potential difference across Rp 60
each individual resistor. 13
1
Ans. \ = 60
Rp
Given: R1 = 16 Ω 60
R2 = 14 Ω \ Rp = 13
V = 18 V \ Rp = 4.615 
To find: Current (I) = ? The effective resistance of the circuit is 4.615 .
Potential across each resistance It is less than the least of the three i.e. 10 Ω.
i.e. V1, V2 = ? * (4) If the resistors 5 Ω, 10 Ω and 30 Ω are
Formula: Rs = R1 + R2 connected in parallel to battery of 12 V, find
the effective resistances of a circuit. Calculate
V
I = the total current and current in each resistor.
R
Solution: Rs = R1 + R2 Ans.
\ Rs = 16 + 14 Given: R1 = 5
\ Rs = 30 Ω R2 = 10 
54 Master Key Science & Technology (Term - I) (Std. IX)

R3 = 30  1 1 1
Also, = +
V = 12 V Rp R1 R2
To find: (i) Total current and current in each 1 (R1 + R2)
resistor i.e. I, I1, I2 and I3? \ =
Rp R1 × R2
(ii) Effective resistance (Rp) = ?
R1 × R2
1 1 1 1 \ Rp =
Formula: (i) = + + (ii) V = IR (R1 + R2)
Rp R1 R2 R3
R1× ( 80 – R1)
V \ 20 =
Solution: (1) I1 = 80
R1
\ 1600 = 80R1 – R12
12
\ I1 = \ R12– 40R1 – 40R1 + 1600 = 0
5
\ I1 = 2.4 A R1 (R1 – 40) – 40 (R1 – 40) = 0
\ (R1 – 40) (R1 – 40) = 0
V
I2 =
R2 \ R1 = 40 OR R1 = 40

12 \ Hence the values of the two resistances

\ I2= R1 and R2 are 40  and 40 .
10
\ I2 = 1.2 A
V NUMERICAL FOR PRACTICE
I3 =
R3
(6) Three resistances of 20 W, 40 W and 60 W are
12
\ I2= connected (i) in series (ii) in parallel.
30
Find their resultant resistance in each case.
\ I3 = 0.4 A
Ans. (i) 120 W, (ii) 10.9 W
I = I1 + I2 + I3
(7) Two resistances each of 20 W are connected
\ I = 2.4 + 1.2 + 0.4
in parallel. The combination is connected
\ I= 4 A in series with a resistance of 20 W. Find the
1 1 1 1 equivalent resistance of the combination.
(ii) = + + Ans. 30 W
Rp R1 R2 R3
1 1 1 1 (8 ) If two resistors are connected in series the
\ = + + total resistance is 9 W and if the same resistors
Rp 5 10 30
are connected in parallel the total resistance
1 6+3+1 becomes 2 W. Find the individual resistors.
\ = 30
Rp
30 Ans. 6 W and 3 W
\ Rp = 10
*Q.12. Activity based questions:
\ Rp = 3. (1) The accompanying figure shows some
(i) The total current is 4 A and current in each electrical appliances connected in a circuit in
resistor is 2.4 A, 1.2 A and 0.4 A respectively. a house. Answer the following questions.
(ii) The effective resistance in parallel is 3.
* (5) If two resistors are connected in series
the total resistance is 80  and if the same
resistors are connected in parallel the total
resistance becomes 20 . Find the individual
resistors.
Ans. Let R1 and R2 be the two resistances.
\ R1 + R2 = 80
\ R2 = (80 – R1) .......... (i)
Current Electricity 55

(i) By which method are the appliances (ii) Does the water stop flowing? Why?
connected? Ans. Yes, the water stops flowing. This happens when
Ans. Appliances are connected in parallel. the level of water becomes equal in both the bottles,
(ii) What must be the potential difference across i.e.; there is no difference in the water levels.
individual appliances. (iii) What will you do to keep the water flowing
Ans. The potential difference across all appliances for a longer duration?
is same in parallel connection. Ans. The difference in the water level has to be
(iii) Will the current passing through each maintained till that time. The difference must
appliance be the same? Justify your answer. never be zero.
Ans. No, as every appliance has a different load (4)
(resistance), current flowing through each
appliance will be different. A B C D
(iv) Why are the domestic appliances connected in
this way?
Ans. The appliances are connected in parallel as the
potential difference remains same.
(v) If the T.V. stops working, will the other Piece of rubber
appliances also stop working? Explain your
answer. Point out the mistakes in the figure above.
Ans. No, the other devices will not stop working Ans. A: Wire is broken at negative terminal. Bulb
as the current flowing through them is along will not glow as circuit is incomplete.
different paths. B: Wire is disconnected at negative terminal.
(2) Think about it. Bulb will not glow as circuit is incomplete.

How will you prove that the unit of resistivity C: Circuit is complete. Therefore bulb will glow.
is W m? D: Rubber is a bad conductor of electricity.
rL Hence it will not allow current to flow and
Ans. R =
A the bulb will not glow.
RA (5)
\ r =
L
A B C
Wm2
\ r =
m
\ r = Wm
(3)
Clamp D E

Why are the bulbs in Figures B, C and D not

lighting up ?
Ans.
Level of water and direction of flow
(i) In B, the blue wire is broken. Hence circuit
Set up the experiment as shown in figure. is incomplete and current does not flow.
Then remove the clamp from the rubber tube.
Therefore bulb will not light up.
(i) What happens when the clamp is removed? (ii) In C, the red wire is broken. Hence circuit
Ans. When the clamp is removed, water flows from is incomplete and current does not flow.
higher level to lower level. Therefore bulb will not light up.
56 Master Key Science & Technology (Term - I) (Std. IX)

(iii) In D, both wires are connected to the same (c) Thus the bulbs which Suresh connected will
terminal. Hence there is no potential difference be brighter.
and current does not flow. Therefore bulb will (2) If the length of a copper wire is doubled and
not light up.
its radius is halved, what is the effect on its
resistivity?
Brain Power Ans. As the resistivity depends only on the material
(1) Ramesh connected number of bulbs with a used for the conductor, the resistivity remains
nichrome wire whereas Suresh connected all the same.
the bulbs with copper wire of same length (3) A fuse is always connected in series. Why?
and thickness. In whose case will the bulbs
Ans.
be brighter?
(a) Fuse protects circuits and electrical appliances
Ans.
by stopping the flow of excess of current.
(a) The resistance offered by copper is less and so
(b) Fuse is connected in series. so that whatever
more current passes through the wire.
current is passing through appliances has to
(b) In nichrome, the resistance is more and less
pass through fuse.
current passes through the wire.

vvv
Current Electricity 57

ASSIGNMENT - 3
Time : 1 hr. Marks : 30

Q.1. (A) Fill in the blanks by choosing the correct alternative from the brackets given below: (2)
(1) To increase the effective resistance in a circuit the resistors are connected in .................. .
(2) If a P.D. of 12 V is applied across a 3  resistor then the current passing through it is .................. .
(B) State whether the following statement is true or false: (2)
(1) The SI unit of resistance is ohm-metre.
(2) Voltmeter is always connected in series with the device.
(B) Match the columns: (2)

Column 'A' Column 'B'

(1) Electric current (a) Coulomb
(2) Electric Charge (b) Volt
(c) Ampere

Q.2. (A) Define / State: (4)

(1) Ohm’s law (2) Potential difference (3) 1 Ohm (4) 1 volt
(B) Answer the following: (6)
(1) Distinguish between Voltmeter and Ammeter.
(2) Wood and glass are good insulators. Why?
(3) Distinguish between : Resistance and Resistivity.
Q.3. Solve / Explain the following: (9)
(1) Umesh has two bulbs having resistance of 15  and 30 . He wants to connect them in
a circuit, but if he connects them one at a time the filament gets burnt. Answer the following.
(A) Which method should he use to connect the bulbs?
(B) What are the characteristics of this way of connecting the bulbs depending on the
answer of A above?
(C) What will be the effective resistance in the above circuit?
(2) The resistance of a conductor of length x is r. If its area of cross-section is a, what is its resistivity?
What is its unit?
(3) Find the total resistance in the circuit.
8

7.2 
12 

– A + + –

Q.4. Answer the following in brief: (5)

(1) Find the expression for the resistance connected in parallel.
vvv
 4 Measurement of Matter
CONCEPT MAP

Atoms
have
have
Size Mass
measured as which determines

Atomic radius in Atomic Mass and measured in

nanometres Molecular Mass Daltons
also expressed in grams
called as
Moles
Also determines the
number of molecules using
Avagadro’s number

which are unstable, such

Atoms combine
according to

Laws of chemical combination

related to mass related to proportion

of atoms
Laws of Conservation of matter Laws of Constant proportion

where compounds are represented by

Chemical Formulae
Written using
Valency of Elements
electrons in the outermost orbit
of atoms determine

MASTER KEY QUESTION SET - 4 (3) According to Law of Conservation of Matter,

in a chemical reaction the total weight of the
Q.1. Fill in the blanks and rewrite the complete is same as the total weight of the
statements: formed due to chemical reactions.
(1) Compounds are formed by chemical (4) The French Scientist inferred from
combination of . his research that ‘There is no rise or drop in
(2) An important principle of Dalton’s atomic the weight of the matter during a chemical
theory is that molecules of a are reaction’.
formed by joining atoms of different elements.
(58)
Measurement of Matter 59

(5) The proportion by weight of hydrogen and (30) Electronic configuration of sodium atom is
oxygen in water is . .
(6) The proportion by weight of carbon and (31) Electronic configuration of chlorine atom is
oxygen in carbon dioxide is . .
(7) A nucleus of an atom is made up of positively (32) Positively charged ions are called as .
charged and electrically neutral (33) Negatively charged ions are called as .
.
(34) The property of elements exhibiting more
(8) The size of at atom is determined by its than one valency is called .
.
(35) Iron (Fe) exhibits the variable valencies .
(9) Atomic radius is expressed in .
(36) Cationic radicals are called as radicals.
(10) 1 m = nm.
(37) Anionic radicals are called as radicals.
(11) The atomic size depends on the number of
(38) The magnitude of charge on any radical is its
in the atom.
.
(12) The mass of an atom is concentrated in its
(39) The force of attraction between a cation and
.
an anion constitutes the .
(13) The total number of protons and neutrons in
(40) Sodium chloride is an compound.
the atomic nucleus is called the .
Ans. (1) elements (2) compound (3) reactants;
(14) Protons and neutrons are together called
products (4) Antoine Lavoisier (5) 1 : 8 (6) 3 : 8
.
(7) protons; neutrons (8) radius (9) nanometres
(15) The relative mass of hydrogen atom is . (10) 109 (11) electron orbits (12) nucleus
(16) A reference atom was required for expressing (13) atomic mass number (14 ) nucleons (15) 1
the of an atom. (16) relative mass (17) Unified mass (18) Dalton
(17) has been accepted as unit of atomic (19) u (20) 1.66053904 × 10–27 (21) atomic
mass. masses (22) Mole (23) Avogadro’s (24) NA
(25) 6.022 × 1023 (26) 6.022 × 1023
(18) Unified mass is called .
(27) molecular mass (28) one mole
(19) Symbol of atomic mass is . (29) valency (30) 2,8,1 (31) 2,8,7 (32) cations
(20) 1 u = kg. (33) anions (34) variable valency (35) 2 and 3
(21) The molecular mass of substance is the sum (36) basic (37) acidic (38) valency (39) ionic bond
of the of all the atoms in single (40) ionic
molecule of that substance. (B) Rewrite the following statements by
(22) A is that quantity of a substance selecting correct options given below:
whose mass in grams is equal in magnitude (1) The unit Dalton is used to express
to the molecular mass of that substance in
(a) atomic mass (b) atomic radius
Daltons.
(c) atomic number (d) mass number
(23) The number of molecules in one mole of only
substance is called number. (2) The valency of element with electronic
configuration is 2.
(24) Avogadro’s number is denoted by the symbol
. (a) (2, 5) (b) (2, 4)
(25) The value of Avogadro’s number is . (c) (2, 6) (d) (2, 7)
(26) A mole of any substance stands for (3) Iron (Fe) exhibits the variable valencies as
molecules. .
(27) The number of molecules in a given quantity (a) 1 and 2 (b) 2 and 3
of substance is determined by its . (c) 1 and 3 (d) 2 and 4
(28) quantities of different substances (4) A mole of any substance stands for
have different masses measured in grams. molecules.
(29) The capacity of an element to combine is (a) 6.022 × 1023 (b) 6.022 × 1022
called its . (c) 60.22 × 1023 (d) 60.22 × 1022
60 Master Key Science & Technology (Term - I) (Std. IX)

(5) The mass of an atom is concentrated in its (6) The proportion by weight of carbon and
. oxygen in carbon dioxide is 3 : 5.
(a) nucleus (b) electrons Ans. False, The proportion by weight of carbon
(c) extra nuclear part (d) protons and oxygen in carbon dioxide is 3 : 8.
(6) The symbol of Avogadro’s number is (7) Relative mass of hydrogen is 1.
(a) ND (b) NO Ans. True
(c) NB (d) NA (8) The number of molecules in a given quantity
of a substance is determined by its atomic
(7) is a bicarbonate radical.
mass.
(a) HCO 2− (b) CO −3
3 Ans. False, The number of molecules in a given
2−
(c) HCO −
3
(d) CO 3
quantity of a substance is determined by its
molecular mass.
(8) Molecular formula of sodium sulphate is
(9) Avogadro’s number is 6.022 × 1023
.
Ans. True
(a) Na(SO4)2 (b) Na2SO4
(10) Valency of sodium is 2.
(c) Na2(SO4)2 (d) NaSO4
Ans. False, Valency of sodium is 1.
(9) is a composite radical.
(a) Fe3+ (b) Ca2+ Q.3. Write the correlated terms:
(c) NH +4 (d) S2– (1) Electron : extra nuclear particle : : Neutron :
.
(10) g of water make 1 mole of water.
(2) Sodium : (2, 8, 1) : : Chlorine : : .
(a) 32 (b) 33
+ –
(3) K : basic radical : : Br : .
(c) 16 (d) 18
+
(4) Cu : simple radical : : NH : . +
Ans. (1) atomic mass (2) (2, 6) (3) 2 and 3 4
(5) Sodium sulphate : Na2SO4 : : Potassium
(4) 6.022 × 1023 (5) nucleus (6) NA (7) HCO −3
Sulphate : .
(8) Na2SO4 (9) NH +4 (10) 18
(6) Mercurous : Hg+ : : Mercuric : .
Q.2. State whether the following statements are (7) Positively charged ion : cation : : Negatively
true or false and if false, write the correct charged ion : .
statement:
(8) 12 : 1 dozen : : 144 : .
(1) Molecular state of oxygen is monoatomic. (9) Hydrogen : : : copper : .
Ans. False, Molecular state of oxygen is diatomic. (10) Law of constant proportions : J. L. Proust : :
(2) The capacity of an element to combine is Law of conservation of mass : .
called its valency. Ans. (1) nucleus (2) (2, 8, 7) (3) acidic radical
Ans. True (4) composite radical (5) K2SO4 (6) Hg2+
(3) Anionic radicals are basic radicals. (7) anion (8) 1 gross (9) c (10) Antoine Lavoisier.
Ans. False, Anionic radicals are acidic radicals. *Q.4. (A) Match the columns:
(4) The magnitude of charge of any radical is its
(1) Column ‘A’ Column ‘B’
atomic number.
Ans. False, Magnitude of charge of any radical is its Example Atomic radius (in metres)
valency. (1) Water molecule (a) 10–10
(5) In a chemical reaction, mass of original matter (2) Haemoglobin (b) 10–9
and mass of matter newly formed as a result molecule
of chemical change are equal. (3) Hydrogen (c) 10–8
Ans. True molecule
Ans. (1 – b), (2 – c), (3 – a)
Measurement of Matter 61

(7) Write molecular formula of two ionic

(2) Column ‘A’ Column ‘B’
compounds containing chlorine.
Element Atomic mass Ans. NaCl, MgCl2
(1) Neon (a) 35.5 (8) Give two monoatomic radicals.
(2) Silicon (b) 32 Ans. Na+, Cl–
(3) Chlorine (c) 28 (9) Give two examples of simple radicals.
(4) Sulphur (d) 20 Ans. Ag+, O2–
(10) Give two composite radicals.
Ans. (1 - d), (2 - c), (3 - a), (4 - b)
4 ,
Ans. SO 2− NH +4
(3) Column ‘A’ Column ‘B’ (10) Give two examples of positive radicals.
Molecule Molecular mass Ans. Na+ - Sodium, K+ - Potassium
(1) H2 (a) 32 g (11) Give two examples of basic radicals.
(2) H2O (b) 34 g Ans. Na+ - Sodium, K+ - Potassium, Ag+ - Silver
(3) O2 (c) 2 g (12) Give two examples of metals with variable
valency.
(4) H2O2 (d) 18 g
Ans.
Ans. (1 - c), (2 - d), (3 - a), (4 - b) (i) Iron (Ferrum)
(a) Fe2+ - Ferrous [Iron - II]
(4) Column ‘A’ Column ‘B’
(b) Fe3+ - Ferric [Iron - III]
Radicals Names (ii) Copper (Cuprum)
(1) Cr2 O72− (a) Carbonate (a) Cu+ - Cuprous [Copper - I]
(2) ClO −3 (b) Chromate (b) Cu2+ - Cupric [Copper - II]
(c) Dichromate (iii) Mercury (Hydragyrum)
(3) CO 2−
3
(d) Chlorate (a) Hg+ - Mercurous [Mercury - I]
(4) CrO 2−
4
(b) Hg2+ - Mercuric [Mercury - II]
Ans. (1 - c), (2 - d), (3 - a), (4 - b)
(13) Give three examples of Bivalent Acidic
Q.5. Name the following. Radicals.
(1) Scientist who gave Law of Conservation of Ans. O2– - Oxide, S2– - Sulphide, CO 2−
3 - Carbonate
Mass. (14) Give three examples of Trivalent Basic
Ans. Antoine Lavoisier radicals.
(2) Scientist who gave Law of Constant Ans. Al3+ - Aluminium, Cr3+ - Chromium, Fe3+ - Ferric.
Proportion. Q.6. State and Define the following:
Ans. J. L. Proust (1) Law of Conservation of Matter.
(3) What are protons and neutrons present in Ans. In a chemical reaction, the total weight of the
nucleus together called as? reactants is same as the total weight of the
Ans. Nucleons products formed due to chemical reactions.
(4) Unit used to express atomic radius. (2) Law of Constant proportion.
Ans. The proportion by weight of the constituents
Ans. Nanometre
elements in the various samples of compound
(5) The number (p + n) in the atomic nucleus is is fixed.
called as.
(3) Molecular Mass:
Ans. Atomic mass number Ans. The molecular mass of the substance is the
(6) Name the unit of atomic mass. sum of the atomic masses of all the atoms in a
Ans. Dalton (u) single molecule of that substance.
62 Master Key Science & Technology (Term - I) (Std. IX)

(4) Mole (3) What is unified mass? Give its value in kg.
Ans. A mole is that quantity of a substance whose Ans. Unified mass is the standard unit of atomic
mass in grams is equal in magnitude to the mass that quantifies mass on an atomic or
molecular mass of that substance in Daltons. molecular scale. Its symbol is ‘u’.
(5) Valency 1 ‘u’ = 1.660539094 × 10–27 kg.
Ans. The capacity of an element to combine is (4) What is molecular mass of a substance?
called its valency. Ans. The molecular mass of a substance is the sum
(6) Electronic definition of Valency of the atomic masses of all the atoms in a
Ans. The number of electrons that an atom of an single molecule of that substance. Like atomic
element gives away or takes up while forming mass, molecular mass is also expressed in the
an ionic bond is called valency of that element. unit Dalton (u).
(7) Radicals (5) What are valence electrons?
Ans. The positively or negatively charged ions that Ans. The electrons present in the outermost orbit of
take part independently in chemical reactions an atom are called valence electrons.
are called radicals. (6) Give the formula to determine the number
Q.7. Answer the following in one or two of moles of a substance.
sentences: Ans. The formula to determine the number of
(1) How is atomic size determined? moles of a substance is as given below.
Ans. The size of an atom is determined by its Number of moles Mass of substance in grams
=
radius. The atomic radius of an isolated atom of a substance (n) Molecular mass of substance
is the distance between the nucleus of an atom (7) What are basic radicals? Give examples.
and its outermost orbit. Ans. The radicals which are formed by removal of
(2) What is atomic mass number? electrons from the atoms of metals are called
Ans. The number of protons and neutrons in the as basic radicals. e.g. Na+, Cu2+
atomic nucleus is called the atomic mass (8) What are acidic radicals? Give examples.
number. Ans. The radicals which are formed by adding
electrons to the atoms of non-metals are called
as acidic radicals. e.g. Cl–, S2–
Q.8. Write symbols of the following elements and the radicals obtained from them and indicate the charge
on the radicals.
Ans.
Elements Symbols Radicals Charge of Radicals

Mercury Hg Hg+ (Mercurous) +1

2+
Hg (Mercuric) +2
+
Potassium K K (Potassium) +1
Nitrogen N N3– (Nitride) –3
+
Copper Cu Cu (Cuprous) +1
2+
Cu (Cupric) +2
2–
Sulphur S S (Sulphide) –2
Carbon C – –
Chlorine Cl Cl– (Chloride) –1
2–
Oxygen O O (Oxide) –2
Measurement of Matter 63

Q.9. Write the steps in deducing the chemical Step - 2 : To write the valency below the
formulae of the following compounds. respective radical.
Ans. In order to write the chemical formulae of Fe PO4
compounds, it is necessary to know the 3 3
symbols and valency of various radicals. 1 1
* (1) Sodium Sulphate: (Dividing valency by common factor)
Step - 1 : To write the symbols of the radicals Step - 3 : To cross - multiply as shown by
(Basic radicals on the left and acidic radicals arrows the number of radicals.
on the right) Fe PO4
Na SO4
1 1
Step - 2 : To write the valency below the
respective radical. Step - 4 : To write down the chemical formula
of the compound.
Na SO4
1 2 FePO4
Step - 3 : To cross - multiply as shown by (Ferric phosphate)
arrows the number of radicals. * (4) Calcium oxide:
Na SO4 Step - 1 : To write the symbols of the radicals
1 2 (Basic radicals on the left and acidic radicals
on the right)
Step - 4 : To write down the chemical formula
of the compound. Ca O
Na2SO4 Step - 2 : To write the valency below the
(Sodium Sulphate) respective radical.
* (2) Potassium Nitrate: Ca O
2 2
Step - 1 : To write the symbols of the radicals
1 1
(Basic radicals on the left and acidic radicals
on the right) (Dividing valency by common factor)
Step - 3 : To cross - multiply as shown by
K NO3
arrows the number of radicals.
Step - 2 : To write the valency below the
respective radical. Ca O

K NO3 1 1
1 1 Step - 4 : To write down the chemical formula
Step - 3 : To cross - multiply as shown by of the compound.
arrows the number of radicals. CaO
K NO3 (Calcium oxide)
1 1 * (5) Aluminium hydroxide:
Step - 4 : To write down the chemical formula Step - 1 : To write the symbols of the radicals
of the compound. (Basic radicals on the left and acidic radicals
KNO3 on the right)
(Potassium Nitrate) Al OH
* (3) Ferric phosphate: Step - 2 : To write the valency below the
Step - 1 : To write the symbols of the radicals respective radical.
(Basic radicals on the left and acidic radicals Al OH
on the right) 3 1
Fe PO4 Step - 3 : To cross - multiply as shown by
arrows the number of radicals.
64 Master Key Science & Technology (Term - I) (Std. IX)

Al OH Step - 4 : To write down the chemical formula

3 1 of the compound.
Step - 4 : To write down the chemical formula CaCO3
of the compound. (Calcium Carbonate)
Al(OH)3 (7) Sodium Dichromate:
(Aluminium hydroxide) Step - 1 : To write the symbols of the radicals
(6) Calcium Carbonate: (Basic radicals on the left and acidic radicals
on the right)
Step - 1 : To write the symbols of the radicals
(Basic radicals on the left and acidic radicals Na Cr2O7
on the right) Step - 2 : To write the valency below the
respective radical.
Ca CO3
Na Cr2O7
Step - 2 : To write the valency below the
respective radical. 1 2
Ca CO3 Step - 3 : To cross multiply as shown by arrows
2 2 ...... Dividing by the number of radicals.
1 1 common factor Na Cr2O7
Step - 3 : To cross - multiply as shown by 1 2
arrows the number of radicals. Step - 4 : To write down the chemical formula
Ca CO3 of the compound.
Na2Cr2O7
1 1
(Sodium Dichromate)
*Q.10. (A) Write the names of the following compounds and deduce their molecular masses.
Na2SO4, K2CO3, CO2, MgCl2, NaOH, AlPO4, NaHCO3
Ans. In order to deduce the molecular masses of given compounds, we require atomic masses of the following
elements in Daltons.
Atomic masses : H(1), O(16), N(14), C(12), K(39), S(32), Ca(40), Na(23), Cl(35.5), Mg(24), Al(27), P(31)
(a) Molecular mass of Na2SO4
Number of Atomic mass Mass of the
Name of Constituent Atomic
Molecule atoms in × number of constituents
compound element mass (u)
molecule atoms u
Na2SO4 Sodium 23 2 23 × 2 46
Sodium Sulphur 32 1 32 × 1 32
Sulphate Oxygen 16 4 16 × 4 64
Molecular mass = Sum of constituent atomic masses Molecular Mass
Molecular mass of (Na2SO4) = (Atomic mass of Na) × 2 + (Atomic mass of Sulphur) × 142
1 + (Atomic mass of Oxygen) × 4
(b) Molecular mass of K2CO3
Number of Atomic mass Mass of the
Name of Constituent Atomic
Molecule atoms in × number of constituents
compound element mass (u)
molecule atoms u
K2CO3 Potassium 39 2 39 × 2 78
Potassium
Carbon 12 1 12 × 1 12
Carbonate
Oxygen 16 3 16 × 3 48
Molecular mass = Sum of constituent atomic masses Molecular Mass
Molecular mass of (K2CO3) = (Atomic mass of K) × 2 + (Atomic mass of C) × 1 + 138
(Atomic mass of Oxygen) × 3
Measurement of Matter 65

(c) Molecular mass of CO2

Number of Atomic mass Mass of the
Name of Constituent Atomic
Molecule atoms in × number of constituents
compound element mass (u)
molecule atoms u
Carbon CO2 Carbon 12 1 12 × 1 12
Dioxide Oxygen 16 2 16 × 2 32
Molecular mass = Sum of constituent atomic masses Molecular Mass
Molecular mass of (CO2) = (Atomic mass of C) × 1 + (Atomic mass of Oxygen) × 2 44
(d) Molecular mass of MgCl2
Number of Atomic mass Mass of the
Name of Constituent Atomic
Molecule atoms in × number of constituents
compound element mass (u)
molecule atoms u
Magnesium MgCl2 Magnesium 24 1 24 × 1 24
Chloride Chlorine 35.5 2 35.5 × 2 71
Molecular mass = Sum of constituent atomic masses Molecular Mass
Molecular mass of (MgCl2) = (Atomic mass of Mg) × 1 + (Atomic mass of Cl) × 2 95
(e) Molecular mass of NaOH
Number of Atomic mass Mass of the
Name of Constituent Atomic
Molecule atoms in × number of constituents
compound element mass (u)
molecule atoms u
NaOH Sodium 23 1 23 × 1 23
Sodium
Oxygen 16 1 16 × 1 16
hydroxide
Hydrogen 1 1 1×1 1
Molecular mass = Sum of constituent atomic masses Molecular Mass
Molecular mass of (NaOH) = (Atomic mass of Na) × 1 + (Atomic mass of O) × 1 40
+ (Atomic mass of H) × 1
(f) Molecular mass of AlPO4
Number of Atomic mass Mass of the
Name of Constituent Atomic
Molecule atoms in × number of constituents
compound element mass (u)
molecule atoms u
AlPO4 Aluminium 27 1 27 × 1 27
Aluminium
Phosphorus 31 1 31 × 1 31
phosphate
Oxygen 16 4 16 × 4 64
Molecular mass = Sum of constituent atomic masses Molecular Mass
Molecular mass of (AlPO4) = (Atomic mass of Al) × 1 + (Atomic mass of P) × 1 122
+ (Atomic mass of O) × 4
(g) Molecular mass of NaHCO3
Number of Atomic mass Mass of the
Name of Constituent Atomic
Molecule atoms in × number of constituents
compound element mass (u)
molecule atoms u
NaHCO3 Sodium 23 1 23 × 1 23
Sodium Hydrogen 1 1 1×1 1
bicarbonate Carbon 12 1 12 × 1 12
Oxygen 16 3 16 × 3 48
Molecular mass = Sum of constituent atomic masses Molecular Mass
Molecular mass of (NaHCO3) = (Atomic mass of Na) × 1 + (Atomic mass of H) × 1 84
+ (Atomic mass of C) × 1 + (Atomic mass of O) × 3
66 Master Key Science & Technology (Term - I) (Std. IX)

(B) Deduce the number of molecules of (iii) 8.8g carbon dioxide

the following compounds in the given Given : Mass of Carbon dioxide (CO2) = 8.8g.
quantities. To find : Number of molecules in 8.8g of
32g of oxygen, 90g of water, 8.8g carbon carbon dioxide.
dioxide, 7.1g chlorine. Solution : Molecular mass of (CO2)
Ans. = (Atomic mass of C) × 1 + (Atomic mass of O) × 2
(i) 32g oxygen ∴ Molecular mass of CO2 = 12 × 1 + 16 × 2
Given : Mass of oxygen = 32g = 12 + 32
To find : Number of molecules in 32g of Molecular mass of CO2 = 44
oxygen. According to the formula,
Solution : Atomic mass of oxygen (O) = 16 Number of moles in the given CO2 (n)
∴ Molecular mass of oxygen (O2) = 16 × 2 = 32 Mass of CO2 in grams
=
According to the formula, Molecular mass of CO2
Number of moles in the given O2 (n) 8.8
= = 0.2
Mass of O2 in grams 44
= ∴ n = 0.2 mol
Molecular mass of O2
∴ 1 mol of CO2 contains 6.022 × 1023 molecules.
= 32
=1 ∴ 0.2 mol of CO2 contains 0.2 × 6.022 × 1023 molecules.
32
∴ n = 1 mol = 1.2044 × 1023 molecules.
∴ 1 mol of O2 contains 6.022 × 1023 molecules that is that is 8.8g of CO2 contains 1.2044 × 1023 molecules
32 g of O2 contains 6.022 × 1023 molecules of O2. of CO2.

32g of oxygen contains 6.022 × 1023 molecules 8.8g of CO2 contains 1.2044 × 1023 molecules
of oxygen. of CO2.

(ii) 90g water (iv) 7.1g chlorine

Given : Mass of water (H2O) = 90g. Given : Mass of Chlorine (Cl2) = 7.1g.
To find : Number of molecules in 90g of To find : Number of molecules in 7.1g of
water. chlorine.
Solution : Molecular mass of (H2O) Solution : Atomic mass of (Cl) = 35.5
= (Atomic mass of H) × 2 + (Atomic mass of O) × 1
∴ Molecular mass of chlorine (Cl2) = 35.5 × 2 = 71
∴ Molecular mass of H2O = 1 × 2 + 16 According to the formula,
∴ Molecular mass of H2O = 18 Number of moles in the given Cl2 (n)
Mass of Cl2 in grams
According to the formula, =
Molecular mass of Cl2
Number of moles in the given H2O (n)
7.1
Mass of H2O in grams =
= 71
Molecular mass of H2O
= 0.1
90
= = 5 ∴ n = 0.1 mol
18 ∴ 1 mol of Cl contains 6.022 × 1023 molecules.
∴ n = 5 mol 2
∴ 0.1 mol of Cl contains 0.1 × 6.022 × 1023 molecules.
∴ 1 mol of H2O contains 6.022 × 1023 molecules. 2
∴ 5 mol of H2O contains 5 × 6.022 × 1023 molecules. = 0.6022 × 1023 molecules.
= 30.11 × 1023 molecules. that is 7.1g of Cl2 contains 0.6022 × 1023 molecules
that is 90g of H2O contains 30.11 × 1023 molecules of Cl2.
of H2O. 7.1g of Cl2 contains 0.6022 × 1023 molecules
90g of water contains 30.11 × 1023 molecules of chlorine.
of water.
Measurement of Matter 67

Q.11. Give scientific reasons: of chloride ion (Cl–) which is negatively

(1) An atom is electrically neutral though it charged as it has gained one electron.
contains charged particles. (5) The valency of Magnesium (Mg) is two.
Ans. Ans.
(i) An atom is made up of a nucleus and an extra- (i) The electronic configuration of Magnesium
nuclear part. Protons and neutrons are present (Mg) is (2, 8, 2), it has 2 electrons in its 3rd
in the nucleus. orbit.
(ii) The nucleus is positively charged. The extra (ii) It tends to give this electrons so that it is left
nuclear part is made up of negatively charged up with (2, 8), having 8 electrons in the second
electrons. orbit, with a stable state.
(iii) Protons are positively charged, electrons are (iii) The loss of two electrons leads to the formation
negatively charged and neutrons are without of Magnesium ion (Mg2+) which is double
any charge. positively charged as it has lost two electrons.
(iv) The magnitude of their charges is same when Q.12. Answer the following questions:
they are equal in number. * (1) Explain how the element sodium is
(v) Hence, the negative charge on all the extra, monovalent.
nuclear electrons together balances the Ans.
positive charge on the nucleus.
(i) The number of protons or electrons (atomic
(vi) Therefore, an atom is electrically neutral number) in Sodium (Na) atom is 11. Therefore
though it contains charged particles. the electronic configuration of sodium atom is
(2) Neon is chemically inert element. (2, 8, 1).
Ans. (ii) In chemical reaction, sodium atom has the
(i) Atomic number of neon is 10, so its electronic capacity to give away 1e– from its outermost
configuration is (2, 8). There are 8 electrons in orbit to form Na+ ion with stable electronic
its 2nd shell, fulfilling its capacity. configuration (2, 8).
(ii) Thus, neon has a complete octet. (iii) As sodium atom gives away 1e– and a cation
of sodium is formed, hence the valency of
(iii) It has a stable orbit therefore, it does not
sodium is 1 and therefore the element sodium
indulge in chemical reactions. Hence, Neon is
is monovalent.
a chemically inert element.
* (2) M is a bivalent metal. Write down the steps to
(3) The valency of sodium (Na) is one.
find the chemical formulae of its compounds
Ans. formed with the radicals, sulphate and
(i) The electronic configuration of sodium (Na) is phosphate.
(2, 8, 1). It has 1 electron in its 3rd orbit. Ans. M is a bivalent metal. Following are the steps to
(ii) It tends to give this electron so that it is left up find the chemical formulae of its compounds
with (2, 8), having 8 electrons in the second formed with the radicals, sulphate and
orbit, with a stable state. phosphate:
(iii) The loss of one electron leads to the formation (i) Compound of metal ‘M’ with radical sulphate
of sodium ion (Na+) which is positively Step - 1: To write the symbols of the radicals
charged as it has lost one electron. (Basic radicals on the left and acidic radicals
(4) The valency of chlorine (Cl) is one. on the right)
Ans. M SO4
(i) The electronic configuration of chlorine (Cl) is
Step - 2: To write the valency below the
(2, 8, 7). It has 7 electrons in its 3rd orbit.
respective radical
(ii) It tends to take one electron from another atom so
M SO4
that it has 8 electrons in the outermost orbit with [Dividing valency
electronic configuration (2, 8, 8) with stable state. 2 2
by common factor]
(iii) The gaining of one electron leads to formation 1 1
68 Master Key Science & Technology (Term - I) (Std. IX)

Step - 3: To cross multiply as shown by arrows (b) Carbon (C) atom : The carbon atom is
the number of radicals selected as reference atom. In this scale,
the relative mass of a carbon atom is
M SO4 accepted as 12.
1 1 (iv) The relative atomic mass of 1 hydrogen
Step - 4: To write down the chemical formula (H) atom compared to the carbon (C) atom
of the compound. 1
becomes 12 × i.e. ‘1’ .
M SO4 12
* (4) What is meant by Unified Atomic Mass?
(ii) Compound of metal ‘M’ with radical
Ans.
phosphate.
(i) During earlier time, relative mass of an atom
Step - 1: To write the symbols of the radicals
was considered for measuring the mass of
(Basic radicals on the left and acidic radicals
an atom directly. But since the founding of
on the right)
unified mass, relative mass is not accepted
M PO4
henceforth.
Step - 2: To write the valency below the (ii) Unified atomic mass is the unit of atomic mass
respective radical called as Dalton.
M PO4 (iii) Its symbol is ‘u’. 1u = 1.66053904 × 10–27 kg.
2 3 * (5) Explain with examples what is meant by a
Step - 3: To cross multiply as shown by arrows ‘mole’ of a substance.
the number of radicals. Ans.
M PO4 (i) A mole is that quantity of a substance whose
mass in grams is equal in magnitude to the
2 3
molecular mass of that substance in Daltons.
Step - 4: To write down the chemical formula (ii) For example: (a) Atomic mass of oxygen atom
of the compound (O) is 16u. Thus the molecular mass of oxygen
M3 (PO4) molecule (O2) is 16 × 2 = 32u. Therefore 32 g of
2
oxygen is 1 mole of oxygen.
* (3) Explain the need for a reference atom for
(6) What is variable valency?
atomic mass. Give some information about
two reference atoms. Ans.
Ans. (i) Under the different conditions the atoms of
some elements give away or take up different
(i) The mass of an atom is concentrated in its
number of electrons.
nucleus and it is due to the protons (p) and
neutrons (n) in it. (ii) In such cases those elements exhibit more than
one valency.
(ii) An atom is very very tiny. It was not possible
to measure atomic mass accurately. Therefore, (iii) This property of elements is called variable
the concept of relative mass of an atom was valency.
formed. *Q.13. If 0.2 mol of the following substances
(iii) To express relative mass of an atom, reference are required how many grams of those
of atom is considered. The two reference substances should be taken?
atoms were as follows: Sodium chloride, Magnesium oxide, Calcium
(a) Hydrogen (H) atom: The hydrogen atom carbonate
is the lightest. The relative mass of a Ans.
hydrogen atom is 1 which has only 1 (i) Sodium Chloride:
proton in its nucleus. On this scale, the
Given: Number of moles of sodium
relative atomic mass of many elements
chloride (NaCl) = 0.2 mol
comes out to be fractional. Therefore,
carbon is selected as a reference atom. To find: Mass in grams of 0.2 mol of NaCl
Measurement of Matter 69

Solution: Solution:
Molecular mass of NaCl Molecular mass of CaCO3
= (Atomic mass of Na) × 1 + (Atomic mass of = (Atomic mass of Ca) × 1 + (Atomic mass of C)
Cl) × 1 × 1 +(Atomic mass of O) × 3
= 23 × 1 + 35.5 × 1 = (40 × 1) + (12 × 1) + (16 × 3) = 40 + 12 + 48
= 23 + 35.5 Molecular mass of CaCO3 = 100
Molecular mass of NaCl = 58.5 According to the formula
According to the formula, Number of moles in the given CaCO3 (n)
Number of moles in the given NaCl (n) Mass of CaCO3 in grams
=
Mass of NaCl in grams Molecular mass of CaCO3
=
Molecular mass of NaCl Mass of CaCO3 in grams
\ 0.2 =
Mass of NaCl in grams 100
\ 0.2 = \ Mass of CaCO3 in grams = 0.2 × 100
58.5
\ Mass of CaCO3 in grams = 20 g
\ Mass of NaCl in grams = 0.2 × 58.5
Mass of 0.2 mole of CaCO3 is 20 g
\ Mass of NaCl in grams = 11.7 g
Mass of 0.2 mole of NaCl is 11.7g Q.14. Answer in brief:
* (1) Two samples ‘m’ and ‘n’ of slaked lime were
(ii) Magnesium Oxide: obtained from two different reactions. The
Given : Number of moles of Magnesium details about their composition are as follows:
oxide (MgO) = 0.2 mol ‘sample m’ mass : 7 g.
To find : Mass in grams of 0.2 mol of MgO Mass of constituent oxygen : 2g
Mass of constituent calcium : 5g
Solution :
‘sample n’ mass : 1.4 g
Molecular mass of MgO Mass of constituent oxygen : 0.4g
= (Atomic mass of Mg) × 1 + (Atomic mass of O) × 1 Mass of constituent calcium : 1.0g
= 24 × 1 + 16 × 1 Which law of chemical combination does
= 24 + 16 this prove? Explain.
Molecular mass of MgO = 40 Ans.
According to the formula (i) The expected proportion by weight of the
Number of moles in the given MgO (n) constituent elements of quick lime that is
calcium oxide would be from its known
Mass of MgO in grams
= Molecular mass of MgO molecular formula CaO. The atomic mass of Ca
and O are 40 and 16 respectively. This means,
Mass of MgO in grams the proportion by weight of the constituent
\ 0.2 =
40 elements Ca and O in the compound CaO is
40 : 16 which is 5 : 2.
\ Mass of MgO in grams = 0.2 × 40
(ii) Now, for the given sample ‘m’ of CaO = 5g
\ Mass of MgO in grams = 8 g.
mass of given sample = 7g
Mass of 0.2 mole of MgO is 8 g
mass of constituent Ca in sample ‘m’ = 5g
(iii) Calcium Carbonate: mass of constituent O in sample ‘m’ = 2g
Given : Number of moles of Calcium (iii) This means that 7g of calcium oxide contains
carbonate (CaCO3) = 0.2 mol 5g of calcium (Ca) and 2g of oxygen (O); and
To find : Mass in grams of 0.2 mol of CaCO3 the proportion by weight of calcium and
oxygen in it is 5 : 2.
70 Master Key Science & Technology (Term - I) (Std. IX)

(iv) Now, for the given sample ‘n’ of CaO mass of * (2) Complete the following chart.
given sample CaO = 1.4 g Ans.
Mass of constituent Ca in sample ‘n’ = 1.0 g
Mass of constituent O in sample ‘n’ = 0.4 g Electronic Valence
Atomic Vale-
Element Configu- Elec-
This means that 1.4g of calcium oxide contains number ncy
ration trons
1.0 g of calcium (Ca) and 0.4g of oxygen (O);
Lithium 3 2, 1 1 1
and the proportion by weight of calcium and
oxygen in it is 5 : 2. Beryllium 4 2, 2 2 2
(v) Above samples ‘m’ and ‘n’ of calcium oxide Boron 5 2, 3 3 3
(CaO) shows that the proportion by weight of Carbon 6 2, 4 4 4
the constituent elements in different samples Nitrogen 7 2, 5 5 3
of a compound is always constant that is the Oxygen 8 2, 6 6 2
proportion by weight of calcium (Ca) and
Fluorine 9 2, 7 7 1
oxygen (O) in different samples of calcium
Neon 10 2, 8 8 0
oxide (CaO) is constant.
Sodium 11 2, 8, 1 1 1
(vi) The experimental value of proportion by
weight of the constituent elements matched Magnesium 12 2, 8, 2 2 2
with the expected proportion calculated by Aluminium 13 2, 8, 3 3 3
molecular mass. This proves and verifies the Silicon 14 2, 8, 4 4 4
law of constant proportion.
* (3) Write down the cations and anions obtained
The law states that ‘The proportion by weight from the compounds in the following chart.
of the constituent elements in the various
samples of a compound is fixed’. Base Cation Anion Acid Cation Anion

Q.15. Complete the following chart: NaOH HCl

* (1) Fill the following tables. KOH HBr

Element Atomic Mass Ca(OH)2 HNO3

Oxygen Ans.

Sodium Base Cation Anion Acid Cation Anion

Aluminium NaOH Na+ OH– HCl H+ Cl–

Phosphorus KOH K+ OH– HBr H+ Br–

Argon Ca(OH)2 Ca2+ OH– HNO3 H+ NO3–

Potassium Q.16. Can you tell?

* (1) How is an element indicated in Chemistry?
Ans. The relative atomic masses of the elements are
Ans. In chemistry an element is indicated by its
given below.
symbol.
Element Atomic Mass * (2) Write down the symbols of the elements you
know.
Oxygen 16
Ans. Symbols of some elements are
Sodium 23
(i) Hydrogen - H (ii) Helium - He
Aluminium 27 (iii) Boron - B (iv) Carbon - C
Phosphorus 31 (v) Aluminium - Al
* (3) Write down the symbols for the following
Argon 39
elements.
Potassium 40 Antimony, Iron, Gold, Silver, Mercury, Lead,
Sodium
Measurement of Matter 71

Ans. The symbols of given elements are as follows: (b) MgCl2

(i) Antimony - Sb (ii) Iron - Fe Molecular mass of MgCl2
(iii) Gold - Au (iv) Silver - Ag = (Atomic mass of Mg) × 1 + (Atomic mass
(v) Mercury - Hg (vi) Lead - Pb of Cl) × 2
(vii) Sodium - Na = (24 × 1) + (35.5 × 2)
* (4) Is it possible to weigh one molecule using a = 24 + 71
weighing balance? = 95
Ans. No, it is not possible to weigh one molecule ∴ Molecular mass of MgCl2= 95
using a weighing balance. (c) KNO3
* (5) Will the number of molecules be the same in Molecular mass of KNO3
equal weights of different substances?
= (Atomic mass of K) × 1 + (Atomic mass of N)
Ans. No, the number of molecules will not be the × 1 (Atomic mass of O) × 3
same in equal weights of different substances.
= (39 × 1) + (14 × 1) + (16 × 3)
* (6) Which are the basic radicals and which are
= 39 + 14 + 48
the acidic radicals among the following?
= 101
Ans.
Basic Radical Acidic Radical ∴ Molecular mass of KNO3 = 101
(i) Ag+ (i) Cl– (d) H2O2
Molecular mass of H2O2
(ii) Cu2+ (ii) I–
= (Atomic mass of H) × 2 + (Atomic mass of
(iii) Fe3+ (iii) SO 2−
4 O) × 2
(iv) Ca2+ (iv) NO −3 = (1 × 2) + (16 × 2)
= 2 + 32
(v) NH4+ (v) S2–
= 34
(vi) K+ (vi) MnO −4 ∴ Molecular mass of H2O2 = 34.
+
(vii) Na (e) AlCl3
Molecular mass of AlCl3
Q.17. Use your brain power!
= (Atomic mass of Al) × 1 + (Atomic mass of
* (1) Following are atomic masses of a few
Cl) × 3
elements in Daltons and the molecular
formulae of some compounds. Deduce the = (27 × 1) + (35.5 × 3)
molecular masses of those compounds. = 27 + 106.5
Atomic masses - H(1), O(16), N(14), C(12), = 133.5
K(39), S(32) Ca(40), Na(23), Cl(35.5), Mg(24), ∴ Molecular mass of AlCl3 = 133.5
Al(27)
(f) Ca(OH)2
Molecular formulae - NaCl, MgCl2, KNO3,
Molecular mass of Ca(OH)2
H2O2, AlCl3, Ca(OH)2, MgO, H2SO4, HNO3,
NaOH = (Atomic mass of Ca) × 1 + (Atomic mass of
O + Atomic Mass of H) × 2
Ans.
= (40 × 1) + (16 + 1) × 2
(a) NaCl
= 40 + (17 × 2)
Molecular mass of NaCl
= 40 + 34 = 74
= (Atomic mass of Na) × 1 + (Atomic mass
of Cl) × 1
∴ Molecular mass of Ca(OH)2 = 74
= (23 × 1) + (35.5 × 1) (g) MgO
= 23 + 35.5 Molecular mass of MgO
= 58.5 = (Atomic mass of Mg) × 1 + (Atomic mass of
∴ Molecular mass of NaCl = 58.5 O) × 1
72 Master Key Science & Technology (Term - I) (Std. IX)

= (24 × 1) + (16 × 1) ∴ 1 mol of H2O contains 6.022 × 1023 molecules.

= 24 + 16 ∴ 2 mol of H2O contains 2 × 6.022 × 1023 molecules.
= 40 = 12.044 × 1023 molecules.
∴ Molecular mass of MgO = 40 that is 36g of H2O contains 12.044 × 1023 molecules
(h) H2SO4 of H2O.
Molecular mass of H2SO4 36g of water contains 12.044 × 1023 molecules
= (Atomic mass of H) × 2 + (Atomic mass of water.
of S) × 1 + (Atomic mass of O) × 4 * (3) How many molecules of H2SO4 are there in a
= (1 × 2) + (32 × 1) + (16 × 4) 49g sample?
= 2 + 32 + 64 Ans. Given : Mass of Sulphuric acid (H2SO4) = 49g
= 98 To find : Number of molecules in 49g of H2SO4
∴ Molecular mass of H2SO4 = 98 Solution :
(i) HNO3 Molecular mass of H2SO4 = (Atomic mass of H)
Molecular mass of HNO3 × 2 + (Atomic mass of S) × 1 + (Atomic
mass of O) × 4
= (Atomic mass of H) × 1 + (Atomic mass
of N) × 1 + (Atomic mass of O) × 3 Molecular mass of H2SO4 = (1× 2) + (32×1) + (16×4)
= (1 × 1) + (14 × 1) + (16 × 3) = 2 + 32 + 64
= 1 + 14 + 48 = 98.
= 63 According to the formula,
∴ Molecular mass of HNO3 = 63 Number of moles in the given H2SO4 (n)
(j) NaOH Mass of H2SO4 in grams
=
Molecular mass of NaOH Molecular mass of H2SO4
= (Atomic mass of Na) × 1 + (Atomic mass 49 1
= = = 0.5
of O) × 1 + (Atomic mass of H) × 1 98 2
= (23 × 1) + (16 × 1) + (1 × 1) ∴ n = 0.5 mol
= 23 + 16 + 1 ∴ 1 mol of H2SO4 contains 6.022 × 1023 molecules.
= 40 ∴ 0.5 mol of H2SO4 contains 0.5 × 6.022 × 1023 molecules.
∴ Molecular mass of NaOH = 40 = 3.011 × 1023 molecules.
* (2) How many molecules of water are there in that is 49g of H2SO4 contains 3.011 × 1023
36g water? molecules of H2SO4.
Ans. Given : Mass of water (H2O) = 36g 49g of Sulphuric acid contains 3.011 × 1023
To find : Number of molecules in 36g of water molecules of H2SO4.
Solution : * (4) How will the compounds, MgCl2 and CaO
Molecular mass of (H2O) = (Atomic mass of H) be formed from their elements?
× 2 + (Atomic mass of O) × 1 Ans.
Molecular mass of H2O = (1 × 2) + 16 (1) Magnesium Chloride (MgCl2)
∴ Molecular mass of H2O = 18 Magnesium atom (Mg). Electron configuration
–
According to the formula, (2,8,2) –2e Magnesium ion Mg2+ (2,8).
Number of moles in the given H2O (n) Chlorine atom (Cl). Electron configuration
–
Mass of O2 in grams (2,8,7) +1e Chloride ion Cl– (2,8,8).
= ∴ Mg2+ + 2Cl– MgCl2 (Magnesium Chloride)
Molecular mass of O2
(i) A Magnesium atom gives away 2e– and a
36
= =2 cation of Magnesium (Mg2+) is formed, hence,
18 the valency of magnesium is two.
∴ n = 2 mol
Measurement of Matter 73

(ii) Two chlorine atoms takes 1e– each and forms (i) Calcium Carbonate
two anions of chlorine (2Cl–) (chloride), and Ans. Symbol Ca CO3
thus, the valency of chlorine is one.
(iii) After the give and take of electrons is over, the Valency 2 2 Dividing by
electronic configuration of all the resulting 1 1 common factor
ions has a complete octet, CaCO3
(iv) Due to the attraction between the unit but ∴ Chemical formula of Calcium carbonate is CaCO3
opposite charges on all the ions, one chemical (ii) Sodium bicarbonate
bond is formed between Mg2+ and 2Cl– each
Ans. Symbol Na HCO3
and the compound MgCl2 is formed.
(2) Calcium Oxide (CaO)
Calcium atom (Ca). Electron configuration Valency 1 1
–
(2,8,8,2) –2e Calcium ion Ca2+ (2,8,8). NaHCO3
∴ Chemical formula of Sodium bicarbonate is
Oxygen atom (O). Electron configuration (2,6)
+2e – NaHCO3
Oxygen ion O2– (2,8).
(iii) Silver chloride
∴ Ca2+ + O2– CaO
Ans. Symbol Ag Cl
(i) A calcium atom gives away 2e– and a cation of
calcium (Ca2+) is formed, hence, the valency of
calcium is two. Valency 1 1
(ii) An oxygen atom takes 2e and forms anions of
–
AgCl
oxygen (O2–) (oxide), and thus, the valency of ∴ Chemical formula of Silver chloride is AgCl
oxygen is two.
(iv) Calcium hydroxide
(iii) After the give and take of electrons is over, the
electronic configuration of both the resulting Ans. Symbol Ca OH
ions has a complete octet.
(iv) Due to the attraction between the unit but Valency 2 1
opposite charges on the two ions, one chemical Ca(OH)2
bond is formed between Ca2+ and O2– and the
∴ Chemical formula of Calcium hydroxide is Ca(OH)2
compound CaO is formed. (v) Magnesium Oxide
(5) Classify the following radicals in to simple Ans. Symbol Mg O

radicals and composite radicals.
Ag+, Mg2+, Cl–, SO 2− 2+
4 , Fe ,
ClO −3 , NH +4 , Br–, Valency 2 2 Dividing by
NO −3 , Na+, Cu+ 1 1 Common factor
Ans. MgO
∴ Chemical formula of Magnesium oxide is MgO
Simple radicals Composite radicals
(vi) Ammonium Phosphate
Ag +
SO 2−
4
Ans. Symbol NH4 PO4
Mg2+ ClO −3
Cl– Valency
NH +4 1
3
Fe2+ (NH4)3PO4
NO −3
Br– ∴ Chemical formula of Ammonium phosphate
+ is (NH4)3PO4
Na
Cu+ (vii) Cuprous bromide
(6) Using the chart of ions / radicals and the cross- Ans. Symbol Cu Br
multiplication method, write the chemical
formulae of the following compounds: Valency 1 1
CuBr
∴ Chemical formula of Cuprous bromide is CuBr.
74 Master Key Science & Technology (Term - I) (Std. IX)

(viii) Copper Sulphate well known experiment called as ‘Gold foil

Ans. Symbol Cu SO4 experiment’. From this experiment it was
discovered that atoms have internal structure.
(5) What are the two parts of an atom? What are
Valency 2 2 Dividing by they made up of?
1 1 common factor
Ans. The two parts of atoms are nucleus and extra
CuSO4
nuclear part. Nucleus is made up of positively
∴ Chemical formula of Copper sulphate is CuSO4. charged protons and electrically neutral
(ix) Potassium Nitrate neutrons and the extra nuclear part is made
Ans. Symbol K NO3 up of negatively charged electrons revolving
around the nucleus in different orbits.
Valency 1 1 (6) Determine the valencies of H, Cl, O and Na
KNO3 from the molecular formulae H2, HCl, H2O
∴ Chemical formula of Potassium nitrate is KNO3. and NaCl.

(x) Sodium dichromate Ans.

Ans. Symbol (i) In the molecular formula HCl

Na Cr2O7
Symbol H Cl
Valency 1 2
Na2Cr2O7 Valency 1 1
∴ Chemical formula of Sodium dichromate is ∴ The valency of H is 1 and Cl is 1.
Na2Cr2O7.
(ii) In the molecular formula H2O
*Q.18. Can you recall? Symbol H O
(1) What is the Dalton’s atomic theory?
Ans. Dalton’s Atomic theory-
Valency 1 2
(i) All matter is made of atoms. Atoms are ∴ The valency of H is 1 and O is 2.
indivisible and indestructible.
(iii) In the molecular formula NaCl
(ii) All atoms of a given element are identical in
Symbol Na Cl
mass and properties.
(iii) Compounds are formed by a combination of
two or more different kinds of atoms. Valency 1 1
(iv) A chemical reaction is a rearrangement of ∴ The valency of Na is 1 and Cl is 1.
atoms. ∴ From all the above, the valencies of the given
(2) How are compounds formed? elements are as follows : H = 1, Cl = 1, O = 2
Ans. Compounds are formed by a combination of and Na = 1.
two or more different kind of atoms. (7) What is the type of chemical bond in NaCl
(3) What are the molecular formulae of salt, and MgCl2?
slaked lime, water, lime, limestone? Ans.
Ans. The molecular formulae for (i) The type of chemical bond in NaCl and MgCl2
Salt - Sodium Chloride - NaCl is ionic bond.
Slaked lime - Calcium Hydroxide Ca(OH)2 Q.18 Activity based questions:
Water - H2O *ACTIVITY - 1
Lime - Calcium Oxide - CaO • Take 56 g calcium oxide in a large conical flask
Lime stone - Calcium Carbonate - CaCO3 and put 18 g water in it.
(4) From which experiments was it discovered • Observe what happens.
that atoms have an internal structure? When? • Measure the mass of the substance formed.
Ans. In 1911 Earnest Rutherford conducted a
Measurement of Matter 75

• What similarity do you find? Write your flask and a solution of sodium sulphate in a
inference. test tube.
Ans. • Tie a thread to the test tube and insert it in the
(i) When 18 g of water is added to 56 g of calcium conical flask.
oxide, calcium oxide combines with water to • Seal the conical flask with an airtight rubber cork.
form calcium hydroxide Ca(OH)2 • Weigh the conical flask using a balance.
(ii) The mass of calcium hydroxide formed is 74 g • Now tilt the conical flask so that the solution
(iii) In this activity the total mass of reactants, in the test tube gets poured in the conical flask.
Calcium Oxide + Water = 56 g + 18 g = 74 g. • Now weigh the conical flask again.
It is equal to the mass of the product formed. Ans.
Ca(OH)2 = 74g (i) In this activity a white precipitate is seen in
This activity verifies the Law of Conservation of the conical flask after the reaction.
Matter. i.e. In a chemical reaction the total weight (ii) There is no change in the weight of the flask
of the reactants is same as the total weight of the before and after the reaction.
products formed due to the chemical reactions. (iii) This activity verifies the Law of Conservation of
*ACTIVITY - 2 Matter i.e. In a chemical reaction the total weight
of the reactants is same as the total weight of the
• Take a solution of calcium chloride in a conical
products formed due to the chemical reactions.

Ions/Radicals
Basic Radicals Acidic Radicals
+ 3+ –
H Hydrogen Al Aluminium H Hydride MnO −4 Permanganate
Na+ Sodium Cr3+ Chromium F– Fluoride ClO −3 Chlorate
K +
Potassium Fe 3+
Ferric Cl –
Chloride BrO −3 Bromate
+ 3+ – −
Ag Silver Au Gold Br Bromide IO 3 Iodate
2−
Cu+ Cuprous Sn4+ Stannic I– Iodide CO 3 Carbonate
2−
Hg +
Mercurous NH +
4 Ammonium O 2–
Oxide SO 4 Sulphate
2+ 2– 2−
Cu Cupric/Copper S Sulphide SO 3 Sulphite
2+ 3– 2−
Mg Magnesium N Nitride CrO 4 Chromate
2+ −2
Ca Calcium Cr2 O 7
Dichromate
Ni2+ Nickel OH– Hydroxide PO 3−
4
Phosphate
2+
Co Cobalt NO −
3
Nitrate
−
Hg 2+
Mercuric NO 2 Nitrite
2+ −
Mn Manganese HCO 3 Bicarbonate
Fe2+ Ferrous (Iron II) HSO −
4
Bisulphate
Sn2+ Stannous HSO −3 Bisulphite
2+
Pt Platinum
76 Master Key Science & Technology (Term - I) (Std. IX)

ASSIGNMENT - 4
Time : 1 Hr. Marks : 30

Q.1. (A) Fill in the blanks: (2)

(1) Protons and neutrons are together called as ................. .
(2) The proportion by weight of hydrogen and oxygen in water is ................. .
(B) State True or False, and if false write the correct statement: (2)
(1) Molecular state of oxygen is diatomic.
(2) Anion radicals are basic radicals.
(C) Match the columns: (2)

Column ‘A’ Column ‘B’

Radicals Names

(1) Cr2 O72− (a) Carbonate

(2) ClO −3 (b) Chromate

(3) CO 2− (c) Dichromate

3

(4) CrO 2− (d) Chlorate

4

Q.2. (A) Calculate the molecular mass of following compounds: (8)

(1) Sulphuric acid (H2SO4) (2) Calcium hydroxide (Ca(OH)2)
(3) Magnesium chloride (MgCl2) (4) Potassium Nitrate (KNO3)
Atomic masses : H(1), S(32), O(16), Ca(40), Mg(24), Cl(35.5), K(39), N(14)
(B) Using the chart of ions / radicals and cross multiplication write the chemical formula of (6)
the following compounds.
(1) Calcium Carbonate (2) Sodium dicromate (3) Magnesium oxide
(4) Ammonium phosphate (5) Ferric chloride (6) Calcium hydroxide
(Ions / Radicals : Mg2+, Ca2+, NH +4 , Na+, O2– , PO 3−
4
, CO 2−
3
, Cr O −2 , OH–, Cl–, Fe3+)
2 7

Q.3. Answer in brief: (10)

(1) Give reason : The valency of sodium (Na) is one.
(2) Solve : Deduce the number of molecules in 8.8g of carbon dioxide. (Atomic Masses : C(12), O(16))
(3) Solve : Find the mass in grams of 0.4 mol of magnesium oxide.
(Atomic Masses : Mg(24), O(16))
(4) M is bivalent metal. Write down the steps to find the chemical formulae of its compounds formed
with the radicals sulphate and phosphate.
(5) State the following laws:
(i) Law of conservation of matter. (ii) Law of constant proportion
vvv
 5 Acids, Bases and Salts
CONCEPT MAP

SUBSTANCES

Can be Can be

ACIDS NEUTRAL SUBSTANCES BASES

strength strength
de

g
in
te

represented by represented by

us
ct
ed

d
pH range pH < 7 pH = 7 pH range pH > 7

e
ct
us

te
in

de
g

Natural Synthetic
Red litmus INDICATORS Phenolphthalein
Cabbage, Beetroot Methyl orange

React with React with

Oxides of Carbonates and with each oxides of

Metals
Metals Bicarbonates other non-metal

to form
Salts

Salts with water of

Carbonates Bicarbonates
crystallization

(6) Substances which are sour to taste are termed

MASTER KEY QUESTION SET - 5 as .
Q.1. Fill in the blanks and rewrite the complete (7) Bases are to touch.
statements: (8) If the basic radical is H+ the type of compound
(1) acid is present in lemon. is .
(2) Tamarind contains acid. (9) Anions are charged particles.
(3) Baking soda is in nature. (10) The name of compound NH3 is .
(4) Butter milk contains acid. (11) The bases which are soluble in water are called
(5) Milk of Magnesia is in nature. as .

(77)
78 Master Key Science & Technology (Term - I) (Std. IX)

(12) HCl is a acid. (a) neutralisation (b) crystallisation

(13) H3PO4 is a acid. (c) electrolysis (d) dissociation
(14) When the concentration of solute is low in the (7) Molecular formula of Red oxide is .
solution, it is called as solution. (a) Fe2O3 (b) CuO
(15) [NaCl] = 1M means the of common (c) Fe3O4 (d) Na2O
salt is 1M
(8) The positive terminal electrode is called as
(16) Accoring to pH scale pure water has a pH of .
.
(a) anode (b) cathode
(17) With reference to neutralization, metallic
(c) anion (d) cation
oxides are in nature.
(9) produced in stomach helps in
(18) CO2 gas turns milky.
digestion.
(19) Molecular formula of blue vitriol is .
(a) Hydrochloric acid (b) Oxalic acid
(20) Crystalline ferrous sulphate is in
(c) Sulphuric acid (d) Nitric acid
colour.
(10) Adding water to acid is an reaction.
(21) molecular formula of crystalline alum is
. (a) endothermic reaction

Ans. (1) Citric (2) tartaric (3) basic (4) butyric (b) exothermic reaction
(5) basic (6) acids (7) soapy (8) acid (9) negatively (c) neutralisation (d) crystallisation
(10) ammonia (11) alkalis (12) monobasic Ans. (1) 4 (2) Na+ and Cl–
(13) tribasic (14) diluted (15) molarity (16) 7 (3) Na2O (4) dibasic
(17) basic (18) lime water (19) CuSO4.5H2O
(5) 0 (6) neutralization
(20) green (21) K2SO4.Al2 (SO4)3.24H2O
(7) Fe2O3 (8) anode
Q.2. Rewrite the statements by selecting correct (9) Hydrochloric acid (10) exothermic
options:
(1) The solution turns blue litmus red, its pH is Q.3. State whether the following statements are
likely to be . true or false and if false, write the correct
statement:
(a) 7 (b) 4
(1) The separation of H+ and Cl– in HCl is in
(c) 14 (d) 9
absence of water.
(2) An ionic compound NaCl is formed by
Ans. False, The separation of H+ and Cl– in HCl is
.
in presence of water.
(a) Na+ and Cl– (b) Na+ and Cl+
Water
(c) Na– and Cl– (d) Na– and Cl+ (2) NaOH(s) Na+ (aq) + OH– (aq)
dissociation
(3) Molecular formula for sodium oxide is Ans. True
. (3) H2SO4 is a strong acid.
(a) Na2O (b) NaO2 Ans. True
(c) NaO (d) Na2O2 (4) NaCl is an ionic compound..
(4) H2CO3 is acid. Ans. True
(a) monobasic (b) dibasic (5) Turmeric is synthetic indicator.
(c) tribasic (d) tetrabasic Ans. False, Turmeric is a natural indicator.
(5) pH of strong acid is . (6) Metal + Dilute acid forms salt and water.
(a) 0 (b) 7 Ans. False, Metal + Dilute acid forms salt and
(c) 8 (d) 14 hydrogen gas.
(6) HCl + NaOH NaCl + H2O is a (7) Copper oxide is called red primer.
reaction. Ans. False, Iron oxide is called red primer.
Acids, Bases and Salts 79

(8) Oxide of non-metal + Acid Salt + Water. Ans. Sodium carbonate is the odd one out, as it is
Ans. False, Oxide of non-metal + Base Salt + made up of a weak acid and strong base, and
Water. rest all are formed from strong acid and strong
(9) Zinc oxide reacts with sodium hydroxide to base.
form sodium zincate. * (f) Calcium oxide, magnesium oxide, zinc oxide,
Ans. True sodium oxide.
(10) Al2O3 is an amphoteric oxide. Ans. Zinc oxide is the odd one out, as it is amphoteric
Ans. True oxide, and rest all are basic oxides.
(11) Blue vitriol is ZnSO4 7H2O. * (g) Crystalline blue vitriol, crystalline common
salt, crystalline ferrous sulphate, crystalline
Ans. False, Blue Vitriol is CuSO4 5H2O.
sodium carbonate.
(12) Molecular formula for crystalline Ferrous
Ans. Crystalline common salt is the odd one out, as
sulphate is FeSO4 5H2O.
it does not contain water of crystallisation. It
Ans. False, Molecular formula for crystalline
is an ionic compound and ionic compounds
Ferrous sulphate is FeSO4 7H2O.
are crystalline in nature and rest all have their
(13) NaCl in water does not conduct electricity. crystalline structure because of their water of
Ans. False, NaCl in water conducts electricity. crystallization.
(14) Phenolphthalein is colourless in base. * (h) Sodium chloride, potassium chloride, acetic
Ans. False, Phenolphthalein is colourless in acid acid, sodium acetate.
and pink in base. Ans. Acetic acid is the odd one out.
Q.4. Find the odd one out and justify: It is an acid, the rest are all salts.
* (a) Chloride, nitrate, hydride, ammonium (i) Rose Petal, Turmeric, phenolphthalein, indigo.
Ans. Ammonium is the odd one out as it is a Ans. Phenolphthalein is odd one out as rest are
basic radical and rest all are acidic radicals. natural indicators while phenophthalein is a
Generally, basic radicals are formed by removal synthetic indicator.
of electrons from the atom of metals such as (j) Lime water, Vinegar, Acetic acid, Tartaric acid.
Na+, Cu2+. But there are some exceptions, such
Ans. Lime water is odd one out as this is basic in
as NH4+.
nature while rest are acidic.
* (b) Hydrogen chloride, sodium hydroxide,
(k) NaHCO3, HCl, H2SO4, HNO3
calcium oxide, ammonia
Ans. Hydrogen chloride is the odd one out. It is Ans. NaHCO3 is odd one out as it is a basic while
acidic and the rest are all basics. rest are acids.
* (c) Acetic acid, carbonic acid, hydrochloric acid, (l) Oxalic acid, Nitric acid, Citric acid, acetic acid.
nitric acid Ans. Nitric acid is odd one out as others are weak
Ans. Carbonic acid is the odd one out. It is a dibasic acids while Nitric acid is a strong acid.
acid and rest are all monobasic acids. (m) Crystalline, Liquid, Gases, Solid
* (d) Ammonium chloride, sodium chloride, Ans. Crystalline is odd one out as this is nature of a
potassium nitrate, sodium sulphate compound while others are physical states of
Ans. Ammonium chloride is the odd one out, as it compounds
is made up of a strong acid and weak base and (n) Ca (OH)2, Mg (OH)2, NaOH, NH4OH.
rest all are formed from strong acid and strong Ans. NaOH is odd one out as all are bases but
base.
NaOH is highly soluble in water compared to
* (e) Sodium nitrate, sodium carbonate, sodium others.
sulphate, sodium chloride.
80 Master Key Science & Technology (Term - I) (Std. IX)

Q.5. Match the columns: Q.6. Answer the following in one or two sentences:
(A) (1) Name the three types of ionic compounds.
Column ‘A’ Column ‘B’ Ans. The three types of ionic compounds are acids,
bases and salts.
(1) HNO3 (a) Acetic acid
(2) Name the two constituents of molecule of an
(2) H3PO4 (b) Carbonic acid
ionic compound.
(3) CH3COOH (c) Phosphoric acid
Ans. The molecule of an ionic compound has two
(4) H2CO3 (d) Nitric acid constituents, namely, cations (positive ion/
Ans. (1 - d), (2 - c), (3 - a), (4 - b) basic radical) and anion (negative ion/acidic
radical).
(B)
(3) Name any three acids with their molecular
Column ‘A’ Column ‘B’ formulae.
(1) NH4OH (a) Aluminium Hydroxide Ans. (i) Hydrochloric acid - HCl
(2) Ca (OH)2 (b) Barium Hydroxide (ii) Sulphuric acid - H2SO4
(3) Al (OH)3 (c) Calcium Hydroxide (iii) Nitric acid - HNO3
(4) Ba (OH)2 (d) Ammonium Hydroxide (4) Name any three bases with their molecular
Ans. (1 - d), (2 - c), (3 - a), (4 - b) formulae.
(C) Ans. (i) Sodium hydroxide - NaOH
(ii) Potassium hydroxide - KOH
Column ‘A’ Column ‘B’
Solution pH (iii) Calcium hydroxide - Ca (OH)2
(5) Name any three salts with their molecular
(1) Milk (a) 1 formulae.
(2) Milk of Magnesia (b) 14 Ans. (i) Sodium chloride - NaCl
(3) 1 M HCl (c) 10.5 (ii) Potassium sulphate - K2 SO4
(4) 1 M NaOH (d) 6.5 (iii) Calcium chloride - CaCl2
Ans. (1 - d), (2 - c), (3 - a), (4 - b) (6) Name any two strong acids.
(D) Ans. (i) Hydrochloric acid - HCl
Column ‘A’ Column ‘B’ (ii) Sulphuric acid - H2 SO4
(1) Urine (a) Butyric acid (7) Name any two weak acids.
(2) Apples (b) Uric Acd Ans. (i) Acetic acid - CH3 COOH
(3) Orange (c) Malic acid (ii) Carbonic acid - H2 CO3
(4) Butter (d) Citric acid (8) Name any two strong bases.
Ans. (i) Sodium hydroxide - NaOH
Ans. (1 - b), (2 - c), (3 - d), (4 - a)
(ii) Potassium hydroxide - KOH
(E)
(9) Name a weak base.
Column ‘A’ Column ‘B’
Ans. Ammonium hydroxide - NH4OH
(1) Crystalline blue (a) FeSO4.7H2O (10) Name any two alkalis.
vitriol (b) K SO .Al (SO ) .24H O Ans. (i) Sodium hydroxide - NaOH
2 4 2 4 3 2
(2) Crystalline green (c) CuSO4.5H2O (ii) Potassium hydroxide - KOH
vitriol
(d) Na2CO3.10H2O (11) Name any two acids with their basicity 1
(3) Crystalline (monobasic)
washing soda
Ans. (i) Hydrochloric acid - HCl
(4) Crystalline alum
(ii) Nitric acid - HNO3
Ans. (1 - c), (2 - a), (3 - d), (4 - b)
Acids, Bases and Salts 81

(12) Name any two acids with their basicity 2 *Q.7. State the difference:
(dibasic) (1) Acids and bases
Ans. (i) Sulphuric acid - H2 SO4 Ans.
(ii) Carbonic acid - H2 CO3 Acids Bases
(13) Name any two acids with their basicity 3 (i) A substance which A substance which
(tribasic) liberates H+ ions liberates OH– ions in
Ans. (i) Boric acid - H3BO3 when dissolved in water is called a base.
(ii) Phosphoric acid - H3PO4 water is an acid
(14) Name any two bases with their acidity 1 (ii) Blue litmus turns red Red litmus turns blue
(monoacidic) in an acid. in a base
Ans. (i) Sodium hydroxide - NaOH (iii) The pH of an acid is The pH of a base is
(ii) Potassium hydroxide - KOH less than 7. greater than 7.
(15) Name any two bases with their acidity 2 (iv) Acids are sour to taste Bases are bitter to
(diacidic) e.g. HCl, H2SO4 taste.
Ans. (i) Calcium hydroxide - Ca (OH)2 e.g. NaOH, KOH.
(ii) Barium hydroxide - Ba (OH)2 (2) Cations and anions
(16) Name any two bases with their acidity 3 Ans.
(triacidic)
Cations Anions
Ans. (i) Aluminium hydroxide - Al (OH)3
(i) Cations are ions with Anions are ions with
(ii) Ferric hydroxide - Fe (OH)3
a net positive charge . a net negative charge.
(17) Name the two units to express the
concentration of the solution. (ii) Cations are generally Anions are generally
formed by metals. formed by non-metals.
Ans. (i) The first unit is the mass of solute in When metals donate When non-metals
gram dissolved in one litre of the solution electrons, they have accept electrons,
(grams per litre, g/L) excess of protons, they have excess of
(ii) The second unit is number of moles of hence they form electrons, hence they
the solute dissolved in one litre of the cations. form anions.
solution. This is called the molarity (M) of (iii) Cations are attracted Anions are attracted
the solution. towards the cathode towards the anode
(18) What is the molarity of a solution? How is it which are negatively which are positively
written? charged electrodes. charged electrodes.
Ans. The number of moles of the solute dissolved (iv) e.g.: Na+, Ca2+, Mg2+, e.g.: O2–, S2–, Cl–, Br–
in one litre of the solution is called the K+ etc. etc.
molarity of that solution. The molarity of a
(3) Negative electrode and positive electrode
solute is indicated by writing its molecular
formula inside a square bracket. For Ans.
example, [NaCl] = 1 means the molarity of Negative Electrode Positive Electrode
the solution of common salt is 1 M (1 molar) (i) Negative electrodes Positive electrodes
(19) What are acid-base indicators? are called as cathode. are called as Anode.
Ans. Some natural and synthetic dyes show two (ii) Positively charged Negatively charged
different colours in acidic and base solution, cations move towards anions move towards
and such dyes are acid-base indicators. the cathode or the anode or positive
negative electrode. electrode.
82 Master Key Science & Technology (Term - I) (Std. IX)

Q.8. Define the following: aqueous solution contains a small proportion

(1) Acid of OH– ions and the concerned basic radicals
Ans. An acid is a substance which on dissolving in along with a large proportion of undissociated
water gives rise to H+ ion as the only cation. molecules of the base. e.g. NH4 OH.
For example, HCl, H2 SO4, H2CO3 (7) Alkali
Ans. The bases which are highly soluble in water
Water
HCl (g) H + –
+ Cl are called alkali. e.g. NaOH, KOH, NH3. Here,
(dissociation) (aq) (aq)
NaOH and KOH are strong alkalies while NH3
Water is a weak alkali.
H2 SO4 (l) H+(aq) + HSO4–(aq) (8) Basicity of acids
(dissociation)
Ans. The number of H+ ions obtainable by the
HSO – (dissociation) H+(aq) + SO42–(aq)
4 (aq) dissociation of one molecule of an acid is
called its basicity.
(2) Base (9) Acidity of bases
Ans. A base is a substance which on dissolving in Ans. The number of OH– ions obtainable by the
water gives rise to the OH– ion as the only dissociation of one molecule of a base is called
anion. For example , NaOH, Ca(OH)2 its acidity.
Water (10) Concentration of solute in the solution.
Na OH(s) Na+(aq) + OH–(aq)
(dissociation)
Ans. The proportion of a solute in a solution is
Water called the concentration of the solute in the
Ca (OH)2 (s) Ca2+(aq) + 2OH(aq) solution.
(dissociation)
(11) Concentrated solution.
(3) Strong Acid Ans. When the concentration of a solute in its
solution is high, it is a concentrated solution.
Ans. On dissolving in water, a strong acid dissociates
almost completely, and the resulting aqueous (12) Dilute solution
solution contains mainly H+ ion and the Ans. When the concentration of a solute in its
concerned acidic radical. solution is low, it is dilute solution.
e.g. HCl, HBr, HNO3, H2SO4. (13) Neutralization
(4) Weak Acid Ans. A reaction in which an acid reacts with a base
Ans. On dissolving in water a weak acid does to form salt and water is called a neutalization.
not dissociate completely, and the resulting NaOH + HCl NaCl + H2O
aqueous solution contains H+ ion and Base + Acid Salt + Water
the concerned acidic radical in small
(14) Cathode
proportion along with large proportion of
Ans. The electrode connected to the negative
the undissociated molecules of the acid.
terminal of a battery by means of a conducting
e.g., H2CO3 (Carbonic acid), CH3COOH
wire is called a cathode.
(Acetic Acid)
(15) Anode
(5) Strong Base
Ans. The electrode connected to the positive
Ans. On dissolving in water, a strong base dissociates
terminal of a battery by means of a conducting
almost completely and the resulting aqueous
wire is called an anode.
solution contains mainly OH– ions and the
(16) Cations
concerned basic radicals.
Ans. Cations are positively charged ions which are
e.g. NaOH, KOH, Ca(OH)2, Na2O.
attracted towards negative electrode (cathode)
(6) Weak Base
when electricity is passed into a solution of an
Ans. On dissolving in water, a weak base does ionic compound.
not dissociates completely and the resulting
Acids, Bases and Salts 83

(17) Anions which are not fit for consumption. They are
Ans. Anions are negatively charged ions which are harmful and may cause food poisoning. So it
attracted towards positive electrode (anode) is not advisable to keep buttermilk in brass or
when electricity is passed into a solution of an copper.
ionic compound. (3) Ionic compound NaCl has very high stability.
(18) Electrolytic cell Ans. The outermost shell of both Na+ and Cl– ions is
Ans. An assembly that consists of a container with a complete octet. An electronic configuration
an electrolyte and two electrodes dipped in it, with a complete octet indicates a stable state.
is called an electrolytic cell. A molecule of NaCl has Na+ and Cl– ions. An
ionic bond is formed between these ions. The
Q.9. Give scientific reasons: force of attraction between them is very strong
* (1) Hydronium ions are always in the form as it is formed between the oppositely charged
H3O+. Na+ and Cl– ions.
Ans. Acids in water gives H+ ions. This H+ ions do Therefore NaCl, an ionic compound has high
not exist freely in water. This is because H+ stability.
is a single proton, a hydrogen atom has only (4) Ionic compound dissociates while forming
one proton and one electron. If the electron an aqueous solution.
is removed to make H+, all that is left is an Ans. On dissolving in water, an ionic compound
extremely tiny positively charged nucleus. forms an aqueous solution. In the solid state,
This H+ ion will immediately combine with the oppositely charged ions in the ionic
the surrounding water (H2O) molecules to compound are sitting side by side. When
form (H3O+) hydronium ion. an ionic compound beings to dissolve in
* (2) Buttermilk spoils if kept in a copper or brass water, the water molecules push themselves
container. in between the ions of the compound and it
Ans. Buttermilk contains an organic acid called separates them from each other, that is to say,
as lactic acid. The lactic acid reacts with an ionic compound dissociates while forming
copper and brass and forms toxic compounds an aqueous solution.
Q.10. *(1) Fill in the columns in the part of the following table:
Ans.
Name of the compound Molecular formula Basic radical Acidic radical Type of the compound
Hydrochloric acid HCl H+ Cl– Acid
+ –
Nitric Acid HNO3 H NO 3
Acid
+ –
Hydrogen Bromide HBr H Br Acid
Sulphuric acid H2SO4 H+ SO42– Acid
Boric acid H3BO3 H+ BO33– Acid
+ –
Sodium hydroxide NaOH Na OH Base
+ –
Potassium hydroxide KOH K OH Base
Calcium hydroxide Ca(OH)2 Ca2+ OH– Base
+ –
Ammonium hydroxide NH4OH NH 4
OH Base
+ –
Sodium chloride NaCl Na Cl Salt
Calcium nitrate Ca(NO3)2 Ca2+ NO3– Salt
Potassium sulphate K2SO4 K+ SO42– Salt
2+ –
Calcium chloride CaCl2 Ca Cl Salt
+ 2–
Ammonium sulphate (NH4)2SO4 NH 4
SO 4
Salt
84 Master Key Science & Technology (Term - I) (Std. IX)

* (2) Complete the following :

NH3 (g) + H2O(l) NH4+ (aq) + OH– (aq) Ans. NH3 (g) + H2O(l) NH4+ (aq) + OH– (aq)
Na2 O (s) + H2O(l) 2Na+ (aq) + ............. Na2 O (s) + H2O(l) 2Na+ (aq) + 2OH–(aq)
CaO (s) + H2O(l) ............. + ............. CaO (s) + H2O(l) Ca2+(aq) + 2OH– (aq)
*(3) Complete the following table.
Ans.
Acid : Number of H+ obtained from one molecule.
HCl HNO3 H2SO4 H2CO3 H3BO3 H3PO4 CH3COOH
1 1 2 2 3 3 1

Base : Number of OH– ions obtained from one molecule

NaOH KOH Ca (OH)2 Ba (OH)2 Al (OH)3 Fe (OH)3 NH4OH
1 1 2 2 3 3 1
* (4) Complete the following table of the concentration of various aqueous solutions.
Ans.
Volume of Concentration of the
Solute Quantity of solute
Solution solution
D D E
A B C D E= F G= H=
C F F
Molarity M
Molecular Molecular Gram Mole Gram/
Name Litre (L) mole/litre
formula mass (u) (g) (mol) Litre (g/L)
(mol/L)
Sodium chloride NaCl 58.5 u 117 g 2 mol 2L 58.5 g/L 1M
Hydrogen
HCl 36.5 u 3.65 g 0.1 mol 1L 3.65 g/L 0.1 M
chloride
Sodium hydroxide NaOH 40 60 1.5 mol 2L 30 g/L 0.75 M

* (5) Complete the following table of neutralization reactions and also write down the names of the acids,
bases and salts in it.
Ans.
Acid + base Salt + Water

HNO3 + KOH KNO3 + H2O

Potassium Potassium
Nitric acid + + water
hydroxide nitrate

H2SO4 + 2NH4OH (NH4)2 SO4 + 2H2O

Sulphuric Ammonium Ammonium
+ + water
acid hydroxide sulphate
HBr + KOH KBr + H2O
Hydrogen Potassium Potassium
+ + water
Bromide hydroxide Bromide
Acids, Bases and Salts 85

* (6) Complete the following reactions. ZnO(s) + 2 HCl(aq) ZnCl2(aq) + H2O(l)

Ans. Metal + Dilute acid Salt + Hydrogen Al2O3(s) + 6 HF(l) 2AlF3(aq) + 3H2O(l)
Mg (s) + 2HCl(aq) MgCl2 (aq) + H2 (g) Fe2O3(s) + 6 HCl(aq) 2FeCl3(aq)+ 3H2O(l)
Zn (s) + H2 SO4 (aq) ZnSO4 (aq) + H2(g) * (8) Complete the following reactions.
Cu(s) + 2 HNO3(aq) Cu(NO3)2(aq) + H2(g) Ans. Oxide of non-metal + base salt + water
* (7) Complete the following. CO2(g) + 2 NaOH(aq) Na2CO3(aq) + H2O(l)
Ans. Metal oxide + Dilute acid Salt + Water
CO2(g) + 2 KOH(aq) K2CO3(aq) + H2O(l)
CaO(s) + 2 HCl (aq) CaCl2 (aq) + H2O(l)
SO3(g) + 2 NaOH(aq) Na2SO4(aq) + H2O(l)
MgO(s) + 2 HCl(aq) MgCl2(aq) + H2O(l)

(9) Complete the reactions in the following table.

Ans.
Carbonate salt of metal + dilute acid Another salt of metal + Carbon dioxide + water

Na2CO3 (s) + 2 HCl (aq) 2 NaCl(aq) + CO2 (g) + H2O(l)

Na2 CO3 (s) + H2SO4 (aq) Na2SO4 (aq) + CO2 (g) + H2O(l)
Ca CO3 (s) + 2 HNO3 (aq) Ca (NO3) 2 (aq) + CO2 (g) + H2O(l)
K2 CO3 (s) + H2SO4 (aq) K2 SO4 (aq) + CO2 (g) + H2O(l)

Bicarbonate salt of metal + dilute acid Another salt of metal + carbon dioxide + water
1. NaHCO3 (s) + HCl (aq) NaCl(aq) + CO2 (g) + H2O(l)
2. KHCO3 (s) + HNO3 (aq) KNO3 (aq) + CO2 (g) + H2O(l)
3. NaHCO3 (s) + CH3 COOH (aq) CH3 COONa(aq) + CO2 (g) + H2O(l)

Q.11. Answer in brief: (3) Give examples to show that proportions

(1) What are acids, bases and salts ? of H+ and OH– ions in aqueous solution
determines the properties of those solutions.
Ans. Some compounds are seen to have H+ as the
basic radical in their molecules. These are all Ans. The examples to show that proportions of H+
acids. Some compounds are seen to have OH– and OH– ions in aqueous solution determines
as the acidic radical in their molecule. All these the properties of those solutions are :
compounds are bases. Those ionic compounds (a) The proportions of H+ and OH– ions divides soil
which have a basic radical other than H+ and an into the acidic, neutral and basic, types of soil.
acidic radical other than OH– are called salts. (b) It is necessary for blood, cellsap etc to have H+
(2) What is ionic bond? and OH– ions in certain definite proportions
Ans. The molecule of an ionic compound has two for their proper functioning.
consitituents namely cation (positive ion / (c) Fermentation carried out with the help of
basic radical). There is a force of attraction micro-organisms, other biochemical processes
between these ions as they are oppositely and also many chemical processes require
charged, and that is called the ionic bond. the proportion of H+ and OH– ions to be
The force of attraction between one positive maintained within certain limits.
charge on a cation and one negative charge on
an anion makes one ionic bond.
86 Master Key Science & Technology (Term - I) (Std. IX)

(4) What is pH scale ? determined by means of a universal indicator

Ans. In 1909, the Danish scientist Sorensen solution or the pH paper made from it.
introduced a convenient scale of expressing H+ However, the most accurate method of
ion concentration which is found to be useful measuring the pH of a solution is to use an
in chemical and biochemical processes. It is the electrical instrument called pH meter. In
pH scale (pH : power of hydorgen). The pH this method, pH is measursed by dipping
scale extends from 0 to 14. According to this electrodes into the solution.
scale pure water has a pH of 7. pH 7 indicates * (7) Classify the following oxides into three
a neutral solution. This pH is the midpoint of types and name the types.
the scale. The pH of an acidic solution is less
CaO, MgO, CO2, SO3, Na2O, ZnO, Al2O3, Fe2O3
than 7 and that of a basic solution is greater
than 7. Ans. There are three types of oxides : Basic oxides,
Acidic oxides and Amphoteric oxides.
(5) Give the pH of following solutions.
Ans. Basic oxides Acidic oxides Amphoteric
oxides
Solution pH CaO CO2 ZnO
MgO SO3 Al2O3
Strong acids 1 M HCl 0.0 Na2O
Gastric juice 1.0 Fe2O3
Lemon juice 2.5
Generally metal oxides are basic in nature.
Vinegar 3.0
Exception Al2O3 and ZnO which are
Tomato juice 4.1 amphoteric.
Black coffee 5.0 Generally non-metal oxides are acidic in
Acid rain 5.6 nature.
weak acids Urine 6.0 * (8) Explain by drawing a figure of the electronic
Neutral Rain, milk 6.5 configuration
Weak bases Pure water, sugar 7.0 (a) Formation of sodium chloride from sodium
solution and chlorine.
Blood 7.4 Ans.
Solution of baking 8.5 p11 p17
soda n12 n18
Toothpaste 9.5
Na Cl
Milk of magnesia 10.5 Sodium atom Chlorine atom
Lime water 11.0 (2, 8, 1) (2, 8, 7)
Strong bases 1 M NaOH 14.0 + –

(6) What is universal indicator? Which is the

p11 p17
most accurate method of measuring the pH
n12 n18
of a solution?
Ans. In the pH scale, the pH of solutions varies
from 0 to 14 in accordance with the strength Na+ Cl–
of the acid or base. To show these variations in Sodium ion Chlorine atom
pH, a universal indicator is used. A universal (2, 8) (2, 8, 8)
(Cation) (Anion)
indicator shows different colours at different
values of pH. A universal indicator is made by
mixing several synthetic indicators in specific NaCl
proportions. The pH of a solution can be
Acids, Bases and Salts 87

(b) Formation of a magnesium chloride from the compound and separate them from each
magnesium and chlorine. other. The proportion of dissociation is large.
Ans. (c) Potassium hydroxide (KOH)
KOH(s) Water K+(aq) + OH–(aq)
p17 p12 p17 dissociation
n18 n13 n18 Potassium hydroxide is a strong base, as
on dissolving in water, it dissociates almost
compeletely and the resulting aqueous
Cl Mg Cl
Chlorine atom Magnesium atom Chlorine atom solution contains mainly OH– ions and the
(2, 8, 7) (2, 8, 2) (2, 8, 7) concerned basic radical. The proportion of
dissociation is large.
(d) Ammonia (NH3)
NH3(g) + H2O(l) Water NH+4(aq) + OH–(aq)
– 2+ –
dissociation
Ammonia dissolves in water to form NH4OH
p17 p12 p17 (ammonium hydroxide). NH4OH does not
n18 n13 n18 dissociate completely as it is a weak base. The
aqueous solution contains a small proportion
of OH– ions and the concerned basic radical
Cl– Mg2+ Cl–
along with a large proportion of undissociated
Chlorine ion Magnesium atom Chlorine ion
(2, 8, 8) (2, 8) (2, 8, 8) molecules of the base i.e. NH4OH.
Anion Cation Anion (e) Acetic acid (CH3COOH)
Water
(CH3COOH) CH3COO – + H+
MgCl2 dissociation
Acetic acid is a weak acid, on dissolving in
* (9) Show the dissociation of the following
water it does not dissociate completely, and
compounds on dissolving in water, with the
the resulting aqueous solution contains H+
help of chemical equation and write whether
ion and the concerned acidic radical in small
the proportion of dissociation is small or
proportion along with large proportion of
large. the undissociated molecules of the acid. The
Hydrochloric acid, Sodium chloride, propotion of dissociation is small.
Potassium hydroxide, Ammonia, Acetic acid, (f) Magnesium chloride (MgCl2)
Magnesium chloride, Copper sulphate.
MgCl2 Water Mg2+ + 2Cl–
Ans.
dissociation
(a) Hydrochloric acid (HCl) Magnesium chloride dissolves in water and
Water forms magnesium ions and chloride ions.
HCl(g) H+(aq) + Cl–(aq)
dissociation When an ionic compound begins to dissolve
Hydrochloric acid is a strong acid, as on in water, the water molecules push themselves
dissolving in water, it dissociates almost in between the ions of the compound and
completely and the resulting aqueous solution separate them from each other. The proportion
contains mainly H+ ions and the concerned of dissociation is large.
acidic radical. The proportion of dissociation (g) Copper sulphate (CuSO4)
is large. Water
CuSO4(s) Cu2+ + SO42–
(b) Sodium chloride (NaCl) dissociation
Water When copper sulphate dissolves in water,
NaCl(g) Na+(aq) + Cl–(aq) water molecules push themselves in between
dissociation
When an ionic compound begins to dissolve the ion of the compound and separate them
in water, the water molecules push themselves from each other. The proportion of dissociation
in between the positive and negative ions of is large.
88 Master Key Science & Technology (Term - I) (Std. IX)

* (10) Write down the concentration of each of the following solutions in g/L and mol/L.
(a) 7.3g HCl in 100ml solution (b) 2g NaOH in 50ml solution
(c) 3g CH3COOH om 100ml solution (d) 4.9g H2SO4 in 200ml solution
Ans. (a) 7.3g HCl in 100ml solution
To find : The concentration in g/L.
Solution :
Volume of Concentration of the
Solute Quantity of solute
Solution solution
D D E
A B C D E= F G= H=
C F F
Molecular Molecular Gram Mole Gram/ Molarity M
Name Litre (L)
formula mass (u) (g) (mol) Litre (g/L) (mol/L)
Hydrochloric acid HCl 36.5 u 7.3 g 0.2 mol 100 ml = 0.1L 73 g/L 2 mol/L
Sodium
NaOH 40 u 2.0 g 0.05 mol 50 ml = 0.05L 40 g/L 1 mol/L
Hydroxide
Acetic Acid CH3COOH 60 u 3.0 g 0.05 mol 100 ml = 0.1L 30 g/L 0.5 mol/L
Sulphuric acid H2SO4 98 u 4.9 g 0.05 mol 200 ml = 0.2L 24.5 g/L 0.25 mol/L

* (11) Answer the following questions. (c) Explain what is meant by electrolysis of
(a) Classify the acids according to their basicity water. Write the electrode reactions and
and give one example of each type. explain them.
Ans. Basicity of acids : The number of H+ ions Ans. Electrolysis of water :
obtainable by the dissociation of one molecule Electrolysis of water is the decomposition of
of an acid is called its basicity. The acids are water into oxygen and hydrogen gas due to an
classified as monobasic, dibasic and tribasic electric current being passed through acidified
acids based on the number of H+ ions present. water.
Examples of monobasic acid : HCl, HNO3, Cathode reaction :
CH3COOH 2H2O (l) + 2e– H2(g) + 2OH–(aq)
Example of dibasic acid : H2SO4, H2CO3 Anode reaction :
Example of tribasic acid : H3BO3, H3PO4 2H2O(l) O2(g) + 4 H+(aq) + 4e–
(b) What is meant by neutralization? Give It is found that in the above activity that the
two examples from everyday life of the volume of gas formed near the cathode is
neutralization reaction. double that of the gas formed near the anode.
Ans. In neutralisation reaction, an acid reacts with a Hydrogen gas is formed near the cathode and
base to form salt and water. In a neutralisation oxygen gas near the anode. From this, it is clear
reaction the acid dissociates to form H+ ions that electrolysis of water has taken place and
and base dissociates to form OH– ions. They its constituent elements have been relased.
combine to form H2O molecules which mixes * (12) Classify aqueous solutions of the following
with the solvent. substances according to their pH into three
Examples in daily life : groups : 7, more than 7, less than 7.
(i) When people suffer from acidity, they take common salt, sodium acetate, hydrochloric
some antacids to neutralise the acid in acid, carbon dioxide, potassium bromide,
their stomach. calcium hydoxide, ammonium chloride,
(ii) If an ant stings us the pain is due to formic vinegar, sodium carbonate, ammonia, sulphur
acid. It is neutralised by rubbing moist dioxide.
baking soda which is basic in nature.
Acids, Bases and Salts 89

Ans. 3 Cu(s) + 8 NHO3 (aq)

Copper + nitric acid (dil.)
(i) pH = 7 (ii) pH > 7 (ii) pH < 7
3 Cu (NO3)2 (aq) + 2 NO(g) + 4 H2O(l)
(a) Aqueous Aqueous Aqueous copper + nitric + water
solution of solution solution of nitrate oxide
common of sodium sulphur dioxide.
(d) A litmus paper was dropped into 2 ml dilute
salt. acetate.
HCl. Then 2 ml concentrated NaOH was
(b) Aqueous Aqueous Aqueous added to it and stirred.
solution of solution solution of
Ans. Blue litmus Paper : HCl is hydrochloric acid,
potassium of sodium hydrochloric
so the blue litmus turns red. When equal
bromide. carbonate acid.
amount of NaOH is added the colour again
(c) Aqueous Aqueous changes to blue and remains the same.
solution of solution of
Red litmus paper : Red litmus paper shows
ammonia. carbon-di-oxide.
no colour change in hydrochloric acid.
(d) Aqueous Aqueous When some amount of NaOH is added the
solution solution of colour changes to blue initially but when the
of calcium ammonium amount of NaOH is sufficient the blue colour
hydroxide. chloride. dissappears.
(e) Aqueous Equal amounts of HCl and NaOH results in
solution of the formation of NaCl, a salt, and the solvent
vinegar water. This reaction is called the neutralization
* (13) Write down the changes that will be seen in reaction.
each instance and explain the reason behind NaOH + HCl NaCl + H2O.
it. Base + Acid Salt + Water.
(a) 50ml water is added to 50ml solution of (e) Magnesium oxide was added to dilute HCl
copper sulphate. and magnesium oxide was added to dilute
Ans. Copper sulphate solution is blue. It is a NaOH.
concentrated solution. When 50 ml of water is Ans. (i) Magnesium oxide + dil HCl.
added to this concentrated solution, it becomes This is a neutralization reaction. Magnesium
a diluted solution. The intensity of the blue oxide is an insoluble base, it reacts with dilute
colour is now different in this homogenous HCl to produce a soluble salt MgCl2 and water
mixture. H2O.
(b) Two drops of the indicator phenolphthalein MgO + 2 HCl MgCl2 + H2O
were added to 10ml solution of sodium
(ii) Magnesium oxide + NaOH.
hydroxide.
No chemical reaction takes place between
Ans. Sodium hydroxide is a base and
magnesium oxide and sodium hydroxide.
phenolphthalein is a synthetic indicator.
Sodium hydroxide solution will turn pink if (f) Zinc oxide was added to dilute HCl and zinc
phenolphthalein is added to it. It is a test for oxide was added to dilute NaOH.
bases. Ans. (i) Zinc oxide reacts with dilute hydrochloric
(c) Two or three filings of copper were added to acid to form zinc chloride and water. It is a
10ml dilute nitric acid and stirred. neutrialization reaction.
Ans. When copper metal reacts with dilute nitric ZnO(s) + 2 HCl(aq) ZnCl2 (aq) + H2O(l)
acid, the metal does not displace hydrogen (ii) Zinc oxide reacts with sodium hydroxide
from the acid like reaction with other metals. to form sodium zincate and water.
Instead the reaction produces nitric oxide, ZnO(s) + 2 NaOH(aq) Na2 ZnO2 (aq) + H2O(l)
(NO).
90 Master Key Science & Technology (Term - I) (Std. IX)

(g) Dilute HCl was added to limestone. electrolysis of water is overall reaction.
Ans. When hydrochloric acid is added to limestone, 2 H 2O 2 H 2 + O2
carbon dioxide is liberated. Limestone is In this activity the volume of the hydrogen gas
calcium carbonate. formed near the cathode is double that of the
CaCO3 + 2 HCl CaCl2 + CO2 + H2O oxygen gas formed near the anode.
Carbon dioxide is prepared in the laboratory
Q.12. Answer in detail:
using these chemicals.
(1) Explain Arrhenius theory of acids and bases.
(h) Pieces of blue vitriol were beated in a test
tube. On cooling, water was added to it. Ans. The Swedish scientist Arrhenius put forth a
theory of acids and bases in the year 1887. This
Ans. On heating, the crystalline structure of blue
theory gives definitions of acids and bases as
vitriol breaks down to form a colourless
follows :
powder and water is released. This water is
part of the crystal structure of blue vitriol. It is Acid : An acid is a substance which on
called water of cystallization. dissolving in water gives to H+ ion as the only
cation. For example, HCl, H2SO4, H2CO3
On adding water to the white powder, a
solution was formed which has the same Water
HCl (g) H+(aq) + Cl–(aq)
colour as the copper sulphate salt solution. dissociation
(i) Dilute H2SO4 was taken in an electrolytic cell Water
and electric current was passed through it. H2 SO4 (l) H+(aq) + HSO4–(aq)
dissociation
Ans. If pure water is used in the electrolyltic cell,
current does not flow even on putting on the HSO4– (aq) dissociation H+(aq) + SO42–(aq)
switch.
Pure water is a bad conductor of electricity. Base : A base is a substance which on dissolving
Dilute H2SO4 is acidulated water. The electrical in water gives rise to the OH– ion as the only
conductivity of water increases on mixing anion, For example , NaOH, Ca(OH)2
with strong acid or base in it due to their Water
NaOH(s) Na+ (aq) + OH– (aq)
dissociation and electrolysis of water takes dissociation
place. Water
Ca(OH)2(s) Ca2+ (aq) + 2OH (aq)
H2SO4 is fully dissociated in aqueous solution. dissociation
H2SO4 2H+ + SO42– (2) Write a short note on Neutralization.
H2O is a weak electrolyte and is only slightly Ans. Take 10 ml of dilute HCl in a beaker, go
dissociated on adding dilute NaOH drop by drop and
H2O H+ + OH– recording the pH. Stop adding the NaOH
when the green colour appears on the pH
During electrolysis, the hydrogen ions migrate
paper, that is when the pH of solution becomes
towards the cathode and are discharged there.
7.
[H+ ions gains electrons and are converted to
hydrogen gas] Both HCl and NaOH dissociate in their
aqueous solutions. Addition of NaOH to HCl
2 H+ + 2 e– H2
solution is like adding a large concentration
Cathode reaction : of OH– ions to a large concentration of H+
2 H2O(l) + 2e– H2 (g) + 2 OH–(aq) ions. However water dissociates into H+ and
Anode reaction : OH– ions to a very small extent. Therefore on
mixing the excess OH– ions combines with
2H2O(l) O2 (g) + 4H+(aq) + 4e– excess H+ ions and forms H2O molecules
For every hydrogen ion discharged at the which mix with solvent water.
anode, another hydrogen ion is formed at the This change can be represented by the ionic
cathode. The net result is that the concentration equation shown as follows.
of the sulphuric acid remains constant and
Acids, Bases and Salts 91

H+ + Cl– + Na+ + OH– Na+ + Cl– + H2O CuSO4 . 5 H2O Heat CuSO4 + 5 H2O
It can be observed that Na+ and Cl– ions are (Blue) (White)
there on both the sides. (anhydrous copper sulphate)
Therefore the net ionic reaction is
Similarly ferrous Sulphate crystals also contain
H+ + OH– H2O 7 molecules of water of crystallization which
As NaOH solution is added drop by drop to are lost on heating. The reaction is represented
the HCl solution, the concentration of H+ goes as
on decreasing due to combination with added FeSO4 . 7 H2O Heat FeSO4 + 7 H2O
OH– ions, and that is how the pH goes on
increasing. (Green) (White)
When enough NaOH is added to HCl, the (anhydrous ferrous sulphate)
resulting aqueous solution contains only Ionic compounds are crystalline in nature.
Na+ and Cl– ions, that is, NaCl, a salt, and These crystals are formed as a result of definite
the solvent water. The only source of H+ and arrangement of ions. In the crystals of some
OH– ions in this solution in dissociation of compounds water molecules are also included
water. Therefore, this reaction is called the in this arrangement. That is the water of
Neutralization reaction. The Neutralization crystallization. The water of crystallization is
reaction is also represented by the following present in a definite proportion of the chemical
simple equation. formula of the compound.
HCl + NaOH NaCl + H2O (4) Explain the conduction of electricity through
Acid + base salt + water solutions of ionic compounds
(3) Explain water of Crystallization. Ans. Electrons conduct electricity through electrical
Ans. Take some crystals of blue vitriol (CuSO4. wires, and ions conduct electricity through a
5H2O) in test tube. Heat the test tube on low liquid or a solution. Electrons leave the battery
flame of a burner. On heating, the crystalline at the negative terminal, complete the electric
structure of blue vitriol broke down to form a circuit and enter the battery at the positive
colourless powder and water came out. This terminal. When there is a liquid or a solution
water was part of crystal structure of blue in the circuit, two rods, wires or plates are
vitroil. It is called water of crystallization. On immersed in it. These are called electrodes.
adding water to the white powder a solution Electrodes are made of conducting solid. The
Copper Drops of water
electrodes conducted to negative terminal of
sulphate a battery by means of a conducting wire is
(Blue) called a cathode and the electrode connected
to the positive terminal of a battery is called
on giving heat to anode.
copper sulphate Copper We have seen that salts, strong acids and
sulphate strong base dissociates almost completely
(White)
in their aqueous solutions. Therefore the
aqueous solutions of all these three contain
large number of cations and anions.
Properties of water of crystallization A characteristic of liquid state is the mobility
was formed which had the same colour as the of its particles. Due to its mobility the positive
solution in the first test tube. From this we charged ions of the solution are attracted
come to know that no chemical change has to the negative electrode or cathode. On the
occurred in the crystals of blue vitriol due to other hand, the negative charged ions of the
heating. Losing water on heating blue vitriol, solution are attracted to the positive electrode
breaking down of the crystal structure, losing or anode. The movement of ions in the solution
blue colour and regaining blue colour on towards the respective electrodes amounts
adding water are all physical changes. to the conduction of electricity through the
92 Master Key Science & Technology (Term - I) (Std. IX)

solution. From this we can understand that (3) When copper reacts with nitric acid.
those liquids or solutions which contain a large Ans. When copper reacts with nitric acid, it forms
number of dissociated ions conduct electricity. copper nitrate and hydrogen gas liberated.
Bulb Cu(s) + 2HNO3 (aq) Cu(NO3)2 (aq) + H2 (g)
Switch Copper Nitric acid Copper Hydrogen
nitrate
(4) When ferric oxide reacts with diluted
hydrochloric acid.
Support Ans. When Ferric oxide reacts with diluted
hydrochloric acid, it forms ferric chloride and
+ – water.
Beaker Fe2O3 (s) + 6HCl (aq) 2FeCl3 (aq) + 3H2O(l)
6V
Battery Ferric Hydrochloric Ferric Water
oxide acid chloride
Solution of sodium chloride (5) When calcium oxide reacts with dilute
hydrochloric acid.
Bare electric wire
Ans. When calcium oxide reacts with dilute
Testing the electrical conductivity of a solution hydrochloric acid, it forms calcium chloride
and water.
CaO(s) + 2HCl (aq) CaCl2 (aq) + H2O (l)
Calcium Hydrochloric Calcium Water
oxide acid chloride
(6) When Magnesium oxide reacts with dilute
hydrochloric acid.
Ans. When magnesium oxide reacts with dilute
hydrochloric acid, it forms magnesium
chloride and water.
Dissociation of ions MgO(s) + 2HCl (aq) MgCl2 (aq) + H2O (l)
Q.13. Explain the following chemical reactions Magnesium Hydrochoric Magnesium Water
with the help of balanced equations: oxide acid chloride
(1) Magnesium reacts with dilute hydrochloric (7) When zinc oxide reacts with dilute
acid. hydrochloric acid.
Ans. When magnesium reacts with dilute Ans. When zinc oxide reacts with dilute
hydrochloric acid, it forms magnesium hydrochloric acid, it forms zinc chloride and
chloride and hydrogen gas is liberated. water.
Mg(s) + 2HCl(aq) MgCl2 (aq) + H2 (g) ZnO(s) + 2HCl (aq) ZnCl2 (aq) + H2O (l)
Magnesium Hydrochloric Magnesium Hydrogen Zinc Hydrochloric Zinc Water
acid chloride oxide acid chloride
* (2) Zinc reacts with dilute sulphuric acid. (8) When aluminium oxide reacts with hydrogen
Ans. When zinc reacts with dilute sulphuric acid, fluoride.
it forms zinc sulphate and hydrogen gas is Ans. When aluminium oxide reacts with hydrogen
liberated. fluoride, it forms Aluminium fluoride and
Zn(s) + H2SO4 (aq) ZnSO4(aq) + H2 (g) water.
Zinc Sulphuric acid Zinc sulphate Hydrogen Al2O3 (s) + 6HF (l) 2AlF3 (aq) + 3H2O(l)
Aluminium Hydrogen Aluminium Water
oxide fluoride fluoride
Acids, Bases and Salts 93

(9) When carbon dioxide reacts with sodium Na2CO3 (s) + H2SO4 (aq)
hydroxide. Sodium sulphuric
Ans. When carbon dioxide reacts with Sodium carbonate acid
hydroxide, it forms Sodium carbonate and Na2SO4 (aq) + CO2 (g) + H2O(l)
water.
Sodium Carbon Water
CO2 (g) + 2NaOH (aq) Na2 CO3 (aq) + H2O(l) sulphate dioxide
Carbon Sodium Sodium Water (15) When calcium carbonate react with nitric
dioxide hydroxide carbonate acid.
(10) When carbon dioxide reacts with potassium Ans. When calcium carbonate reacts with nitric
hydroxide. acid, it forms calcium nitrate, carbon dioxide
Ans. When carbon dioxide reacts with potassium and water.
hydroxide, it forms potassium carbonate and CaCO3 (s) + 2HNO3 (aq)
water.
Calcium Nitric
CO2 (g) + 2KOH (aq) K2 CO3 (aq) + H2O(l) carbonate acid
Carbon Potassium Potassium Water Ca(NO3)2 + CO2 (g) + H2O(l)
dioxide hydroxide carbonate
Calcium Carbon Water
(11) When sulphur trioxide reacts with sodium nitrate dioxide
hydroxide. (16) When potassium carbonate react with
Ans. When sulphur trioxide reacts with sodium sulphuric acid.
hydroxide, it forms sodium sulphate and water. Ans. When potassium carbonate reacts with
SO3 (g) + 2NaOH (aq) Na2 SO4 (aq) + H2O(l) sulphuric acid, it forms potassium sulphate,
Sulphur Sodium Potassium Water carbon dioxide and water.
trioxide hydroxide sulphate K2CO3 (s) + H2SO4 (aq)
(12) When calcium hydroxide reacts with carbon Potassium Sulphuric
dioxide. carbonate acid
Ans. When calcium hydroxide reacts with carbon K2SO4 (aq) + CO2 (g) + H2O(l)
dioxide, it forms calcium carbonate and water.
Potassium Carbon Water
Ca (OH)2 (aq) + CO2 (g) CaCO3 (s) + H2O(l) sulphate dioxide
Calcium Carbon Calcium Water * (17) When sodium bicarbonate react with
hydroxide dioxide carbonate hydrochloric acid. OR
(13) When sodium carbonate reacts with Dilute HCl was poured on baking soda
hydrochloric acid.
Ans. When sodium bicarbonate reacts with
Ans. When sodium carbonate reacts with hyrdochloric acid, it forms sodium chloride,
hydrochlric acid, it forms sodium chloride , carbon dioxide and water.
carbon dioxide and water.
NaHCO3 (s) + HCl (aq)
Na2CO3 (s) + 2HCl(aq)
Sodium Hydrochloric
Sodium Hydrochloric bicarbonate acid
carbonate acid
NaCl (aq) + CO2 (g) + H2O(l)
2NaCl(aq) + CO2 (g) + H2O(l)
Sodium Carbon Water
Sodium Carbon Water chloride dioxide
chloride dioxide
(18) When potassium bicarbonate react with
(14) When sodium carbonate react with sulphuric nitric acid.
acid.
Ans. When potassium bicarbonate reacts with
Ans. When sodium carbonate reacts with sulphuric nitric acid, it forms potassium nitrate, carbon
acid, it forms sodium sulphate, carbon dioxide dioxide and water.
and water.
94 Master Key Science & Technology (Term - I) (Std. IX)

KHCO3 (s) + HNO3 (aq) Q.14. Use your brain power!

Potassium Nitric (1) What are the names of the following
bicarbonate acid compounds? NH3, Na2O, CaO.
KNO3 (aq) + CO2 (g) + H2O(l) Ans. NH3 : Ammonia
Potassium Carbon Water Na2O : Sodium oxide
nitrate dioxide CaO. : Calcium oxide
(19) When sodium bicarbonate react with acetic (2) Into which type will you classify the above
acid. compounds. acid, base or salt?
Ans. When sodium bicarbonate reacts with acetic Ans. NH3 base
acid, it forms sodium acetate, carbon dioxide
Na2O base
and water.
CaO base
NaHCO3 (s) + CH3COOH(aq)
(3) Give examples of monobasic, dibasic and
Sodium Acetic
tribasic acids.
bicarbonate acid
Ans. Monobasic acid examples: HNO3, HCl,
CH3 COONa (aq) + CO2 (g) + H2O(l)
CH3COOH
Sodium Carbon Water
Dibasic acid examples: H2SO4, H2CO3
acetate dioxide
Tribasic acid examples: H3BO3, H3PO4
(20) When copper sulphate is heated.
(4) Give the three types of bases with their examples.
Ans. When copper sulphate is heated it loses it’s
water of crystallation to form white anhydrous Ans. Types of bases:
copper sulphate. Monoacidic base examples : NaOH, KOH,
Heat NH4OH
CuSO4. 5 H2O CuSO4 + 5H2O
Copper (White) Water Diacidic base examples: Ca(OH)2, Ba(OH)2
sulphate (blue) anhydrous Triacidic base examples: Al(OH)3, Fe(OH)3
Copper sulphate (5) What would be the definition of an acid and
(21) When Ferrous sulphate is heated. a base with reference to the neutralization
Ans. When ferrous sulphate is heated it loses its reaction?
water of crystallation to form white anhydrous Ans. Acid: An acid is a substance which neutralises
ferrous sulphate. a base to form salt and water.
Heat Base: A base is a substance which neutralises
FeSO4. 7 H2O FeSO4 + 7H2O
Ferrous anhydrous Water an acid to form salt and water.
sulphate (green) Ferrous sulphate (6) Take aqueous solution of sodium chloride,
(White) copper sulphate, glucose, urea, dil H2SO4 and
* (22) NaOH solution was added to HCl solution. dil NaOH in a beaker and test the electrical
conductivity of the solutions. Answer the
Ans. When NaOH reacts with HCl, it gives NaCl
given below questions.
and water.
(a) With which solutions did the bulb glow?
NaOH (aq) + HCl (aq) NaCl (aq) + H2O (l)
Ans. Solutions with which bulb glows: Aqueous
Sodium Hydrochloric Sodium Water
solution of NaCl, CuSO4, H2SO4 and NaOH.
hydroxide acid chloride
(b) Which solutions are electrical conductors?
* (23) Dilute nitric acid was added to calcium oxide.
Ans. Solutions which are electrical conductors:
Ans. When dilute nitric acid reacts with calcium
NaCl, CuSO4, H2SO4 and NaOH.
oxide, it forms calcium carbonate and water.
(7) During electrolysis of copper sulphate,
2HNO3 (l) + CaO (g) Ca(NO3)2 (s) + H2O (l)
if electric current is passed through the
dil + calcium calcium + water electrolytic cell for a long time, what change
nitric acid oxide nitrate would be seen at the anode?
Acids, Bases and Salts 95

Ans. When electricity is passed for a long time difference in the tastes of the solutions in the
through copper sulphate solution, the two beakers? What is that difference?
following reaction is seen at the anode: Ans. (i) In the above activity, the sour taste of the
2+ –
Anode Reaction: Cu(s) Cu (aq)+ 2e solutions is because of the solute, lemon
All the copper atoms will get converted into juice in them.
copper ions and get deposited on the cathode. (ii) The quantity of the lemon juice is the
This process continues till the copper anode same in both the solutions. Yet their taste
exists. is different.
(8) Would water be a good conductor of (iii) The solution in the first beaker is more
electricity? sour than the one in the second.
Ans. Pure water is not a good conductor of (iv) Although the quantity of the solute is the
electricity. same in both the solutions, the quantity
(9) (a) Write down chemical equations for of the solvent is different.
(i) Zinc oxide reacts with sodium hydroxide (v) Ratio of the quantity of the solute to
(ii) Aluminium oxide reacts with sodium the quantity of the resulting solution
hydroxide. is different. This ratio is larger for the
solution in the first beaker and therefore
Ans. (i) When zinc oxide reacts with sodium
that solution tastes more sour.
hydroxide,it forms sodium zincate and
water (vi) On the other hand, the proportion of the
lemon juice in the total solution in the
ZnO + 2NaOH Na2ZnO2 + H2O
second beaker is smaller and taste is less
zinc + sodium sodium + water sour.
oxide hydroxide zincate
(vii) The taste of foodstuff depends upon the
(ii) When Aluminiuum oxide reacts with nature of the taste-giving ingredient and
sodium hydroxide, it forms sodium its proportions in the foodstuff.
aluminate.
(viii) Similarly, all the properties of a solution
Al2O3 + 2NaOH 2NaAlO2 + H2O depend on the nature of the solute and
aluminium + sodium sodium + water solvent and also on the proportion of the
oxide hydroxide aluminate solute in a solution
(b) Can we call Al2O3 and ZnO acidic oxides on (ix) The proportions of a solute in a solution
the basis of above reactions. is called the concentration of the solute in
Ans. No, because they also react with acids to form the solution.
their respective salts and water. So, they show (2) Take a big test tube. Choose a rubber stopper
the properties of basic oxides also. in which a gas tube can be fitted. Take a few
(c) Define ‘amphoteric oxides’ and give two pieces of magnesium ribbon on the test tube
examples. and add some dilute HCl to it. Take a lighted
Ans. Amphoteric oxides are those oxides which candle near the end of the gas tube and
react with both acids as well as bases to form observe. What did you observe?
their respective salts and water. Ans. (i) Magnesium metal reacts with dilute HCl
Amphoteric oxides show the properties of and an inflammable gas, hydrogen, is
both acidic oxides as well a basic oxides. formed.
(ii) During this reaction, the reactive metal
Q.15. Activity based questions. displaces hydrogen from the acid to
(1) Cut a lemon into two equal parts. Take the release hydrogen gas.
juice of each part into two separate beakers. (iii) At the same time, the metal is converted
Pour 10 ml of drinking water in one beaker into basic radical which combines with
and 20 ml in the second. Stir the solutions in the acidic radical from the acid to form the
both the beakers and taste them. Is there any salt.
96 Master Key Science & Technology (Term - I) (Std. IX)

Mg(s) + 2 HCl(aq) MgCl2(aq) + H2(aq) effervescence, it turns milky. This is a chemical

test for carbon dioxide gas. When lime water
(3) Take some water in a test tube and add a little
turns milky, we infer that the effervescence
red oxide (the primer used before painting
is of CO2. This gas is produced on reaction of
iron articles) to it. Now add a small quantity
acids with carbonate and bicarbonate salts of
of dilute HCl to it, shake the test tube and
metals. A precipitate of CaCO3 is produced on
observe.
its reaction with the lime water Ca (OH)2. This
(i) Does the red oxide dissolve in water? reaction can be represented by the following
(ii) What change take place in the particles of chemical equation.
red oxide on adding dilute HCl? Ca (OH)2 (aq) + CO2 (g) CaCO3 (s) + H2O(l)
Ans. The chemical formula of red oxide is Fe2O3. Washing soda is sodium carbonate Na2CO3. It
It is insoluble in water. The water insoluble will react same as baking soda (NaHCO3).
red oxide reacts with HCl to produce a water
Vinegar and HCl are acids, they do not react
soluble salt FeCl3. This gives a yellowish colour
chemically with lime juice.
to the water. The following chemical equation
can be written for this chemical change. * (5) Obtain a sample of rainwater. Add to it a
few drops of universal indicator. Measure
Fe2O3 (s) + 6 HCl(aq) 2 FeCl3 (aq) + 3 H2O(l)
its pH. Describe the nature of the sample of
(4) Fit a bent tube in a rubber cork. Take some rainwater and explain the effect it has on the
lime water in a test tube and keep it handy. living world.
Take some baking soda in another test tube Ans. pH of rain water is 6.5 that means rain water
and add some lime juice to it. Immediately fit is slightly acidic. When we add universal
the bent tube over it. Insert its other end into indicator to rain water it turns orangish red,
the lime water. Note down your observations indicating pH value is between 0 to 7, which
of both the test tubes. Repeat the proceduce tells us that rain water is acidic in nature.
using washing soda, vinegar and dilute HCl Most of the plants grow best when pH of soil
properly. What do you see? is close to 7. If the soil is too acidic or too basic,
Ans. In this activity, when limewater comes in it affects plant growth.
contact with the gas released in the form of an

vvv
Acids, Bases and Salts 97

ASSIGNMENT - 5
Time : 1 Hr Marks : 30

Q.1. (A) Fill in the blanks and write the complete statements: (2)
(1) The bases which are soluble in wate are called as
(2) CO2 gas turns milky.
(B) State whether the following statements are true or false and if false write the correct
satement: (2)
(i) Copper oxide is called red primer. (ii) H2SO4 is a strong acid.
(C) Match the Columns:
Column ‘A’ Column ‘B’
(1) Crystalline blue vitriol (a) FeSO4.7 H2O
(2) Crystalline green vitriol (b) K SO .Al (SO ) .24 H O
2 4 2 4 3 2

(3) Crystalline washing soda (c) CuSO4.5 H2O

(4) Crystalline alum (d) Na CO .10 H O
2 3 2

Q.2. (A) Answer the following in one or two sentences: (2)

(i) Name any two bases with their acidity 2. (ii) What is molarity of a solution? How is it written?
(B) Define the following: (2)
(i) Weak acid (ii) Neutralisation.
Q.3. (A) Differentiate Between: (2)
(i) Cations and Anions
(B) Give Scientific Reasons: (Any Two) (4)
(i) Buttermilk spoils if kept in a copper or brass containers.
(ii) Ionic compounds dissociates while forming an aqueous solution.
(iii) Hydronium ions are always in the form H3O+
Q.4. (A) Answer in brief: (Any three) (6)
(i) What is PH scale?
(ii) Classify the following oxides in to three types and name the types.CaO, MgO, CO2, SO3, Na2O,
ZnO, Al2O3, Fe2O3
(iii) Explain by drawing a figure of the electronic configuration of formation of a magnesium chloride
from magnesium and chlorine
(iv) Write down the concentration of each of the folloing solutions in g/L and Mol/L.
(a) 7.3 g HCl is 100 ml solution. (b) 2 g NaOH in 50 ml solution.
(B) Explain the following chemical reactions with the help of balanced equations: (Any Two)(4)
(i) Magnesium reacts with dilute hydrochloric acid.
(ii) When Sodium carbonate reacts with Sulphuric acid.
(iii) When Carbon dioxide reacts with Sodium hydroxide.
(C) Answer in Detail: (Any One) (6)
(i) Explain Arrhenius theory of acid and bases. (ii) Explain water of crystallination.
vvv
6 Classification of Plants

Points to Remember:
• Robert Whittaker (1959) proposed the five kingdom classification for the study of living
organisms.
• According to the five kingdom classification living organisms are classified into kingdom
Monera, Kingdom Protista, Kingdom Plantae, Kingdom Fungi and Kingdom Animalia.
• The group of autotrophic living organisms having eukaryotic cell walls is the group of plants.
They are autotrophic as they can perform photosynthesis with the help of chlorophyll.
CRITERIA FOR CLASSIFICATION:
(i) Presence or absence of organs like roots, stems, leaves and flowers.
(ii) Presence or absence of seperate conducting tissues for conduction of water and food.
(iii) Presence or absence of seeds.
(iv) Whether the seeds are enclosed in a fruit or not.
• At the higher levels of plant classification, different characteristics are considered for
classification e.g. depending upon the absence or presence of flower, fruits and seeds, plants
are classified as crytogams or phanerogams.
• Depending upon whether seeds are enclosed within a fruit or not, phanerogams are classified
as gymnosperms and angiosperms.
• Angiosperms are further classified as monocots and dicots depending upon the number of
cotyledons in seeds.
• Cryptogams are further classified into Thallophyta, Bryophyta and pteridophyta.
• Thallophyta group of plants do not have specific parts like root-stem-leaves-flowers but are
autotrophic due to the presence of chlorophyll and are called algae. e.g. Spirogyra, Ulothrix,
Ulva, Sargassum etc.
• Various types of fungi like yeasts and moulds which do not have chlorophyll are also
included in Thallophyta.
• Bryophyta group of plants are called the "amphibians' of the plant kingdom because they
grow in moist soil but need water for reproduction.
• The structure of the plant body of bryophytes is flat, ribbon-like long, without true roots,
stem and leaves. Instead, they have stem-like or leaf-like parts and root-like rhizoids. e.g.
Moss(Funaria), Marchantia, Anthoceros, Riccia etc.
• Pteridophyta group of plants have well-developed roots, stem and leaves and separate
tissues for conduction of food and water.
• Pteridophyta plants do not bear flowers and fruits. They reproduce with the help of spores
formed along the back or posterior surface of their leaves.
• Pteridophyta plants reproduce asexually by spore-formation and sexually by zygote
formation. e.g. Nephrolepis, Marsilea, Pteris, Adiantum, Equisetum, Selaginella, Lycopodium
etc.

(98)
Classification of Plants 99

• Phanerogams have special structures for reproduction and produce seeds.

• Depending upon whether the seeds are enclosed in a fruit or not, phanerogams are classified
into gymnosperms and angiosperms.
• In Gymnosperms, the seeds do not have natural coverings, i.e. these plants do not form
fruits and are therefore called gymnosperms. e.g. Cycas, Picea (Christmas tree), Thuja
(Morpankhi), Pinus (Deodar) etc.
• In Angiopserms, flowers are their reproductive organs. Flowers develop into fruits and seeds
are formed within fruits, thus the seeds are covered. Hence they are called angiosperms.
• The plants whose seeds can be divided into two equal halves or dicotyledons are called
dicotyledonous plants and those whose seeds cannot be divided into equal parts are called
monocotyledonous plants.

(B) Fill in the blanks:

MASTER KEY QUESTION SET - 6
(1) The five kingdom classification was proposed
*Q.1. (A) Complete the sentences by filling in the by .
blanks and explain those statements: (2) In 1883, classified plants in two
(angiosperm, gymnosperms, spore, bryophyta, subkingdoms.
thallophyta, zygote)
(3) Various types of fungi like yeasts and moulds
(1) plants have soft and fibre-like body. are included in the group .
Ans. Thallophyta: These plants grow mainly in
(4) Bryophytes have root-like structure called
water i.e. fresh water as well as in saline water.
.
therefore they usually have a soft and fibre-
like (filamentous) body. (5) reproduce with the help of spores
(2) is called the ‘amphibian‘ of the plant formed along the back or posterior surface of
kingdom. their leaves.
Ans. Bryophyta: They grow in moist soil but need (6) In the reproductive organs cannot
water for reproduction. Therefore they are be seen.
called ‘amphibians of plant kingdom‘. (7) are mostly evergreen, perennial and
(3) In pteridophytes, asexual reproduction occurs woody.
by formation and sexual reproduction (8) Gymnosperms bear male and female flowers
occurs by formula.
on different of the same plant.
Ans. Spore, zygote: Pteridophyta plants show
(9) In the seeds are not enclosed by
alteration of generation. One generation
fruits.
reproduces by spore-formation and the next
generation reproduces sexually by zygote (10) In , the seeds are covered by fruits.
formation (11) The plants whose seeds cannot be divided
(4) Male and female flowers of are borne into equal parts are called .
on different sporophylls of the same plant. Ans. (1) Robert Whittaker (2) Eichler (3) thallophyta
Ans. Gymnosperms: As these plants do not take (4) rhizoids (5) Pteridophyta (6) Cryptogams
the assistance of pollinators i.e. vectors. The (7) Gymnosperms (8) sporophylls (9) gymnosperms
male and female flowers are present on the (10) angiosperms (11) monocotyledons
different sporophyll of the same plant for
successful fertilisation.
100 Master Key Science & Technology (Term - I) (Std. IX)

(C) Rewrite the following statements by *Q.2. (A) Match the proper terms from columns A
selecting correct options given below: and C with the description in column B:
(1) The five kingdom classification was proposed Column ‘A’ Column ‘B’ Column ‘C’
by .
(1) Thallophyta Seeds are Fern
(a) Robert Whittaker (b) Robert Hooke formed in fruits
(c) Eichler (d) Louis Pasteur
(2) Bryophyta No natural Cycas
(2) In 1883, classified plants into two covering on
sub-kingdoms. seeds
(a) Robert Whittaker
(3) Pteridophyta These plants Tamarind
(b) Alexander Fleming mainly grow in
(c) Eichler water
(d) Robert Hooke (4) Gymnosperms These plants Moss
(3) Ulothrix, ulva, sargassum belong to need water for
(a) Bryophyta (b) Thallophyta reproduction
(c) Pteridophyta (d) Gymnosperms (5) Angiosperms Tissues are Algae
(4) is a bryophyte. present for
(a) Ulva (b) Nephrolepis conduction of
water and food
(c) Funaria (d) Equisetum
Ans.
(5) Lycopodium belongs to .
(a) thallophyta (b) bryophyta Column ‘A’ Column ‘B’ Column ‘C’
(c) gymnosperms (d) pteridophyta (1) Thallophyta These plants Algae
(6) In the seeds are naked. mainly grow in
water
(a) Pteridophyta (b) Angiosperms
(2) Bryophyta These plants Moss
(c) Gymnosperms (d) Bryophyta
need water for
(7) In the flowers are reproductive reproduction
organs.
(3) Pteridophyta Tissues are Fern
(a) Angiosperms (b) Gymnosperms
present for
(c) Pteridophyta (d) Bryophyta conduction of
(8) Leaves of show reticulate venation. water and food
(a) Bamboo (b) Banana (4) Gymnosperms No natural Cycas
(c) Onion (d) Banyan covering on
(9) In the flowers are tetramerous or seeds
pentamerous. (5) Angiosperms Seeds are Tamarind
(a) Monocotyledons (b) Dicotyledons formed in fruits
(c) Gymnosperms (d) Pteridophyta (B) Match the columns:
(10) In monocotyledonous plants, the stem is
. (1) Column ‘A’ Column ‘B’
(a) hollow (b) false (1) Ulva (a) Bryophyta
(c) disc-like (d) all of these. (2) Marsilea (b) Gymnosperm
Ans. (1) Robert Whittaker (2) Eichler (3) Thallophyta (3) Marchantia (c) Pteridophyta
(4) Funaria (5) pteridophyta (6) Gymnosperms (4) Thuja (d) Thallophyta
(7) Angiosperms (8) Banyan (9) Dicotyledons
Ans. (1-d); (2-c); (3-a); (4-b)
(10) all of these
Classification of Plants 101

(6) Pteridophytes have well developed roots,

(2) Column ‘A’ Column ‘B’
stems and leaves.
(1) Onion (a) Dicotyledon
Ans. True
(2) Cyas (b) Pteridophyta (7) Pteridophytes reproduce with the help of
(3) Mango (c) Monocotyledon spores formed along the back or posterior
surface of their leaves.
(4) Lycopodium (d) Gymnosperm
Ans. True
Ans. (1-c); (2-d); (3-a); (4-b) (8) Nephrolepis belongs to division Pteridophyta.
Q.3. Odd man out: Ans. True
(1) Ulothrix, Ulva, Nephrolepis, Sargassum (9) Depending upon whether seeds are enclosed
Ans. Nephrolepis: It belongs to division in a fruit or not, phanerogams are classified
pteridophyta whereas the others belong to into monocots and dicots.
division thallophyta. Ans. False, Depending whether seeds are enclosed
(2) Funaria, Marchantia, Anthoceros, Equisetum in a fruit or not, angiosperms are classified
Ans. Equisetum: It belongs to division pteridophyta into monocots and dicots.
whereas the others belong to division bryophyta. (10) Gymnosperms are mostly evergreen, perennial
(3) Nephrolepis, Marsilea, Cycas, Lycopodium and woody.
Ans. Cycas: It is a gymnosperm whereas others are Ans. True
pteridophyta. (11) Gymnosperms bear male and female flowers
(4) Spirogyra, Riccia, Ulva, Ulothrix on different sporophylls of different plants.
Ans. Riccia: It is a bryophyte whereas the others Ans. False, Gymnosperms bear male and female
are thallophytes. flowers on different sporophylls of the same
plant.
(5) Corn, Rice, Wheat, Groundnut
(12) In Angiosperms, the seeds are covered by fruits.
Ans. Groundnut: It is a dicotyledonous plant
whereas others are monocotyledonous plants. Ans. True
(6) Cycas, Pinus, Thuja, Hibiscus (13) Dicotyledonous plants show reticulate venation.
Ans. Hibiscus: It is an angiosperm whereas rest are Ans. False, Dicotyledonous plants show parallel
gymnosperms. venation.
Q.4. State whether the following statements are true (14) Moncotyledonous plants have trimerous
or false and if false, write the correct statement: flowers.
(1) Thallophyta are called as the amphibians of Ans. True
the plant kingdom. (15) In dicotyledonous plants, the stem is strong
Ans. False, Thallophyta plants grow mainly in water. and hard.
(2) Fungi like yeasts and moulds are included in Ans. True
division byophyta. Q.5. Complete the analogy:
Ans. False, Fungi like yeasts and moulds are (1) Spirogyra : Thallophyta : : Riccia :
included in division thallophyta.
(2) Moss : Bryophyta : : Selaginella :
(3) Moss (Funaria) belongs to division bryophyta.
(3) Nephrolepis : Pteridophyta : : Ulothrix :
Ans. True
(4) Pteridophyta : Roots : : Bryophyta :
(4) Bryophyta have specific tissues for conduction
(5) Gymnosperms : naked seeds : : Angiosperms :
of food and water.
Ans. False, Bryophyta do not have specialised
tissues for conduction of food and water. (6) Dicotyledon : Reticulate venation : :
Monocotyledon :
(5) Plants belonging to Thallophyta group are
only unicellular. (7) Bamboo stem : Hollow : : Onion Stem :
Ans. False, Plants belonging to thallophyta group (8) Dicotytedon flower : tetramerous : :
may be unicellular or multicellular. Monocotylendon :
102 Master Key Science & Technology (Term - I) (Std. IX)

(9) Monocotylendon : tap root : : Dicotyledon : (v) Instead they have stem-like or leaf-like parts
and root-like rhizoids.
Ans. (1) Bryophyta (2) Pteridophyta (3) Thallophyta (vi) They do not have specific tissues for
(4) Rhizoids (5) covered seeds (6) parallel venation conduction of food and water.
(7) disc like (8) trimerous (9) fibrous roots (vii) Examples: Moss (Funaria), Anthoceros, Riccia etc.
Q.6. Answer the following in your own words: * (4) Collect a Monocot and dicot plant available
* (1) Write the characteristics of subkingdom in your area. Observe the plant carefully and
phanerogams. describe them in scientific language.
Ans. Ans. Monocot Plant: Lily
(i) Plants which have special structures for (i) Its seeds cannot be divided into two equal
reproduction and produce seeds are called halves.
phanerogams. (ii) Its roots are fibrous.
(ii) In these plants, after the process of (iii) Its stem is hollow.
reproduction, seeds are formed which contain (iv) Its leaves show parallel venation.
the embryo and stored food.
(v) Flowers with 3 parts or in multiples of three
(iii) During germination of the seed, the stored (trimerous).
food is used for the initial growth of the
Dicot Plant : Hibiscus
embryo.
(i) Its seeds can be divided into two equal halves.
(iv) Depending upon whether seeds are enclosed
in a fruit or not phanerogams are classified (ii) It has well developed roots. There is a primary
into gymnosperms and angiosperms. root (tap root) and many secondary roots arise
from the primary roots.
* (2) Write a paragraph in your own words about
(iii) Its stem is strong and hard.
the ornamental plants called ferns.
(iv) Its leaves show reticulate venation.
Ans.
(v) Its flowers has four to five petals (Pentamerous).
(i) Ferns belong to the group of plants called
Pteridophyta. * (5) Which criteria are used for the classification
(ii) They have well developed roots, stem and of plants? Explain with reason.
leaves but do not bear flowers and fruits. Ans. Criteria for classification of plants:
(iii) They have separate tissues for conduction of (i) Presence or absence of organs.
food and water. (ii) Presence or absence of separate conducting
(iv) They reproduce with the help of spores tissues for conduction of water and food.
formed along the back or posterior surface of (iii) Whether the plants bear seeds or not.
their leaves. (iv) If they bear seeds, then whether the seeds are
(v) They reproduce asexually by spore formation enclosed in a fruit or not.
and sexually by zygote formation. (v) Number of cotyledons in the seeds.
* (3) Write the characteristics of the plants *Q.7. Sketch, label the figures of the following
belonging to division bryophyta. plants and explain them in brief:
Ans. (1) Spirogyra.
(i) Bryophyta group of plants are called the Ans.
amphibians of the plant kingdom because
Cell wall Nucleus Pyrenoid
they grow in moist soil but need water for
reproduction.
(ii) These plants are thalloid, multicellular and
autotrophic.
(iii) They reproduce by spore-formation.
Spiral
(iv) Their plant body structure is flat, ribbon-like, Ulva Chara chloroplasts Spirogyra
long, without true roots, stem and leaves.
Classification of Plants 103

(i) Spirogyra belongs to the division thallophyta. (ii) This group of plants, which do not have
They are called as algae. specific parts like root-stem-leaves-flowers
(ii) It grows mainly in water. but are autotrophic due to the presence of
(iii) It does not have specific parts like root-stem- chlorophyll are called algae.
leaves-flowers but are autotrophic due to the (iii) Algae show great diversity. They may be
presence of chlorophyll. unicellular or multicellular and microscopic
(iv) The plant body of Spirogyra is soft and fibre-like. or large.
(2) Funaria and Marchantia (Bryophyta) (iv) Some of these are found in fresh water while
some are found in saline water.
Ans.
(v) Various types of fungi like yeasts and moulds
Capsule Capsule
Capsule which do not have chlorophyll are also
included in this group.
Stalk
Stalk (vi) Examples: Spirogyra, Ulothrix, Ulva etc.
leaf -
like parts (2) Write the characteristics of Gymnosperms.
leaf -
like parts Ans.
(i) Gymnosperms are mostly evergreen, perennial
Rhizoids leaf -
like parts and woody.
Rhizoids
(ii) Their stems are without branches.
Funaria Marchantia Anthoceros
(iii) The leaves form a crown.
(i) These plants are called ‘amphibians‘ of the (iv) These plants bear male and female flowers on
plant kingdom because they grow mostly in different sporophylls of the same plant.
soil and need water for reproduction. (v) Seeds of these plants do not have natural
(ii) They do not have specific tissues for coverings, i.e. these plants do not form
conduction of food and water. fruits and are therefore called gymnosperms
(3) Fern (Pteridophyta): (gmnos: naked, sperms: seeds)
Ans. (vi) Examples: Cycas, Picea (christmas tree), Thuja,
Pinus (deodar) etc.
leaflets
Q.9. Distinguish between:
(1) Bryophyta and Pteridophyta:
Bryophyta Pteridophyta
(1) Bryophytes grow in (1) Pteridophytes grow
soil but need water in soil.
for reproduction.
(2) Plant body is (2) Plant body is
without specific differentiated into
roots
Sporangia in sori parts like true roots, true roots, stem and
on leaflet Ferns stem and leaves. leaves.
(3) Conducting tissues (3) Conducting tissues
(i) They have well developed roots, stem and
for food and water for food and water
leaves for conduction of food and water.
absent. present.
(ii) They do not bear flowers and fruits.
(4) Examples: (4) Examples:
Q.8. Answer in brief: Moss (Funaria), Nephrolepis, Marsilea,
(1) Write the characteristics of Thallophyta. Marchantia, Pteris, Adiantum,
Ans. Anthoceros, etc. Lycopodium etc.
(i) Thallophyta plants grow mainly in water.
104 Master Key Science & Technology (Term - I) (Std. IX)

(2) Angiosperms and Gymnosperms. in animal cells. Organelles like centrosome are
absent in plant cell whereas they are present
Angiosperms Gymnosperms
in animal cells.
(1) In Angiosperms, (1) In Gymnosperms,
the stems have the stems are Q.11. Use your brain power:
branches. without branches. * (1) What is the similarity between the plants
(2) Reproductive (2) Reprodcutive of the groups Thallophyta, Bryophyta and
organs are flowers. organs are cones. Pteridophyta irrespective of differences in
their body structure?
(3) Seeds are enclosed (3) Seeds are not
Ans.
in natural coverings, enclosed in natural
i.e., fruits. coverings. (i) All the three divisions thallophyta, bryophyta
(4) Examples: (4) Examples: and pteridophyta are autotrophic. They
Mango, Bamboo etc. Cycas, Picea etc. contain chlorophyll and can prepare this own
food by photosynthesis.
(3) Cryptogams and Phanrogams.
(ii) All these plants reproduce by spore formation.
Cryptogams Phanrogams (iii) They are all called Cryptogams as their
(1) Their reproductive (1) Their reporductive reproductive organs cannot be seen.
organs are hidden. organs are exposed. (Cryptos : hidden, gams: reproductive organs)
(2) They reproduce by (2) They reproduce by Q.12. Activity based Question / Observe and discuss.
forming spores. forming seeds.
(1) You may have seen a lush green soft carpet
(3) They are less (3) They are highly on old walls, bricks and rocks in the rainy
evolved plants. evolved plants. season. Scrape it gently with a small ruler,
(4) They are divided (4) They are divided observe it under a magnifying lens and
into thallophyta, into gymnosperms discuss.
bryophyta, and angiosperms. Ans.
pteridophyta. (i) It shows considerable tissue complexity and
* (4) Dicots and Monocots. differntiated into two main parts: a root and a
shoot.
Dicots Monocots
(ii) They have a variety of specialised tissues
Seed Two cotyledons Single cotyledon within these two regions of the body.
Root Well developed, Fibrous roots (iii) Same kind of cells are seen throughout the
primary root (Tap whole body except reproductive cells.
root)
(2) You may have seen ferns among the
Stem Strong, hard. e.g. Hollow, e.g. Bamboo ornamental plants in a garden. Take a leaf of
Banyan tree False, e.g. Banana fully grown fern and observe it carefully.
Disc-like, e.g. Onion. Ans.
Leaf Reticulate venation Parallel venation (i) New leaves typically expand by the unrolling
Flower Flowers with 4 or 5 Flowers with 3 parts in a tight spiral manner.
parts or in their or in multiples of (ii) The anatomy of fern leaves can either be
multiples three (trimerous). simple or highly divided.
(tetramerous or
(iii) They show the presence of spores formed
pentamerous)
along the back or posterior surface of their
Q.10. Can you tell! leaves.
* (1) Which are the special cell organelles that
differentiate plant cells from animal cells. (3) Observe all garden plants like Cycas,
Ans. Organelles like cell wall and plastids are Christmas tree, Hibisus, Lily etc. and compare
present in plant cell whereas they are absent them. Note the similarities and differences
Classification of Plants 105

among them. Which differences did you coverings whereas in angiosperms seeds are
notice in gymnosperms and angiosperms? enclosed in natural coverings called fruits.
Ans. Cycas and Christmas tree are gymnosperms, (4) Soak the seeds of corns, beans, groundnut,
whereas Hibiscus and lily are angiosperms. tamarind, mango, wheat, etc. in water for 8
Similarities: These plants have special to 10 hrs. After they are soaked, check each
structures for reproduction and produce seeds. seed to see whether it divides into two
During germination of the seed, the stored food equal halves or not and categorize them
is used for the initial growth of the embryo. accordingly.
Differences: In gymnosperms reproductive Ans. Monocots: corn, wheat (it cannot be divided
organs have cones whereas in angiosperms into equal halves)
reproductive organs have flowers. In Dicots: beans, groundnut, tamarind and
gymnosperms seeds are without natural mango (it can be divided into two equal halves)

vvv
106 Master Key Science & Technology (Term - I) (Std. IX)

ASSIGNMENT - 6
Time : 1 Hr. Marks : 30

Q. 1 (A) Complete the sentences by filling in the blanks and explain those statements: (6)
(gymnosperms, thallophyta, gamete, spore)
(1) Male and female flowers of ................. are borne on different sporophylls of the same plant.
(2) ................. plants have soft and fibre-like body.
(3) In Pteridophytes, asexual reproduction occurs by ................. formation and sexual reproduction
occurs by ................. formation.
(B) Match the columns: (4)

Column 'A' Column 'B'

(1) Ulva (a) Bryophyta
(2) Marsilea (b) Gymnosperm
(3) Marchantia (c) Pteridophyta
(4) Thuja (d) Thallophyta

(C) Select the odd man out: (2)

(1) Cycas, Pinus, Thuja, Hibiscus.
(2) Corn, Rice, Wheat, Groundnut.
Q. 2 Answer the following questions. (8)
(1) Write the characteristics of subkingdom Phanerogams.
(2) Distinguish between monocots and dicots.
(3) Sketch, label and describe the spirogyra.
(4) Write the characteristics of the plants belonging to division Bryophyta.
Q. 3 Answer the following in brief. (10)
(1) Write down the characteristics of Thallophyta with examples.
(2) Write down the characteristics of Gymnosperms with examples.
vvv
7 Energy Flow in an Ecosystem

Points to Remember:
• According to mode of nutrition organisms are classified as producers, consumers, saprotrophs
(saprophytes) and decomposers.
• Primary consumers are directly dependent on autotrophs (producers). Eg.: grasshopper,
squirrel, elephant)
• Secondary consumers use herbivores as their food. Eg.: Frog, owl, fox, etc.
• Apex or top consumers use herbivores and carnivores as their food. No animals feed on top
consumers. Eg.: Tiger, lion, etc.
• Omnivores feed on herbivores and carnivores. Eg.: Humans, bear, etc.
• Continuous interactions between producers, consumers and decomposers in a definite
sequence is called as food chain.
• Many food chains interconnected at various levels is called as food web.
• Each level in the food chain is called a trophic level. A trophic level is the step at which the
organism obtains its food in the chain.
• The initial quantity of energy goes on decreasing at every level of energy exchange. Similarly,
the number of organisms also decreases from the lowest level to the highest level. This pattern
of energy exchange in an ecosystem is called a ‘Pyramid of Energy’.
• After the death of apex consumers, their energy becomes available to the decomposers.
• Energy is passed on from one trophic level to the other. Decomposers dissipate some amount
of energy in the form of heat. However, no part of the energy ever returns to the sun. Hence,
such passage of energy is referred to as ‘one way’ transport.
• The cyclical flow of nutrients within an ecosystem is called the bio-geo-chemical cycle.
• Nutrients, necessary for the growth of organisms are continuously transferred from abiotic
to biotic factors within an ecosystem. This cycle operates continuously through the medium
of the biosphere formed by the lithosphere, atmosphere and hydrosphere.
• There a two types of bio-geo-chemical cycles - Gaseous cycle and sedimentary cycle.
• Gaseous cycle includes nitrogen, oxygen, carbon dioxide, water vapour, etc.
• Sedimentary cycle includes soil components like iron, calcium, phosphorus etc.
• The circulation and recycling of carbon from the atmosphere to living organisms and after
their death back to the atmosphere is called the carbon cycle.
• Abiotic carbon atones are circulated and recycled into biotic form mainly through
photosynthesis and respiration.
• The circulation and recycling of oxygen within the biosphere is called the oxygen cycle.
• Oxygen is released in the process of photosynthesis and used up in the process like respiration,
combustion, decomposition, corrosion, rusting, etc.

(107)
108 Master Key Science & Technology (Term - I) (Std. IX)

• The circulation and recycling of nitrogen gas into the form of different compounds through
various biotic and abiotic process in nature is called the nitrogen cycle.
• Important processes of nitrogen cycle are:
(i) Nitrogen fixation: Conversion of nitrogen into nitrates and nitrites through atmospheric,
industrial and biological processes.
(ii) Ammonification: Release of ammonia through decomposition of dead bodies and
excretory wasters of organisms.
(iii) Nitrification: Conversion of ammonia into a nitrite and then nitrate.
(iv) Denitrification: Conversion of nitrogen compounds into gaseous nitrogen.

(15) The flow of nutrients in an ecosystem is

MASTER KEY QUESTION SET - 7
.
Q.1. (A) Fill in the blanks and rewrite the (16) The cyclical flow of nutrients within an
complete statements: ecosystem is called .
(1) in, 1942 studied the food chain and (17) is an accumulation of the main
energy flow through it. abiotic gaseous nutrient materials found in
the earth’s atmosphere.
(2) After the death of apex consumers, energy
(18) Oxygen is released into the atmosphere by the
becomes available to .
process of .
(3) Green plants of the ecosystem store
(19) Charles Eiton Studied the of the Beer
in the form of food.
islands in England.
(4) Plants convert carbon dioxide into
Ans. (1) Lindeman (2) decomposers (3) solar energy
by the process of photosynthesis.
(4) carbohydrates (5) herbivores (6) oxygen
(5) Carnivores feed upon . (7) 78 (8) nitrogen (9) Charles Elton (10) Eltonian
(6) is used up in the processes like pyramid (11) Ozone (12) food chain (13) food
respiration, combustion, decomposition, web (14) heat (15) Cyclical (16) bio-geo-chemical
corrosion, rusting etc. (17) Gaseous cycle (18) photosynthesis (19) Tundra
(7) Nitrogen forms % of the atmosphere. Ecosystem

(8) Most organisms cannot use the free form of (B) Write down the correct answers for the
. sentences from the given options:
(1) is a primary consumer.
(9) first proposed the concept of
Ecological Pyramid in 1927. (a) Elephant (b) Frog (c) Owl (d) Tiger
(10) Ecological Pyramid is called . (2) is a secondary consumer.
(11) is produced from oxygen through (a) Grasshopper (b) Elephant
various atmospheric processes. (c) Frog (d) Human
(12) Interactions between producers, consumers (3) Tiger is a .
and saprophytes in a definite sequence is (a) producer (b) primary consumer
called . (c) apex consumer (d) secondary consumer
(13) Many food chains interconnected at various (4) An intricate network of food chains is called
levels is called . .
(14) Decomposers dissipate pate some amount of (a) biosphere (b) food web
energy in the form of . (c) energy pyramid (d) ecosystem
Energy Flow in an Ecosystem 109

(5) Fungi and other microbes are called . (16) Flow of energy in an ecosystem is .
(a) producers (b) consumers (a) cyclical (b) two way transport
(c) decomposers (d) omnivores (c) one way transport (d) to and fro transport
(6) Oxygen forms of the atmosphere. (17) The Indian Institute of Ecology and
(a) 78% (b) 21% (c) 10% (d) 90% Environment, Delhi, has published .
(7) Microbes which do not need oxygen are called (a) Invasive species in a changing Environment
.
(b) Encyclopaedia of Ecology and Environment
(a) producers (b) aerobes
(c) Environment and Ecology Magazine
(c) anaerobes (d) decomposers
(d) Biodiversity and Disaster Management
(8) The pattern of energy exchange in an
ecosystem is called . (18) Oxygen is released in the process of .
(a) food chain (b) food web (a) respiration (b) decomposition
(c) pyramid of energy (d) trophic levels (c) combustion (d) photosynthesis
(9) Carbon atoms are circulated and recycled (19) cycle is a gaseous cycle.
through . (a) Carbon (b) Phosphorus
(a) nitrification and denitrification (c) Calcium (d) Iron
(b) photosynthesis and respiration (20) is a sedimentary cycli.
(c) respiration and nitrification (a) Carbon (b) Nitrogen (c) Oxygen (d) Calcium
(d) photosynthesis and ammonification
Ans. (1) Elephant (2) Frog (3) apex consumer
(10) Carbon dioxide is released into the atmosphere (4) food web (5) decomposers (6) 21% (7) anaerobes
through . (8) pyramid of energy (9) photosynthesis and
(a) burning of fossil fuels (b) volcanic activity respiration (10) all of these (11) nitrification
(c) respiration (d) all of these (12) denitrification (13) nitrogen (14) decreases
(11) Conversion of ammonia into a nitrite and then (15) sun (16) one way transport (17) Encyclopaedia
nitrate is called . of Ecology and Environment (18) photosynthesis
(a) nitrogen fixation (b) denitrification (19) carbon (20) Calcium
(c) nitrification (d) nitrogen fixation *(C) Complete the following table:
(12) Conversion of nitrogen compounds into
gaseous nitrogen is called . Bio-geo-
chemical Biotic Processes Abiotic Processes
(a) nitrogen fixation (b) denitrification
cycles
(c) ammonification (d) nitrification
(13) is an important component of (1) Carbon Photosynthesis, Burning of fossil
proteins and nucleic acids. cycle Respiration, fuels, forest fires,
Decomposition. volcanic activity.
(a) Carbon (b) Nitrogen
(c) Phosphorus (d) Oxygen (2) Oxygen Photosynthesis, Combustion,
(14) Amount of matter and energy from cycle Respiration, Corrosion,
the lowest level to the highest level. Decomposition. rusting, formation
(a) decreases (b) increases of ozone (O3).
(c) remains the same (d) multiplies (3) Nitrogen Biological Atmospheric
(15) is the most important source of cycle nitrogen fixation, nitrogen fixation,
energy in any ecosystem. ammonification, industrial
nitrification, nitrogen fixation.
(a) sun (b) moon
denitrification.
(c) producers (d) decomposers
110 Master Key Science & Technology (Term - I) (Std. IX)

*(D) Correct and rewrite the following increasing at every level in a food chain.
statements and justify your corrections: Ans. False, The amount of matter and energy goes
(a) Carnivores occupy the second trophic level in on decreasing at every level in a food chain.
the food chain. (8) Robert Brown first proposed the concept of
Ans. False. Producers form the first trophic level Ecological Pyramid.
in the food chain. Herbivores depend directly Ans. False, Charles Elton first proposed the concept
on producers. So they form the second of ecological pyramid.
trophic level whereas carnivores depend on
(9) After the death of apex consumers, the energy
herbivores so they form the third trophic level
becomes available to decomposers.
in the food chain.
Ans. True.
(b) The flow of nutrients in an ecosystem is
(10) The gaseous cycle is a speedier cycle than the
considered to be a ‘one way’ transport.
sedimentary cycle.
Ans. False. The flow of nutrients in an ecosystem is
Ans. True.
cyclic. The nutrients are circulated and recycled
from the biosphere to living organisms and (11) Climatic changes and human activities
after their death back to the biosphere. seriously affect the speed, intensity and
equilibrium of bio-geo-chemical cyles.
(c) Plants in an ecosystem are called primary
consumers. Ans. True.
Ans. False. Plants are autotrophs. They produce their (12) Carbon dioxide is released in the atmosphere
own food by the process of photosynthesis. All through photosynthesis
animals in the ecosystem directly or indirectly Ans. False, Carbon dioxide is released in the
depend on plants for food. atmosphere through respiration, burning of
fossil fuels and wood, forest fires and volcanic
Q.2. State whether the following statements are
activity.
true or false and if false, write the correct
statement: (13) The equilibrium of oxygen and carbon dioxide
gases is maintained by decomposers.
(1) Herbivores occupy the third trophic level in a
food chain. Ans. False, The equilibrium of oxygen and carbon
Ans. False, herbivores occupy the second trophic dioxide gases is maintained by plants.
level in a food chain as they are directly (14) The conversion of ammonia into a nitrite and
dependent on producers. then nitrate is called nitrogen fixation.
(2) Apex consumers use herbivores and Ans. False, The conversion of ammonia into a
carnivores as their food. nitrite and then nitrate is called nitrification.
Ans. True. (15) Conversion of nitrogen compounds into
(3) Humans are apex consumers. gaseous nitrogen is called nitrogen fixation
Ans. True. Ans. False, Conversion of nitrogen compounds
(4) Omnivores feed only on carnivores. into gaseous nitrogen is called denitrification.
Ans. False, Omnivores feed on both herbivores and (16) Release of ammonia through decomposition
carnivores. of dead plants and excretory wastes of
(5) A food chain has two links. organisms is called ammonification.
Ans. False, A food chain consists of four, five or Ans. True.
more links. (17) The cyclic flow of nutrients within an
(6) The number of consumers in a food web is ecosystem is called Energy Pyramid.
fixed. Ans. False, The cyclic flow of nutrients within an
Ans. False, A food web can have many consumers. ecosystem is called bio-geo-chemical cycle.
(7) The amount of matter and energy goes on
Energy Flow in an Ecosystem 111

Q.3. Find the odd man out: (11) Microbes using oxygen : Aerobes : : Microbes
(1) Frog, Owl, Squirrel, Fox. not using oxygen :
Ans. Squirrel. It is a primary consumer whereas the Ans. (1) Apex consumer (2) Primary consumer
rest are secondary consumers. (3) Apex consumer (4) Cyclic (5) Decomposers
(6) Sedimentary cycle (7) 78% (8) Nitrogen
(2) Grasshopper, squirrel, elephant, lion.
cycle (9) Nitrogen cycle (10) Abiotic process
Ans. Lion. It is an apex consumer, the others are (11) Anaerobes
primary consumers (herbivores).
Q.5. Name the following:
(3) Nitrogen cycle, oxygen cycle, carbon cycle,
phosphorus cycle. (1) The animals that feed on herbivores.
Ans. Phosphorus cycle. It is a sedimentary cycle Ans. Carnivores.
whereas the others are gaseous cycle. (2) Organisms that feed on herbivores and
carnivores.
(4) Photosynthesis, Nitrification, Ammonification,
Denitrification. Ans. Omnivores.
Ans. Photosynthesis. It is a process in carbon and (3) Two examples of primary consumers.
oxygen cycle whereas the others are processes Ans. Grasshopper, squirrel.
in nitrogen cycle. (4) Two examples of secondary consumers.
(5) Burning of fossil fuels, forest fire, respiration, Ans. Frog, owl.
volcanic activity. (5) Two examples of Apex consumers.
Ans. Respiration. It is a biotic process of releasing Ans. Lion, Tiger.
carbon dioxide whereas the others are abiotic (6) Levels in the food chain.
processes of releasing carbon dioxide.
Ans. Trophic level.
(6) Photosynthesis, combustion, decomposition, (7) Organisms that decompose the dead bodies
corrosion. of plants and animals.
Ans. Photosynthesis. It is a process that releases Ans. Decomposers.
oxygen whereas the others use up oxygen. (8) Process which release oxygen.
Q.4. Complete the analogy: Ans. Photosynthesis.
(1) Grasshopper : primary consumer : : Tiger (9) Release of ammonia through decomposition
: of dead bodies and excretory wastes of
(2) Owl : secondary consumer : : squirrel organisms.
: Ans. Ammonification.
(3) Elephant : Primary consumer : : Lion (10) Conversion of nitrogen into nitrates and
: nitrites through atmospheric, industrial and
(4) Flow of energy : one way : : Flow of nutrients biological processes.
: Ans. Nitrogen fixation.
(5) Plants : Producers : : Bacteria and Fungi : Q.6. Match the columns:
(A) Column ‘A’ Column ‘B’
(6) Nitrogen : Gaseous cycle : : Phosphorus
: (1) Flow of nutrients. (a) Sedimentary cycle.

(7) Oxygen : 21% : : Nitrogen : (2) Flow of energy. (b) One way.
(8) Photosynthesis : Carbon cycle : : Ammonification (3) Carbon. (c) Gaseous cycle
:
(4) Phosphorus (d) Cyclical
(9) Respiration : Oxygen cycle : : Nitrification :
Ans. (1 - d) (2 - b) (3 - c) (4 - a)
(10) Respiration : Biotic process : : Combustion :
112 Master Key Science & Technology (Term - I) (Std. IX)

(iv) Decomposers dissipate some amount of

(B) Column ‘A’ Column ‘B’
energy in the form of heat.
(1) Producers (a) 2nd trophic level (v) However, no part of the energy ever returns
(2) Herbivores (b) 3rd trophic level to the sun. Hence, energy flow through an
ecosystem is ‘one way’.
(3) Carnivores (c) 1st trophic level * (2) Equilibrium is necessary in the various bio-
Ans. (1 - c) (2 - a) (3 - b) geo-chemical cycles.
Ans.
Q.7. Define the following:
(i) The cyclic flow of nutrients within an
(1) Food chain ecosystem is called bio-geo-chemical cycles.
Ans. Interactions between producers, consumers (ii) Nutrients, necessary for the growth of
and decomposers in a definite sequence is organisms are continuously transferred from
called as a food chain. abiotic to biotic factors and biotic to abiotic
(2) Food web factors with an ecosystem.
Ans. The interconnection among different food (iii) Any imbalance in the cycles will break the
chains in an ecosystem at various levels is link between the biotic and abiotic factors.
called as a food web. (iv) Therefore, equilibrium is necessary between
(3) Trophic level: bio-geo-chemical cycles.
Ans. A trophic level is the step at which the * (3) Flow of nutrients through an ecosystem is
organism obtains its food in the chain. cyclic.
(4) Pyramid of energy Ans.
Ans. The pattern of energy exchange in an (i) All organisms need nutrients for their growth.
ecosystem is called a ‘Pyramid of energy’. (ii) The nutrients carbon, oxygen, nitrogen, iron,
calcium etc. are circulated and recycled from
(5) Bio-geo-chemical cycle
the biosphere to living organisms and after
Ans. The cyclical flow of nutrients within an their death back to the biosphere.
ecosystem is called bio-geo-chemical cycle.
(iii) Nutrients are taken up by plants and then
(6) Carbon cycle passed on to the consumers.
Ans. The circulation and recycling of carbon from (iv) Eventually, after their death, all types of
the atmosphere to living organisms and after consumers, are decomposed by decomposers
their death back to the atmosphere is called like bacteria and fungi and the nutrients are
the carbon cycle.’ again released into the biosphere and is, used
(7) Oxygen cycle again by living organisms.
Ans. The circulation and recycling of oxygen within Therefore, flow of nutrients through an
the biosphere is called as oxygen cycle. ecosystem is cyclic.
(8) Nitrogen cycle Q.9. Distinguish between:
Ans. The circulation and recycling of nitrogen gas (1) Gaseous Cycle and Sedimentary Cycle.
into the form of different compounds through
Gaseous Cycle Sedimentary Cycle
various biotic and abiotic processes in nature
is called the nitrogen cycle. (1) It is an accumulation (1) It is an accumulation
Q.8. Give scientific reasons: of the main abiotic of the main abiotic
gaseous nutrient nutrient materials
* (1) Energy flow through an ecosystem is ‘one
materials found found in the soil,
way’.
in the earth’s sediment and
Ans. atmosphere. sedimentary rocks,
(i) The sun is the most important source of energy etc. of the earth.
in any ecosystem.
(ii) Green plants of the ecosystem store some (2) It includes nitrogen, (2) It includes soil
amount of solar energy in the form of food. oxygen, carbon components like
(iii) Before reaching the decomposers, this energy dioxide, water iron, calcium,
is passed on from one trophic level to the next. vapour etc. phosphorus etc.
Energy Flow in an Ecosystem 113

(2) Carbon Cycle and Nitrogen Cycle. (ii) A trophic level is the step at which the
organism obtains its food in the chain.
Carbon Cycle Nitrogen Cycle
(iii) The amount of matter and energy gradually
(1) The circulation (1) The circulation
decreases from producers at lowest level to
and recycling of and recycling of
carbon from the nitrogen into the top consumers at the highest level.
atmosphere to living form of different (2) Food web.
organisms and after compounds through Ans.
their death back to various biotic and
the atmosphere is abiotic processes in (i) An ecosystem consists of many food chains
called carbon cycle. nature is called the that are interconnected at various levels. This
nitrogen cycle. is called food web.

(2) Main processes (2) Main processes (ii) A organism may be the prey for many other
involved in involved in organisms.
carbon cycle are nitrogen cycle are (iii) For example, an insect feeds upon leaves of
photosynthesis and nitrogen fixation, various plants but the same insect is the prey
respiration. ammonification, for different animals like wall lizards, birds etc.
nitrification and
(iv) This forms an intricate web instead of a linear
denitrification.
food chain. Such an intricate network is called
(3) Carbon in the form (3) Nitrogen gas as food web.
of carbon dioxide cannot be directly (v) Generally food webs are formed everywhere
is directly absorbed absorbed by plants. in nature.
by plants for So nitrogen is fixed
(3) Pyramid of Energy.
photosynthesis. by the process of
nitrogen fixation
and then absorbed 10 kcal
from the soil. Humans
* (3) Flow of matter and Flow of energy.
100 kcal
Flow of matter Flow of energy Fishes

(1) It involves (1) It involves the 1000 kcal

Zooplanktons
circulation and flow of energy
recycling of from one trophic 10,000 kcal
nutrients in a cyclic level to another in Phytoplanktons
manner within the unidirectional or
Energy Pyramid
biosphere. non-cyclic manner.
Ans.
(2) There is no (2) There is dissipation (i) Each level in the food chain is called a trophic
dissipation of matter of energy at every level.
at any level. level.
(ii) The amount of matter and energy gradually
(3) Biosphere is the (3) Sun is the most decreases from producers at lowest level to
source of nutrients. important source of top consumers at the highest level.
energy. (iii) The initial quantity of energy goes on
decreasing at every level of energy exchange.
Q.10. Write short notes on:
(iv) Similarly, the number of organisms also decreases
(1) Trophic level.
from the lowest level to the highest level.
Ans.
(v) This pattern of energy exchange in an
(i) Each level in the food chain is called a trophic
ecosystem is called a Pyramid of energy.
level.
114 Master Key Science & Technology (Term - I) (Std. IX)

Q.12. Answer the following: through decomposition of dead bodies and

(1) What is the importance of oxygen? excretory wastes of organisms is called as
ammonification.
Ans.
(i) Oxygen forms 21% of the atmosphere. (4) What is nitrification?
(ii) It is also present in hydrosphere and lithosphere. Ans.
(i) Ammonia is converted first into a nitrite and
(iii) Oxygen is required for the process of
then nitrate.
respiration, combustion, decomposition,
(ii) This conversion of ammonia into a nitrite and
corrosion, rusting etc.
then a nitrate is called as nitrification.
(iv) Oxygen is important for the synthesis of
(5) What is denitrification?
proteins, carbohydrates and fats.
Ans.
(v) It is also used in various chemical reaction.
(i) Nitrogen compounds in the soil are converted
(vi) Ozone (O3) is produced from oxygen through into free gaseous nitrogen by the denitrifying
various atmospheric processes. This ozone bacteria present in the soil.
layer protects us from the harmful ultraviolet (ii) This process of conversion of nitrogen
rays of the sun. compounds into gaseous nitrogen is called as
(2) What is nitrogen fixation? How does it take denitrification.
place? (6) Write the balanced chemical equations for
Ans. The process of conversion of free nitrogen gas photosynthesis and respiration.
of the atmosphere into nitrogen compounds is Ans.
called as nitrogen fixation. (i) Photosynthesis:
It takes place in following ways: Sunlight
(a) Atmospheric nitrogen fixation: 6CO2 + 12H2O C H O + 6H2O+6O2
Chlorophyll 6 12 6
(i) Lightning results in a reaction between
nitrogen and oxygen present in the air to (ii) Respiration:
Mitochondria
produce oxides of nitrogen. C6H12 + 6O2 6CO2 + 6H2O
(ii) These oxides dissolve in rainwater + Energy
forming dilute nitric acid. (7) The cycle of gases and the sedimentary cycle
(iii) This nitric acid reacts with the alkalis cannot be completely separated from each
of the soil (like limestone) to turn into other. Give two examples to support this
nitrates. statement.

(b) Biological nitrogen fixation: Ans.

(i) Nitrogen is present in the form of a gas in the
(i) It is the conversion of atmospheric
atmosphere and in the form of compounds
nitrogen into nitrogen compounds by
like nitrogen oxide in the soil and sediments.
living organisms.
(ii) Similarly, carbon, occurs in abiotic form
(ii) Nitrogen fixing bacteria, called rhizobium
mainly in coal, granite, diamond, limestone,
are found in the root nodules of the
etc. in the earth’s crust and in form of carbon
leguminous plants. dioxide gas in the atmosphere.
(iii) They can fix atmospheric nitrogen into (iii) Therefore, the cycle of gases and the
nitrates. sedimentary cycle cannot be completely
(3) What is ammonification? separated from one another.
Ans. (8) How does interaction take place between
(i) When plants and animalls die, their remains biotic and abiotic factors of an ecosystem?
are converted into ammonia and ammonium Ans.
compounds by decay bacteria and fungi
(i) All living organisms depend upon abiotic
(decomposers) present in the soil.
factors.
(ii) This process of release of ammonia
(ii) Plants use the abiotic factors like carbon
Energy Flow in an Ecosystem 115

dioxide, water and energy from the sun to (ii) Human activities that are known to be
produce food by photosynthesis. environmentally unfriendly can disrupt this
(iii) Also, the type of soil and the climatic balance.
conditions determine the type of flora and (iii) We should avoid deforestation as trees play
fauna in that region. an important role in maintaining the balance.
(iv) Thus, the biotic and abiotic factors interact (iv) We should avoid overuse of fertilizers. The
with each other through biogeochemical fertilizers get washed away in the nearby
cycles. water bodies disrupting the balance.
(9) (i) Make a list of the various consumers of (v) Avoid burning of fossil fuels as these fuels
the ecosystem around you and classify release a large amount of carbon in the form
them according to mode of nutrition. of carbondioxide thus disrupting the balance.
Ans. (vi) Vehicular emissions is another contributor to
the disruption in balance of the various cycles.
Primary Secondary Apex Mixed
These emissions release oxides of nitrogen and
Consumers Consumers Consumers Consumers
carbon and other hazardous air pollutants. So
Rabbit, Frog, owl, Tiger, lion, Humans, we must use better quality fuel like CNG or
Deer, fox, lizards crocodiles, bears, crows ethanol to reduce vehicular emissions.
Monkey, Leopards *(2) Explain in detail the inter-relationship
Zebra, Birds between the food chain and food web.
(ii) Pictures of various organisms are given Ans.
below. Construct a food web from these (i) Interaction go on continuously between
pictures. producers, consumers and decomposers.
Ans. Food web (diagram) (ii) There is a definite sequence in these
interactions which is called the food chain.
(iii) Each chain consists of four, five or more links.
(iv) An ecosystem consists of many food chains
that are interconnected at various levels. Thus
a food web is formed.
(v) An organism may be the prey for many other
organisms.
(vi) For example, an insect feeds upon leaves of
various plants but the same insect is the prey
for different animals like frog, wall lizard,
birds, etc.
(vii) Thus many food chains interconnected
together form an intricate web called as food
web.
*(3) State the different types of bio-geo-chemical
cycles and explain the importance of these cycles.
Q.13. Answer in brief: Ans.
*(1) What would you do to help maintain the (i) The different types of bio-geo-chemical cycles
equilibrium in the various bio-geo-chemical are nitrogen, oxygen, carbon, water vapour,
cycles? Explain in brief. iron, calcium, phosphorus, etc.
Ans. (ii) Nutrients, necessary for the growth of the
(i) Biogeochemical cycles always involve the organisms are continuously transferred from
achievement of equilibrium, i.e., a balance abiotic to biotic factors and biotic to abiotic
in the cycling of the nutrients between the factors within an ecosystem.
spheres. (iii) These cycles operate continuously through
the medium of the biosphere formed by the
116 Master Key Science & Technology (Term - I) (Std. IX)

lithosphere, atmosphere and hydrosphere. components into gaseous nitrogen.

(iv) The recycling of biological, geological and (6) Explain the following questions with
chemical sources of nutrients takes place suitable diagrammatic representation:
through these cycles. *(a) Carbon cycle.
(v) Nutrients from the biosphere enter the bodies Ans.
of plants and animals. Eventually, after death,
all types of consumers are decomposed by
decomposers like bacteria and fungi and they Sunlight
CO2 from factories
are again released into the biosphere and are
used again by living organisms.
(vi) Therefore these cycles helps in maintaining Respiration in plants
the flow of nutrients and energy through Respiration in
ecosystem and maintaining the equilibrium in Biotic carbon animals
the ecosystem.
*(4) Explain the following with suitable example.
What type of changes occur in the amount Biotic
of energy during its transfer from plants to decompositions
apex consumers? Absorption in water

Ans.
Fossil fuels
(i) Plants of the ecosystem store some of the solar
The carbon cycle
energy in the form of food.
(ii) Before reaching the decomposers, this energy (i) The circulation and recycling of carbon from
is passed on from one trophic level to the next. the atmosphere to living organisms and after
their death back to the atmosphere is called
(iii) At every trophic level, some amount of
the carbon cycle.
energy is used by the organism for its own life
processes and some amount of energy is lost (ii) Abiotic carbon atoms are circulated and
to the surroundings. recycled into biotic form mainly through
(iv) Decomposers dissipate some amount of photosynthesis and respiration. Hence, the
energy in the form of heat. carbon cycle is one of the important bio-geo-
(v) However, no part of the energy ever returns chemical cycles.
to the sun. Hence, such passage of energy is (iii) Plants convert carbon dioxide into
referred to as ‘one way’ transport. carbohydrates by the process of
(vi) Therefore energy is maximum at the base photosynthesis.
of the pyramid and is least at the apex, e.g. (iv) Similarly, they produce carbon compounds
phytoplanktons which form the base of like proteins and fats, too.
pyramid have 10,000 kcal of energy while (v) Carnivores feed upon herbivores. In this way,
humans at apex have 10 kcal of energy. biotic carbon is transported from plants to
(5) Write the important processes of nitrogen herbivores, from herbivores to carnivores and
cycle. from carnivores to apex consumers.
Ans. Main processes in the carbon cycle
(i) Nitrogen fixation: Conversion of nitrogen
into nitrates and nitrites through atmospheric, Sunlight
6CO2 + 12H2O C6H12O6 + 6H2O+6O2
industrial and biological processes. Chlorophyll
(ii) Ammonification: Release of ammonia ¯
C6H12O6 + 6O2 Mitochondria 6CO2 + 6H2O + Energy
through decomposition of dead bodies and
excretory wastes of organisms. (vi) Eventually, after death, all types of consumer,
(iii) Nitrification: Conversion of ammonia into a are decomposed by decomposers like bacteria
nitrite and then nitrate. and fungi and carbon dioxide is released
(iv) Denitrification: Conversion of nitrogen
Energy Flow in an Ecosystem 117

again into the atmosphere and is used again (4) Denitrification: Conversion of nitrogen
by living organisms. In this way, carbon compounds into gaseous nitrogen.
is continuously passed on from one living *(c) Oxygen cycle.
organism to another. After the death of living Ans.
organisms, carbon goes to the atmosphere
and is again taken up by living organisms.
*(b) Nitrogen cycle.
Ans.
Plants produce
oxygen
N2
Plants absorb
CO2 and
produce food
material
Animals breathe in
oxygen

Animals give out

CO2
Breakdown of sugar molecules by animals

The oxygen cycle

NH4
NO2
(i) Oxygen forms 21% of the atmosphere. It is also
present in the hydrosphere and lithosphere.
NH3 NO3 Circulation and recycling of oxygen within
the biosphere is called the oxygen.
(ii) This cycle, includes both the biotic and
The nitrogen cycle
abiotic components. Oxygen is continuously
(i) Nitrogen forms 78% i.e. the maximum portion produced as well as used up in the atmosphere.
of the atmosphere. It is necessary for the (iii) Oxygen is highly reactive and it readily reacts
maintenance of the cycle of nature. with other elements and compounds.
(ii) The circulation and recycling of nitrogen gas (iv) As oxygen is found in various forms like
into the form of different compounds through molecular oxygen (O2), water (H2O), carbon
various biotic and abiotic processes in nature dioxide (CO2), inorganic compounds etc, the
is called the nitrogen cycle. oxygen cycle of the biosphere is extremely
(iii) All organisms participate in the nitrogen cycle. complex.
It is an important component of proteins and (v) Oxygen is released in the process of
nucleic acids. photosynthesis whereas it is used up in
(iv) As compared to other elements, it is inactive processes like respiration, combustion,
and does not easily combine with other decomposition, corrosion, rusting, etc.
elements. Most organisms cannot use the free
*Q.14. Use your brain power:
form of nitrogen.
(1) Why are the number of tertiary consumers
(v) Important processes of nitrogen cycle.
(apex carnivores) always less than those of
(1) Nitrogen fixation: Conversion of nitrogen other consumers?
into nitrates and nitrites through atmosphere,
Ans.
industrial and biological processes.
(i) In a food chain, at each trophic level some
(2) Ammonification: Release of ammonia through
amount of energy is used by the organism for
decomposition of dead bodies and excretory
its own life processes and some amount of
wastes of organisms.
energy is lost to the surroundings in the form
(3) Nitrification: Conversion of ammonia into a of heat energy.
nitrite and then nitrate.
(ii) Therefore, after a few trophic levels, the
118 Master Key Science & Technology (Term - I) (Std. IX)

amount of energy in the food chain cannot chain, energy flows from the grass (producer)
support a higher trophic level. to the deer (primary consumer) to the tiger
(iii) Therefore, the number of tertiary consumers (secondary consumer).
is less than that of other consumers. (ii) Food chain in an aquatic ecosystem (Pond):
(2) Is the number of consumers in a food web
fixed?
Ans. No. The number of consumers in a food web is
not fixed.
(3) What will be the effect on an ecosystem if
only one type of organism in it forms the
food for several different consumers in that Algae Insects small fish big fish Fish eating bird
ecosystem?
Ans. If only one type of organism forms the food In a aquatic ecosystem algae are eaten by
for several consumers in an ecosystem, there insects. Insects are eaten by small fish, small
will be competition for that food among fish are in turn eaten by big fish. And the big
organisms. Slowly the organism that is the fish are eaten by fish eating birds. In this food
prey will go on declining and other organisms chain energy flows from the algae (producer)
will die of starvation. This will lead to an to the insects (primary consumers) to the
imbalance in the ecosystem. small fish (secondary consumers) to the big
(4) Why is balance or equilibrium necessary in a fish (tertiary consumer) and to the fish eating
food web? birds (apex consumer).
Ans. It is necessary to maintain the balance or (6) What would happen if the energy remains
equilibrium in a food web as the survival trapped in the body of apex consumers even
of consumer is dependent on another. For after their death? What will happen if there
example, the carnivorous animals will
were no decomposers like microbes and
starve and their number will dwindle due
fungi in nature?
to starvation if the primary consumers are
removed from the food web. On the other Ans.
side, if secondary consumers are removed (i) After the death of apex consumers, their
from the food web the population of primary energy becomes available to the decomposers.
consumers would remain unchecked and that If energy remains trapped in the body of apex
will directly affect the producers. Therefore consumers then energy will not be available
removing any one of the consumers from the for decomposers and they will not survive
food web would affect the whole food web in thus disturbing the balance of the ecosystem.
general.
(ii) Decomposers like microbes and fungi
(5) Explain the food chain of various ecosystems break down the bodies of dead plants and
which you have studied last year.
animals and convert them into simple carbon
Ans.
compounds. These substances easily mix with
(i) Food chain in a forest ecosystem:
air, water and soil from where they are again
absorbed by the plants and incorporated into
the food chain. If there were no decomposers,
decomposition will not happen and the
nutrients will be trapped in the bodies of
plants and animals and this will disturb the
food chain, food web and the equilibrium in
Grass Deer Tiger
the ecosystem.
In a forest ecosystem grass is eaten by a deer,
which in turn is eaten by a tiger. The grass,
deer and tiger form a food chain. In this food
Energy Flow in an Ecosystem 119

*Q.15. Think about it: play a major role in carbon cycle. Trees
(1) What happens to the energy during its absorb carbondioxide and convert it into
transfer from producers to apex consumers? food (Chemical energy) by a process of
Does it remain trapped in apex consumers? photosynthesis. Thus, carbon cycle is very
Does it remain in the body of apex consumer effective in temperate regions.
till its death? (3) Even though the carbon content on the earth
Ans. is constant, why is there a rise in temperature
(i) When energy is transferred from producers due to carbon dioxide?
to apex consumers, some amount of energy Ans. Carbon content on earth is constant but the
is used by the organisms for their own life burning of wood, and fossil fuels releases CO2
processes at every trophic level and some into the atmosphere which is a greenhouse
amount of energy is lost to the surroundings gas and causes more heat to be trapped on
as heat energy. the earth’s surface leading to increase in
(ii) No, the energy does not remain trapped temperature.
in apex consumer, it is passed on to the (4) Identify the relationship between carbon
decomposers. in the air and the rise in atmospheric
(iii) Yes, it does remain in the body of apex temperature.
consumers till its death. Only after its death Ans. There is a direct relationship between carbon
the energy is passed on to the next consumer. in air and rise in atmospheric temperature.
(2) The carbon cycle is very effective in the More the level of carbon dioxide, more the heat
temperate region. Why is it so? trapped and hence higher rise in temperature.
Ans. Temperate regions are rich in forests. Forest

vvv
120 Master Key Science & Technology (Term - I) (Std. IX)

ASSIGNMENT - 7
Time : 1 Hr. Marks : 30

Q.1. (A) Fill in the blanks: (2)

(1) Plants convert carbon dioxide into ................. by the process of photosynthesis.
(2) After the death of apex consumers, energy becomes available to ................. .
(B) Match the columns: (2)

Column ‘A’ Column ‘B’

(1) Flow of nutrients (a) Sedimentary cycle
(2) Flow of energy (b) One way
(3) Carbon (c) Gaseous cycle
(4) Phosphorus (d) Cyclical

(C) Select the odd man out: (2)

(1) Grasshopper, squirrel, elephant, lion.
(2) Photosynthesis, nitrification, ammonification, denitrification
Q.2. Answer the following questions in short: (8)
(1) Give reason : Energy flow through an ecosystem is one way.
(2) Distinguish between gaseous cycle and sedimentary cycle.
(3) Write a short note on Food web.
(4) Write a note on pyramid of energy.
Q.3. Answer the following questions in brief. (6)
(1) Explain in detail the inter-relationship between food chain and food web.
(2) What would you do to help maintain the equilibrium in the various biogeochemical cycles?
Q.4. Answer in detail: (10)
(1) Describe the carbon cycle with a suitable diagrammatic representation.
(2) Describe the oxygen cycle with a suitable diagrammatic representation.

vvv
8 121

8 Useful and Harmful Microbes

Points to Remember:
l Microbes are tiny organisms which cannot be seen with the unaided eye. They can only be seen
with the help of microscope.
l Some microbes are useful while some are harmful.

l Useful microbes:
– Lactobacilli are useful microbes that convert milk into yoghurt. They convert lactose, the
sugar in milk, into lactic acid. This process is called fermentation.
– Lactobacilli are also used to produce milk products, cider, cocoa, pickles, leavened fodder,
wine, probiotics etc.
– Rhizobium bacteria present in the root nodules of leguminous plants produce nitrogenous
compounds from atmospheric nitrogen. They supply nitrates, nitrites and amino acids to
that plant and in exchange get energy in the form of carbohydrates from it . Such a mutually
beneficial relationship is called symbiosis.
– Yeast cells convert carbohydrates into alcohol and carbon dioxide . This is called fermentation.
– Yeast is used to produce bread as it makes the bread soft, spongy and fluffy.
– Antibiotics are carbon compounds obtained from some bacteria and fungi for destroying or
preventing the growth of harmful micro-organisms. Some antibiotics are broad –spectrum
while some are narrow-spectrum.
– The antibiotic Pencillin was discovered by Alexander Fleming from the fungus Penicillium.

l Harmful Microbes:
– Fungi grow on articles like gunny bags, leather items, wooden items in the presence of
moisture and spoil them.
– Various species of fungi grow on food items like pickles, murabba, jam, sauce, chutney etc.
They release poisonous chemicals called mycotoxins and spoil them.
– Clostridium bacteria spoil cooked food and cause food poisoning.
– Different kinds of harmful bacteria, fungi and viruses cause various diseases in plants,
animals and humans.
– These diseases can be prevented by following proper preventive measures.

(121)
122 Master Key Science & Technology (Term - I) (Std. IX)

(20) Fungi release into the food, making

MASTER KEY QUESTION SET - 8
the food poisonous.
Q.1. (A) Fill in the blanks: (21) produce bottle-shaped endospores
(1) The rod-shaped bacteria found in milk or in adverse conditions.
buttermilk are called . (22) Clostridium bacteria grow in
(2) Lactobacilli are bacteria. conditions.
(3) In fermentation, the pH of milk decreases (23) conducted important research on
causing of milk proteins. the toxin responsible for gas gangrene and the
(4) Yoghurt has a specific sour taste due to antitoxin responsible for treating it.
.
(24) is a smokeless and high quality fuel.
(5) Lactobacilli kill the harmful bacteria like
in the alimentary canal and help to (25) Nowdays, seeds are coated with
improve our immunity. before sowing.
(6) Bacteria found in the root nodules of Ans. (1) lactobacilli (2) anaerobic (3) coagulation
leguminous plants are . (4) lactic acid (5) costridium (6) rhizobium
(7) symbiosis (8) Lactobacilli (9) Yeast (10) eukaryotic
(7) A mutually beneficial relationship is called
(11) sugarcane juice (12) glucose, fructose
.
(13) Alcanivorax (14) antibiotics (15) broad-
(8) bacteria convert lactose into lactic
spectrum (16) narrow-spectrum (17) National
acid.
Institute of Virology (18) penicillium (19) fungi
(9) is a unicellular fungus with 1500 (20) mycotoxins (21) Clostridium (22) anaerobic
different species in existence. (23) Ida Bengston (24) Ethanol (25) rhizobial
(10) The yeast cell is a type of cell. solution or powder
(11) Molasses is produced from .
(B) Write the sentence with the correct answer
(12) The sugars and in grape from the options given below:
juice are fermented for making wines.
(1) The lactobacilli convert lactose, the sugar in
(13) Oil spills in oceans are cleaned with the help
the milk, into .
of bacteria.
(14) Carbon compounds obtained from bacteria (a) lactic acid (b) acetic acid
and fungi for destroying or preventing the (c) alcohol (d) citric acid
growth of harmful micro-organisms are called (2) The destroys harmful microbes
. present in the milk.
(15) Antibiotics useful against wide variety of (a) high pH (b) neutral pH
bacteria are called antibiotics. (c) low pH (d) none of these
(16) When a pathogenic micro-organism is
(3) Lactobacilli kill the harmful bacteria like
difinitely known, then antibiotics
present in the alimentary canal.
are used.
(17) The in Pune undertakes research (a) rhizobium (b) saccharomyces
related to diseases like measles, jaundice, (c) clostridium (d) alcanivorax
fever and diseases of the lungs with support (4) During fermentation, yeast cells convert
from the World Health Organization. carbohydrates into .
(18) Penicillin is a group of antibiotics obtained (a) glucose and fructose
from the fungus . (b) alcohol and carbon dioxide
(19) Ants grow in their anthill and obtain (c) proteins and fats
food from it. (d) fatty acids and amino acids
Useful and Harmful Microbes 123

(5) Molasses is fermented with the help of yeast (16) Pneumonia is caused by .
called .
(a) virus (b) bacteria (c) fungi (d) protozoa
(a) Yarrowia lipolytica (b) Alcanivorax
(17) can be prevented by vaccination.
(c) Rhizobia (d) Saccharomyces
(a) Malaria (b) AIDS
(6) A yeast is used to absorb the toxins
(c) Leprosy (d) Chicken pox
released during the production of palm oil.
(18) Malaria is caused by .
(a) Yarrowia lipolytica (b) Alcanivorax
(c) Saccharomyces cereviceae (a) protozoa (b) bacteria
(d) Penicillium (c) fungi (d) virus
(7) Antibiotics mainly act against . (19) Bacteria causes .
(a) Bacteria (b) Viruses (a) malaria (b) scabies
(c) Algae (d) Fungi (c) cholera (d) bird flu
(8) is a broad-spectrum antibiotic. (20) Bird flue (H7N9) and swine flu (H1N1) are
(a) Gentamycin (b) Penicillin caused by .
(c) Amoxicillin (d) Erythromycin (a) bacteria (b) protozoa
(9) is a narrow-spectrum antibiotic. (c) fungi (d) virus

(a) Ampicillin (b) Amoxicillin Ans. (1) lactic acid (2) low pH (3) clostridium (4) alcohol
(c) Tetracyclin (d) Penicillin and carbondioxide (5) Saccharomyces (6) Yarrowia
lipolytica (7) Bacteria (8) Amoxicillin (9) Penicillin
(10) Antibiotic penicillin was discovered by
(10) Alexander Fleming (11) Clostridium (12) Viruses
.
(13) Van Ermengem (14) Virus (15) mosquito
(a) Louis Pasteur (b) Alexander Fleming bite (16) bacteria (17) Chicken pox (18) protozoa
(c) Ida Bengston (d) Van Ermengem (19) cholera (20) virus
(11) The bacteria which spoil cooked food are
(C) Complete the statements using the proper
.
option from those given below. Explain the
(a) Saccharomyces (b) Lactobacilli statements:
(c) Clostridium (d) Rhizobium
(mycotoxins, budding, rhizobium, molasses,
(12) can grow and reproduce only in living endospores, broad-spectrum, lactobacilli)
cells. * (1) Yeast reproduces asexually by the
(a) Bacteria (b) Viruses method.
(c) Fungi (d) Protozoa Ans. Budding.
(13) proved that the anaerobic bacterium The yeast cells develop small round bodies
clostridium botulinum, is responsible for food on the parent cell. These are called buds. New
poisoning. daughter cells develop from these buds.
(a) Louis Pasteur (b) Ida Bengston * (2) Toxins of fungal origin are called .
(c) Alexander Fleming (d) Van Ermengem Ans. Mycotoxins.
(14) AIDS is caused by . Mycotoxins are poisonous chemicals released
(a) Virus (b) Bacteria (c) Protozoa (d) Fungi into the food by fungi. This makes the food
poisonous.
(15) Dengue is caused by .
(3) bacteria are used for making yoghurt.
(a) droplets spread in air
Ans. Lactobacilli.
(b) contact with infected person
(c) mosquito bite The lactobacilli convert lactose, the sugar in
(d) contaminated water and food the milk, into lactic acid. As a result, the pH
124 Master Key Science & Technology (Term - I) (Std. IX)

of milk decreases causing coagulation of milk (5) Yeast cell is a prokaryotic cell.
proteins. Milk changes into yoghurt. Ans. False: Yeast cell is an eukaryotic cell.
(4) The use of has helped to reduce the (6) The use of rhizobium has helped to reduce the
use of chemical fertilizers. use of chemical fertilizers.
Ans. Rhizobium. Ans. True.
Rhizobium bacteria are found in the root (7) Ethanol is a smokeless and high quality fuel.
nodules of leguminous plants. They help to
Ans. True.
convert atmospheric nitrogen into nitrogen
compounds and provide it to the plants. This (8) A yeast, Saccharomyces cereviceae is used for
helps to reduce the use of chemical fertilizers absorbing toxins released during palm oil
and their adverse effects. production.
(5) Amoxicillin is a antibiotic. Ans. False: A yeast, Yarrowia lipolytica is used
to absorb the toxins released during the
Ans. Broad-spectrum.
production of palm oil.
This antibiotic is useful against a wide variety
(9) Gentamycin is a narrow-spectrum antibiotic.
of bacteria. It is used against pathogens which
connot be identified during symptoms of a Ans. True.
disease. (10) Antibiotics mainly act against bacteria.
(6) Ethanol is produced by the fermentation of Ans. True.
. (11) Oil spills in oceans are cleared with the help of
Ans. Molasses. clostridium bacteria.
Molasses is produced from sugarcane juice. It Ans. False: Oil spills in oceans are cleared with the
is rich in carbohydrates. When it is fermented help of Alcanivorax bacteria.
with the help of the yeast called saccharomyces, (12) Tetracycline is a narrow-spectrum antibiotic.
ethanol (C2H5OH) is produced.
Ans. False: Tetracycline is a broad-spectrum
(7) Clostridium bacteria produce bottle-shaped antibiotic.
.
(13) Amoxicillin is a broad-spectrum antibiotic.
Ans. Endospores.
Ans. True.
These endospores help them to survive in
(14) Penicillin is a group of antibiotics obtained
adverse conditions.
from a fungus Saccharomyces.
Q.2. State whether the following statements are Ans. False: Penicillin is a group of antibiotics
true or false and if false, write the correct obtained from a fungus Penicillium.
statement:
(15) Antiobiotic penicillin was discovered by
(1) Lactobacilli are aerobic bacteria. Alexander Fleming.
Ans. False: Lactobacilli are anaerobic bacteria. Ans. True.
(2) The lactobacilli convert lactose sugar into (16) The bacteria lactobacilli cause food-poisoning.
alcohol.
Ans. False: The bacteria clostridium cause food-
Ans. False: The lactobacilli convert alctose sugar poisoning.
into lactic acid.
(17) Clostridium bacteria grow in aerobic
(3) Yoghurt has a specific sour taste due to acetic conditions.
acid.
Ans. False: Clostridium bacteria grow in anaerobic
Ans. False: Yoghurt has a specific sour taste due to conditions.
lactic acid.
(18) AIDs is caused by a virus.
(4) The bacteria clostridium are present in the
Ans. True.
root nodules of leguminous plants.
(19) Influenza is caused by a bacteria.
Ans. False: The bacteria rhizobium are present in
the root nodules of leguminous plants. Ans. False: Influenza is caused by a virus.
Useful and Harmful Microbes 125

(20) Antibiotics useful to one person can be whereas others are narrow-spectrum
suggested to others also. antibiotics.
Ans. False: Antibiotics useful to one person cannot
*(B) Write the names of the microbes found
be suggested to others as different diseases
in following food materials:
require different antibiotics.
yoghurt, bread, root nodules of leguminous plants,
(21) Dengue is caused by a bacteria.
idli, dosa, spoiled potato curry.
Ans. False: Dengue is caused by a virus.
Ans. Yoghurt - Lactobacilli
(22) Dandruff and ringworm are caused by fungi.
Bread - Yeast
Ans. True.
Root nodules of leguminous plants -
(23) Pneumonia is spread through droplets spread Rhizobium
in air by infected person.
Idli - Yeast, bacteria
Ans. True.
Dosa - Yeast, bacteria
(24) Chicken pox is spread due to contaminated
Spoiled potato curry - Clostridium
food and water.
Ans. False: Chicken pox is spread due to contact Q.4. Complete the analogy:
with infected person. (1) Dengue : Virus : : Malaria : .
(25) Ida Bengston was honoured with the ‘Typhoid Ans. Protozoa.
Medal’ in 1947. (2) Hepatitis : Virus : : Pneumonia : .
Ans. False: Ida Bengston was honoured with the Ans. Bacteria.
‘Typhus Medal’ in 1947. (3) Cholera : Bacteria : : Swine flu : .
Q.3. (A) Find the odd man out: Ans. Virus.
* (1) Pneumonia, Diphtheria, Chickenpox, Cholera. (4) Swine flu : H1N1 : : Bird Flu : .
Ans. Chickenpox. It is caused by a virus whereas Ans. H7N9.
others are caused by bacteria. (5) Measles : Virus : : Ringworm : .
* (2) Lactobacilli, Rhizobia, Yeast, Clostridia. Ans. Fungi.
Ans. Yeast. It is a fungus whereas the rest are (6) Yoghurt : Lactobacilli : : Bread : .
bacteria. Ans. Yeast.
* (3) Root rot, rust (tambere), rubella, mozaic. (7) Oil spills : Alcanivorax : : Absorption of
Ans. Rubella. It is a disease of humans whereas the arsenic : .
rest are diseases of plants. Ans. Saccharomyces cereviceae.
(4) AIDS, Hepatitis, Leprosy, Dengue. (8) Rhizobium : Nitrogen fixation : : Clostridium
Ans. Leprosy. It is caused by bacteria whereas the : .
rest are caused by viruses. Ans. Food poisoning.
(5) Cholera, Leprosy, Pneumonia, Influenza.
Q.5. Match the columns:
Ans. Influenza. It is caused by a virus whereas the
rest are caused by bacteria. *(1) Column ‘A’ Column ‘B’
(6) Ampicillin, Amoxycillin, Penicillin, (1) Rhizobium (a) Food poisoning
Tetracycline. (2) Clostridium (b) Nitrogen fixation
Ans. Penicillin. It is a narrow-spectrum antibiotic (3) Penicillium (c) Bakery products
whereas others are broad-spectrum antibiotics. (d) Production of
(4) Yeast
(7) Tetracycline, Penicillin, Gentamycin, antibiotics
Erythromycin.
Ans. (1 - b), (2 - a), (3 - d), (4 - c)
Ans. Tetracycline. It is a broad-spectrum antibiotic
126 Master Key Science & Technology (Term - I) (Std. IX)

(2) Column ‘A’ Column ‘B’ Ans.

(i) Antibiotics are a group of medicines used
(1) Leprosy (a) Virus to kill disease - causing bacteria and certain
(2) Ringworm (b) Fungi protozoa.
(3) Influenza (c) Protozoa (ii) The doctor selects and prescribes the antibiotic
(4) Malaria (d) Bacteria best suited for our disease.
(iii) If taken in extra dose, they can kill the useful
Ans. (1 - d), (2 - b), (3 - a), (4 - c)
bacteria present in our body.
Q.6. Give reasons: (iv) If the course of antibiotics is not completed, the
* (1) Foam accumulates on the surface of ‘dal’ bacteria develop resistance to that antibiotic
kept for a long time in summer. making it ineffective.
Ans. (v) Therefore, antibiotics should be taken only
when prescribed by a doctor.
(i) Dal is rich in proteins.
(5) Nowadays, seeds are coated with rhizobial
(ii) During summer, bacteria attack the dal and
solution or powder before sowing.
cause fermentation resulting in the production
of carbon dioxide gas. Ans.

(iii) Therefore foam accumulates on the surface of (i) When seeds coated with rhizobial solution or
powder are sown, rhizobia enter the plantlets.
the ‘dal’ kept for long time in summer.
(ii) This is called rhizobial inoculation.
* (2) Why are naphthalene balls kept with clothes
(iii) Rhizobia can produce nitrogenous compounds
to be put away?
from atmospheric nitrogen.
Ans.
(iv) This experiment has helped in the supply of
(i) Naphthalene balls are balls of chemical nitrogen to cereal and other crops, besides
pesticide and deodorant. leguminous crops.
(ii) They help to kill or repel insects such as moths, (v) Therefore, nowadays seeds are coated with
cockroaches, mice etc. rhizobial solution or powder before sowing.
(iii) Therefore, naphthalene balls are kept with (6) Antibiotics are not effective against common
clothes to be put away to prevent clothes from cold or influenza.
getting damaged. Ans.
(3) Lactobacilli are used for making yoghurt (i) Antibiotics are a group of medicines used to
from milk. control inflections caused by bacteria.
Ans. (ii) Common cold or influenza is caused by a
(i) Lactobacilli convert lactose, the sugar in the virus.
milk, into lactic acid. This process is called (iii) Antibiotics are not effective against viruses.
fermentation. (iv) Therefore antibiotics are not effective against
(ii) As a result, the pH of milk decreases causing common cold or influenza.
coagulation of milk proteins. (7) Cotton fabrics, gunny bags, leather items
(iii) Thus, milk proteins are separated from other and wooden items do not last long.
constituents of milk and milk changes into Ans.
yoghurt. (i) Microscopic spores of fungi are present in the
(iv) Yoghurt has a specific sour taste due to lactic air.
acid. The low pH destroys harmful microbes (ii) If there is sufficient moisture, spores germinate
present in the milk. Therefore, lactobacilli are on cotton fabric, gunny bags, leather, wooden
used for making yoghurt from milk. items etc.
(4) Antibiotics should be taken only when (iii) The fungal hyphae (fires of the fungus)
prescribed by a doctor. penetrate deep into the material to obtain
nutrition and to reproduce.
Useful and Harmful Microbes 127

(iv) This causes the materials to wear and become the growth of harmful micro-organisms are
weak. called antibiotics.
(v) As a result, cotton fabric, gunny bags, leather (ii) Antibiotics, a discovery of the 20th century,
and wooden items do not last long. have brought a revolution in the field of
medicine.
(8) Food on which fungi has grown cannot be
(iii) Antibiotics mainly act against bacteria. Some
eaten.
antibiotics can destroy protozoa.
Ans.
(iv) Some antibiotics are useful against a wide
(i) Various species of fungi grow on food items
variety of bacteria they are called broad-
like pickles, murabba, jam, sauce, chutney etc.
spectrum antibiotics . Examples - ampicillin,
(ii) They use the nutrients in these food items for amoxicillin, tetracycline, etc.
growth and reproduction.
(v) When the pathogen cannot be identified even
(iii) During this activity, fungi release mycotoxins, though the symptoms of disease are visible,
certain poisonous chemicals, into the food and broad spectrum antibiotics are used.
thus food becomes poisonous.
(vi) Whenever a pathogenic micro-organism is
(iv) Hence, the food on which fungi have grown definitely known, then narrow-spectrum
cannot be eaten. antibiotics are used. Examples : Penicillin,
Q.7. Write short notes: gentamycin, erythromycin, etc.

(1) Rhizobial inoculation. (4) Clostridium.

Ans. Ans.
(i) Nowadays seeds are coated with rhizobial (i) Clostridium are the bacteria that spoil food.
solution or powder before sowing. (ii) Out of about 100 different species of this
(ii) After sowing, rhizobia enter the plantlets. bacterium, some are free living in the soil
(iii) This is called rhizobial inoculation. wheras some live in the alimentary canals of
the humans and other animals.
(iv) In this experiment has helped in the supply
of nitrogen to cereal and other crops, besides (iii) These bacteria are rod-shaped and produce
leguminous crops. bottle-shaped endospores in adverse
conditions.
(2) Bio-remediation.
(iv) One special characteristic of these bacteria is
Ans. that they cannot withstand the normal oxygen
(i) Bio-remediation is a technique that involves level of the air because they grow in anaerobic
the use of organisms to break down conditions.
environmental pollutants.
(ii) Generally, fungi like yeast and bacteria are Q.8. Answer the following questions:
used for bio-remediation. * (1) Which vaccincs are given to infants? Why?
(iii) A yeast, Yarrowia lipolytica is used to absorb Ans.
the toxins released during the production of (i) Hepatitis A and B, DTP (Diphtheris, Tetanus,
palm oil and the heavy metals and minerals Pertussis.) Polio, MMR (Measles, Mumps,
released in some other industrial processes. Rubella), Chicken pox, Influenza, Tetanus,
(iv) Saccharomyces cereviceae is used for absorption BCG, Rotavirus etc.
of a pollutant, arsenic. (ii) Vaccines consist of dead or weakend microbes.
(v) Oil spills in oceans are cleaned with the help When these are swallowed or injected, the
of Alcanivorax bacteria. body produces antibodies to fight them. These
(3) Antibiotics. antibodies remain in the body and protect it
Ans. from any future attack of the disease causing
microbes. Therefore, vaccines are given to
(i) Carbon compounds obtained from some
infants for preventing diseases.
bacteria and fungi for destroying or preventing
128 Master Key Science & Technology (Term - I) (Std. IX)

* (2) How is a vaccine produced? (ii) In the process of obtaining nutrition, yeast
Ans. cells convert the carbohydrates into alcohol
(i) Vaccines are made using the disease causing and carbon dioxide. This process is called
bacteria or virus but in a form that will not fermentation.
harm the human beings. (iii) The bubbles of carbon dioxide given off cause
(ii) Vaccine is made from dead or weakened the dough to rise.
microbes or their toxins. (iv) This dough can be used to make bread.
(iii) Vaccine stimulates the immune system to (v) When this dough is baked, more bubbles of
produce antibodies which give lift-long carbon dioxide are formed due to heat. As the
protection against the disease. gas escapes, the bread rises and becomes soft
(iv) There are specific vaccines for specific diseases. and fluffy.
* (3) How do antibiotics cure disease? (7) What is the advantage of Rhizobium to
Ans. farmers?
(i) Antibiotics cure diseases by destroying or Ans.
preventing the growth of harmful micro- (i) The use of rhizobium has helped to reduce the
organisms. use of chemical fertilizers and thereby their
* (4) Are the antibiotics given to humans and adverse effects.
animals the same? Why? (ii) It has also helped to reduce expenses on
Ans. fertilizers and thus beneffited the farmers.
(i) Generally antibiotics work against any (8) How can we observe lactobacilli in buttermilk?
harmful bacteria, whether it is attacking Ans.
humans or animals.
(i) Smear a drop of fresh buttermilk on a glass
(ii) But some of them are better suited to humans slide.
while some are better for animals. This is due
(ii) Stain it with methylene blue and put a
to the adverse effects they show in different
coverslip over it.
species.
(iii) Observe the smear under the 10X objective of
(iii) Also, the dosages of antibiotics for humans
and animals differ. a compound microscope and then with the
more powerful 60X objective.
* (5) Why is it necessary to safely store the
pathogens of a discase against which (iv) The blue rod-shaped organisms moving about
vaccines are to be produced? are lactobacilli.
Ans. * (9) What is fermentation?
(i) Pathogens are microbes which can cause Ans.
diseases in us. (i) Yeast uses sugar for food.
(ii) For the preparation of a vaccine, a particular (ii) Yeast grows and multiplies rapidly due to the
pathogen is cultured and grown in a laboratory. carbon compounds in the sugar solution.
(iii) If these pathogens are not safely stored, they (iii) In the process of obtaining nutrition, yeast
many get modified due to environmental cells convert the carbohydrates in the food
factors, resulting in decrease in the efficiency into alcohol and carbondioxide.
of the vaccine.
(iv) Also, the bacteria lactobacilli convert lactose,
(iv) Also, the live pathogens may escape and cause
the sugar in milk into lactic acid.
diseases in us.
(v) This process is called fermentation.
(6) How is bread made?
(10) What is symbiosis? Give example.
Ans.
Ans.
(i) Bread is made using flour, yeast, salt and
water. The yeast uses sugar as food. (i) Symbiosis is a mutually beneficial relationship.
Useful and Harmful Microbes 129

(ii) Example: Rhizobia living in root rodules of (iv) Leavened fodder offered to domestic cattle
leguminous plants supply nitrates, nitrites like cows and buffaloes is fodder fermented
and amino acids to that plant and in exchange with the help of lactobacilli.
get energy in the form of carbohydrates. (v) The lactobacilli fermentation process is used
(11) Name different species of clostridium to make wine and some types of bread.
bacteria and the diseases caused by them. (3) What is Penicillin? What is it used for?
Ans. Ans.
(i) Clostridium tetani - Tetanus (i) Penicillin is a group of antibiotics obtained
(ii) Clostridium Perfringens - Food poisoning from a fungus, penicillium.
(iii) Clostridium botulinum - Botulism (Paralysis (ii) It is used for controlling the infections caused
of muscles) by bacteria like staphylococci, clostridia,
(iv) Clostridium difficile - colitis (Infection of streptococci etc.
intestive) (iii) Medicines containing penicillin are useful
to treat certain bacterial infections of the ear,
Q.9. Answer in brief:
nose, throat and skin as well as diseases like
(1) How is alcohol produced? pneumonia and scarlet fever.
Ans.
(4) How was the antibiotic penicillin discovered?
(i) Alcohol is often produced along with sugar in
Ans.
sugar factories.
(i) Alexander Fleming, a professor of
(ii) Molasses is produced from sugarcane juice. It microbiology at St. Mary’s Hospital had
is rich in carbohydrates. cultured varieties of bacteria and fungi in
(iii) Molasses is fermented with the help of the Petri dishes in his laboratory.
yeast saccharomyces. (ii) On 3rd September 1928, while observing
(iv) In this process, ethanol (C2H5OH) alcohol is staphylococci cultures, he made an interesting
produced as a primary product and ester and observation in one petri dish.
other alcohols are produced as secondary (iii) In that petri dish, fungal colonies had grown
products. but the area around those colonies was clean
(v) Besides molasses, maize, barley and other and clear. i.e. the bacteria had actually been
grains are also used for industrial production destroyed.
of alcohol. (iv) After further studies, he confirmed that the
(vi) Glucose and fructose, the sugars present in fungus growing there was Penicillium and its
grape juice are also fermented with the help secretion had destroyed the bacerial colonies.
of yeast to produce alcohol which is used to (v) Thus, the first antibiotic - penicillin had been
make wines. discovered accidentlly and this formed the
(2) Give the uses of Lactobacilli. basis to find cures for incurable discases.
Ans. Uses of Lactobacilli. (5) What are the precautions to be followed
(i) Various milk products like yoghurt, while taking antibiotics?
buttermilk, ghee, cheese, shrikhand, etc. can Ans.
be obtained by fermentation of milk. (i) Antibiotics should be taken only when
(ii) Lactobacilli fermentation is useful for large prescribed by a doctor.
scale production of cider, cocoa, pickles of (ii) Don’t purchase any antibiotic from medical
vegetables etc. stores without a prescription from a doctor.
(iii) Lactobacilli and some other useful microbes (iii) Don’t consume antibiotics on your own to
taken together are used to treat abdominal treat common diseases like a throat infection,
discomfort. common cold or influenza.
130 Master Key Science & Technology (Term - I) (Std. IX)

(iv) Even if you feel well before completing of the (4) Write down the modes of infection and
prescribed course of the antibiotic you must preventive measures against Malaria and
continue and complete it. dengue.
(v) Don’t suggest to others the antibiotics which Ans. Mode of infection : Mosquito bite, unclean
were useful to you. surroundings.
(6) How can we observe Rhizobium bacteria in Preventive measure : Cleanliness of
the roots of leguminous plant? surroundings, preventing stagnation of water,
Ans. controlling mosquitoes.
(i) Take a plantlet of fenugreek, groundnut or (5) Write down the modes of infection and
any other bean and sterilize it with a 3 to 5% preventive measures against Peumonia.
solution of hydrogen peroxide. Ans. Mode of infection : Droplets spread in air by
(ii) Afterwards, keep it in a 70% solution of ethyl infected person.
alcohol for 4 to 5 minutes. Preventive measure : Vaccination, avoiding
(iii) Clean the roots with sterile water and take contact with infected person.
thin sections of the root nodules.
(6) Write down the modes of infection and
(iv) Select good section and place it an a solution preventive measures for leprosy.
of safranin for 2 to 3 minutes.
Ans. Mode of infection : Long erm contact with
(v) Place the stained section on a glass slide, infected person.
cover it with a coverslip and observe it under
Preventive measure : Avoiding contact with
the compound microscope. The pinkish rod-
infected persons and their belongings.
shaped organisms are the rhizobium bacteria.
(7) What are the mode of infection and
Q.10. Write down the mode of infection and preventive measures for Hepatitis?
preventive measures for the following:
Ans. Mode of infection : Contaminated water and
* (1) Write down the modes of infection and the food.
preventive measures against fungal disease.
Preventive measure : Use clean and filtered
Ans. Mode of infection : Contact with infected water, proper storage of food.
person or his/her belongings like clothes.
(8) What are the mode of infection and
Preventive measure : Personal hygiene avoid
preventive measures for Influenza.
contact with infected person.
Ans. Mode of infection : Contact with infected
(2) Write down the causative pathogen, mode of person.
infection and preventive measures of AIDs.
Preventive measure : Personal hygiene and
Ans. Causative Pathogen : Virus. avoiding contact with infected person.
Mode of infection : Through blood and
semen of infected person and milk of mother Q.11. Can you recall?
suffering from AIDS. (1) What is meant by microbes? What are their
Preventive measure : Safe sexual contact, characteristics?
avoid resuse of needles and injections. Ans. Microbes are tiny microscopic organisms
(3) Write down the modes of infection and which cannot be seen with the unaided eye.
preventive measures against Bird Flu (H7N9) Characteristics of Microbes.
and swine Flue (H1N1). (i) They are smallest organisms on earth.
Ans. Mode of infection : Contact with infected (ii) They are composed of prokaryotic or
birds and animals. eukaryotic cells.
Preventive measure : Personal hygiene, (iii) They can be seen only with the help of
properly cooked neat. microscope.
Useful and Harmful Microbes 131

(iv) They are found in any kind of environment Q.13. Use your brain power!
ranging from coolest polar regions to hottest (1) Why do doctors advise you to take yoghurt
of deserts. Also found in soil, water and air. or buttermilk if you have indigestion or
(v) Some of them are useful whereas some of abdominal discomfort?
them are harmful micro-organisms. Ans.
Q.12. Can you tell? (i) The lactobacilli present in yoghurt or
(1) How many different industries depend upon buttermilk helps to restore the natural
the lactobacilli bacteria? microbial flora in the intestine thus helping in
Ans. Industries like milk products, cider, cocoa, digestion and absorption of nutrients.
pickles, pharmaceuticals depend on (ii) Also buttermilk helps to cool down the
lactobacilli bacteria. stomach and works as a laxative to ease the
(2) Which types of cottage industries and congestion during abdominal discomfort.
factories can be started in areas with (2) Sometimes, yoghurt becomes bitter and
abundant milk production? froths up. Why does this happen?
Ans. Cottage industries like manufacture of milk Ans. Sometimes yoghurt becomes bitter due
products like ghee, cheese, paneer, curd, to excess fermentation by bacteria. Excess
shrikhand, etc. chocolate making can be started amount of lactic acid is produced making the
in areas with abundant milk production. curd bitter.
(3) Which changes do you notice in leather (3) Which different milk products are obtained
articles and gunny (jute) bags during the at home by fermentation of the cream from
rainy season? the milk?
Ans. In rainy season we can notice whitish green Ans. Yoghurt, buttermilk, ghee, cheese, shrikhand,
cotton - like growth or black powder or white sour cream, etc.
discs on leather articles and gunny (jute) bags
during the rainy season as these articles are (4) Recently, it has been made compulsory in
infected by fungus. India and some other countries to mix 10%
ethanol with fuels like petrol and diesel.
(4) For how long afterwards can you use those
What is the reason for this?
articles?
Ans.
Ans. Those articles cannot be used for long as they
wear out and do not last long. (i) Ethanol is a smokeless and high quality fuel.
So it helps to reduce pollution when mixed
(5) Why do these articles not get spoilt during
with petrol or diesel.
the summer or winter?
(ii) As petrol or diesel is a fossil fuel less
Ans.
consumption of it will lead to resourceful use
(i) Spores of fungi can germinate when there is of it and making the country self-efficient by
sufficient moisture. moving towards sustainable fuel like ethanol.
(ii) During summer or winter the weather is hot
(5) Why are wineries located near Nashik in
and dry and so fungus cannot grow in such
Maharashtra?
weather.
(iii) Also microbes cannot survive extreme hot Ans.
or cold temperatures of summer or winter. (i) Nashik in Maharashtra is the leading grape
Therefore, these articles do not get spoilt producer in the country as it has the soil
during summer or winter. suitable for the production of grapes.
(ii) Glucose and fructose, the sugars present in
grape juice are fermented with the help of
132 Master Key Science & Technology (Term - I) (Std. IX)

yeast to produce wines. Therefore, wineries (iii) Fungi are also used to derive antibiotics like
are located near Nashik in Maharashtra. penicillin which are useful to animals.
(6) Chapattis made from wheat only swell up (iv) Ants grow fungi in their anthill and obtain
but bread becomes spongy, soft and easy to food from it.
digest. Why is it so? (v) Some species of wasps and insects lay their
Ans. eggs in the fungal bodies growing on trees
(i) The chapatti dough has water, which on thus ensuring a food supply for their larvae.
heating converts into steam and tries to (10) What is the structure of lichen, a condiment?
escape. While doing so, it lifts up the upper Where else is it used?
layer of the chapatti. Therefore, the chapatti
Ans.
swells up.
(i) Lichen is a symbiotic association between a
(ii) Bread is made by adding yeast to the flour. In
the process of obtaining nutrition, the yeast fungus and an algae (cyanobacterium).
cells convert the carbohydrates into alcohol (ii) Lichens are sensitive to environmental
and carbondioxide. When this dough is disturbances and are used in assessing air
baked, the carbon dioxide escapes out making pollution in an area.
the bread spongy, soft and easy to digest. (iii) Lichens are also used in making dyes,
(7) Salt is applied on the inner surface of pickle perfumes and in traditional medicines.
jars and the pickle is covered with oil. Why (iv) A few lichen species are eaten by insects or
is this done? animals such as reindeer.
Ans.
Q.13. Collect information.
(i) Salt acts as a preservative. It prevents the
(1) Which plant and animal diseases are caused
growth of bacteria by forcing the microbes to
lose water by osmosis. Hence, salt is applied by micro-organisms and what are the
on the inner surface of pickle jars. measures to be taken against them?

(ii) Pickle is covered with oil as oil acts as Ans. Plant diseases:
preservative. It seals off the air from the (i) Citrus canker is a bacterial disease that affects
item that is being pickled and provides an trees of citrus fruits.
environment in which microbes cannot grow. (ii) Rust of wheat is a fungal disease that affects
(8) Which preservatives are mixed with ready- wheat crops.
to-eat foods to prevent them from spoiling? (iii) Yellow vein mosaic is a viral disease which
Ans. Common salt, sugar, sodium benzoate, citric affect vegetables like bhindi (okra).
acid, sodium metabi-sulphite etc. are some
Preventive Measures:
of the preservatives mixed with ready-to-eat
(i) Seeds which are healthy and disease free
foods to prevent them from spoiling.
should be selected for sowing.
(9) Find out the uses of fungi to plants and
(ii) Infected plants should be removed.
animals?
(iii) Plants should be sprayed with fungicides and
Ans.
germicides to prevent diseases.
(i) Fungi decompose the bodies of dead animals
and convert them into simple carbon Animal diseases:
compounds. These substances easily mix with (i) Anthrax is a disease that affects cattle. It is
air, water and soil from where they are again caused by a bacterium.
absorbed by plants and enter the food chain. (ii) Foot and mouth is a dangerous disease in
(ii) Some fungi living in symbiotic association cattle caused by a virus.
with plants help to absorb water and inorganic
(iii) Rabies is a viral disease that affects animals.
compounds like nitrate and phosphate.
Useful and Harmful Microbes 133

Preventive Measures: Bring ‘active dry yeast’ from the market. Mix
(i) The place where animals are kept should be a spoonful of yeast, two spoonfuls sugar with
washed with germicides. a sufficient quantity of lukewarm water in a
bottle. Fix a colourless, transparent balloon
(ii) Animals should be dewormed regularly. on the mouth of that bottle.
(iii) The animals should be treated with necessary What changes do you observe after 10
antibiotics for infectious diseases. minutes? Mix limewater with the gas
(iv) They should be regularly vaccinated. accumulated in the balloon. Collect that
limewater in a beaker and observe it. What
(v) Take the animals to veterinary hospital for
do you notice?
proper treatment and vaccination.
Ans.
Q.14. Activity based question. (i) After 10 minutes, the balloon is filled with a
gas and gets inflated.
(ii) Lime water turns milky thus proving that the
Bud
gas accumulated is carbon dioxide.

Cell wall

Nucleus

Cytoplasm

vvv
134 Master Key Science & Technology (Term - I) (Std. IX)

ASSIGNMENT - 8
Time : 1 Hr. Marks : 30

Q.1. (A) Fill in the blanks: (2)

(1) The rod-shaped bacteria found in milk or buttermilk are called ............. .
(2) Fungi release ............. in the food, making the food poisonous .

(B) Match the columns: (4)

Column ‘A’ Column ‘B’

(1) Rhizobium (a) Food poisoning
(2) Clostridium (b) Nitrogen fixation
(3) Penicillium (c) Bakery products
(4) Yeast (d) Production of
antibiotics

(C) Find the odd man out: (2)

(1) Pneumonia, Diphtheria, Chickenpox, Cholera.
(2) Root rot, Rust (tambere), Rubella, Dengue.

Q.2. Answer the following questions in short. (Any four): (12)

(1) What is fermentation?
(2) Write down the modes of infection and the preventive measures against fungal disease.
(3) Write down the modes of infection and preventive measures against AIDS.
(4) Give Reason : Napthaline balls are kept with clothes to be put away.
(5) What is penicillin? What is it used for?
(6) Which vaccines are given to infants? Why?

Q.3. Answer the following questions in brief. (Any two): (10)

(1) Write a note on Antibiotics.
(2) How is alcohol produced?
(3) How was the antibiotic penicillin discovered?

vvv
9 Environmental Management

Points to Remember:
• Atmospheric conditions at a specific time at a particular place are referred to as weather.
• The climate of a particular region is the average of daily readings of various weather-related
parameters recorded for several years.
• Weather is related to a specific location and specific time whereas climate is related to a longer
duration and larger area.
• Climate plays a very important role in our day to day life. It influences our basic needs like
food, clothing and shelter as well as our occupations.
• The science that studies the inter-relationships between the various components of air, natural
cycles, geological movements of the earth and climate is called meteorology.
• Meteorology includes the study of storms, clouds, rainfall, thunder, lightning, etc. Depending
upon the study of such factors, weather forecasts are made. They are useful to common
people, farmers, fisheries, aviation services, water transport and various other organizations.
• The World Meteorological Organization was established by the United Nations Organization
on 23rd March 1950. This organization plays an important role in food security, water
management, transportation and communication.
• The Indian Meteorological Department was founded by the British in 1875 at Shimla. Its
head office is at Pune and its Regional Offices are at Mumbai, Kolkata, Chennai, Nagpur and
Delhi. In this institute, research goes on continuously on various aspects like instruments
for climatic readings, predictions about climate made using radar, predictions about climate
related to seismology, predictions regarding rainfall by satellites, air pollution, etc.
• After the famine of 1877, H. F. Blanford, the founder of IMD had made a prediction for
monsoon for the first time taking the snowfall in the Himalayas as the parameter for this
prediction. In the decade of the 1930’s Sir Gilbert Walker had underlined the relationship
between various worldwide climatic factors and the Indian monsoon, and based on available
observations and previous recordings related to this relationship he put forth a hypothesis
regarding the nature of the monsoon. With the initiative of Dr. Vasantrao Govarikar in the
decade of the 1990’s a monsoon model based upon 16 worldwide climatic parameters was
developed. This model was in use from 1990 to 2002.
• Various models are used for monsoon and climate predictions are used like the Mathematical
model (Dynamic model), Statistical model and Holistic model.
• Waste materials generated through various daily human activities are called solid waste.
• Solid waste is of different types like domestic waste, industrial waste, hazardous waste, farm
or garden waste, electronic waste, biomedical waste, urban waste, radioactive waste and
mining waste depending upon its source.

(135)
136 Master Key Science & Technology (Term - I) (Std. IX)

• Solid waste is classified as Biodegradable waste and Non-biodegradable waste. Biodegradable

waste is easily degraded by microbes. It mainly includes kitchen waste (spoiled food, fruits,
vegetables), ash, soil, dung, parts of the plants etc. Non-biodegradable waste is not easily
degraded because it requires a very long period of time and the use of various techniques. It
includes plastic, metal and other similar materials.
• It is the need of the hour to implement solid waste management practices to avoid the possible
problems due to solid waste generated from urban and industrial areas and to maintain a
clean environment.
• There are 7 principles of solid waste management - Reuse, Refuse, Recycle, Rethink, Reduce,
Research and Regulation and public awareness.
• Disaster management is action implemented through proper planning, organized activity
and co-ordination.
• The main objective of first aid is prevention of death, preventing deterioration of health and
starting the process of rehabilitation.
• Basic principles of first aid: Life and Resuscitation – ABC – Airway, Breathing and Circulation.
• Different ways of transporting victims or patients of disaster should be used depending upon
the situation like Cradle method, Carrying piggy back, Human crutch method, Pulling or
lifting method, Carrying on four-hand chair, Carrying on two-hand chair, Stretcher.

(9) India has launched several .................. to

MASTER KEY QUESTION SET - 9
provide predictions regarding calamities like
Q.1. (A) Fill in the blanks: dust storms, sand storms, heavy rainfall,
tsunami etc.
(1) .................. is that which remains constant in a
region for a long duration. (10) In the decade of 1930s, .................. had
underlined the relationship between various
(2) .................. influences our basic needs like
worldwide climatic factors and the Indian
food, clothing and shelter as well as our
Monsoon.
occupations.
(11) Data about current climatic parameters is
(3) .................. is observed as ‘World Meteorological
mathematically analysed with the help of
Day’.
.................. .
(4) Various climatic factors bring about the
(12) Waste materials generated through the various
.................. of rocks in the earth’s crust.
daily human activities are called .................. .
(5) .................. in the soil play an important role in
(13) Bandages, dressings, gloves, medicines,
formation of organic materials.
needles etc. are classified as .................. waste.
(6) The science that studies the inter-relationships
(14) Remains of heavy metals like lead, cadmium,
between the various components of air, natural
etc. from mines are .................. waste.
cycles, geological movements of the earth and
climate is called .................. . (15) The waste that can be easily degraded by
microbes is called .................. .
(7) .................. plays an important role in food
security, water management, transportation (16) If organic waste is carefully decomposed, we
and communication. can get .................. and .................. out of it.

(8) Meteorological departments have .................. (17) It is the need of the hour to implement
which are equipped with modern instruments .................. practices.
and technology. (18) Paper and glass can be .................. .
Environmental Management 137

(19) If the victim has difficulty in breathing, the (4) The ..................... was established by the United
head should be held in a .................. position. Nations Organization on 23rd March 1950.
(20) If breathing has stopped, the victim should be (a) World Health Organization
given artificial ventilation by .................. . (b) National Oceanographic and Atmospheric
(21) Mouth to mouth respiration and pressing the Administration
heart down performed alternately is called (c) World Meteorological Organization
.................. .
(d) Indian Institute of Tropical Meteorology
(22) .................. is action implemented through
(5) .................. is/are related to various weather
proper planning, organized activity and co-
and climatic factors.
ordination.
(a) Salinity of marine water
(23) For injuries like sprains, twisting and
(b) Formation of ocean currents
contusion , .................. should be applied to the
injured part. (c) Water cycle
(24) A .................. is a portable appliance that is (d) All of these
used to put out a fire. (6) .................. is the founder of IMD.
Ans. (1) Climate (2) Climate (3) 23rd March (a) Dr. Vasantrao Govarikar
(4) weathering (5) Microbes (6) Meteorology (b) H.F. Blanford
(7) The World Meteorological Organization (c) Sir Gilbert Walker
(8) observatories (9) satellites (10) Sir Gilbert
(d) Dr. Radhakrishnan Nair
Walker (11) Param supercomputer (12) solid
waste (13) biomedical waste (14) mining waste (7) The monsoon model based upon 16 worldwide
(15) biodegradable waste (16) compost, fuel parameters was developed by the initiative of
(17) solid waste management (18) recycled .................. .
(19) backward sloping (20) mouth to mouth (a) Dr. Vasantrao Govarikar
resuscitation (21) cardio-pulmonary resuscitation (b) H.F. Blanford
(CPR) (22) Disaster management (23) ice (c) Sir Gilbert Walker
(24) fire-extinguisher.
(d) Virghese Kurien
(B) Write the sentence with the correct (8) In .................. , forecasts are made taking into
answer from the options given below: account the estimates of current weather
(1) Atmospheric conditions at a specific time at a related events and ongoing physical activity.
particular place are referred to as .................. . (a) Statistical model
(a) environment (b) weather (b) Holistic model
(c) climate (d) biosphere (c) Mathematical model
(2) .................. is a long term predominant (d) All of these
condition of the atmosphere. (9) In .................., predictions are based upon
(a) Climate (b) Weather those parameters used in other models which
(c) Pressure (d) Biosphere have the greatest effect on the monsoon.
(3) Various climatic factors like .................. are (a) Holistic model
considered during construction of runways, (b) Mathematical model
seaports, huge bridges and skyscrapers, etc. (c) Statistical model
(a) direction and speed of wind (d) Scientific model
(b) temperature (10) In, .................. the current climatic observations
(c) atmospheric pressure in a region are compared with earlier
(d) all of these parameters such as oceanic temperature,
138 Master Key Science & Technology (Term - I) (Std. IX)

atmospheric pressure and the nature of the (19) Period of natural degradation for banana
monsoon rainfall for several years. peels is .................. .
(a) Mathematical model (a) 1 month (b) 1-2 weeks
(b) Holistic model (c) 3-4 weeks (d) 2 months
(c) Statistical model (20) Period of natural degradation for cloth bags is
(d) Dynamic model .................. .

(11) Mumbai generates .................. of solid waste (a) 2-3 weeks (b) 1 month
per day. (c) 5 months (d) 1 year
(a) 1700 tons (b) 900 tons (21) Period of natural degradation for wood is
.................. .
(c) 5000 kgs (d) 5000 tons
(a) 1 month (b) 5 months
(12) Pune generates .................. of solid waste per
day. (c) 10-15 years (c) 40-50 years

(a) 500 tons (b) 1700 tons (22) Period of natural degradation for certain
plastic bags is .................. .
(c) 900 tons (d) 600 tons
(a) 50-100 years (b) infinite duration
(13) Nagpur generates .................. of waste per day.
(c) 10 lakh years (d) 1000 years
(a) 900 tons (b) 1700 tons
(23) Period of natural degradation for thermocol
(c) 500 tons (d) 5000 tons or Styrofoam cup is .................. .
(14) Radioactive materials, explosives and (a) 10 lakh years (b) infinite duration
infectious materials are classified as ..................
(c) 200-250 years (d) 1 year
waste.
(24) If any bone is fractured, it is essential that the
(a) Industrial waste (b) Biomedical waste
fractured part be .................. .
(c) Urban waste (d) Hazardous waste
(a) mobilized (b) immobilized
(15) .................. are radioactive waste.
(c) pulled (d) massaged
(a) Remains of heavy metals like arsenic, (25) For transporting children and under-weight
cadmium etc. victims, .................. method is used.
(b) Strontium-10, Ceium-141, Barium_140 (a) carrying piggy back
(c) Waste from blood banks and laboratories (b) human crutch method
(d) All of these (c) cradle method
(16) Chemicals, pigments, sludge, ash, metals, etc. (d) stretcher
are classified as .................. waste.
(26) ................. method is useful to carry patients
(a) Domestic waste (b) Industrial waste who are unconscious.
(c) Urban waste (d) Hazardous waste (a) Cradle
(17) Waste food, paper, plastic, vegetable and fruit (b) Carrying piggy back
waste etc. are classified as .................. waste. (c) Human crutch
(a) Industrial waste (b) Farm waste (d) Carrying on four-hand chair
(c) Domestic waste (d) Urban waste (27) .................. method is used for carrying an
(18) .................. is the 3 R mantra. unconscious patient through a short distance.
(a) Refuse, Research, Recycle (a) Carrying piggy back
(b) Reduce, Reuse, Recycle (b) Cradle method
(c) Reduce, Reuse, Refuse (c) Carrying on two-hand chair
(d) Rethink, Recycle, Reuse (d) Pulling or lifting method
Environmental Management 139

(28) ................ method is useful to carry patients Ans. Climate.

who cannot use their hands but can hold their Climate influences our basic needs like
body upright. food, clothing and shelter as well as our
(a) Carrying on four-hand chair occupations. Various factors of climate like
(b) Carrying on two-hand chair temperature, atmospheric pressure, sunlight,
rainfall, humidity etc. will decide which kind
(c) Carrying piggy back
of plants and animals can survive there.
(d) Cradle method
(2) A description of the climatic conditions of
(29) .................. method is used to carry patients
short duration in a particular area is ............. .
when support is needed for the part below the
Ans. Weather.
waist.
Atmospheric conditions at a specific time at
(a) carrying on four-hand chair
a particular place are referred to as weather.
(b) carrying on two-hand chair
Weather is related to a specific location and
(c) Stretcher specific time whereas climate is related to a
(d) Pulling or lifting method longer duration and larger area.
(30) .................. is the largest producer of electricity (3) Irrespective of the progress of human beings,
from solid waste. we have to think about .................. .
(a) India (b) America Ans. Geographical favourability.
(c) Japan (d) China Geographical favourability includes location,
(31) For injuries like sprains, twisting and availability of water, availability of natural
contusion, .................. should be applied on resources and climate of a region. This has a
the injured part. great impact on the progress of human beings.
(a) turmeric powder (b) antiseptic pad Countries that have more favourable factors
will progress more.
(c) ice-pack (d) pressure
(4) Establishments where various climatic factors
Ans. (1) weather (2) Climate (3) all of these (4) World
are recorded are called ............. .
Meteorological Organization (5) All of these
(6) H. F. Blanford (7) Dr. Vasantrao Govarikar Ans. Observatory.
(8) Mathematical model (9) Holistic model Most countries in the world have established
(10) Statistical model (11) 5000 tons meteorology departments for recording
(12) 1700 tons (13) 900 tons (14) Hazardous climatic factors. These departments have
waste (15) Strontium-10, Ceium-141, observatories which are equipped with
Barium_140 (16) Industrial waste modern instruments and technology.
(17) Domestic waste (18) Reduce, Reuse, Recycle Q.2. Match the columns:
(19) 3-4 weeks (20) 1 month (21) 10-15 years
(22) 10 lakh years (23) infinite duration (1) Column ‘A’ Column ‘B’
(24) immobilized (25) cradle method (26) Carrying (1) Harmful waste (a) Glass, rubber, carry
piggy back (27) Pulling or lifting method bags etc.
(28) Carrying on two-hand chair (29) Carrying on (2) Domestic waste (b) Chemicals,
four-hand chair (30) America (31) ice-pack pigments, ash, etc.
*(C) Complete the statements using the (3) Biomedical waste (c) Radioactive material
proper option from those given below. (4) Industrial waste (d) Left over food,
Explain the statements: vegetables, peeling
of fruits
(Geographic favourability, climate, weather,
(5) Urban waste (e) Bandages, cotton,
observatory)
needles etc.
(1) Of the abiotic factors that affect biodiversity
by far the most important is ............. . Ans. (1 - c), (2 - d), (3 - e), (4 - b), (5 - a)
140 Master Key Science & Technology (Term - I) (Std. IX)

(2) Column ‘A’ Column ‘B’ climatic changes are slow and of a limited
nature.
(1) Mining waste (a) Leaves, flowers,
(5) Climate plays a very important role in the
crop residue.
formation and enrichment of soil.
(2) Electronic waste (b) Remains of heavy
metals like lead, Ans. True.
arsenic, cadmium. (6) Prediction maps are prepared once in 24
(3) Farm waste (c) Strontium-10, hours.
Cerium-141, Ans. False. Prediction maps are prepared twice in
Barium-140 every 24 hours.
(4) Radioactive waste (d) Cell phones, TV (7) The first prediction of monsoon in India was
sets, Computers made by Dr. Vasantrao Govariakar.
Ans. (1 - b), (2 - d), (3 - a), (4 - c) Ans. False. The first prediction of monsoon in India
was made my H.F. Blanford.
(3) Column ‘A’ Column ‘B’ (8) H.F. Blanford used the rainfall in Kerala as the
(1) Banana peelings (a) 10 lakh years. parameter for prediction of monsoon in India.
(2) Plastic bags (b) 200-250 years. Ans. False. H.F. Blanford used the snowfall in
(3) Leather shoes (c) 3-4 weeks Himalyas as a parameter for prediction of
monsoon in India.
(4) Aluminium cans (d) 40-50 years
(9) In Holistic model, predictions are made
Ans. (1 - c), (2 - a), (3 - d), (4 - b) taking into account estimates of current
weather related events and ongoing physical
(4) Column ‘A’ Column ‘B’ interactions between them.
(1) Thermocol (a) 1 year. Ans. False. In Holistic model, predictions are based
(2) Tin cans (b) Infinite duration. upon those parameters used in other models
(3) Woollen socks (c) 10-15 years which have the greatest effect on monsoon.
(4) Wood (d) 50-100 years (10) Any meteorological model depends upon the
inter-relationships between parameters used
Ans. (1 - b), (2 - d), (3 - a), (4 - c) in that model and the results expected from it.
Q.3. State whether the following statements are Ans. True.
true or false and if false, write the correct (11) Remains of heavy metals like lead, arsenic,
statement: cadmium etc. from mines are industrial waste.
(1) Climate is a long term predominant condition Ans. False. Remains of heavy metals like lead,
of the atmosphere. arsenic, cadmium etc. from mines are mining
Ans. True. waste.
(2) Climate changes continuously. (12) Use of ‘use and throw’ type of articles like
Ans. False. Climate does not change continuously. pens, canned cold drinks, tetra packs should
It remains constant in a region for a long be encouraged in waste management.
duration. Ans. False. Use of ‘use and throw’ type of articles like
(3) If present climatic conditions are analysed pens, canned cold drinks, tetra packs should
with reference to the past climatic conditions, be strictly avoided in waste management.
we can predict climatic changes of the future. (13) We should use tissue paper instead of
Ans. True. one’s own handkerchief for effective waste
(4) Forecasting is difficult for places where management.
climatic changes are slow and of a limited Ans. False. We should use one’s own handkerchief
nature. instead of tissue paper for effective waste
Ans. False. Forecasting is easy for places where management.
Environmental Management 141

(14) Certain plastic bags take 1 month to degrade. Q.5. Complete the analogy:
Ans. False. Certain plastic bags take 10 lakh years (1) Specific duration and specific time: Weather : :
to degrade. Longer duration and longer time : ............... .
(15) Banana peelings can degrade in 3-4 weeks. (2) Mumbai : 5000 tons solid waste : : Pune : ......... .
Ans. True. (3) Kitchen waste, parts of plants : Wet solid waste
(16) If the victim has burn injuries, it is beneficial : : Plastic, metals : ............... .
to cover the burnt part with blanket. (4) Largest producer of electricity from solid
Ans. False. If the victim has burn injuries, it is waste : America : : Production of useful
beneficial to hold the injured part under clean materials from banana peelings : ............... .
and cold flowing water for at least 10 minutes. (5) Cloth bags : 1 month : : Rags : ............... .
(17) CPR helps to bring the circulation to normal. (6) Tin cans : 50-100 years : : Aluminium cans :
Ans. True. ............... .
(18) If breathing has stopped, the head should be (7) Wood : 10-15 years : : Styrofoam : ............... .
held in backward sloping position. Ans. (1) Climate (2) 1700 tons solid waste (3) Dry solid
Ans. False. If breathing has stopped, the victim waste (4) Japan (5) 5 months (6) 200-250 years
should be given artificial ventilation by mouth (7) Infinite duration
to mouth resuscitation.
Q.6. Define:
(19) Japan is the largest producer of electricity
from solid waste. (1) Weather
Ans. False. America is the largest producer of Ans. Atmospheric conditions at a specific time at a
electricity from solid waste. particular place are referred to as weather.
(20) China has developed the projects of production (2) Climate
of threads, paper and other useful materials Ans. The climate of a particular region is the
from banana peelings. average of daily readings of various weather-
Ans. False. Japan has developed the projects of related parameters recorded for several years.
production of threads, paper and other useful (3) Meteorology
materials from banana peelings.
Ans. The science that studies the inter-relationships
Q.4. Find the odd man out: between the various components of air,
(1) Waste food, paper, plastic, bandages. natural cycles, geological movements of earth
and climate is called meteorology.
Ans. Bandages. It is a biomedical waste whereas
the others are domestic waste. (4) Solid waste
(2) Pesticides, fertilizers, crop residue, Sludge. Ans. Waste materials generated through daily
Ans. Sludge. It is an industrial waste whereas the human activities are called solid waste.
others are farm waste. Q.7. Answer the following:
(3) Strontium -10, Cerium – 141, Barium – 140, * (1) Why is e-waste harmful? Express your
Cadmium. opinion about this.
Ans. Cadmium. It is a mining waste whereas the Ans.
others are radioactive waste.
(i) E-waste is electronic waste which includes
(4) Banana peels, Cloth bag, Food waste, Plastic non-functional TV Sets, cell phones, music
bag. systems, computers and their parts, etc.
Ans. Plastic bag. It is a non-biodegradable waste (ii) E-waste contains heavy metals like lead,
whereas the others are degradable wastes. beryllium, mercury and cadmium.
(5) Fruits, Ash, Metals, Vegetables. (iii) These metals accumulate in the soil for long
Ans. Metal. It is a non-biodegradable waste periods and thus affect the biodiversity of the
whereas the others are degradable wastes. soil.
142 Master Key Science & Technology (Term - I) (Std. IX)

(iv) Many a times e-waste like battery etc. contain (ii) However, as these inter-relationships with
acids which make the soil acidic. reference to the ocean and atmosphere are
(v) E-waste can cause ground water pollution, never constant, meteorological models need
which also affects living organisms when they to be changed continually.
drink this polluted water. * (6) Explain with suitable examples, the
(vi) Thus E-waste affects human health and soil relationship between weather forecasting
microorganisms directly or indirectly. and disaster management.
(2) What is the necessity of solid waste Ans.
management? (i) Depending upon the factors such as storms,
Ans. Necessity of solid waste management: clouds, rainfall etc. weather forecasts are
made. It is useful in aviation, shipping, fishing,
(i) For preventing environmental pollution and
industries as well as during natural calamities
to keep the surroundings clean.
like dust storms, sand storms, heavy rainfall,
(ii) For energy as well as fertilizer production tsunami etc where proper predictions are
and through that to generate work and made with well equipped satellites and
employment opportunities. highclass technology.
(iii) To reduce the strain on natural resources (ii) Observatories at several locations are
through treatment of solid waste. doing excellent work in the analysis of the
(iv) To improve the health and quality of life and information received from these satellites.
to maintain environmental balance. (iii) This data can be used in prevention of losses
(3) What are the harmful effects of solid waste? and danger, improving tolerance, providing
Ans. Harmful effects of solid waste: relief from disaster, minimising the intensity
and extent of harm as well as preparation to
(i) Effect on biodiversity.
face the disaster.
(ii) Releases bad odour.
(7) Forecasts about which weather related
(iii) Produces toxic gases.
factors are given during the news bulletins
(iv) Leads to degradation of natural beauty. on Doordarshan and Akashwani?
(v) Leads to pollution of air, water and soil. Ans. Forecasts about weather related factors like
(vi) Spreads diseases. atmospheric pressure, sunlight, clouds,
(4) What first-aid should be given for injuries velocity, humidity, rainfall, visibility and
like sprains, twisting and contusion? temperature are given during the news
bulletins on Doordarshan and Akashwani.
Ans. For injuries like sprains, twisting and
contusion, the ‘RICE’ remedy should be (8) What is urban waste? What does it include?
applied: Ans.
(i) Rest: Allow the victim to sit in a relaxed (i) Waste generated through household
position. industries and large commercial and industrial
(ii) Ice: Apply an ice-pack to the injured part. establishments is called urban waste.
(iii) Compression: After the ice-pack treatment, (ii) It includes carry bags, glass, metal pieces and
the injured part should be massaged gently. rods, threads, rubber, paper, cans from shops,
waste from vegetable and meat markets,
(iv) Elevate: The injured part should be kept in a
construction waste etc.
raised/elevated position.
(9) What does biomedical waste include?
(5) Why do meteorogical models need to be
Ans. Biomedical waste includes bandages,
changed continually?
dressings, gloves, needles, saline bottle,
Ans. medicines, medicine bottles, test tubes, body
(i) Any meteorological model depends upon the parts, blood etc. from clinics, hospitals, blood
inter-relationship between parameters used in banks and laboratories.
that model and the results expected from it.
Environmental Management 143

Q.8. Answer in brief: using cloth bags or bags prepared from old
* (1) State the scientific and eco-friendly methods sarees, bed-sheets, curtains etc.
of waste management. (iv) Using both sides of a paper for writing.
Ans. Following are the scientific and eco-friendly Reusing greeting cards and gift papers.
methods of waste management: (v) Avoiding use of tissue paper and preferring to
(i) Waste separation: In this method, dry and use one’s own handkerchief.
wet wastes are separated, stored and later (vi) Using rechargable batteries instead of lead
collected for proper use. batteries.
(ii) Composting: Decomposition of degradable (vii) Implementing various programmes of
kitchen waste in small pits in the backyard, solid waste management and educating,
garden or terrace is called composting. encouraging the family and society in this
Good quality manure can be produced by regard.
composting leftover food, peels of fruits, (viii) Avoiding ‘use and throw’ type of articles like
vegetables etc. pens, canned cold drinks and tetra-packs etc.
(iii) Vermicomposting: Converting solid waste
(3) What are the principles of solid waste
into manure or compost with the help of
management?
earthworms is called vermicomposting.
Ans. Principles of solid waste management:
Vermicompost manure is highly nutritious
and can be used for agricultural purposes and (i) Reuse: After use, materials should be reused
garden plants. for some other proper purposes.
(iv) Secured landfill: Solid waste is disposed off in (ii) Refuse: Refusal to use articles made from non-
secured landfills. The site for secured landfill degradable articles like plastic and thermocol.
is selected 2 km away from water bodies and (iii) Recycle: Production of useful articles by
human habitation. Care is taken to see that the recycling solid wastes. For example, paper
site does not fall in sensitive zone. The landfills and glass can be recycled.
are layered with clay and plastic and then (iv) Rethink: Rethinking our habits, activities and
the garbage is spread and left to decompose their consequences in connection with the use
naturally. of various articles of daily use.
(v) Pyrolysis: In this method, the waste is heated (v) Reduce: Restriction the use of resources to
to a high temperature to obtain gas and avoid their wastage. Old materials should
electricity. Semi-combustible waste is burnt be reused. One thing should be shared by
in pyrolysis. It is suitable for municipal solid many use and throw type of objects should be
waste management. avoided.
(vi) Incineration: Biomedical waste is burnt in (vi) Research: Conducting research related to
incinerators to kill the pathogens. Disinfection reuse of materials that are temporarily out of
and sterilization is also done while treating use.
the biomedical waste. (vii) Regulation and Public awareness:
* (2) How will you register your individual Following the laws and rules related to waste
participation in solid waste management? management and motivating others to do the
Ans. We can register our individual participation same.
in solid waste management in the following (4) What is disaster management? What actions
ways: does it include?
(i) Following the 3R mantra: Reduce (reducing Ans. Disaster management is action implemented
the waste), reuse (reuse of waste) and recycle through proper planning, organized activity
(recycling of waste). and co-ordination.
(ii) Throwing plastic wrappers of chocolates, ice- It includes the following:
creams, biscuits, etc. into dust bins. Avoid (i) Prevention of loss and danger.
littering. (ii) Improving tolerance.
(iii) Avoiding the use of plastic bags and instead
144 Master Key Science & Technology (Term - I) (Std. IX)

(iii) Providing relief from disaster, minimising the is used when support is needed for the part
intensity and extent of harm. below the waist.
(iv) Preparation to face the disaster. (vi) Carrying on two-hand chair: This method is
(v) Immediate action in the disaster situation. useful for those patients who cannot use their
(vi) Assessment of damages and intensity of the hands but can hold their body upright.
disaster. (vii) Stretcher: In an emergency, if a conventional
(vii) Arranging for rescue work and help. stretcher is not available, then a temporary
(viii) Rehabilitation and rebuilding. stretcher can be made using bamboo, blanket,
etc.
* (5) Give examples of the importance of climate
in the living world with explanations, in * (7) How is first aid provided to victims of
your own words. disasters who are injured?
Ans. Ans.
(i) Daily weather as also long term climatic (i) Bleeding: If the victim is injured and bleeding
conditions influence human lifestyle directly through the wound, should be covered with
or indirectly. Land, water bodies, plants an antiseptic pad and pressure applied on it
and animals collectively form the natural for 5 minutes with either thumb or palm.
environment on earth. This environment is (ii) Fracture and impact on vertebrae: If any bone
responsible for the development of organisms. is fractured, it is essential that the fractured
(ii) The climate of a particular region helps part be immobilized. It can be done with the
to determine the diet, clothing, housing, help of any available wooden rods / batons /
occupations and lifestyle of the people of that rulers. If there is an impact on the back or
region. For example, the characteristic lifestyle vertebral column; the patient should be kept
of Kashmiri and Rajasthani people. immobile on a firm stretcher.
(iii) Salinity of marine water, formation of oceanic (iii) Burns: If victims have burn injuries, it is
currents, water cycle, etc. are all related to beneficial to hold the injured part under clean
various weather and climatic factors. and cold flowing water for at least 10 minutes.
(iv) Various climatic factors bring about the (8) How is Solid Waste classified? OR
weathering of rocks in the earth’s crust. What are the sources of Solid Waste?
(v) Climate plays a very important role in the Ans.
formation and enrichment of soil. (i) Domestic waste: Waste food, paper, plastic
(vi) Microbes in the soil play an important role in paper, plastic bags, vegetable waste, fruit
formation of organic materials. This process skins, glass and sheet metal articles, etc.
depends upon various climatic factors. (ii) Industrial waste: Chemicals, pigments,
sludge, ash, metals, etc.
* (6) Explain with suitable examples, the care to be
taken when using methods of transporting (iii) Hazardous waste: Chemicals generated in
patients. various industries, radioactive materials,
explosives, infectious materials, etc.
Ans.
(iv) Farm/Garden waste: Leaves, flowers,
(i) Cradle Method: This method is used for
branches of trees, crop residues like straw,
children and under-weight victims.
animal urine and dung, pesticides, remains of
(ii) Carrying piggy back: This method is used for various chemicals and fertilizers, etc.
carrying patients who are unconscious.
(v) Electronic waste: Non-functional TV sets, cell
(iii) Human crutch method: If one of the legs is phones, music systems, computers and their
injured, the victim should be supported with parts, etc.
minimum load on the other leg.
(vi) Biomedical waste: Bandages, dressings,
(iv) Pulling or lifting method: This method is gloves, needles, saline bottles, medicines,
used for carrying an unconscious patient, medicine bottles, test tubes, body parts, blood,
through a short distance. etc. from clinics, hospitals, blood banks and
(v) Carrying on four-hand chair: This method laboratories.
Environmental Management 145

(vii) Urban waste: Waste generated through founder of IMD had made such a prediction
household industries and large commercial for the first time taking the snowfall in
and industrial establishments, carry bags, Himalayas as a parameter for this prediction.
glass, metal pieces and rods, threads, rubber, (iii) In the decade of the 1930’s, the then director
paper, cans from shops, vegetable and meat of IMD, Sir Gilbert Walker had underlined
markets, construction waste, etc. the relationship between various worldwide
(viii) Radioactive waste: Radioactive materials climatic factors and the Indian monsoon and
like Strontium-10, Cerium-141, Barium-140 based on available observations and previous
and heavy water, etc. generated from atomic recordings related to this relationship, he put
energy plants, uranium mines, atomic research forth a hypothesis regarding the nature of the
centres, nuclear weapons testing sites, etc. monsoon.
(ix) Mining waste: Remains of heavy metals like (iv) With the initiative of Dr. Vasantrao Govarikar
lead, arsenic, cadmium, etc. from mines. in the decade of the 1990’s a monsoon model
Q.9. Write short notes on: based upon 16 worldwide climatic parameters
was developed. This model was in use from
* (1) Meteorology:
1990 to 2002.
Ans.
(v) Presently, new models are being developed at
(i) The science that studies the inter-relationship IITM.
between the various components of air,
Work is in progress at two levels, namely
natural cycles, geological movements of the
designing new models and developing new
earth and climate is called meteorology.
technology.
(ii) Meteorology includes the study of storms,
(vi) The main focus is on development of the radar
clouds, rainfall, thunder, lightning etc.
system and satellite technology.
(iii) Depending upon the study of such factors,
weather forecasts are made. * (4) Plastic waste:
(iv) They are useful to common people, farmers, Ans.
fisheries, aviation services, water transport (i) Plastic waste is the accumulation of plastic
and various other organizations. products in the environment that adversely
* (2) Climatic factors: affects environment, humans and animals.
Ans. (ii) Plastic waste is excessively generated as
plastic is inexpensive and durable.
(i) The climate of a particular region is the
average of daily readings of various weather- (iii) Plastic is slow to degrade. It takes around 10
related parameters recorded for several years. lakh years for certain plastic bags to degrade.
(ii) Climatic factors include direction and speed (iv) Plastic waste affects land and water.
of wind, temperature, atmospheric pressure, (v) It also affects the health of animals, cattle
clouds, rainfall, humidity, visibility etc. unknowingly ingest these plastic bags leading
(iii) These factors influence our basic needs to stomach cancer in them.
like food, clothing shelter as well as our (vi) Plastic also releases toxic chemicals which are
occupations. carcinogenic to humans.
(iv) Various climatic factors bring about the (vii) To avoid plastic waste, cloth bags should be
weathering of rocks in the earth’s crust. used instead of plastic bags. Plastic articles
(v) Microbes in the soil play an important role in should be recycled.
formation of organic materials. This process
* (5) Industrial waste:
also depends upon various climatic factors.
Ans.
* (3) Monsoon model:
(i) Industrial waste is the waste produced by
Ans. industrial processes or activities.
(i) The tradition of forecasting the monsoon (ii) There is a huge variety of industries producing
season in India is older than 100 years. different types of materials and articles. All of
(ii) After the famine of 1877, H.F. Blanford, the
146 Master Key Science & Technology (Term - I) (Std. IX)

these use raw materials and give out a lot of related to seismology, predictions regarding
waste. rainfall by satellites, air pollution etc.
(iii) There are hundreds of mines which extract (v) The Indian Meteorological Department
copper, silver, gold, iron, coal etc. Huge provides information regarding weather and
quantities of waste are produced while climatic conditions to other departments like
processing them. aviation, shipping, agriculture, irrigation,
(iv) Cement industries give out solid, liquid and marine oil exploration and production etc.
gaseous wastes. (vi) Predictions regarding calamities like dust
(v) While refining crude oil, a lot of poisonous storms, sand storms, heavy rainfall, hot and
gaseous and liquid wastes are produced. cold waves, tsunami, etc. are communicated
(vi) Construction units produce huge quantities to various departments, all types of mass
of waste stones, pebbles, broken bricks, wood communication media and all citizens.
waste etc. Mostly they are dumped in landfills. (vii) India has launched several satellites equipped
(vii) It also includes chemicals, pigments, sludge, with highclass technology.
ash, metal, etc. given out from mining, textile, (viii) Observatories at several locations are
construction, chemical industries. doing excellent work in the analysis of the
information received from these satellites.
* (6) Principles of first aid:
Ans. First aid is provided to disasters victims in life (8) Mathematic model (Dyanic model):
and resuscitation manner - ABC. Ans.
(i) Airway: If the victim has difficulty in breathing, (i) Forecasts are made with the help of
the head should be held in a backward sloping mathematical models which take into account
position or the chin should be raised so that estimates of current weather related events
the respiratory passage remains open. and ongoing physical interactions between
(ii) Breathing: If breathing has stopped, the them.
victim should be given artificial ventilation by (ii) Data about current climatic parameters is
mouth to mouth resuscitation. mathematically analysed with the help of the
(iii) Circulation: If the victim is unconscious, Param Supercomputer.
then after giving mouth to mouth respiration (iii) Various mathematical models based upon
twice, the heart should be pressed down daily geographic events are developed by
hard by pressing the chest with both the supercomputer technology.
palms. These two actions should be repeated (9) Statistical Model:
alternately about 15 times. This is called
Ans.
cardio-pulmonary resuscitation (CPR). If
helps to bring the circulation back to normal. (i) In this model, current climatic observations in
a region are compared with earlier parameters
(7) Indian Meteorological Department: such as oceanic temperature, atmospheric
Ans. pressure and the nature of the monsoon
(i) The Indian Meteorological Department was rainfall for several years.
founded by the British in 1875 at Shimla. (ii) This data is comparatively analysed by
(ii) Its head office is at Pune and its Regional statistical methods and predictions are made
offices are at Mumbai, Kolkata, Chennai, about the monsoon in the present conditions.
Nagpur and Delhi. (10) Holistic Model:
(iii) Maps are prepared every day which indicate Ans.
the daily predictions about the weather. Such
(i) In this model, predictions are based upon
maps are prepared and published twice in
those parameters used in other models which
every 24 hours.
have the greatest effect on the monsoon.
(iv) In this institute, research goes on continuously
(ii) Nowadays, predictions declared by IMD are
on various aspects like instruments for
the collective outcome of various model. This
climatic readings, predictions made about
climate using radar, predictions about climate is called a holistic model.
Environmental Management 147

Q.10. Distinguish between: (2) In which different ways do our surroundings

* (1) Weather and Climate: get polluted?
Ans.
Weather Climate
(i) Air pollution is caused due to emissions from
(i) A t m o s p h e r i c (i) The climate of a industries, vehicles, burning of fossil fuels,
conditions at a particular region is construction, mining and agriculture.
specific time at a the average of daily
(ii) Water pollution is caused by domestic sewage
particular place readings of various
and industrial waste water released into the
are referred to as weather-related
water bodies.
weather. parameters recorded
for several years. (iii) Soil pollution is caused due to industrial
wastes, domestic waste, chemical fertilizers,
(ii) Weather can change (ii) Climate remains
biomedical waste and pesticides.
continuously. constant in a region
for a long duration. (iv) Noise pollution is caused by machines,
vehicular traffic, loudspeakers and household
(iii) Weather is related (iii) Climate is related
appliances.
to a specific location to a longer duration
and specific time. and larger area. (3) What is meant by solid waste?
(iv) Changes in the (iv) Changes in the Ans. The waste materials generated through the
weather may occur climate take place various daily human activities are called solid
for short periods of slowly over a much waste.
time. long duration. (4) What are the different things included in
solid waste?
* (2) Degradable and non-degradable wastes:
Ans. Domestic waste, industrial waste, hazardous
Degradable Waste Non-degradable Waste waste, electronic waste, biomedical waste,
(i) This type of waste is (i) This type of waste is urban waste, radioactive waste and mining
easily degraded by not easily degraded waste are the different things included in solid
microbes. by microbes because waste.
it takes a very long (5) What are the different types of casualties
period of time and that are seen to occur in different types of
the use of various disasters?
techniques. Ans. (i) Death
(ii) It includes kitchen (ii) It includes plastic, (ii) Injuries
waste (spoiled food, metal and other
(iii) Loss of limbs or body parts
fruits, vegetables), similar materials.
ash, soil, dung, parts (iv) Burns
of the plants etc. (v) Diseases
(iii) It is also called wet (iii) It is also called dry (vi) Fractures
solid waste or wet solid waste or dry (vii) Bleeding
garbage. garbage. (viii) People becoming unconscious
(iv) If it is carefully (iv) It can be recycled.
decomposed, we can Q.12. Use your brain power.
get compost and fuel (1) Which factors are affected favourably or
of good quality from unfavourably by climate? What must we do
it. to minimize the effect?
Q.11. Can you tell? Ans.
(1) What is meant by pollution? (i) Climate plays a very important role in our day
to day life.
Ans. Contamination of natural environment that
can harmfully affect the ecosystem is called as (ii) It influences our basic needs like food, clothing
pollution. and shelter as well as our occupations.
148 Master Key Science & Technology (Term - I) (Std. IX)

(iii) Climate is especially important for an agrarian (2) Why is it necessary to recycle non-degradable
country like India. Also climatic factors like waste?
direction and speed of the wind, temperature, Ans.
atmospheric pressure etc. are also considered (i) Non-degradable waste cannot be easily
during construction work. degraded because it takes a very long period
(iv) The science of meteorology helps in predicting of time and the use of various techniques.
climatic conditions by satellites in different (ii) Therefore non-degradable waste should be
ways such as prediction of rainfall, air recycled so, that it does not accumulate and
pollution, dust storms, hot and cold waves cause hazards to the environment.
tsunamic etc so that all the citizens are well- (3) Which materials are included in solid dry
equipped beforehand and can take preventive waste?
measures. Ans. Solid dry waste includes paper, plastic, metals,
glass, cardboard, thermocol etc.

(4) Make a list of various waste materials and articles in your area and prepare a chart as follows:
Ans.

Non-
Degradable
Material degradable Recycling Reuse Toxic
(Organic)
(Inorganic)
(1) Plastic bottle No Yes Yes Yes Yes
(2) Paper Yes No Yes Yes No
(3) Vegetable and fruit peels Yes No No No No
(4) Empty tins No Yes Yes Yes Yes
(5) Glass pieces No Yes Yes Yes No
(6) Dried flowers Yes No No No No
(7) Rags Yes No Yes Yes No
(8) Fused bulbs and tube lights No Yes Yes Yes Yes
(9) Leftover food Yes No No No No
(10) Plastic bags No Yes Yes Yes Yes

Q.13. Think about it: (2) Which waste management processes are
(1) Into which two categories can the waste used in your village / town / city?
materials in the lists above be classified? Ans.
Ans. The waste materials can be classified as (i) The Municipal Corporation or Municipality
biodegradable waste and non-biodegradable collects the various kinds of wastes like dry
waste. waste, solid waste, biomedical waste in
different coloured containers and transports
Q.14. Find out: them to areas where they are treated and
(1) Nowadays, an electronic device - the cell disposed off.
phone - is very popular. From a mobile shop (ii) Industrial waste is mostly recycled and
near your house, find out how they dispose biomedical waste is treated by the scientific
off old and broken down cell phones. methods mentioned below.
Ans. Old and broken down cell phones are sold (a) Solid waste is disposed off in secured land
to scrap dealers, who sell to a bigger dealer fills. The site for secured landfill is selected
where reusable parts are taken out and useless 2 km away from water bodies and away from
parts are sent for recycling. human habitation. Care is taken to see that
Environmental Management 149

the site does not fall in sensitive zone. The (ii) Out of these left over food from tiffins and
landfills layered with clay and plastic and fruit peels and pencil shaving can be used to
then the garbage is spread and left. make compost manure in school garden.
(b) Pyrolysis is done for semi combustible The remaining waste can be sold to scrap
material. Semi combustible materials are dealers and sent for recycling.
heated to high temperature by gas and (iii) Yes, we can do the same with the garbage
electricity. generated in the house.
(c) The municipality can also set up biogas plants
(2) What is the main difference between
where the solid waste is converted to biogas
what we see in the two pictures alongside
by anaerobic fermentation. The biogas can
(A and B).
be used to generate power and also a good
manure which can be used for agriculture.
(d) Bimedical waste is burnt in incinerators to kill
the pathogens. Disinfection and sterilization
is also done while treating biomedical waste
by the Municipal Corporation.
These are some of the waste management
processes used in village / town / city.

Q.15. Activity based Questions:

(1) Observe the garbage collected in the dustbin
of your classroom and make a list of the
various materials in it. (A)
Discuss with your teacher, how these
materials can be properly disposed off. Can
we do the same with the garbage generated
in our house? Think about it.

(B)
Ans.
(i) We see that in picture A there is lot of garbage
spread around making the place very dirty,
whereas in picture B, there is no garbage and
Solid Waste the place is absolutely neat and clean.
Ans. (3) What should we do to permanently maintain
(i) Garbage collected in classroom dustbin: the condition seen in picture B?
(a) Waste paper and paper bits. Ans. To permanently maintain the condition seen
(b) Pencil shavings in picture B, we should follow the 3R mantra
(c) Wrappers of chocolates, biscuits etc. (Reduce, Reuse, Recycle). Also, we must avoid
(d) Left over food from tiffins and fruit peels. littering, throwing plastic bags, wrappers of
(e) Empty ball pen refills. chocolates, ice-creams, biscuits etc.
vvv
150 Master Key Science & Technology (Term - I) (Std. IX)

ASSIGNMENT - 9
Time : 1 Hr. Marks : 30

Q.1. (A) Fill in the blanks: (2)

(1) ............. influences our basic needs like food, clothing and shelter as well as our occupations.
(2) ............. is action implemented through proper planning, organized activity and co-ordination.

(B) Match the columns: (2)

Column ‘A’ Column ‘B’

(1) Harmful waste (a) Glass, rubber, carry bags, etc.
(2) Domestic waste (b) Chemicals, pigments, ash, etc.
(3) Biomedical waste (c) Radioactive material
(4) Industrial waste (d) Left over food, vegetables,
peelings of fruits.
(e) Bandages, cotton, needles, etc.

(C) State whether the following statements are true or false. If false, rewrite the correct
statement: (2)
(1) If the victim has burn injuries, it is beneficial to cover the burnt part with blanket.
(2) Certain plastic bags take 1 month to degrade.

Q.2. Answer the following questions in short: (8)

(1) Why is e-waste harmful? Express your opinion about this.
(2) Write a note on meteorology.
(3) Write a note on Plastic waste.
(4) Distinguish between weather and climate.

Q.3. Answer the following questions in brief. (Any two): (6)

(1) What are the principles of first aid?
(2) How is first-aid provided to victims of disasters who are injured?
(3) Explain with suitable examples, the relationship between weather forecasting and disaster
management.

Q.4. Answer the following in detail: (10)

(1) State the scientific and eco-friendly methods of waste management.
(2) Explain with suitable examples, the care to be taken when using methods of transporting
patients.

vvv
 Information Communication Technology:
10 The new direction of progress

CONCEPT MAP

Information Communication Technology: The new direction of progress

Devices

Computer Radio Television Set Mobile

Components Generations Opportunities

RAM
Internal Software field
Memory 1st Generation
External ROM 2nd Generation Hardware field
Operating System
3rd Generation Training
Program 4th Generation Marketing
5th Generation
Data

Hardware
Microsoft Word
Software
Microsoft Powerpoint

Microsoft Excel

Adobe Reader

MASTER KEY QUESTION SET - 10 information obtained in an experiment, one

uses .
*Q.1. (A) Fill in the blanks and rewrite the
(4) The first generation computers used to shut
complete statements:
down because of .
(1) While working with a computer we can read
the information stored in its memory and (5) A computer will not work unless is
perform other actions in memory. supplied to it.
(2) While presenting pictures and videos about Ans. (1) RAM (Random Access Memory) (2) Microsoft
the works of scientists, we can use . Powerpoint (3) Microsoft Excel (4) excessive heat
(3) To draw graphs based on the quantitative generation (5) operating system

(151)
152 Master Key Science & Technology (Term - I) (Std. IX)

(B) Rewrite the following statements by (8) Full form of ROM is .

selecting the correct options given below: (a) Roaming Only Memory
(1) includes communication devices (b) Random Output Media
and the use of those devices as well as the (c) Read Only Memory
services provided with their help. (d) None of the above
(a) Operating System (9) RAM and ROM are 2 types of
(b) Office memory.
(c) Computers (a) external (b) internal
(d) Information Communication Technology (c) physical (d) garbage
(2) are used for sharing information. (10) The information stored in ROM is only
(a) Telephones (b) Hard disks , changes cannot be made.
(c) RAM (d) ROM (a) external memory (b) readable
(3) Hard disks are used for information. (c) accessible (d) physical
(a) Storing (b) Communicating (11) is a group of commands to be given
(c) Sharing (d) All of the above to the computer.
(4) Computers are used for information. (a) Program (b) Memory
(a) Storing (b) Managing (c) Data (d) Operating System
(c) Sharing (d) All of the above (12) communicates between the
(5) Computers have gone through computer and the person working on it.
generations. (a) Program (b) Memory
(a) 5 (b) 7 (c) 10 (d) 8 (c) Data (d) Operating System
(6) First generation of Computers were considered (13) is a raw information.
to be present in the period of . (a) Program (b) Memory
(a) 2000 – 2001 (b) 1901 – 2001 (c) Data (d) Operating System
(c) 1946 - 1959 (d) 1996 - 2001 Ans. (1) Information Communication Technology
(7) Full form of RAM is . (2) Telephones (3) Storing (4) All of the above (5) 5
(a) Roaming Application Memory (6) 1946-1959 (7) Random Access Memory (8) Read
(b) Random Accessible Media Only Memory (9) Internal (10) readable (11) Program
(c) Random Access Memory (12) Operating System (13) Data
(d) None of the above
(C) Complete the table:
Name of the device What is it used for? Where is it used? Benefits from its use
Computer / laptop
Mobile
Radio
Television set
Ans.

Name of the device What is it used for? Where is it used? Benefits from its use

1. Faster Processing
Computer / laptop To process the data Office, Schools
2. Larger storage of data
Mobile Communication Office, Schools 1. Portable
1. Music
Radio Mass Communication House, Office
2. News
1. Entertainment
Television set Mass Communication House, Office
2. News
Information Communication Technology: The new direction of progress 153

Q.2. State whether the following statements are Q.4. Match the columns:
true or false and if false, write the correct
Column ‘A’ Column ‘B’
statement:
(1) Antivirus (a) Output Device
(1) RAM and ROM are the types of external
memory. (2) OS (b) Software
Ans. False, RAM and ROM are the types of internal (3) CPU (c) Input Device
memory. (4) Printer (d) Operating System
(2) ICT includes communication devices and
(5) Mouse (e) Brain of the computer
the use of those devices as well as services
provided with their help. Ans. (1 - b), (2 - d), (3 - e), (4 - a), (5 - c)
Ans. True. Q.5. Answer the following in one or two
(3) A computer cannot be used without operating sentences:
system. (1) Name the computer which was made
Ans. True. between 1946 - 1959.
(4) Microsoft Excel is used to make PowerPoint. Ans. The ENIAC computer was made in the period
Ans. False, Microsoft Excel is used to make of 1946 – 1959.
spreadsheets. (2) Give one example of Input Unit.
(5) Software refers to the set of commands given Ans. Keyboard.
to the computer. (3) Name the 3 major parts of the processing
Ans. True units.
Ans.
Q.3. Write the Full forms of the following:
(i) Memory unit
(1) ICT
(ii) Control unit
Ans. Information Communication Technology
(iii) ALU unit
(2) OS
(4) What precautions need to the taken care
Ans. Operating System
while entering formula into the excel?
(3) RAM
Ans. While using a formula, the ‘=’ sign should
Ans. Random Access Memory be typed first. Similarly, no space should be
(4) ROM inserted while typing any formula.
Ans. Read Only Memory (5) What is internet?
(5) CPU Ans. This is a kind of Search Engine. It helps to
Ans. Central Processing Unit find the information we want from all the
information available on the internet.
(6) DOS
(6) What is a PDF?
Ans. Disk Operating System
Ans. A PDF or Portable Document Format file can
(7) PDF
be used to view the file to print it or to handle
Ans. Portable Document Format files.
(8) ALU (7) What is C-DAC?
Ans. Arithmetic Logical Unit Ans. C-DAC, is a well-known Centre for
(9) GUI Development of Advanced Computing,
Ans. Graphical User Interface situated in Pune.
(10) C-DAC *(8) What devices will you use to share with
Ans. Centre for Development of Advanced others the knowledge that you have?
Computing Ans. Devices like radios, televisions, pendrives,
(11) ISCII computers, laptops, mobiles, landlines, hard
drives, CDs, memory cards help us in sharing
Ans. Indian Script Code for Information Interchange
our knowledge with others.
154 Master Key Science & Technology (Term - I) (Std. IX)

*(9) Make a list of various hardware and software (iii) Without the operating system, the user won’t
items of a computer. be able to input any data or run any program.
Ans. Hardware: Mouse, Keyboard, Pendrive, Thus, a computer cannot run without an
Monitor and other parts of computer. operating system.
Software: Operating Systems, Application
(2) ROM is a Read Only Memory.
Programs, Antivirus, etc.
Ans.
Q.6. Define the following:
(i) ROM also known as Read Only Memory is a
(1) Memory: part of internal memory of a computer where
Ans. Memory is the place for storing data obtained the information stored can only be read.
from the input and also the generated solution
(ii) ROM helps store data permanently for a long
or answer by the computer.
period of time and the information stored
(2) RAM:
cannot be deleted.
Ans. RAM is created from electronic components
and can function only as long as it is supplied (iii) Thus, data in a ROM can only be read and
with electricity. cannot be altered or modified and hence it is
(3) ROM: called as Read Only Memory.
Ans. Information stored in ROM can only be *Q.8. Answer the following in short:
read and changes cannot be made to the *(1) Explain the role and importance of
information originally stored here.
information communication in science and
(4) Operating System: technology.
Ans. It is a program which provides a means of
Ans. ICT plays a key role in creating, displaying,
communication between the computer and
collecting, processing and communicating
the person working on it. It is called the DOS
(Disk Operating System). information in the field of science and
technology.
(5) Program:
Ans. A program is a group of commands to be Following is the importance of ICT in science
given to a computer. and technology:
(6) Data and Information: (i) Access to wide range of information
Ans. Data is information in its raw (unprocessed) (ii) Storing of Data
form. (iii) Processing of Data
(7) Hardware: (iv) Securing work files
Ans. Hardware consists of all the electronic and (v) Proper representation of data
mechanical parts used in computers.
*(2) Which application software in the computer
(8) Software:
system did you find useful while studying
Ans. Software refers to the commands given to the science, and how?
computer, information supplied to it (input)
Ans.
and the results obtained from the computer
after analysis (output). (i) Microsoft word: To write down the
information collected and making a document
Q.7. Give scientific reasons:
for further evaluation.
(1) Computer cannot function without its
operating system. (ii) Microsoft excel : To draw graph based on
Ans. the obtained numerical information from the
(i) Operating system is like a link between the experiment.
computer and the person working on it. (iii) Internet explorer: To search for information in
(ii) Operating system manages all the activities finding out the solution or solving the queries
performed by the computer. by reading the available information.
Information Communication Technology: The new direction of progress 155

*(3) What precautions should be taken while Television: Help in getting information about
using various types of software on the the new and innovative technology.
computer?
Q.9. Answer in brief:
Ans.
*(1) Which technical difficulties did you face
(i) Antivirus must be installed. while using the computer? What did you do
(ii) Software should be legal and from a trusted to overcome them?
place. Ans.
(iii) Application should be scanned before using. (i) Lagging: Due to lot of applications running
(iv) Pirated Software should not be used at the same time, the computer starts lagging
and becomes slow. Closing a few applications
(v) Provide all necessary data to obtain the best
helped solve the problem of lagging.
possible results.
(ii) Viruses and Bugs: Cybercrimes are rising
*(4) Which are the various devices used in daily, even from single mail the computer
information communication? How are they can be attacked by viruses. Installing a valid
used in the context of science? antivirus help solve the problem of viruses
Ans. Various devices used in information and bugs.
communication are: Computers, Laptops, (iii) Breach of Privacy: Confidential information
Mobiles, Radios, Television, etc. being accessed by anyone is the breach of
privacy. Putting privacy setting in place helps
Computers, Laptops and Mobiles: Help solve the problem.
in accessing, collecting, processing, (iv) Physical Damage: Hardwares over a period
communicating, sharing and storing of of time might get physically damaged. Taking
information. It helps in determining the precautions while using helps solve the
appropriate conclusions in all fields, including problem.
the field of science.

*(2) Using a spreadsheet, draw graphs between distance and time, using the information about the
movements of Amar, Akbar and Anthony given in the table 4, in the lesson on Laws of Motion. What
precautions will you take while drawing the graph?
Ans.

5.00 5.30 6.00 6.30 7.00 7.30 8.00

Distance covered by Amar in km Distance covered by Akbar in km Distance covered by Anthony in km

156 Master Key Science & Technology (Term - I) (Std. IX)

Precautions to be taken while drawing a Characteristics:

graph: (i) Huge in size
(i) The data should be kept in tabular form. (ii) Expensive
(ii) Whenever there is ‘drag and fill’ option used, (iii) Lot of Electricity Consumption
‘smart tag’ option should be used after ‘drag (iv) Heat Generation
data’ to fill data as required.
Generation: 2nd
(iii) Entered data should be formatted in the Time Period: 1956 – 1963
manner required.
Development: Transistors
(iv) Various types of graphs can be created by Characteristics:
using the same data, so appropriate graph
(i) Frequent Shutdowns
should be selected.
(ii) Superior to 1st Generation
(v) Chart titles and axes titles should be updated
(iii) Small in size and Fast
as per the data.
(iv) Cheaper as compared to 1st Generation
*(3) Using information communication
(v) Less consumption of Electricity
technology, prepare PowerPoint presentations
on at least three topics in your textbook. Generation: 3rd
Make a flowchart of the steps you used while Time Period: 1963 – 1971
making these presentations. Development: IC
Ans. Steps for preparation of PowerPoint Characteristics:
presentations: (i) Keyboards and Monitors
(ii) OS
STEP 1: Select Microsoft PowerPoint from the start
(iii) Smaller and further Cheaper
option.
Generation: 4th
STEP 2: Create a new file from the program Time Period: 1971 – 2010
command Development: Microprocessor
Characteristics:
STEP 3: Choosing a Design/Layout for the (i) Use of Internet
background (ii) GUI
(iii) Introduction of Portable devices like mobiles,
laptops, etc.
STEP 4: Create appropriate Title Page
Generation: 5th
STEP 5: Add slides according to the requirement Time Period: 2010 – Till Date
Development: Artificial Intelligence (AI)
Characteristics:
STEP 6: Add pictures, videos, charts etc. to support
(i) Voice Recognition
your presentation
(ii) Sensors
(iii) Nano Technology
STEP 7: Add transitions to your slides and
animation to your content 1st Generation computers occupied the entire
room, but due to advancement in science and
technology, today’s computer fits into our
STEP 8: Preview and Play the presentation pockets.
Initially computers needed a specific language
*(4) Explain the differences between the different
to interact but today we use voice recognition
generations of computers. How did science
for the same.
contribute to these developments?
In these ways, science has contributed in
Ans. Generation: 1st
making the computers faster, smaller, cheaper
Time Period: 1940 – 1956
and much more useful.
Development: Vacuum Tubes
Information Communication Technology: The new direction of progress 157

(5) Write in short the opportunities in the field who are experienced in the working of
of ICT. computers as well as skilled in marketing.
Ans. (iv) Training: The training of new entrants for
(i) Software Field: This is an important field. various jobs is a vast field. It is very important
to have dedicated teachers who are competent
Having accepted the challenge of creating
in the field of computers.
software, many companies have entered this
field. The opportunities in the software field (6) Write in short about the industries conducting
can be classified as follows - application research in the field of computers.
program development, software package Ans.
development, operating systems and utility (i) C-DAC, the well-known Centre for
development, special purpose scientific Development of Advanced Computing,
applications. situated in Pune, is the leading institute in
(ii) Hardware Field: Today, there are several India which conducts research in the field of
companies in our country too, which make computers.
computers. They sell computers that they (ii) The first Indian supercomputer was made with
have themselves made. Others sell computers help from this institute. Valuable guidance for
brought from outside as well as repair making this computer (the Param computer)
them and take maintenance contracts to was received from the senior scientist Vijay
keep computers in big companies working Bhatkar. Param means the supreme.
efficiently without a break. Plenty of jobs are (iii) This computer can perform one billion
available here. There are job opportunities in calculations per second. It is used in many
hardware designing, hardware production, fields like space research, movements in the
hardware assembly and testing, hardware interior of the earth, research in oil deposits,
maintenance, servicing and repairs, etc. medicine, meteorology, engineering, military
etc. C-DAC has also participated in developing
(iii) Marketing: There are many establishments the ISCII code for writing different language
which make and sell computers and related scripts. (Indian Script Code for Information
accessories. They need good sales personnel Interchange).

(7) Using Microsoft Word to create a document and write equations.

Ans.
(i) Click on the Microsoft word 2010 icon on the desktop
(ii) Select the ‘New option in the ‘File’ tab, and then select the ‘Blank document’ option.
(iii) Type your material on the blank page on the screen using the keyboard. Use the language, font size, bold,
etc. options in the Home tab to make the typed material attractive.
(iv) To type equations in the text, select the ‘Equation’ option in the ‘Insert’ tab.

(v) Select the proper equation and type it using mathematical symbols.
158 Master Key Science & Technology (Term - I) (Std. IX)

(8) What precautions will you take when (2) How does a computer work?
entering data? Ans.
Ans.
Input unit Processor Output Unit
(i) As far as possible, the data should be kept in
tabular form. Different types of data should All types of Processing Unit The result /
be entered in different cells. Data should be information/ 1. Memory unit solution/
entered neatly and in one ‘flow’. Unnecessary data is 2. Control unit answer is
space and special characters should not be entered into 3. ALU unit eventually
used. the computer sent to the
through this output unit.
(ii) Many times we ‘drag and fill’ data. At such
unit. Generally, Generally a
times, the ‘smart tag’ can be used after ‘drag
a keyboard s c r e e n /
data’ to fill any data in any manner as required.
is used to monitor or
(iii) Once the data has been entered it can be
enter data or printer is used
formatted in different ways. Similarly, we can
information as an output
perform different types of calculations, using
unit.
different formulae.
(iv) While using a formula, the ‘=’ sign should Q.11. Think about it:
be typed first. Similarly, no space should be (1) How is information communication
inserted while typing any formula. technology important for dealing with
*Q.10. Can you tell! explosion of information?
(1) Which devices do we directly or indirectly Ans. Information explosion means a situation
use for collecting, sharing processing and where information is available in abundance,
communicating information? in other words, too much information.
Ans. (1) Computers (2) Laptops (3) Mobiles Devices like computers, laptops help us in
(4) Memory Cards (5) Pendrives 6) Landlines easier accessment of information that we need
(7) Hard disks etc. from all the data.

vvv
Information Communication Technology: The new direction of progress 159

ASSIGNMENT - 10
Time : 1 Hr. Marks : 30

Q.1. (A) Fill in the blanks: (2)

(1) While working with a laptop or a computer, we can read the information stored in its memory and
perform other actions in .
(2) Graph based on quantitative information obtained is displayed in .
(B) Fill in the blanks by selecting the appropriate option: (2)
(1) RAM and ROM are two types of memory.
(a) external (b) internal (c) physical (d) garbage
(2) is a group of commands to be given to the computer.
(a) Program (b) Memory (c) Data (d) Operating System
Q.2. State whether the following statements are true or false and if false, write the correct (2)
statement:
(1) RAM and ROM are the types of external memory.
(2) A computer cannot be used without operating system.
Q.3. Write the full forms of the following: (3)
(1) ICT (2) OS (3) CPU
Q.4. Answer in one line: (2)
(1) What precautions need to the taken care while entering formula into the Excel?
(2) What is internet?
Q.5. Give scientific reasons: (2)
(1) Computer cannot function without its operating system.
Q.6. Write in short the opportunities in the field of ICT: (8)
(1) Software Field (2) Hardware Field
(3) Marketing (4) Training
Q.7. Answer in brief: (9)
(1) What precautions should be taken while using various types of software on the computer?
(2) Which are the various devices used in information communication? How are they used in the
context of science?
(3) Write in short about the industries conducting research in the field of computers.

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 11 Reflection of Light
CONCEPT MAP

Torch and Light

head lamps
of vehicles Spherical Mirror
Flood
lights Rear view
mirror of car
Projector Uses Uses
lamps Concave (Converging) Convex (Diverging)
Big security
Position of object
Solar mirrors in shops
devices Image
Position of Any Portion Behind the mirror
Shaving object
mirror and
dentist
mirror

At Infinity At Focus Between F and C Beyond C At C Between P and F

Image at Image at Image Image Image Image

Focus Infinity Beyond C Between F and C At C Behind the mirror

(8) The image of a word appears in the

MASTER KEY QUESTION SET - 11 mirror.
Q.1. (A) Fill in the blanks: Ans. (1) focus (2) convex (3) same (4) pole (5) focal length
(6) focus (7) principal axis (8) laterally inverted
(1) A ray of light parallel to principal axis after
reflection from concave mirror passes through (B) Rewrite the following statements by
. selecting the correct options given below:
(2) The focal length of mirror is positive. (1) If the reflected rays do not actually meet, such
(3) The image formed by a plane mirror is of the an image is called as image.
size as the source. (a) real (b) virtual
(4) All distances parallel to principal axis are (c) magnified (d) inverted
measured from the of the mirror. (2) In a plane mirror, the perpendicular distance
(5) The is the distance between principal of the image from the mirror is equal to
focus and the pole. .
(6) In torches, the source of light is kept at the (a) the perpendicular distance of the source
of the mirror. from the object.
(7) The straight line passing through the pole (b) the perpendicular distance of the source
and centre of curvature of the mirror is called from the mirror.
.
(5)
6 Master Key Science & Technology (Term - II) (Std. IX)

(c) the parallel distance of the source from the (10) A rear view mirror of a car is .
object. (a) plane mirror (b) concave mirror
(d) the parallel distance of the source from the (c) convex mirror (d) cylindrical mirror
mirror. (11) An image of an object placed at infinite
(3) In order to see the full image of a person distance from a concave mirror is formed at
standing in front of a mirror, the minimum .
height of the mirror must be . (a) the focus of the mirror
(a) same height as that of the person (b) behind the mirror
(b) double the height of the person (c) centre of curvature
(c) half the height of the person (d) infinity
(d) quarter the height of the person (12) A concave mirror is also called as a
(4) If the inner surface of the spherical mirror is mirror.
reflecting then it is mirror, and if the (a) converging (b) diverging
outer surface is reflecting then it is (c) plane (d) outward curved
mirror. (13) A ray of light parallel to principal axis after
(a) convex, concave (b) convex, plane reflection from concave mirror passes through
(c) concave, plane (d) concave, convex .
(5) The image formed in a convex mirror is always (a) centre of curvature (b) focus
. (c) pole (d) optical centre
(a) virtual, smaller and behind the mirror (14) The centre of the mirror surface is called its
(b) virtual, smaller and front of the mirror .
(c) real, smaller and behind the mirror (a) pole (b) centre of curvature

(d) real, smaller and front of the mirror (c) principal axis (d) focus
(15) The image made by a plane mirror is a
(6) The image formed by a concave mirror is
image.
.
(a) real (b) virtual
(a) always virtual and erect
(c) inverted (d) diminished
(b) always virtual and inverted
(16) According to the new sign convention, the
(c) virtual if the object is placed between the
of the mirror is taken as origin.
pole and the focus
(a) focus (b) pole
(d) virtual if the object is beyond the focus
(c) optical centre (d) centre of curvature
(7) No matter how far you stand from a spherical
(17) The size of the image of an object placed at the
mirror, your image appears erect. The mirror
focus of a concave mirror is .
may be .
(a) erect (b) very large
(a) plane (b) concave
(c) same size (d) diminished
(c) convex (d) either plane or convex
(18) A convex mirror is also called as a
(8) In case of a concave mirror, an erect image is mirror.
.
(a) converging (b) plane
(a) real and enlarged
(c) diverging (d) inward curved
(b) real and diminished
(19) For virtual images, the height is
(c) virtual and diminished while for real images, it is .
(d) virtual and enlarged (a) positive, positive (b) negative, positive
(9) images can be displayed on a screen. (c) negative,negative (d) positive, negative
(a) Virtual (b) Real Ans. (1) virtual (2) the perpendicular distance of the
(c) Virtual and erect (d) Virtual and inverted source from the mirror (3) half the height of the
Reflection of Light 7

person (4) concave, convex (5) virtual, smaller (11) A concave mirror always forms a real and
and behind the mirror (6) virtual if the object is inverted image.
placed between the pole and the focus (7) either Ans. False, a concave mirror can also form a virtual
plane or convex (8) virtual and enlarged (9) Real and erect image.
(10) convex mirror (11) the focus of the mirror (12) Doctors use diverging beam of light to study
(12) converging (13) focus (14) pole (15) teeth, ears and eyes.
virtual (16) pole (17) very large (18) diverging Ans. False, doctors use converging beam of light to
(19) positive, negative study teeth, ears and eyes.
Q.2. State whether the following statements are Q.3. Find the odd man out:
true or false and if false, write the correct (1) Torches, flood lights, head lamps of vehicles,
statement: rear view mirror.
(1) If the mirrors are kept at right angle to each Ans. Rear view mirror. In rear view mirrors convex
other then the number of images formed will mirror is used. Concave mirrors are used in
be 4. the rest.
Ans. False, if the mirrors are kept at right angle to (2) Side mirrors of cars, parking mirrors, flood
each other then the number of images formed lights, mirror fitted in shops.
will be 3. Ans. Flood lights. In flood lights concave mirror is
(2) A convex mirror is used in flood lights. used. Convex mirrors are used in the rest.
Ans. False, a concave mirror is used in flood lights. (3) Virtual and enlarged, virtual and diminished,
(3) A concave mirror always forms a magnified real and inverted, real and magnified
image. Ans. Virtual and diminished type of image is not
formed by a concave mirror. Rest all type of
Ans. False, a concave mirror can sometimes form a
images are formed by a concave mirror.
diminished image as well.
(4) Image is laterally inverted, Image is of same
(4) Images formed by convex mirrors are always
size, image is at same distance, image is
virtual.
diminished.
Ans. True Ans. Image is diminished is not a characteristic of
(5) The distance between the focus and the pole is image formed in a plane mirror. Rest of them
called the radius of curvature. are characteristics of plane mirror.
Ans. False, the distance between the focus and the Q.4. (A) Match the columns:
pole is called the focal length.
(1) Column ’A’ Column ’B’
(6) Reflection from a spherical mirror obeys laws
of reflection. (1) Plane mirror (a) Rear view mirror
Ans. True (2) Concave mirror (b) At laughing gallery
(7) The reflecting surface of a concave mirror is (3) Convex mirror (c) At a hair dresser
curved. (4) Irregular curved (d) At a dentist
Ans. True mirror

(8) Distances measured in the direction of the Ans. (1 - c), (2 - d), (3 - a), (4 - b)
incident light are taken as positive.
(2) Column ’A’ Column ’B’
Ans. True
(1) Plane mirror (a) Virtual and diminished
(9) If the image is erect, the height of the image is
image
negative.
(2) Concave mirror (b) Virtual and same size
Ans. False, if the image is erect, the height of the image
image is positive..
(3) Convex mirror (c) Real and inverted image
(10) A real image can be displayed on a screen.
Ans. True Ans. (1 - b), (2 - c), (3 - a)
8 Master Key Science & Technology (Term - II) (Std. IX)

Q.5. Answer the following in one or two sentences:

(2) It is called as (2) It is called as
* (1) What is a mirror? diverging mirror. converging mirror.
Ans. A mirror is a reflecting surface which reflects
light and creates clear images. (3) The focus of a convex (3) The focus of a con-
* (2) What is light ? mirror is virtual. cave mirror is real.
Ans. Light is a form of electromagnetic radiation (4) It can form only a (4) It can form a real
that produces the sensation of vision. virtual image. as well as a virtual
(3) What kind of mirror will a doctor use to image.
concentrate on teeth, eyes, ears etc.?
Ans. The doctor will use a concave mirror to (5) It can form only a (5) It can form an
concentrate on teeth, eyes, ears etc. diminished image. enlarged, diminished
(4) What do the nature, position and size of the as well as the same
image depend on? size image.
Ans. The nature, position and size of the image (2) Real image and Virtual image
depend upon the distance of the object from
the surface. Real image Virtual image
(5)
Give the expression for mirror formula. (1) A real image is (1) A virtual image is
1 1 1
Ans. v + u = f formed only when formed only when
the reflected rays the reflected rays
(6) State any four uses of concave mirror. actually meet at a appear to meet at a
Ans. Concave mirrors are used in torches, point. point.
headlights, shaving mirrors, dentists’ mirrors,
solar devices etc. (2) Real images can be (2) Virtual images
obtained on a screen. cannot be obtained
(7) What are the two types of spherical mirror?
on a screen.
Ans. Convex mirror and concave mirror are the
two types of spherical mirror. (3) All real images are (3) All virtual images
inverted. are erect.
* (8) What is meant by reflection of light and what
are the types of reflection? * (3) Concave and Convex Mirror
Ans. The bouncing back of light when if hits an Principal Focus of the Principal Focus of the
opaque surface is called reflection of light. Concave Mirror Convex Mirror
The two types of reflection are regular and
(1) Incident rays which (1) Incident rays parallel
irregular reflection.
are parallel to the to the principal axis,
* (9) What are the laws of reflection. principal axis of a after reflection,
Ans. concave mirror, after appear to come from
(i) The incident ray, reflected ray and normal at reflection from the a particular point
the point of incidence all lie in the same plane. mirror, meet at a behind the mirror
particular point in lying along the
(ii) The angle of incidence is equal to angle of
front of the mirror principal axis. This
reflection.
on the principal point is called the
(iii) The incident ray and the reflected ray lie on axis. This point (F) is principal focus of
opposite sides of the normal. called the principal the convex mirror.
Q.6. Distinguish between: focus of the concave
(1) Convex mirror and Concave mirror mirror.
Convex mirror Concave mirror (2) It is formed in front (2) It is formed behind
of the mirror. the mirror.
(1) In a convex mirror, (1) In a concave mirror,
the reflecting surface the reflecting surface (3) Focus of concave (3) Focus of convex
is on the outer side. is on the inner side. mirror is real. mirror is virtual.
Reflection of Light 9

Q.7. Define the following: is placed at the focus of a concave mirror, a

(1) Centre of curvature of mirror (C) parallel beam of light rays is obtained.
Ans. The centre of the sphere of which the mirror is (ii) This helps us to see things upto a considerable
a part, is called the centre of curvature of the distance in the darkness.
mirror. (3) A dentist uses a concave mirror while
(2) Radius of curvature (R) examining teeth.
Ans. The radius of the sphere of which the mirror is Ans.
a part, is called the radius of curvature of the
(i) A concave mirror produces an erect, virtual
mirror.
and magnified image of an object placed
(3) Pole (P) between its pole and focus.
Ans. The centre of the mirror surface is called its (ii) A dentist uses this principle to get a clear and
pole.
distinct image of teeth, hence a dentist uses a
(4) Principal axis of a mirror concave mirror.
Ans. The straight line passing through the pole and Q.9. Answer the following in short:
centre of curvature of the mirror is called its
* (1) Explain the difference between a plane
principal axis.
mirror, a concave mirror and a convex mirror
(5) Focus of a concave mirror (F)
with respect to the type and size of the
Ans. Incident rays which are parallel to the principal images produced.
axis of a concave mirror, after reflection from
Ans.
the mirror, meet at a particular point in front
of the mirror on the principal axis. This point Plane Concave Convex
(F) is called the principal focus of the concave mirror mirror mirror
mirror. Type Virtual Virtual (erect) Virtual
(6) Focus of a convex mirror (F) of and as well as Real and Erect
Ans. Incident rays parallel to the principal axis, image Erect (inverted)
after reflection, appear to come from a Size Same Diminished, Dimini-
particular point behind the mirror lying along of size Same size and shed
the principal axis. This point is called the image magnified
principal focus of the convex mirror.
*(2) Describe the positions of the source of light
(7) Focal length of a mirror (f)
with respect to a concave mirror in (i) Torch
Ans. The distance (f) between the pole and the light (ii) Projector lamp (iii) Flood light.
principal focus of the mirror is called the focal
length. This distance is half of the radius of Ans.
R (i) Torch light : The source of light is placed at
curvature of the mirror. f =
2 the focus.
Q.8. Give scientific reasons:
(ii) Projector lamp : The source of light is placed
(1) A concave mirror is called a converging
at the centre of curvature.
mirror.
(iii) Flood light : The source of light is placed just
Ans.
beyond the centre of curvature.
(i) When rays of light parallel to the principal axis
are incident on concave mirror, they converge. *(3) Why are concave mirrors used in solar
(ii) After convergence, they meet at one point on devices?
the principal axis, hence concave mirror is Ans.
called converging mirror. (i) Solar devices like solar cooker or solar water
(2) Concave mirrors are used in torches and in heater use solar energy to cook food or heat
car headlights. water.
Ans. (ii) When sun rays fall on the concave mirror,
(i) Concave mirrors are used in torches and car they converge and come together in the focal
headlights because when a source of light plane.
10 Master Key Science & Technology (Term - II) (Std. IX)

(iii) Due to convergence, the intensity of sun rays Q.10. Answer in detail:
increases and the food or water is heated * (1) What sign conventions are used for reflection
faster. Hence concave mirrors are used in from a spherical mirror?
solar devices. Ans.
* (4) Why are the mirrors fitted on the outside of
Direction of incident rays Y axis
cars convex?
Ans. Distances on
Distances on
Distances
(i) A convex mirror is used as rear view the left the right
upward
mirror because they form erect, virtual, and (Positive +) (negative –) (positive +) X axis
diminished images.
Distances Principal axis
(ii) This, allows the driver to view a large area in
downward
a small mirror. (Negative –)
*(5) Why does obtaining the image of the sun
on a paper with the help of a concave mirror
burn the paper?
Ans. According to the Cartesian sign convention,
(i) When sun rays fall on the concave mirror, the pole of the mirror is taken as the origin.
they converge and come together in the focal The principal axis is taken as the X-axis of the
plane. frame of reference. The sign conventions are
(ii) Due to convergence the intensity of sun rays as follows.
increases. (i) The object is always kept on the left of the
(iii) Hence, image of the sun on a paper with the mirror. All distances parallel to the principal
help of a concave mirror burn the paper. axis are measured from the pole of the mirror.
* (6) If a spherical mirror breaks, what type of (ii) All distances measured towards the right of
mirrors are the individual pieces? the pole are taken to be positive, while those
Ans: measured towards the left are taken to be
negative.
(i) When a spherical mirror brakes into smaller
pieces, the radius of curvature and focal length (iii) Distance measured vertically upwards from
does not change. the principal axis are taken to be positive.
(ii) Hence, it will continue to behave like a (iv) Distance measured vertically downwards
spherical mirror only. from the principal axis are taken to be negative.
(7) What are the rules for drawing ray diagrams (v) The focal length of a concave mirror is negative
for the formation of image by spherical while that of a convex mirror is positive.
mirror ? *(2) Draw ray diagrams for the cases of images
Ans. The rules are as follows : obtained in concave mirrors:
Rule 1 : If an incident ray is parallel to the (i) A ray diagram for object at infinity for a
principal axis then the reflected ray passes concave mirror.
through the principal focus. Ans.
Rule 2 : If an incident ray passes through the
principal focus of the mirror, the reflected ray
A
is parallel to the principal axis.
Rule 3 : If an incident ray passes through the
centre of curvature of the mirror, the reflected C F P
ray traces the same path back.
B
Reflection of Light 11

Image position : At focus. (v) A ray diagram for object at focus for a
Nature : Real, inverted and point image. concave mirror.
Ans.
(ii) A ray diagram for object beyond centre of
curvature for a concave mirror.
Ans. A

C BF P

A
B’
B C F P
A’ Image position : At infinity.
Nature : Real, inverted and highly magnified.
(vi) A ray diagram for object between pole and
Image position : Between centre of curvature focus for a concave mirror.
and focus. Ans.
Nature : Real, inverted and diminished. A’

(iii) A ray diagram for object at centre of curvature A

for a concave mirror.
C F B P B’

A
B C
B’ P
Image position : Behind the mirror.
F
A’ Nature : Virtual, erect and magnified.
*(3) Which type of mirrors are used in the
following?
Image position : At centre of curvature. Periscope, floodlights, shaving mirror,
kaleidoscope, street lights, head lamps of a
Nature : Real, inverted and same size.
car.
(iv) A ray diagram for object between F and C for Ans. Periscope – Plane mirror
a concave mirror. Floodlights – Concave mirror
Ans. Shaving mirror – Concave mirror
Kaleidoscope – Plane mirror
Street lights – Convex mirror
A Head lamps of car – Concave mirror
(4) Draw ray diagrams for the image obtained in
convex mirrors.
B’
C B F P Ans. Object between Infinity and P of a Convex
mirror

A
A’
A’
B P B’ F C
Image position : Beyond centre of curvature.
Nature : Real, inverted and magnified.
12 Master Key Science & Technology (Term - II) (Std. IX)

Position of Image : behind the mirror Proof :

Nature of Image : (A) Virtual, (B) Erect (i) In the figure, the point at the top of the head,
(C) Diminished. the eyes and a point at the feet of a person are
(5) In order to see the full image of a person indicated by H, E and F respectively.
standing in front of a mirror, the minimum (ii) R and S are midpoints of HE and EF
height of the mirror must be half the height respectively.
of the person. Explain. (iii) The mirror PQ is at a height of NQ from the
Ans. ground and is perpendicular to it. PQ is the
M minimum height of the mirror in order to
H H’
obtain the full image of the person.
R R’
P For this, RP and QS must be perpendicular to
E the mirror.
Minimum height of the mirror
Q
S S’ PQ = RS
= RE + ES
HE EF HF
F F’ = + =
N 2 2 2
= Half of the person’s height.

(6) Determine the sign of magnification in each of the 6 cases in the table and verify that they are same
using formulae
h2 –v
M= and M =
h1 u
Ans.

Position of image h –v
No. Position of object (u) Name of image M = h2 M=
(v) 1 u

Between Pole and Behind the mirror v erect and virtual +ve –(+ve)
M= M=
1.
focus u is (–ve) is (+ve) h2 is (+ve) +ve (–ve)
= +ve = +ve

inverted and real –ve –(–ve)

At the focus. u is (–ve) At infinity v is (–ve) M= M=
2.
h2 is (–ve) +ve –ve
= –ve = –ve
Between focus and –ve –(–ve)
Beyond centre of inverted and real M= M=
3. centre of curvature u +ve –ve
curvature v is (–ve) h2 is (–ve) = –ve = –ve
is (–ve)

At the centre of At the centre of inverted and real –ve –(–ve)

M= M=
4.
curvature u is (–ve) curvature v is (–ve) h2 is (–ve) +ve –ve
= –ve = –ve
Between centre –ve –(–ve)
Beyond centre of inverted and real M= M=
5. of curvature and +ve –ve
curvature u is (–ve) h2 is (–ve) = –ve = –ve
focus v is (–ve)

At very large distance inverted and real –ve –(–ve)

At focus v is (–ve) M= M=
6.
(infinity) u is (–ve) h2 is (–ve) +ve –ve
= –ve = –ve
Reflection of Light 13

Q.11. Solve the following numericals. Solution: n = 360° – 1

A
Tips for solving numericals :
(i) Object distance (u) is always –ve n + 1 = 360°
A
(ii) If Image distance (v) is +ve then image is
behind the mirror and virtual. A = 360°
n+1
If v is –ve then image is in front of the mirror
= 360°
and real. 3+1
(iii) Object height (h1) is always +ve since it is
= 360°
erect. 4
(iv) Image height (h2) can be +ve for virtual or –ve A = 90°
for real.
The mirrors are inclined at an angle of 90° to
TYPE – A
360° each other.
n= – 1
A (3) An image is formed 5 cm behind a convex
n = number of images mirror of focal length 10 cm. At what distance
A = angle between mirror. is the object placed from the mirror?
1 1 1
Mirror formula: v + u = f Solution:
Given : Image distance (v) = 5 cm
(1) A bird is sitting in front of two plane mirrors
Focal length (f) = 10 cm
inclined at an angle of 60° to each other. How
To find : Object distance (u) = ?
many images does the bird see in the mirror?
Formula: 1 1 1
Solution: + =
v u f
Given : Angle between mirror A = 60° 1 1 1
Solution: + =
To find : Number of images formed n = ? v u f
1 1 1
Formula: 360°
n= – 1  = –
A u f v
1 1 1
Solution: n = 360° – 1  = –
A u 10 5
360° 1 1 – 2
= – 1  u
=
10
60°
1 –1
= 6 – 1  u
=
10
 u = –10 cm
n=5
The object is placed at a distance of 10 cm in
The bird sees 5 images in the mirror. front of the mirror.

(2) A coin is kept in front of two plane mirrors (4) An object placed 20 cm in front of a convex
inclined to each other. If images of the coin mirror is found to have an image 15 cm
behind the mirror. Find the focal length of
are seen then what is the angle A between the
the mirror.
mirrors?
Solution:
Solution:
Given : Object distance (u) = –20 cm
Given : no. of images formed n = 3
Image distance (v) = 15 cm
To find : Angle between mirror A = ?
To find : focal length (f) = ?
360°
Formula: n= – 1 1 1 1
A Formula: + =
v u f
14 Master Key Science & Technology (Term - II) (Std. IX)

Solution: 1 1 1 (2) An object 2 cm high is placed at a distance of

+ =
v u f 16 cm from a concave mirror which produces
1 1 1 a real image 3 cm high. Find the image
 +
15 (–20)
=
f distance.
1 1 1
 – = Solution:
15 20 f
Given : Object height (h1) = 2 cm
4 – 3 1
 60
=
f Object distance (u) = –16 cm
1 1 Image height (h2) = –3 cm
 60
=
f To find : Image distance (v) = ?
h2 v
 f = 60 cm Formula : M = h = – u .. (As image is real.)
1
 The focal length of the convex mirror is 60 h2 v
cm. Solution: h = – u
1
–3 –v
=
NUMERICAL FOR PRACTICE 2 –16
(5) An object is placed at a distance of 36 cm from –16 × 3
 v =
a concave mirror of focal length 12 cm. Find the 2
image distance.  v = –24 cm
Ans. –18 cm The image is formed at a distance of 24 cm in
(6) An arrow is placed at a distance of 25 cm from front of the mirror.
a diverging mirror of focal length 20 cm. Find
the image distance. NUMERICAL FOR PRACTICE
Ans. 11.1 cm (3) An object 10 cm in height is placed at a
distance of 36 cm from a concave mirror. If
TYPE – B
h2 v the image is formed at a distance of 18 cm in
Magnification formula: M = = – front of the mirror, find the height of image.
h1 u
Ans. –5 cm
(1) An object 4 cm in height is placed at a distance
of 36 cm from a concave mirror. The image is (4) A converging mirror forms a real image of
formed 18 cm in the front of the mirror. Find height 4 cm of an object of height 1 cm placed
the height of the image. 20 cm away from the mirror. Find the image
distance.
Solution:
Ans. –80 cm
Given : Object height (h1) = 4 cm
TYPE – C
Image distance (v) = –18 cm
Numericals based on the formulae :
Object distance (u) = –36 cm
To find : Height of image (h2) = ? 1
+
1
=
1
v u f
h2 v
Formula : M = h = – u .. (As image is real.) M=
h2
= –
v
1 h1 u
h2 v
Solution: h = – u
1
*(1) Rajashree wants to get an inverted image of
hv
 h2 = – 1 height 5 cm of an object kept at a distance of
u
30 cm from a concave mirror. The focal length
of the mirror is 10 cm. At what distance from
 h2 = the mirror should she place the screen ? What
will be the type of the image, and what is the
 h2 = – 2 cm height of the object?
The height of the image is 2 cm and it is Solution:
inverted.
Reflection of Light 15

Given : Focal length (f) = –15 cm

Focal length = f = –10 cm, To find : Image distance (v) = ?
Object distance = u = –30 cm Image size (h2) = ?
Height of the image = h2 = 7 cm 1 1 1
Formulae: + =
To find : Height of the object = h1 = ? v u f
Image distance = v = ? M=
h2
= –
v
1 1 1 h1 u
Formulae: + =
v u f 1 1 1
h2 v Solution : + =
M= = – v u f
h1 u 1 1 1
 = –
v f u
1 1 1
Solution : + = 1 1 1
v u f  = –
v –15 –25
1 1 1
= – 1 1 1
v f u  = +
v –15 25
1 1 1
= – –5 + 3
v –10 –30 1
 v
=
75
1 –3 + 1
= 1 –2
v 30
 =
1 –2 v 75
=
v 30 1 1
1 1  v
=
–37.5
= cm
v –15  v = –37.5 cm
 v = –15 cm The screen should be kept 37.5 cm in front of
the mirror. The image is real.
Rajashree has to place the screen 15 cm to the
left of the mirror.  M =
h2
= –
v
Magnification formula h1 u
–vh1
h v  h2 =
M = 2 = – u
h1 u
–uh2  h2 =
h1 = v
–262.5
–(–30) × (–5)  h2 =
h1 = 25
–15
 h2 = –10.5 cm
h1 = (–2) × (–5)
The height of the is 10.5 cm, it is an inverted
h1 = 10 cm and enlarged image.
The height of the object is 10 cm. Thus, the
*(3) A 10 cm long stick is kept in front of a
image will be real and diminished.
concave mirror having focal length of 10 cm
* (2) An object of height 7 cm is kept at a distance in such a way that the end of the stick closest
of 25 cm in front of a concave mirror. The to the pole is at a distance of 20 cm. What will
focal length of the mirror is 15 cm. At what be the length of the image?
distance from the mirror should a screen be Solution:
kept so as to get a clear image? What will be
Given: Object size (h1) = 10 cm
the size and nature of the image?
Object distance (u) = –20 cm
Solution:
Focal length (f) = –10 cm
Given : Object size (h1) = 7 cm
To find : Image size (h2) = ?
Object distance (u) = –25 cm
16 Master Key Science & Technology (Term - II) (Std. IX)

1 1 1 Using mirror formula for concave mirror,

Formulae: + =
v u f 1 1 1
h2 v Solution: =v +u
f
M= = – 1 1
h1 u 1 1 1
v1 = f – u1
1 1 1
Solution: + = 1 1
v u f = –
–10 –20
1 1 1
 + = 1 1
v –20 –10 = –
20 10
1 1 1
 = +
v –10 20 = –
1
20
1 (–2 + 1)
 v
=
20  v1 = –20 cm
1 –1 Also, for other end of the stick,
 v
=
20 1 1 1
v2 = f – u2
 v = –20 cm
1 1
–v = –
h2 –10 –30
M = h = – u
1 1 1
= –
h2 v 30 10
= –
h1 u 1
= –
–(v × h1) 15
 h2 = u
 v2 = –15 cm
–(–20 × 10)
 h2 =
–20 Here, negative signs indicate that images are
 h2 = –10 cm formed on the left of the mirror.
The height of the image is 10 cm and it is a real
and inverted image.
(4) A 10 cm long stick is kept horizontally in 10 cm
B A 20 cm
front of the concave mirror having focal
P
length of 10 cm in such a way that the end of
F
the stick closest to the pole is at a distance of A’ B’
20 cm. What will be the length of the image?
Solution:
For the stick kept parallel to the principal axis,
as the end of the stick closest to pole is at 20
The length of the image formed is given by,
cm,
v = v2 – v1 = –15 – (–20) = 5 cm.
say, u1 = 20 cm
The length of the image is 5 cm.
Hence, the other end of the stick is at distance,
*(5) A convex mirror has a focal length of 18 cm.
u2 = (u1 + 10) = 30 cm from pole of the mirror.
The image of an object kept in front of the
mirror is half the height of the object. What
is the distance of the object from the mirror?

B 10 cm A Solution:
10 cm Given:
P 1
F Image size (h2) = h
2 1
20 cm Focal length (f) = 18 cm
To find : Object distance (u) = ?
Reflection of Light 17

Formulae: Q.12. Can you tell?

h2 v 1 1 1 (1) If we hold a page of a book in front of a
(i) M = = – (ii) + =
h1 u v u f mirror, we see laterally inverted letters in the
h2 mirror. Why does it happen?
Solution: M =
h1 Ans.
1 h (i) When we hold a page of a book in front of the
 M= × 1
2 h1 mirror, the image of the words appear laterally
1 inverted.
M=
2 (ii) The image of every point of the word is formed
v behind the mirror at the same distance from
Now M = – u the mirror as the point itself.
(iii) Because of this the left and right side of the
v 1
 – = image is interchanged.
u 2
(iv) Hence, if we hold a page of a book in front of a
1
 v= – u mirror, we see laterally inverted letters in the
2
mirror.
1 1 1 (2) Which letters of the English alphabet form
+ =
v u f
images that look the same as the original
–2 1 1 letters?
+ =
u u f Ans. A, H, I, M, O, T, U, V, W, X, Y
(–2 + 1) 1
= *Q.13. Use your brain power!
u 18
(1) If we keep the mirrors parallel to each other,
–1 1 how many images will we see ?
=
u 18
Ans. When two mirrors are kept parallel to each
 u = –18 cm other infinite images are formed, this is
because light gets reflected infinite times.
 The object is placed in front of the convex
mirror at a distance of 18 cm. (2) Three mirrors are created from a single
sphere. Which of the following - pole, centre
NUMERICAL FOR PRACTICE of curvature, radius of curvature, principal
axis - will be common to them and which
(1) An object 2 cm in height is placed at a distance
will not be common?
of 16 cm from a concave mirror. If the focal
length of the mirror is 9.6 cm., find the image
distance, nature and size of the image.
Ans. v = –24 cm, h2 = –3 cm; real, inverted and
enlarged.
(2) An arrow of 2.5 cm height is placed at a
distance of 25 cm from a diverging mirror of
focal length 20 cm. Find the nature, position
and size of the image formed.
Ans. v = 11.1 cm, h1 = 1.1 cm; virtual and in
diminished form.
18 Master Key Science & Technology (Term - II) (Std. IX)

Ans. Ans. The Relation between the angle between the

(i) Centre of curvature and Radius of curvature mirrors and the number of images formed is
will be common for all three pieces. given by

(ii) Pole and Principal axis will not be common. n = 360° – 1

A
* (3) When a person stands in front of a plane
n = number of images,
mirror, how is the image formed? What is the
A = angle between the mirrors
nature of the image?
Ans. Angle Number of images

(i) The image of a person is formed from every 120º 2

point of the source, thereby forming an 90º 3
extended image of the whole source. 60º 5
(ii) The image formed would be virtual, upright 45º 7
and left-right reversed. 30º 11
*Q.14. Activity based questions. (1) A = 120º (2) A = 90º
(1) Place two plane mirrors at an angle of 90º to 360 360
each other. Place a small object between them. n= – 1 n = – 1
120 90
Images will be formed in both mirrors. How = 3 – 1 = 2 = 4 – 1 = 3
many images do you see? Now change the
angle between the mirrors as given in the (3) A = 60º (4) A = 45º
following table and count the number of n=
360
– 1 n=
360
– 1
images each time. How is this number related 60 45
to the measure of the angle? = 6 – 1 = 5 = 8 – 1 = 7
(5) A = 30º
360
n= – 1
30
= 12 – 1 = 11

vvv
Reflection of Light 19

ASSIGNMENT - 11
Time : 1 Hr. Marks : 30

Q.1. (A) Fill in the blanks: (2)

(1) The focal length of ................. mirror is positive.
(2) The straight line passing through the pole and centre of curvature of the mirror is called
................. .
(B) State True or False, and if false write the correct statement: (2)
(1) If the mirrors are kept at right angle to each other than the number of images formed will be 4.
(2) A convex mirror is used in flood lights.
(C) Match the column: (2)

Column ‘A’ Column ‘B’

(1) Plane mirror (a) Virtual and diminished image
(2) Concave mirror (b) Virtual and same size image
(c) Real or virtual image

Q.2. (A) Define and state: (4)

(1) Pole (2) Centre of curvature
(3) Focus of concave mirror (4) Focal length
(B) Answer the following: (6)
(1) Distinguish between Concave mirror and Convex mirror.
(2) Why is concave mirror used in solar devices?
(3) Describe the positions of the source of light with respect to a concave mirror.
Q.3. Solve/Explain the following: (9)
(1) An object of height 7 cm is kept at a distance of 25 cm in front of a concave mirror. The focal
length of the mirror is 15 cm. At what distance from the mirror should a screen be kept so as
to get a clear image? What will be the size and nature of the image?
(2) A 10 cm long stick is kept in front of a concave mirror having focal length of 10 cm in such a
way that the end of the stick closest to the pole is at a distance of 20 cm. What will be the
length of the image?
(3) An object 10 cm in height is placed at a distance of 36 cm from a concave mirror. If the image
is formed at a distance of 18 cm in front of the mirror, find the height of image.
Q.4. Answer the following in brief: (5)
Explain the sign conventions for reflection by spherical mirrors.

vvv
 12 Study of Sound
CONCEPT MAP

Sound

Produces
Vibration Speed (v) Reflection

Waves Frequency × Wavelength Echo

u ×l
Repeat

Transverse Longitudinal waves Reverberation

Velocity in gaseous
waves
Requires medium depends on: Effect To reduce
medium
(1) Temperature Jumbling and Use sound
Characteristics
( ) Prolonged absorbent
(1) Wavelength sound in hall material in
(2) Molecular weight
(2) Amplitude roofs and
(3) Frequency (M) walls of hall
(4) Time Period (3) Density (r)
(5) Pitch

< 20 Hz 20 Hz 20000 Hz 20000 Hz

Infra sound Audible sound Ultra sound

(7) The velocity of sound is highest in

MASTER KEY QUESTION SET - 12 medium and least in medium.
Q.1. (A) Fill in the blanks and rewrite the (8) The value of frequency determines the
complete statements: of the sound.
* (1) Sound does not travel through . (9) When oscillations are perpendicular to the
direction of propagation of the wave, such
* (2) The velocity of sound in steel is than
waves are called waves.
the velocity of sound in water.
(10) Increasing the temperature four times
* (3) The incidence of in daily life shows
the velocity of sound.
that the velocity of sound is less than the
velocity of light. Ans. (1) vacuum (2) greater (3) lightning (4) sonar
(5) longitudinal (6) Pinna (7) solid, gaseous
* (4) To discover a sunken ship or objects deep
(8) pitch (9) transverse (10) doubles
inside the sea, technology is used.
(5) When particles of a medium vibrate parallel (B) Rewrite the following statements by
to the direction of propagation of a wave such selecting the correct options given below:
waves are called waves. (1) The unit of frequency is .
2
(6) Outer ear is also called as . (a) Hertz (b) m/s
(c) decibels (d) m/s
(20)
Study of Sound 21

(2) The normal hearing range for humans is (8)Sound waves with frequency greater than 20
. kHz are called .
(a) 0 Hz to 20 Hz (a) infrasound (b) ultrasound
(b) greater than 20,000 Hz (c) sonic (d) damped sound
(c) 20 Hz to 20,000 Hz (9) The receives the vibrations coming
from the membrane and converts them into
(d) None of these
electrical signals which are sent to the brain
(3) Sound will not travel through . through the nerve.
(a) vacuum (b) liquid (a) cochlea (b) Tympanic cavity
(c) solid (d) gases (c) Stapes (d) Pinna
(4) SI unit of is Hertz (Hz). Ans. (1) Hertz (2) 20 Hz to 20,000 Hz (3) vacuum
(a) wavelength (b) frequency (4) frequency (5) amplitude (6) high frequency
(c) speed of wave (d) velocity ultrasound (7) square root of density (8) ultrasound
(9) cochlea
(5) The loudness of a sound depends upon
. Q.2. Find the odd man out:
(a) amplitude (b) speed (1) Bats, rats, cats, dolphins
(c) density (d) wavelength Ans. Cats, cannot produce ultrasonic sound
(6) are used in sonography. (2) Clothes, paper, curtains, mirror
(a) high frequency ultrasound Ans. Mirror, is a good reflector of sound, while
others are poor reflectors
(b) stationary waves
(3) Submarines, icebergs, internal organ,
(c) high frequency infrasound
sunken ships,
(d) high frequency micro waves
Ans. Internal organ, sonography is used , while for
(7) The velocity of sound is inversely proportional others sonar system is used
to the .
(4) Temperature, density, molecular weight, pressure
(a) pressure
Ans. Pressure, for a fixed temperature, the speed of
(b) square root of temperature sound does not depend on the pressure of the
(c) square root of density (d) humidity gas, all other factors affect speed of sound

Q.3. (A) Match the columns:

Column ‘I’ Column ‘II’ Column ‘III’
(1) Transverse wave Particles oscillate parallel to direction of Wave produced in a slinky
propagation
(2) Longitudinal wave Particles oscillate perpendicular to direction Frequency less than 20 Hz
of propagation
(3)Ultrasound Echo formation is heard under particular Wave produced in string
conditions
(4) Infrasound High frequency waves Frequency between 20 Hz to 20000 Hz
(5) Audible frequency Low frequency waves Frequency greater than 20000 Hz
Ans.
Column ‘I’ Column ‘II’ Column ‘III’
(1) Transverse wave Particles oscillate perpendicular to direction Wave produced in string
of propagation
(2) Longitudinal wave Particles oscillate parallel to direction of Wave produced in a slinky
propagation
22 Master Key Science & Technology (Term - II) (Std. IX)

(3) Ultrasound High frequency waves Frequency greater than 20000 Hz

(4) Infrasound Low frequency waves Frequency less than 20 Hz

(5) Audible frequency Echo formation is heard under particular Frequency between 20 Hz to 20000 Hz
conditions
(B) Match the columns:
Column ‘I’ Column ‘II’ Column ‘III’
(1) Amplitude T Pitch of sound
(2) Frequency A Loudness of sound
(3) Wavelength u Reciprocal of frequency
(4) Time period l v/u
Ans.
Column ‘I’ Column ‘II’ Column ‘III’
(1) Amplitude A Loudness of sound
(2) Frequency u Pitch of sound
(3) Wavelength l v/u
(4) Time period T Reciprocal of frequency

Q.4. Name the following: (3) What is velocity of sound wave ?

(1) A form of energy which produces sensation Ans. The distance covered by a point on the wave
of hearing in our ears. in unit time is the velocity of the sound wave.
Ans. Sound energy (4) What is the minimum distance of the
(2) Repetitions of sound due to reflection . reflecting surface to hear an echo ?
Ans. Echo Ans. To be able to hear a distinct echo, the reflecting
(3) The audible range of sound for human surface should be at a minimum distance of 17.2 m.
being. (5) What is sonar system ?
Ans. 20 Hz to 20,000 Hz Ans.
(4) A method to obtain images of internal organs (i) SONAR is the short form for Sound Navigation
of the human body. and Ranging.
Ans. Sonography (ii) It is used to determine the direction, distance
(5) The matter or substance through which and speed of an underwater object with the
sound gets transmitted. help of ultrasonic sound waves.
Ans. Solid, liquid, gases (6) Name the three major parts of the ear.
Ans. The three major parts of the ear are the external
Q.5. Answer in one or two sentences:
ear, the middle ear and the inner ear.
(1) How can one produce sound?
(7) State any two examples in which infrasound
Ans. Vibration set up in an object produces sound is produced.
(or) sound is produced when an object is
Ans. Pendulum, earthquake are examples where
disturbed and starts vibrating.
infrasound is produced.
(2) What kind of waves are created when a stone
(8) Name the living beings that can produce
is dropped in water ?
ultrasound.
Ans. When a stone is dropped in water, the particles
Ans. Bats, dolphins, mice are living beings that can
of water oscillate up and down. These
produce ultrasound.
oscillations are perpendicular to the direction
of propagation of the wave, such waves are (9) Suppose you and your friend are on the
called transverse waves. moon. Will you be able to hear any sound
Study of Sound 23

Ans. Sound waves need a material medium for their (2) Amplitude (A)
propagation. Since there is no atmosphere on Ans. The maximum value of pressure or density is
the moon, we cannot hear any sound on the called amplitude.
moon.
(3) Frequency ()
(10) State the laws of reflection of sound.
Ans. The frequency of a sound wave is defined as
Ans. the number of complete oscillations of density
(i) The direction of the incident sound wave and (or pressure of the medium) per second.
reflected sound wave make equal angles with (4) Time Period (T)
the perpendicular to the surface.
Ans. The time taken for one complete oscillation of
(ii) All these three lie in the same plane. pressure or density at a point in the medium
Q.6. Distinguish between: is called the time period.
(1) Infrasound and Ultrasound (5) Echo
Infrasound Ultrasound Ans. An echo is the repetition of the original sound
because of reflection by some surface.
(1) Longitudinal waves (1) Longitudinal waves
whose frequencies whose frequencies (6) Transverse waves
are below 20 Hz are lie above 20,000 Hz Ans. Particles of the medium vibrate at right angles
called Infrasonic or are called Ultra- to the direction of propagation of the wave.
Infrasound waves. sonic or ultrasound (7) Longitudinal waves
waves. Ans. Particles of the medium vibrate parallel to the
(2) Whales, elephants (2) Bats produce (30 Hz direction of propagation of the wave.
produce sound in the to 50 Hz) frequency (8) Velocity of wave
infrasound range. and dolphins produce Ans. The distance covered by a point on the wave
ultrasound (for example the point of highest density or
(100 kHz). lowest density) in unit time is the velocity of
(2) Transverse waves and Longitudinal waves the sound wave.

Transverse waves Longitudinal waves Q.8. Give scientific reasons:

(1) Particles of the medium (1) Particles of the * (1) The roof of a movie theatre and a conference
vibrate at right angles medium vibrate hall is curved.
to the direction of parallel to the Ans.
propagation of the direction of (i) Sound waves get reflected from the walls and
wave. propagation of the roof of a room multiple times. This causes
wave. a single sound to be heard not once but
(2) They produce crests (2) They produce continuously. This is called reverberation.
and troughs. compression and (ii) Due to reverberation some auditoriums
rarefaction. or some particular seats in an auditorium
(3) For transverse waves, (3) For
have inferior sound reception which can be
longitudinal
compensated with curtains.
a wavelength is made waves, a wavelength
up of one crest and is made up of one (iii) Ceilings of these halls are made curved so that
one trough. compression and sound after reflecting from the ceiling, reaches
one rare-faction. all parts of the hall and the quality of sound
improves.
Q.7. Define the following: * (2) The intensity of reverberation is higher in a
(1) Wavelength(l) closed and empty house.
Ans. The distance between two consecutive Ans.
compressions (or crests) or two consecutive
(i) Reverberation occurs due to multiple reflection
rarefactions (or troughs) is called the
of sound.
wavelength.
24 Master Key Science & Technology (Term - II) (Std. IX)

(ii) The furniture in the house acts as a sound (iii) Our brain retains a sound for 0.1 s. Thus, for
absorbing material. us to be able to hear a distinct echo, the sound
(iii) So if the house is closed and empty, reflection should take more than 0.1 s after starting from
of sound will be maximum and hence intensity the source to get reflected and come back to
of reverberation is higher. us.
* (3) We cannot hear the echo produced in a (iv) We know that,
classroom. Distance = speed × time
Ans. = 344 m/s × 0.1 s
(i) For distinct echoes, the minimum distance of = 34.4 m
the reflecting surface from the source of sound (v) Thus, to be able to hear a distinct echo, the
must be 17.2 m. reflecting surface should be at a minimum
(ii) benches in the classroom are sound absorbing distance of half of the above i.e. 17.2 m.
materials which prevent echo of sound. (vi) As the velocity of sound depends on the
(iii) Because of these two reasons echo is not heard temperature of air, this distance depends on
in a classroom. the temperature.
(4) Bats can navigate in dark. * (2) Where and why are sound absorbing
Ans. materials used?
(i) The ultrasonic sound produced by bats, gets Ans.
reflected on hitting an obstacle. The sound absorbing materials are used in :
(ii) This reflected sound is received by their ears (i) School, cinema hall, concert hall, houses or
and they can locate the obstacle and estimate places where quality of sound is important.
its distance even in the dark. (ii) In the absence of sound absorbing material
(iii) Hence, bats can navigate in dark. the sound will undergo multiple reflection
(5) A SONAR system is installed in a ship. causing reverberation of sound.
Ans. (3) What are the factors on which velocity of
sound in gaseous medium depend?
(i) A SONAR system determines the depth of the Ans.
sea.
The velocity of sound in a gaseous medium
(ii) It locates underwater hills, valleys, icebergs,
depends on the physical conditions i.e.
submarines and sunken ships. It also locates
the temperature, density of the gas and its
the positions of other ships or submarines.
molecular weight.
(iii) Hence a SONAR system is installed in a ship.
(i) Temperature (T): The velocity of sound is
(6) Sound travels faster in iron than in air. directly proportional to the square root of the
Ans. temperature of the medium. This means that
(i) Sound requires a material medium for its increasing the temperature four times doubles
propagation and travels in the form of a the velocity.
longitudinal wave.
(ii) The denser the medium, faster is the (ii) Density( ): The velocity of sound is inversely
propagation of sound. proportional to the square root of density.
(iii) Hence, sound travels faster in iron then in air. Thus, increasing the density four times,
reduces the velocity to half its value.
Q.9. Answer in brief:
* (1) What is an echo? What factors are important
to get a distinct echo? (iii) Molecular weight (M): The velocity sound is
Ans. inversely proportional to the square root of
(i) An echo is the repetition of the original sound molecular weight of the gas. Thus, increasing
because of reflection by some surface. the molecular weight four times, reduces the
(ii) At 22°C, the velocity of sound in air is 344 m/s. velocity to half its value.
Study of Sound 25

(b) Middle ear

There is a thin membrane in the cavity of
(4) What are the uses of ultrasonic sound?
the middle ear called the eardrum. When
Ans. Uses of ultrasonic sound are as follows: a compression in a sound wave reaches the
(i) For communication between ships at sea. eardrum, the pressure outside it increases and
(ii) To join plastic surfaces together. it gets pushed inwards. The opposite happens
(iii) To sterilize liquids like milk by killing the when a rarefaction reaches there. The pressure
bacteria in it so that the milk keeps for a longer outside decreases and the membrane gets
duration. pulled outwards. Thus, sound waves cause
vibrations of the membrane.
(iv) Echocardiography which studies heartbeats,
is based on ultrasonic waves (Sonography (c) Inner ear
technology). The auditory nerve connects the inner ear
(v) To obtain images of internal organs in a human to the brain. The inner ear has a structure
body. resembling the shell of a snail. It is called the
cochlea. The cochlea receives the vibrations
(vi) In industry, to clean intricate parts of machines
coming from the membrane and converts
where hands cannot reach.
them into electrical signals which are sent
(vii) To locate the cracks and faults in metal blocks. to the brain through the nerve. The brain
(5) Explain with the help of neat labelled analyses these signals.
diagram the working of human ear. (6) Write short note on SONAR
Ans. Ans.

Chain of
three bones Semi-circular
canals Ship
Auditory
canal Stapes
Cochlea Transmiter Receiver

Inner ear

Eustachian Transmitted pulse Reflection pulse

Outer ear tube
(Pinna) Eardrum
Middle
ear Water Seabed
Tympanic
cavity

Structure Human ear

The ear is an important organ of the human The SONAR technique
body. When sound waves fall on the eardrum,
(i) SONAR is the short form for Sound Navigation
it vibrates and these vibrations are converted
and Ranging. It is used to determine
into electrical signals which travel to the brain
the direction, distance and speed of an
through nerves.
underwater object with the help of ultrasonic
The ear can be divided into three parts: sound waves. SONAR has a transmitter and a
(a) Outer ear (b) Middle ear (c) Inner ear. receiver, which are fitted on ships or boats.
(a) Outer ear or Pinna (ii) The transmitter produces and transmits
The outer ear collects the sound waves and ultrasonic sound waves. These waves travel
passes them through a tube to a cavity in the through water, strike underwater objects and
middle ear. Its peculiar funnel like shape helps get reflected by them. The reflected waves are
to collect and pass sounds into the middle ear. received by the receiver on the ship.
26 Master Key Science & Technology (Term - II) (Std. IX)

(iii) The receiver converts the ultrasonic sound * (9) What should be the dimensions and the
into electrical signals and these signals are shape of classrooms so that no echo can be
properly interpreted. The time difference produced there?
between transmission and reception is noted. Ans.
This time and the velocity of sound in water (i) The distance between the opposite walls of
give the distance from the ship, of the object the classroom should be less than 17.2m so no
which reflects the waves. echo is heard.
(iv) SONAR is used to determine the depth of the (ii) There should be no dome shaped structure as it
sea. SONAR is also used to search underwater produces reverberation and multiple sounds.
hills, valleys, submarines, icebergs, sunken (iii) Benches in the classrooms are also of sound
ships etc. absorbing materials and prevent echo of sound.
(7) Write a short note on Sonography.
Q.10. Solve the following:
Ans.
Type - A
(i) Sonography technology uses ultrasonic sound
Formulae :
waves to generate images of internal organs of
distance
the human body. (i) Velocity =
time
(ii) This is useful in finding out the cause of
swelling, infection, pain, condition of the * (1) Nita heard the sound of lightning after 4
heart, the state of the heart after a heart attack seconds of seeing it. What was the distance
as well as the growth of foetus inside the of the lightning from her?
womb of a pregnant woman. (The velocity of sound in air is 340 m/s)
(iii) This technique makes use of a probe and a Ans. Given :
gel. The gel is used to make proper contact Speed of sound (v) = 340 m/s
between the skin and the probe so that the full Time taken (t) = 4 sec
capacity of the ultrasound can be utilized.
To find :
(iv) High frequency ultrasound is transmitted
Distance (s) = ?
inside the body with the help of the probe.
The sound reflected from the internal organ Formulae :
is again collected by the probe and fed to a distance
Velocity =
computer which generates the images of the time
internal organ. As this method is painless, it Solution :
distance
is increasingly used in medical practice for Velocity =
time
correct diagnosis.
\ Distance = velocity × time
* (8) Study the construction of the Golghumat = 340 × 4 = 1360 m
at Vijapur and discuss the reasons for the
The lightning has struck at a distance of 1360 m
multiple echoes produced there.
from the observer.
Ans.
(i) The Golghumat at Vijapur is a mausoleum, * (2) Ultrasonic waves are transmitted downwards
having a unique structure i.e. a circular gallery into the sea with the help of a SONAR. The
called whispering gallery and a dome on the reflected sound is received after 4 s. What is
upper side. the depth of the sea at that place?
(ii) The sides of the chamber are semi-octagonal (Velocity of sound in seawater = 1550 m/s)
in shape with the diameter of the dome more Ans. Given :
than 40 metres and height of 5 metres. This Time to hear echo = 4 sec
meets the condition for echo i.e. 17.2 metres. Time taken by sound waves to reach the bottom
(iii) Due to this larger distance and petal shaped 4
domed structure, the sound is reflected of sea (t) =
2
sec = 2 sec
multiple time and therefore multiple echoes Velocity of sound in sea water (v) = 1550 m/s
can be heard.
Study of Sound 27

To find : Formulae :
Depth of sea(s) = ? distance
Velocity =
Formulae : time
Solution :
distance distance
Velocity =
time (i) Velocity = \ v1 =
time
Solution :
distance 660
Velocity = = = 330 m/s
time 2
\ Distance = velocity × time (ii) Also, v1= v2 \ v2 = 330 m/s
= 1550 × 2 = 3100 m
The depth of the sea is 3100 m. \ v2 =

(3) A person standing near a hill fires a gun 330 =

and hears the echo after 1 second. If speed
330 × 3 = S2
of sound in air is 340 m/s. Find the distance
between the hill and the person. S2 = 990m
Ans. Given : \ Distance between two walls = S1 + S2
Time to hear echo = 1 sec = 660 + 990
1 = 1650 m
Time taken (t) = sec
2 The velocity of sound in air is 330 m/s and the
= 0.5 sec distance between two walls is 1650m.
Velocity of sound (v) = 340 m/s
To find : NUMERICALS FOR PRACTICE
Distance (s) = ? (1) If you hear the thunder 20 seconds after you
Formulae : see the flash of lightning, how far from you
distance has the lightning occurred? (Speed of sound
Velocity = in air = 340 m/s)
time
Solution : Ans. 6800m
distance
Velocity = (2) Boy observes smoke from the cannon 3
time
seconds before he hears the bang. If the
\ Distance = velocity × time
cannon is 1020 m from the observer, find the
= 340 × 0.5
velocity of sound.
= 170 m
Ans. 340 m/s
Distance between the person and hill is 170 m.
(3) A soldier standing between the two buildings
* (4) Sunil is standing between two walls. The fires a gun. He heard the echo of the sounds
wall closest to him is at a distance of 660 m. from the first building after 2 seconds and
If he shouts, he hears the first echo after 4 s echo from the second building after 3 seconds.
and another after another 2 seconds. Find the distance between two buildings.
(i) What is the velocity of sound in air? (Speed of sound in air = 340 m/s)
(ii) What is the distance between the two walls?
Ans. 850m
Ans. Given :
Type - B
Distance of the closer wall (S1) = 660 m
Formulae :
Time of echo from closer wall = 4 sec
4 (i) Velocity = Frequency × Wavelength
\ Time taken (t1) = sec = 2 sec
2 distance
Time of echo from distant wall = 6 sec (ii) Velocity =
6 time
\ Time taken (t2) = sec = 3 sec
2
To find : * (1) Sound waves of wavelength 1 cm have a velocity
Velocity of sound in air (v) = ? of 340 m/s in air. What is their frequency? Can
this sound be heard by the human ear?
Distance between two walls (S1 + S2) = ?
28 Master Key Science & Technology (Term - II) (Std. IX)

Ans. Given : Ans. Given :

wavelength (l) = 1cm = 1× 10–2m frequency () = 1000 Hz
Velocity of sound (v) = 340m/s wavelength (l) = 0.25 m
To find : time (t) = 5 seconds
frequency (υ) = ? To find :
Formulae : Distance (d) = ?
Formulae :
v=υλ
v=υλ
Solution :
Solution :
v=υλ
v v =υλ
υ= \ v = 1000 × 0.25
λ
\ v = 250 m/s
\ υ=
distance
Also, velocity =
\ υ = 340 × 102 time
\ distance = velocity × time
\ υ = 34000 Hz
= 250 × 5
The frequency is higher than 20000 Hz and
therefore this sound cannot be heard by the = 1250 m.
human ear. The distance travelled by the sound wave is
1250 m.
* (2)How long will it take for a sound wave of 25
cm wavelength and 1.5 kHz frequency of, to (4) The audible range of sound is 20 Hz to
travel a distance of 1.5 km? 20000 Hz. At 22°C in air speed of sound is
Ans. Given : 344 m/s. Express the range of sound in terms
frequency (υ) = 1.5 kHz = 1.5 × 103Hz of wavelength by calculating the respective
values.
Wavelength (λ) = 25 cm = 0.25 m
Ans. Given :
Distance (s) = 1.5km = 1.5 × 103m
frequency (υ1) = 20 Hz
To find :
frequency ( υ2) = 20,000 Hz
time (t)= ? Velocity (v)=?
velocity (v) = 344 m/s
Formulae :
distance To find :
(1) v = υ λ (2) velocity =
time Wavelengths l1 and l2 = ?
Solution :
Formulae :
v=υλ
v=υλ
v = 1.5 × 103 × 0.25
Solution :
v = 0.375 × 103
v = υ1 l1
\ v = 375 m/s
distance \ l1 =
time =
velocity
344
1.5 × 103 \ l1 =
= 20
375
1500 \ l1 = 17.2 m
=
375 Also, l2 = υ2
= 4 sec
344
\ l2 =
The sound wave takes 4 sec to travel the 20000
distance of 1.5 km.
\ l2 = 17.2 × 10–3 m
(3) Calculate distance travelled by a sound wave
Audible range of wavelength of sound is from
having frequency 1000 Hz and wavelength 0.25
17.2 × 10–3 m to 17.2 m.
m, if it travels for 5 seconds in a certain medium
Study of Sound 29

vH = 4 vO
NUMERICALS FOR PRACTICE
Hence proved that velocity of sound in
(1) A sound wave has frequency 320 Hz and hydrogen is four times that in oxygen.
wavelength 0.25 m. How much distance will
* (2)Hydrogen gas is filled in two identical
it travel in 10 second?
bottles, A and B, at the same temperature.
Ans. The distance travelled is 800 m. The mass of hydrogen in the two bottles is 12
Type - C gm and 48 gm respectively. In which bottle
Formulae: will sound travel faster? How may times as
(i) , , fast as the other?
Ans. Given:
(ii) =
m
; v = velocity of sound Mass of hydrogen in bottle A ( mA) = 12gm
V V = volume Mass of hydrogen in bottle B( mB) = 48gm
* (1) The molecular weight of oxygen gas (O2) is To find:
32 while that of hydrogen gas (H2) is 2. Prove In which bottle sound travels faster.
that under the same physical conditions, the Formulae:
velocity of sound in hydrogen is four times m
=
that in oxygen. V
Ans. Given:
Molecular wt of Oxygen ( MO) = 32
Molecular wt of hydrogen ( MH) = 2 \
To Find:
In which bottle sound travel faster = ? \
\
Formulae:
Solution:

vO = vA = (i) Since both bottles are

identical hence the
\ vO= ... (i) volume is same i.e. V
vB = (ii)
vH=
Dividing (i) and (ii)
\ vH = ...(ii)
=
Dividing equation 1 by 2 we get
=
=
= = =2

\ vA = 2 vB
=
(i) Velocity of sound will be more in bottle A
= (ii) Velocity of sound in bottle A (vA) is twice
that in bottle B (vB)
=
* (3) Helium gas is filled in two identical bottles A
1 and B. The mass of the gas in the two bottles
=
4 is 10 gm and 40 gm respectively. If the speed
1 of sound is the same in both bottles, what
vO = vH
4 conclusions will you draw?
30 Master Key Science & Technology (Term - II) (Std. IX)

Ans. Given: Ans. Given :

Mass of Helium in bottle A = (mA) = 10gm Initial speed of sound at 0°C = 332 m/s.
Mass of Helium in bottle B = (mB) = 40gm Final speed of sound = 344 m/s.
Formulae: Rate of increase per degree rise in temp. = 0.6m/s
, , m
= v To find:
Temperature when speed is 344m/s
Solution:
Formulae :
vA = ...(i) Increase in temperature
increase in speed of sound
= Rate of increase per degree rise in temperature
vB= ...(ii) Solution :
344 – 332
Increase in temperature =
From (i) and (ii) 0.6
12
=
= ...[ vA = vB] 0.6
= 20°C
Temperature when the speed of sound is
\ =
344 m/s is 20°C

NUMERICALS FOR PRACTICE

\ = ...[ mB = 4mA]
Taking square (1) Velocity of sound in air at 0°C is 332m/s. It
1 increases by 0.6m/s for each °Celsius rise in
= temperature. At what temperature of air, the
4
\ TB = 4TA velocity will be 359m/s?
The temperature of B is 4 times the temperature of A Ans. 45°C
(2) Velocity of sound in air at 0°C is 332m/s. It
NUMERICALS FOR PRACTICE increases by 0.6m/s for each °Celsius rise in
temperature. What will be the velocity of
(1) Hydrogen gas is filled in two identical bottles,
sound at 60°C?
A and B, at the same temperature. The mass of
hydrogen in the two bottles is 10 gm and 90gm Ans. 368 m/s
respectively. In which bottle will sound travel Q.11. Use your brain power:
faster? How many times as fast as the other? * (1) To hear the echo distinctly, will the distance
Ans. In A; Thrice from the source of sound to the reflecting
(2) Argon gas is filled in two identical bottles X surface be same at all temperatures? Explain
and Y. The mass of the gas in the two bottles your answer.
is 5 gm and 25gm respectively. If the speed Ans.
of sound is the same in both bottles, what (i) No,the distance from the source of sound to
conclusions will you draw? the reflecting surface will not be the same at
(Ans. Temperature of Y is 5 times the temperature of X.) all temperatures.
Type - D (ii) Velocity of sound is directly proportional to
the square root of temperature.
Based on increase in velocity of sound
(iii) One of the conditions of echo is that the time
* (1) The speed of sound in air at 0 °C is 332 m/s. If
interval between the original and reflected
it increases at the rate of 0.6 m/s per degree,
sound should be more than 0.1 sec.
what will be the temperature when the
velocity has increased to 344 m/s? (iv) So if the temperature increases, the velocity
of sound increases and the reflected sound
reaches in less than 0.1 sec.
Study of Sound 31

(v) So for echo to be heard the distance between the (ii) Shape: The classrooms should have curved
observer and the reflecting surface has to increase. ceilings and walls so that the reflected sound
* (2) When is the reflection of sound harmful? is directed towards the observer instantly
Ans. within 0.1 s

(i) Reflected sound of high intensity called as Q.13. Activity based questions:
noise is disturbing and harmful to the ears. * (1) How are the frequencies of notes sa, re, ga,
(ii) When sound reverberates i.e it undergoes multiple ma, pa, dha, ni related to each other?
reflection, poor quality of sound is produced. Ans. The frequencies of notes sa, re, ga, ma, pa,
* (3) How will you reduce reverberation in public dha, ni are related in the ratio.
halls or buildings? Symbols Sa Re Ga Ma Pa Dha Ni Sa
Ans.
9 5 4 3 5 15
(i) By using sound absorbing materials like Ratio with Sa 1 2
8 4 3 2 3 8
curtains on wall, carpets on the floor.
(ii) By keeping the windows open, as sound will eg.: Sa = 240 Hz
not get reflected. 9
Re = 240 × 8 = 270 Hz
Q.12. Find out 5
* (1) How is ultrasound used in medical science? Ga = 240 × 4 = 300 Hz
Ans. 4
Ma = 240 × 3 = 320 Hz
(i) Sonography: Sonography technology uses
ultrasonic sound waves to generate images of 3
Pa = 240 × 2 = 360 Hz
internal organs of the human body.
5
(ii) Echocardiography: Echocardiography is a test Dha = 240 × 3 = 400 Hz
that uses ultrasonic sound waves to produce 15
live images of your heart. Ni = 240 × 8 = 450 Hz
* (2) Study the construction of the Golghumat at Sa = 240 × 2 = 480 Hz
Vijapur and discuss the reason for multiple i.e if first sa is 240Hz then the next sa will be
echoes produced there. 240 × 2 = 480Hz
Ans. * (2) What is the main difference between the
(i) Golghumat with a height of 51 metres and frequencies of the voice of a man and that of
diameter of 37 metres with 3 metres thick a woman?
walls is spread over approximately 1700 Ans.
square metres.
(i) Voice of a woman is high pitch i.e shorter
(ii) This meets the conditions for echo i.e. : 17.2 wavelength and higher frequency
metres minimum. (ii) Voice of man is low pitch i.e larger wavelength
(iii) The dome of the golghumat is curved and and smaller frequency.
hence sound reflects multiple times before * (3)
reaching the observer.
(iv) This is the reason for multiple echoes being Wall
produced.
* (3) What should be the dimensions and the
shape of classrooms so that no echo can be q1 q2
produced there ?
Ans.
Cardboard
(i) Dimensions: The distance between opposite Clock tubes
walls in a classroom must be less than 17.2
m so that the reflected sound returns to the Reflection of sound
observer within 0.1 s.
32 Master Key Science & Technology (Term - II) (Std. IX)

(a) In the above activity, what will happen if you (i) Fig A shows changes in density. The region
lift one of the tubes to some height? where particles are crowded is called
Ans. If one of the tubes is lifted, angle of incidence compression and where they are far apart are
will not be equal to angle of reflection, hence rarefaction.
the spound will not be clearly audible. (ii) Fig B show change in pressure. The lines
(b) Measure the angle of incidence q1 and the represent layers of air. The region when lines
angle of reflection q2. Try to see if they are are crowded are high pressure region while
related in any way. when they are far apart are of low pressure.
Ans. Angle of incidence is same as the angle of (iii) Fig. C shows changes in density or pressure.
reflection.
The crest represents high pressure region
* (4) How does the velocity of sound depend on while trough represents low pressure region.
its frequency?
Ans. The velocity of sound is directly proportional Brain Power
to its frequency
v = υl (a) Consider two cases
when v = velocity ( i ) whistle of train (ii) roar of a lion
υ = frequency (1) In which case the sound is high pitch?
l = wavelength Ans. Whistle of a train is high pitch as compared to
roar of a lion, as the frequency is higher.
* (5) How is the direction of the oscillation of
the particles of the medium related to the (2) What is the real cause of sound production?
Explain with examples.
direction of propagation of the sound wave?
Ans.
Ans. Sound travels as a longitudinal wave.
(i) Vibrations in the object are responsible to
In longitudinal wave, the particle of the produce a sound.
medium oscillate parallel to the direction of (ii) Vibration is a rapid to and fro motion of an object.
propagation of the wave. (iii) Sometimes the vibrations may be strong
*Q.14 Observe and discuss: enough to be seen by eyes, e.g. string
Observe the graph/ diagram and discuss your vibrations in string instruments, vibration on
observation. a mobile phone, blowing air in the cap of your
pen by holding it near the lips.
Ans.
(3) Three sounds 5Hz, 500Hz and 50,000Hz are
Loudspeaker Change in density produced by different sources.
(a) Which sound will be heard by humans?
A A (b) Which sounds may be produced by bats?
(c) Which sounds may be produced by
C R C R C R C
elephants ?
Loudspeaker Change in pressure
Ans.
B (a) 500Hz - Humans can hear sounds in the range
of 20Hz – 20,000Hz
C R C R C R C (b) 50,000Hz – Bats produce ultrasonic sounds
A l above 20,000Hz
Density or C
pressure (c) 5Hz – Elephants can produce infrasonic
sounds below 20Hz
Average
density or pressure

Sound waves

vvv
Study of Sound 33

ASSIGNMENT - 12
Time : 1 Hr. Marks : 30

Q.1. (A) Choose the correct alternatives and rewrite the complete sentences: (4)
(1) Sound will not travel through .
(a) vacuum (b) liquid (c) solid (d) gases
(2) SI unit of is Hertz (Hz).
(a) wavelength (b) frequency (c) speed of wave (d) velocity
(3) The loudness of a sound depends upon .
(a) amplitude (b) speed (c) density (d) wavelength
(4) are used in sonography.
(a) high frequency ultrasound (b) stationary waves
(c) high frequency infrasound (d) high frequency micro waves
(B) Match the columns: (4)

Column ‘A’ Column ‘B’

(1) Amplitude (a) T
(2) Frequency (b) A
(3) Wavelength (c) u
(4) Time period (d) l

Q.2. (A) Answer the following: (8)

(1) The roof of a movie theatre and a conference hall is curved. Why?
(2) The ntensity of reverberation is higher in a closed and empty house. Why?
(3) What is an echo? What factors are important to get a distinct echo?
(4) To hear the echo distinctly, will the distance from the source of sound to the reflecting surface be
same at all temperatures? Explain your answer.
(B) Define or state: (4)
(1) Frequency (2) Time Period (3) Echo (4) Transverse wave
Q.3. Solve the following numericals. (4)
(1) Nita heard the sound of lightning after 4 seconds of seeing it. What was the distance
of the lightning from her? (The velocity of sound in air is 340 m/s)
(2) Hydrogen gas is filled in two identical bottles, A and B, at the same temperature.
The mass of hydrogen in the two bottles is 12 gm and 48gm respectively. In which
bottle will sound travel faster? How many times as fast as the other?
Q.4. Answer in brief: (6)
(1) What are the factors on which velocity of sound in gaseous medium depend?
(2) What are the uses of ultrasonic sound?

vvv
34 Master Key Science & Technology (Term - II) (Std. IX)

13 Carbon : An Important Element

CONCEPT MAP

COMPOUNDS

are

obtained from minerals obtained directly or indirectly

organic compounds can be from plants and animals
synthesized from inorganic compounds
INORGANIC ORGANIC
main constituent

CARBON
occurrence Allotropic forms are

COMBINED STATE FREE STATE CRYSTALLINE NON-CRYSTALLINE

FORMS FORMS
as as
as as
• Carbon dioxide
Peat
• Carbonates
• Diamond Lignite
• Coal
• Fossil Fuel Bituminous
• Graphite
• Carbonaceous Nutrients Anthracite
• Fullerene
• Natural fibres • Charcoal

• Coke

combines with hydrogen

HYDROCARBONS

Continued on the next page

(34)
Carbon : An Important Element 35

HYDROCARBONS
are

SATURATED UNSATURATED
are having only are having
MULTIPLE BONDS
SINGLE BONDS
as
as
H DOUBLE BOND TRIPLE BOND
H H
• CH4 Methane H C H • C H Ethyne
• C2H4 Ethene H–C≡C–H
C=C 2 2

H (HC ≡ CH)
(H2C = CH2) H H H
H H
• C2H6 Ethane H • C3H4 Propyne H C C≡C–H
C C H H H
CH3 – CH3 (CH3 – C ≡ CH)
H H • C3H6 Propene H
H C C=C
(CH3 – CH = CH2) H H H
H H H
• C3H8 Propane H C C C H
CH3 – CH2 – CH3
H H H

(10) is an allotrope of carbon used to

MASTER KEY QUESTION SET - 13
make ornaments.
Q.1. Fill in the blanks: (11) The number of valence electrons in carbon is
* (1) A carbon atom forms a bond with .
other atoms. In this bond the two atoms (12) In saturated hydrocarbons two carbon atoms
electrons. are linked by .
* (2) All the carbon bonds in a saturated (13) Atomic number of carbon is .
hydrocarbon electrons. (14) Carbon has 4 valence electrons in its outermost
* (3) At least one carbon bond in an unsaturated shell, hence it is .
hydrocarbon is . (15) Bond formed by sharing of electrons is .
* (4) is the essential element in all the
(16) A carbon atom forms a bond with
organic compounds.
other atoms. In this bond the two atoms
* (5) The element hydrogen is present in electrons.
organic compounds.
(17) Production of Biogas is an process.
(6) The organic compound having double or
(18) Methanogenic bacteria act on the organic
triple bond in them is termed as .
acids to produce .
(7) Covalent compounds are generally insoluble
(19) is used to remove caffeine from coffee.
in solvents.
(20) Exhaled air contains about CO2.
(8) Hydrocarbons necessarily contain
and . (21) Electronic configuration of carbon is .
(9) Methane is also called as . (22) The density of graphite is .
36 Master Key Science & Technology (Term - II) (Std. IX)

(23) In the earlier days, the compounds obtained (8) Biogas contains about of methane.
from animal or plant kingdom were called as (a) 55% to 60% (b) 20% to 25%
. (c) 90% to 95% (d) 40% to 45%
(24) Molecular formula of ethane is . (9) Wohler, a German scientist synthesized
(25) Methane and chlorine gases react with each the compound from an inorganic
other to form mainly methyl chloride, this compound ammonium cyanate.
reaction is called . (a) methane (b) ethylene
(26) Molecular mass of carbon dioxide is . (c) urea (d) acetic acid.
(27) On heating a mixture of hydrogen and carbon (10) Molecular mass of methane is .
monoxide gases at 300°C in the presence of
(a) 19 (b) 16 (c) 17 (d) 18.
nickel (catalyst) is formed.
(11) coal contains highest percentage of
Ans. (1) covalent, share (2) share (3) multiple (4) Carbon
carbon
(5) all (6) Unsaturated hydrocarbon (7) organic
(8) Hydrogen, Carbon (9) Marsh gas (10) Diamond (a) Bituminous (b) Peat
(11) four (12) single bond (13) 6 (14) tetravalent (c) Anthracite (d) Lignite
(15) covalent bond (16) covalent, share (12) H2C = CH2 is .
(17) Anaerobic (18) Methane gas (19) Liquified CO2 (a) Propane (b) Ethyne
(20) 4% (21) 2, 4 (22) 1.9 to 2.3 g/cm3 (23) Organic (c) Ethane (d) Ethene
compounds (24) C2H6 (25) Chlorination of methane
(13) CH3 – C  CH is .
(26) 44 (27) Methane gas
(a) Propene (b) Propyne
Q.2. Rewrite the following statements by (c) Ethyne (d) Ethene
selecting the correct options given below:
(14) is not a property of carbon dioxide
(1) Ethane with molecular formula C2H6 has gas.
covalent bonds.
(a) Supports combustion
(a) six (b) seven (c) eight (d) nine
(b) Odourless
(2) Melting point of diamond is . (c) Colourless (d) Turns blue litmus red
(a) 3700ºC (b) 3500ºC (c) 4000ºC (d) 2500ºC
(15) Carbon dioxide gas is not used in .
(3) Weight of Kohinoor Diamond was . (a) Photosynthesis (b) Aerated drinks
(a) 186 carats (b) 27 carats (c) Glass cutting (d) Fire extinguishers
(c) 252 carats (d) 23 carats Ans. (1) seven (2) 3500ºC (3) 186 carats (4) low melting point
(4) Covalent compounds have . (5) CH4 (6) –56.6ºC (7) –182.5ºC (8) 55% to 60% (9)
urea (10) 16 (11) Anthracite (12) Ethene (13) Propyne
(a) high melting point
(14) Supports combustion (15) Glass cutting
(b) low melting point
(c) moderate melting point Q.3. State whether the following statements are
(d) very high melting point true or false and if false, write the correct
statement:
(5) Methane is .
(1) Study of organic compounds is called as
(a) C2H6 (b) C3H8 (c) CH2 (d) CH4
organic chemistry.
(6) Melting point of CO2 is .
Ans. True.
(a) 26ºC (b) 56ºC (c) –56.6ºC (d) –98ºC
(2) Hydrocarbons with double bonds are called
(7) Melting point of methane is . as saturated hydrocarbons.
(a) –182.5ºC (b) –161.5ºC. Ans. False: Hydrocarbons with double bonds are
(c) 182.5ºC (d) 161.5ºC called as unsaturated hydrocarbons.
Carbon : An Important Element 37

(3) Ethene is saturated hydrocarbon. (2) Column ‘A’ Column ‘B’

Ans. False: Ethene is unsaturated hydrocarbon.
(1) Peat (a) 60-70% of Carbon
(4) Covalent compounds are good conductor of
(2) Lignite (b) 95% of Carbon
electricity.
(3) Bituminous Coal (c) less than 60% of Carbon
Ans. False: Covalent compounds are bad conductor
(4) Anthracite (d) 70 - 90% of Carbon
of electricity.
(5) Methane is a covalent compound. Ans. (1 - c), (2 - a), (3 - d), (4 - b)

Ans. True. (3) Column ‘A’ Column ‘B’

(6) Covalent compounds are soluble in organic (1) Propyne (a) CH3 – CH2 – CH3
solvents.
(2) Propene (b) CH3 – C º CH
Ans. True. (3) Propane (c) CH3 – CH = CH2
(7) Graphite is used in making lubricants and
Ans. (1 - b), (2 - c), (3 - a)
lead pencils.
Ans. True. (4) Column ‘A’ Column ‘B’
(8) The density of diamond is 9.8 g/cm3. (1) Fullerene (a) Lubricants
Ans. False: The density of diamond is 3.5 g/cm . 3 (2) Diamond (b) Insulator
(9) Diamond knives are used in eye surgery. (3) Graphite (c) Ornaments
Ans. True. Ans. (1 - b), (2 - c), (3 - a)
(10) Fullerenes are used as insulators.
(5) Column ‘A’ Column ‘B’
Ans. True.
(1) Water gas (a) CH4
(11) Coke is used in production of water gas i.e.
(2) Methane gas (b) CO + H2
(CO2 + H2O).
(3) Producer gas (c) CO2
Ans. False: Coke is used in production of water gas
(4) Carbon dioxide gas (d) CO + H2 + CO2 + N2
i.e. (CO + H2).
(12) Structural formula of propyne is CH3 – C = CH. Ans. (1 - b), (2 - a), (3 - d), (4 - c)
Ans. False: Structural formula of propyne is Q.5. Write the correlated terms:
CH3 – C º CH. (1) Propene : Double bond : : Propyne : .
(13) CO2 is used to make aerated drinks. (2) Ethane : CH3 – CH3 : : Ethene : .
Ans. True. (3) Hydrogen : Monovalent : : Carbon : .
(14) Methane gas is black in colour. (4) Methane : Low melting point i.e. –182.5ºC
Ans. False: Methane gas is colourless. Diamond : .
(15) Production of biogas is aerobic process. (5) Graphite : Hexagonal layered : : Diamond :
Ans. False: Production of biogas is anaerobic process. .
(6) Density of Diamond : 3.5 g/cm3 : : Density of
Q.4. Match the columns:
Graphite : .
(1) Column ‘A’ Column ‘B’
(7) Peat : 60% of carbon : : Anthracite : .
(1) Diamond (a) Hexagonal layered (8) Melting point of CO2 : –56.6ºC : : Melting point
(2) Fullerenes (b) Tetrahedral structure of CH4 : .
(3) Graphite (c) Geodesic dome Ans. (1) Triple Bond (2) CH2 = CH2 (3) Tetravalent
Ans. (1 - b), (2 - c), (3 - a) (4) High melting point i.e. 3500ºC (5) Tetragonal
(6) 1.9 to 2.3 g/cm3 (7) 95% of carbon (8) –182.5ºC
38 Master Key Science & Technology (Term - II) (Std. IX)

Q.6. Find the odd man out: (2) CH4 + Cl2 CH3Cl + HCl
(1) Propane, Methane, Ethene, Pentane. (3) 2NaOH + CO2 Na2CO3 + H2O
Ans. Ethene. It is a unsaturated hydrocarbon with
(4) 2NaHCO3 +H2SO4 Na2SO4 + 2H2O + 2CO2
double bond between two carbon atoms while
rest are saturated hydrocarbons with single (5) CaCO3 + 2HCl CaCl2 + H2O + CO2
bond between two carbon atoms.
Q.8. Answer in one or two sentences :
(2) CH4, C2H6, C3H8, CaCO3.
(1) What happens when substances like milk,
Ans. CaCO3. It is a salt while rest are hydrocarbon sugar, wool, dry leaves, hair and seeds are
compounds. heated strongly in hard glass test tube?
(3) C2H2, C3H8, C2H6, CH4. Ans. When milk, sugar, wool, dry leaves, hair and
Ans. CH4. It is a saturated hydrocarbon with seeds are heated strongly in hard glass test
single bonds while rest are unsaturated tube, they get charred and a black substance
hydrocarbons with multiple bonds between is left behind. This black substance is carbon.
two carbon atoms.
(2) What are organic and inorganic compounds?
(4) Diamond, Fullerene, Graphite, Methane.
Ans. Compounds obtained directly or indirectly
Ans. Methane. It is a marsh gas while rest are from plants and animals are called organic
allotropes of carbon. compounds and compounds obtained from
(5) Coal, Petroleum, Natural gas, Cotton minerals are called inorganic compounds.
Ans. Cotton. Cotton is a natural fibre rest all are (3) What is allotropy?
fossil fuels.
Ans. Allotropy - Some elements occur in nature in
(6) Cotton, Silk, Proteins, Wool more than one form. The chemical properties
Ans. Proteins. Proteins are carbonaceous nutrients of these different forms are the same but
rest all are natural fibres. their physical properties are different. This
(7) Carbohydrates, Coal, Proteins, Fats property of elements is called allotropy.
Ans. Coal. Coal is a fossil fuel while rest all are (4) What are basic organic compounds? What
carbon nutrients. are they also called as?
(8) Peat, Charcoal, Lignite, Bituminous Ans. The compounds formed from only carbon and
Ans. Charcoal. Charcoal is a non-crystalline form hydrogen are called basic organic compounds.
of carbon rest all are types of coal. These are also called hydrocarbons.

(9) Lubricants, Electrodes, Ornaments, Arc (5) Where is methane in the form of natural gas
Lamps used?
Ans. Ornaments. Ornaments are made from Ans. Methane in the form of natural gas is used
diamonds rest all are made from graphite. in industries such as fabric mills, paper
mills, food processing industry and petrol
Q.7. Complete the following chemical reactions: purification.
* (1) + CO2 + 2H2O + Heat (6) Name the organic compounds prepared from
methane.
* (2) + CH3Cl + HCl
Ans. Methane is used for production of organic
* (3) 2NaOH + CO2 + compounds such as ethanol, methyl chloride,
methylene chloride and acetylene.
(4) 2NaHCO3 + H2SO4 + +
(7) Name the chemicals used in regular fire
(5) CaCO3 + 2HCl + H2O + CO2 extinguisher.
Ans. Ans. Sodium bicarbonate and dilute sulphuric
acid are the chemicals used in regular fire
(1) CH4 + 2O2 CO2 + 2H2O + Heat extinguisher.
Carbon : An Important Element 39

(8) What does biogas contain?

Ans. Biogas contains about 55% to 60% methane Carbon
and the rest is carbon dioxide.
(9) Name the organic solvents in which
Fullerenes are soluble.
Ans. Fullerenes are soluble in organic solvents such
as carbon disulphide and chlorobenzene.
13.1 Structure of carbon atoms in diamond
(10) How is carbon dioxide used in dramas and
(4) With neat diagram explain the structure of
movies?
graphite?.
Ans. Carbon dioxide is used for getting special
Ans. Every carbon atom in graphite is bonded to
effects of a mist in dramas and movies.
three other carbon atoms in such a way that
Q.9. Answer in short: a hexagonal layered structure is formed. A
(1) What was the contribution of chemist Wohler graphite crystal is made of many sheets or
in organic chemistry? layers of carbon atoms. These layers slip over
Ans. The German chemist Wohler synthesized an each other on applying pressure. One layer of
organic compound urea from an inorganic graphite is called graphene.
compound ammonium cyanate. Ever since
Carbon
then, many organic compounds have been
made from inorganic compounds. Carbon
was found to be the main element in all these
compounds.
Hence, organic chemistry is also referred to as
chemistry of carbon compounds. 13.2 Graphite and structure of carbon atoms in graphite
Heat
NH4+ CNO– NH2CONH2 * (5) Give the properties of diamond.
ammonium cyanate urea Ans. Properties of diamond are:
(2) Give the following information of Carbon? (i) Brilliant and pure diamond is the hardest
natural substance.
(1) Symbol of Carbon (2) Atomic number
(ii) The density of diamond is 3.5 g/cm3.
(3) Atomic mass (4) Electron configuration
(iii) The melting point of diamond is 3500ºC.
(5) Valency
(iv) When diamond is heated at 800ºC in the
(6) Metallic or Non-metallic element
presence of oxygen CO2 is given away. In
Ans. (1) Symbol of Carbon – C this process no other product besides CO2 is
(2) Atomic number – 6 formed.
(3) Atomic mass – 12 (v) Diamond does not dissolve in any solvent.
(4) Electron configuration – (2, 4) (vi) Acids/bases have no effect on diamond.
(5) Valency – 4 (6) Non-metallic element (vii) Diamond is a bad conductor of electricity as it
does not have free electrons.
(3) With neat diagram explain the structure of
diamond. * (6) Give the uses of diamond.
Ans. In diamond, every carbon atom is bonded to Ans. Uses of diamonds are:
four neighbouring atoms by covalent bonds. (i) Diamonds are used in glass cutting and rock
Therefore, diamond has a tetragonal three drilling machines.
dimensional structure which makes it very (ii) Diamonds are used in ornaments.
hard. (iii) Diamond knives are used in the eye surgery.
40 Master Key Science & Technology (Term - II) (Std. IX)

(iv) Diamond dust is used for polishing other nitrogen, phosphorus and sulphur. It occurs in
diamonds. the solid state. It is of four types - peat, lignite,
(v) Diamond is used to make windows giving bituminous and anthracite.
protection from radiation in space and in (12) What is Charcoal?
artificial satellites.
Ans. The charcoal that is made from animals is
(7) Give the properties of graphite. made from their bones, horns, etc. On the
Ans. Properties of graphite are: other hand, the charcoal made from plants
is formed by combustion of wood in an
(i) Graphite found in nature is black, soft, brittle
insufficient supply of air.
and slippery.
(ii) Inside each layer of graphite, free electrons (13) What is Coke?
move continuously within the entire layer. Ans. The pure coal that remains when coal gas has
That is why graphite is a good conductor of been taken away from coal, is called coke.
electricity.
* (14) Give the uses of Coal.
(iii) Due to the layered structure graphite can be
Ans. Uses of Coal are:
used for writing on paper.
(i) Coal is used as fuel in factories and homes.
(iv) The density of graphite is 1.9 to 2.3 g/cm3.
(ii) Coal is used to obtain coke, coal gas and coal tar.
(v) Graphite does not dissolve in most solvents.
(iii) Coal is used in thermal power plants for
* (8) Give the uses of graphite. generation of electricity.
Ans. Uses of graphite are:
* (15) Give the uses of Coke.
(i) Graphite is used for making lubricants.
Ans. Uses of Coke are:
(ii) Graphite is used for making carbon electrodes.
(i) Used as domestic fuel.
(iii) Graphite is used in pencils for writing.
(ii) Coke is used as a reducing agent.
(iv) Graphite is used in paints and polish.
(iii) Coke is used in production of water gas
(v) Graphite is used in arc lamps which give a (CO + H2) and producer gas
very bright light. (CO + H2 + CO2 + N2)
* (9) Give the properties of fullerenes. (16) Name the types of coal and give the
Ans. Properties of fullerenes are: differences in them.
(i) Molecules of fullerenes are found in the form Ans. The four types of coal are Peat, Lignite,
of buckyballs and buckytubes. Bituminous and Anthracite.
(ii) There are 30 to 900 carbon atoms in one Points of Peat Lignite Bitumi- Anthracite
molecule of a fullerene. differences nous
(iii) Fullerenes are soluble in organic solvents such
as carbon disulphide, chlorobenzene. (1) Forma- First Second Third Last
tion step
* (10) Give the uses of fullerenes. number
Ans. Uses of Fullerenes are:
(2) Carbon Less 60% 70% about
(a) Fullerenes are used as insulators. content than to to 95%
(b) Fullerenes are used as a catalyst in water 60% 70% 90%
purification.
(3) Heat Lowest More More Highest of
(c) At a certain temperature fullerene exhibits produced of all than than all the rest
superconductivity. the rest peat lignite
(11) What is Coal? but less but less
Ans. Coal is a fossil fuel. It contains carbon, than than
hydrogen and oxygen. It also contains bitumi- anthra-
nous cite
Carbon : An Important Element 41

(17) Give the properties of covalent compounds. (v) The colour of universal indicator turns
Ans. Properties of covalent compounds: orange/yellow in CO2 indicating its pH value
(i) Covalent compounds have low melting points between 4 and 6.
and boiling points. * (22) Give the uses of Carbon dioxide.
(ii) Generally they are insoluble in water and Ans. Uses of Carbon dioxide are:
soluble in organic solvents. (i) CO2 is used to make aerated drinks
(iii) They are poor conductors of heat and (ii) Solid carbon dioxide is used in cold storage
electricity. and also to keep milk and milk products and
(18) What are saturated hydrocarbons? Give frozen substances cool during transport. It is
examples. also used for getting special effects of a mist in
dramas and movies.
Ans. The hydrocarbons having only single
bonds between carbon atoms are called (iii) CO2 obtained by chemical reaction or kept
saturated hydrocarbons. For example under pressure is used in fire extinguishers.
ethane (C2H6) which is (CH3 – CH3), propane (iv) Liquified CO2 is used to remove caffeine from
(CH3 – CH2 – CH3). coffee.
(19) What are unsaturated hydrocarbons? Give (v) Liquid CO2 is used as solvent in modern eco-
examples. friendly dry cleaning.
Ans. Some hydrocarbons have a multiple bond (vi) Plants use CO2 in air for photosynthesis.
between two carbon atoms. A multiple (23) Give the occurrence of methane.
bond can be a double bond or a triple bond. Ans. Occurrence of methane are as follows:
Hydrocarbons having at least one multiple
(i) Methane occurs in natural gas to the extent of
bond are called unsaturated hydrocarbons.
87%.
For example, ethene (H2C = CH2), ethyne
(HC º CH), propene (CH3 - CH=CH2), propyne (ii) Decomposition of organic matter in the
(CH3-C º CH). absence of air (anaerobic) produces methane.
(iii) Methane is present in biogas.
(20) Give the following information of carbon
dioxide: (iv) Methane is found in coal mines.
Molecular formula, Molecular mass, Melting (v) Methane is found at the surface of marshy
point, Percentage occurrence in air. places which is why it is also called marsh gas.
Ans. Molecular formula - CO2, Molecular mass - 44, (vi) On heating a mixture of hydrogen and carbon
Melting point - –56.6ºC monoxide gases at 300ºC in the presence of
Percentage occurrence in air - 0.03%. nickel (catalyst) methane gas is formed.
(vii) Fractional distillation of natural gas gives
(21) Give the physical and chemical properties of
methane in pure form.
carbon dioxide.
Ans. Physical properties of carbon dioxide are: (24) Give the physical properties of methane.

(i) It is odourless gas. (ii) It is colourless gas. Ans. Physical properties of methane are:
(i) Melting point of methane is (-182.5ºC).
Chemical properties of carbon dioxide are:
(ii) Boiling point of methane is (-161.5ºC).
(i) It is non-combustible and does not support
combustion. (iii) It is a colourless gas.

(ii) It turns lime water milky. (iv) The density of liquid methane is less than that
of water.
(iii) It is fairly soluble in water and dissolves in
water forming carbonic acid. (v) Methane is sparingly soluble in water. It
is highly soluble in organic solvents like
(iv) It turns blue litmus red indicating it is acidic
gasoline, ether and alcohol.
in nature.
42 Master Key Science & Technology (Term - II) (Std. IX)

(vi) Methane is in gaseous state at room the four types of coal in the increasing order
temperature. of their carbon content and heat produced
respectively. Charcoal and coke are the other
(25) Give the uses of methane.
amorphous forms of carbon used as fuel.
Ans. Uses of methane are:
(iii) Compounds of carbon such as hydrocarbons
(i) Methane in the form of natural gas is used in
consists of carbon and hydrogen and they are
industries such as fabric mills, paper mills,
easily combustible. For example, methane
food processing industry, petrol purification.
(CH4) which occurs in natural gas is highly
(ii) Being the smallest hydrocarbon, the inflammable. It burns by reacting with oxygen
proportion of CO2 released in the combustion to give a bluish flame. In, this reaction 213
of methane is small and, therefore, it is used as Kcal/mol of heat is given out. Methane burns
a domestic fuel. completely.
(iii) Methane is used for production of organic CH4 + 2O2 CO2 + 2H2O + Heat
compounds such as ethanol, methyl chloride,
(iv) Thus when hydrocarbons are burnt in air, large
methylene chloride and acetylene.
amount of heat is evolved with formation of
(26) How is the methane formed? Give structural carbon dioxide (CO2) and water (H2O). Due to
formula and electron dot model of methane. evolution of heat on combustion, carbon and
Ans. Atomic number of carbon is 6, The electronic its compounds are used as fuels.
configuration of carbon is (2, 4). The valency * (2) In which compound forms does carbon
of carbon is 4. Carbon atom can form four occur?
covalent bonds with other carbon atoms or
Ans. Carbon in its combined state exists as various
atoms of different elements. When a carbon
compounds such as:
atom shares one electron each with four
(i) Carbon dioxide and in the form of carbonates
hydrogen atoms and forms four C-H bonds, a
such as calcium carbonate, marble, calamine
methane CH4 molecule is formed.
(ZnCO3).
(ii) Fossil fuel - coal, petroleum, natural gas.
(iii) Carbonaceous nutrients - carbohydrates,
proteins, fats.
(iv) Natural fibres - cotton, wool, silk.
(v) Hydrocarbons - compound of carbon and
hydrogen.
13.3 Structural formula and electron dot model of methane Q.11. Explain the difference:
Q.10. Answer the following questions: * (1) Diamond and graphite.
* (1) Why are carbon and its compounds used as Ans.
fuels? Diamond Graphite
Ans.
(i) Diamond is (i) Graphite is black,
(i) The name ‘carbon’ is derived from Latin brilliant, hard soft, brittle and
word ‘carbo’ meaning coal. In the earth’s crust and crystalline slippery crystalline
carbon is present to an extent of approximately allotrope of allotrope of carbon.
0.27% in the form of carbonate, coal and carbon.
petroleum. One of the non-crystalline and
amorphous form of carbon is coal. Coal is a
fossil fuel.
(ii) Peat, lignite, bituminous and anthracite are
Carbon : An Important Element 43

Q.12. Write scientific reasons:

(ii) In diamonds, (ii) In graphite, every
every carbon atom carbon atom is * (1) Graphite is a conductor of electricity.
is bonded to four bonded to three Ans.
neighbouring other carbon atoms (i) In graphite each carbon is bonded to three
atoms by covalent by covalent bonds other carbon atom in such a way that a
bonds forming in such a way that a hexagonal layered structure is formed.
tetragonal three hexagonal layered
(ii) Due to this structure, graphite has free
dimensional structure is formed.
electrons available.
structure which A graphite crystal is
makes it very made of many such (iii) These free electrons move continuously within
hard. layers of carbon the entire layer.
atoms. This layers (iv) Hence graphite is a good conductor of
slip over each other electricity.
on applying pressure.
* (2) Graphite is not used in ornaments.
(iii) Density of diamond (iii) Density of graphite is Ans.
is 3.5 g/cm3. 1.9 to 2.3 g/cm3. (i) Graphite is a black, soft, brittle and dull form
of carbon.
(iv) Diamond is a (iv) Inside each layer of
bad conductor graphite, free electrons (ii) It is neither malleable nor ductile.
of electricity as it move continuously (iii) These properties of graphite make it unsuitable
does not have free within the entire layer. for the making of ornaments.
electrons. Hence graphite is a (iv) Hence graphite is not used for making
good conductor of ornaments.
electricity.
* (3) Limewater turns milky when CO2 is passed
* (2) Crystalline and non-crystalline forms of through it.
carbon. Ans.
Ans.
(i) Limewater traditionally means a weak
Crystalline forms of Non-crystalline forms of solution of the alkali calcium hydroxide
carbon carbon Ca(OH)2.
(ii) When CO2 is passed through limewater
(i) A crystalline form (i) A non-crystalline
it reacts with calcium hydroxide to form
has a regular form does not have a
insoluble particulates (precipitate) of calcium
and definite regular and definite
carbonate CaCO3.
arrangement of arrangement of
atoms. atoms. (iii) Calcium carbonate is weak basic salt and this
gives a milky white impression.
(ii) They have high (ii) They have low
melting points and melting points and CO2 + Ca(OH)2 CaCO3 + H2O
Carbon Calcium Calcium
boiling points. boiling points.
dioxide hydroxide carbonate
(Lime water)
(iii) A crystalline form (iii) They are amorphous
has a definite hence they do (iv) Hence lime water turns milky when CO2 gas
geometrical shape, not have definite is passed through it.
sharp edges and geometrical shape. * (4) Biogas is an eco-friendly fuel.
plane surfaces.
Ans.
(iv) Diamond, graphite (iv) Coal, charcoal and (i) Biogas is formed by decomposition of animal
and fullerene coke are different dung, dry leaves, wet garbage in a biogas
are different non-crystalline/ plant.
crystalline forms amorphous forms of
of carbon. carbon. (ii) This produces methane gas also called biogas.
44 Master Key Science & Technology (Term - II) (Std. IX)

(iii) Biogas is a very cheap fuel option which meets C60 resembles the structure of the geodesic
the demand for cooking gas. dome he designed. Molecules of fullerenes
(iv) Biogas is eco-friendly as it contains about 55% are found in the form of buckyballs and
to 60% of methane and rest is carbon dioxide, buckytubes. There are 30 to 900 carbon atoms
hence on combustion it does not produce in one molecule of a fullerene. C60 , C70 , C76 , C82
harmful gases which cause pollution. and C86 are other examples of fullerene. Their
molecules occur in small numbers in soot.
(v) Biogas is a fuel which is convenient to use and
in addition to this it produces a very good * (2) Methane is called marsh gas.
manure as a side product of the process. Ans. Methane is formed by the decomposition of
(vi) Hence biogas is an eco-friendly fuel. plant and animal matter in swamps or marshy
areas. As methane gas bubbles out from
Q.13. Explain the following: marshy area, it is called as marsh gas.
* (1) Diamond, graphite and fullerenes are
* (3) Petrol, diesel, coal are fossil fuels.
crystalline forms of carbon.
Ans.
Ans. Carbon exhibits a property of allotropy in
(i) A fossil fuel is a fuel formed by natural
which an element exists in more than one
processes, such as anaerobic decomposition
form in nature. The chemical properties
of buried dead organisms. Fossil fuels contain
of these different forms are the same but
high percentages of carbon. The word carbon
their physical properties are different.
is derived from the Latin word ‘Carbo’
Carbon exists in crystalline as well as non-
meaning coal.
crystalline (amorphous form). Crystalline
form has a regular and definite arrangement (ii) Coal is formed from the remains of trees and
of atoms. They have high melting points other vegetation. Approximately 350 million
and boiling points. A crystalline form has a years ago, these remains were trapped on the
definite geometrical shape, sharp edges and bottom of swamps, accumulating layer after
plane surfaces. Carbon has three crystalline layer and creating a dense material called
allotropes such as diamond, graphite and peat. As this peat was burried under more
fullerene. and more ground, the high temperature and
pressure transformed it into coal.
In the structure of diamond, every carbon
(iii) Petrol and diesel are obtained from mineral
atom is bonded to four neighbouring atoms
oil. Mineral oil also called as crude oil or
by covalent bonds. Therefore, diamond has
petroleum oil is formed from the remains of
a tetragonal three dimensional structure
plant and animal that lived in the seas millions
which makes it very hard. Brilliant and pure
of years ago. This plant and animal matter has
diamond is the hardest natural substance.
been drawn down and subjected to extremes
In the structure of graphite, every carbon
of temperature and pressure over millions of
atom in graphite is bonded to three other
years ago.
carbon atoms in such a way that a hexagonal
(iv) Mineral oil is commonly formed in rocks
layered structure is formed. A graphite crystal
under the sea bed. The word petroleum is
is made of many sheets or layers of carbon
derived from Latin word ‘Rock oil’. Petrol and
atoms. These layers slip over each other on
Diesel are obtained from mineral oil by the
applying pressure. One layer of graphite is
process called as fractional distillation.
called graphene.
Thus petrol, diesel and coal are fossil fuels.
Fullerene is rarely found in nature. It is
found in soot and in interstellar space. The * (4) Practical uses of CO2 .
first example of fullerene is Buckminster Ans. Uses of CO2 are:
fullerene (C60). This allotrope of carbon is
(i) CO2 is used to make aerated drinks.
named fullerene after the architect Richard
(ii) CO2 obtained by chemical reaction or kept
Buckminster Fuller because the structure of
under pressure is used in fire extinguisher.
Carbon : An Important Element 45

(iii) Liquified CO2 is used to remove caffeine from (A) Crystalline forms:
coffee. Carbon has three crystalline allotropes:
(iv) Liquid CO2 is used as solvent in modern eco- Diamond, Graphite and fullerene.
friendly dry cleaning. Properties of crystalline forms of carbon are as
(v) Solid carbon dioxide is used in cold storage follows:
to keep milk and milk products and frozen (i) A crystalline form has a regular and definite
substances cool during transport. arrangement of atoms.
Q.14. Answer the following in brief: (ii) They are made up of only carbon atoms.
(iii) They have high melting points and boiling
* (1) How will you prove experimentally that
points.
graphite is good conductor of electricity?
(iv) A crystalline form has a definite geometrical
Ans. Apparatus required: Lead pencil, electrical
shape, sharp edges and plane surfaces.
wires, battery/cell, small bulb, etc.
(B) Amorphous forms or non-crystalline:
Step-I: Remove the lead from a pencil and
assemble the apparatus as shown in the Coal, charcoal, coke are the non-crystalline
diagram. forms of carbon.
Properties of non-crystalline forms of carbon
are as follows:
Pencil (i) The arrangement of carbon atoms in this form
is not regular.
(ii) Apart from carbon atoms they also contain
Bulb hydrogen, oxygen, nitrogen, phosphorus and
sulphur atoms.
Cell (iii) Compare to crystalline form they have low
melting and boiling points.
+ –
(iv) Most of them are used as fuels.
* (3) Classify carbon.
Fig. 13.4 - Flow of electric current through graphite
Ans. Carbon is classified as follows:
Step-II: Start the electric current in the circuit,
Carbon (Allotropic forms)
the moment the electric current is passed
through the circuit the bulb glows. This
experiment proves that graphite is a good Crystalline Non-crystalline/
conductor of electricity as graphite has free forms Amorphous forms
electrons moving continuously within the
entire layer and these free electrons conduct Diamond Graphite Fullerene
electricity in the lead of the pencil.
* (2) Explain the properties of carbon. Coal Charcoal Coke
Ans. Allotropic nature of Carbon: Some elements
occur in nature in more than one form. The Peat Lignite Bituminous Anthracite
chemical properties of these different forms
are the same but their physical properties are * (4) How will you verify the properties of carbon
different. This property of elements is called dioxide?
allotropy. Carbon shows the property of Ans. Properties of carbon dioxide can be verified in
allotropy. the following ways.
(i) When a burning candle is placed in a gas jar of
Carbon allotropes are of two types:
carbon dioxide, it extinguishes indicating that
46 Master Key Science & Technology (Term - II) (Std. IX)

carbon dioxide is a non-combustible gas and (ii) CO2 based fire extinguishers do not cause
does not support combustion. corrosion and are non-conductors of electricity.
(ii) When carbon dioxide gas is passed through Therefore they are used when electrical and
lime water, it turns lime water milky due to electronic equipment catches fire.
the formation of insoluble calcium carbonate. (iii) CO2 based fire extinguishers are used to
(iii) Moist blue litmus turns red in a gas jar of extinguish small scale fire. It is beyond their
carbon dioxide indicating it is acidic in nature. capacity to extinguish a big fire.
(iv) Carbon dioxide is fairly soluble in water, it (iv) In modern fire extinguishers liquid and solid
dissolves in water forming carbonic acid. CO2 is filled under pressure. On reducing the
* (5) What are the different types of coal? What pressure if becomes gaseous and comes out
are their uses? forcefully through the horn-like hose pipe.
Ans. Coal is a fossil fuel. It contains carbon, (v) Chemical reaction:
hydrogen and oxygen. It also contains 2NaHCO3 + H2SO4  Na2SO4 + 2H2O + 2CO2
nitrogen, phosphorus and sulphur. It occurs
in the solid state. It is of four types.
(i) Peat: Formation of peat is the first step in the
formation of coal. It contains a high proportion
of water and less than 60% of carbon. Therefore,
not much heat can be obtained from peat.
(ii) Lignite: Peat was transformed into Lignite due
to increased pressure and temperature inside
the earth. It contains 60 to 70% of carbon.
Lignite is the second step of the formation of
coal.
The knob
(iii) Bituminous coal: Bituminous coal was
formed as the third step of formation of coal. Capsule
It contains 70 to 90% of carbon.
(iv) Anthracite: Anthracite is known as the pure Sulphuric
form of coal. This coal is hard and contains acid
about 95% of carbon.
Uses of coal:
(i) Coal is used as fuel in factories and homes. Powder
of sodium
(ii) Coal is used to obtain coke, coal gas and coal bicarbonate
tar.
(iii) Coal is used in thermal power plants for
Fig. 13.5 Internal structure of fire extinguisher
generation of electricity.
(2) Biogas plant.
Q.15. Write short notes on the following with neat
Ans. Biogas plant :
labelled diagram:
(i) Animal dung, dry leaves, wet garbage get
(1) Regular fire extinguisher. decomposed by anaerobic microbes in a
Ans. Regular fire extinguisher - biogas plant.
(i) A fire extinguisher contains sodium (ii) This produces methane gas also called biogas.
bicarbonate powder. There is also dilute (iii) Biogas is a very cheap fuel option which meets
sulphuric acid placed in a glass capsule. On the demand for cooking gas. It is also used for
pressing the knob, the capsule breaks and production of an electricity.
sulphuric acid comes in contact with the (iv) Biogas contains about 55% to 60% methane
sodium bicarbonate. The two reacts chemically and the rest is carbon dioxide.
to release CO2 which comes out.
Carbon : An Important Element 47

(v) Biogas is a fuel which is convenient to use the above reaction is as follows.
and, in addition to this, a very good manure is CaCO3 + 2HCl  CaCl2 + H2O + CO2 
also produced as a side product of the process.
(vi) Biogas production process - Production of Thistle funnel
biogas is an anaerobic process. It takes place Dilute hydrochloric acid
in two stages. Retort
Gas delivery tube
(1) Production of acids - The microbes act on the Stand
biodegradable complex organic compound
and produce organic acids. Upward
(2) Methane gas production - The methanogenic displacement
CaCO3 of air
bacteria act on the organic acids to produce
methane gas. Round Gas jar
bottom
CH3COOH  CH4 + CO2 flask
CO2

Mixing tank Exit of gas

(Slurry of
cattle dung) Fig. 13.7 Preparation of Carbon dioxide
Slab Overflow tank
cover Q.17. Explain the following chemical reactions
Spent slurry
with balanced chemical equation.
Inlet (1) Preparation of urea from Ammonium cyanate:
chamber
Outlet chamber
Organic compound Urea can be synthesized
Dung and
Underground from an inorganic compound Ammonium
water mixture
digester tank
cyanate.
Heat
Fig. 13.6 Biogas plant
Ans. NH4+ CNO– NH2CONH2
Ammonium Cyanate Urea
Q.16. With the help neat labelled diagram explain
the laboratory preparation of Carbon dioxide (2) Coal when burnt in air:
gas. When coal is burnt in air, the carbon present
Ans. The laboratory preparation of Carbon dioxide in coal combines with oxygen present in air to
form carbon dioxide gas.
gas is as follows:
Ans. C + O2 CO2
Apparatus : Retort stand, round bottom flask,
Carbon Oxygen Carbon dioxide
thistle funnel, gas delivery tube, gas jars.
Chemicals : Calcium carbonate (Pieces of (3) Calcium carbonate reacts with dilute
Shahabad tiles / marble pieces / limestone), hydrochloric acid:
dilute hydrochloric acid. When Calcium Carbonate reacts with dilute
hydrochloric acid it forms Calcium chloride,
Procedure :
water and Carbon dioxide gas is evolved.
(i) Assemble the apparatus as shown in the
Ans. CaCO3 + 2HCl CaCl2 + H2O + CO2
figure. While assembling place CaCO3 in the Calcium Dilute Calcium Water Carbon
round bottom flask. carbonate hydrochloric chloride dioxide
acid
(ii) Add dilute HCl in the flask through thistle
(4) Carbon dioxide is passed through an aqueous
funnel. See to it that the end of the funnel dips
solution of Sodium hydroxide:
in the acid.
When Carbon dioxide gas is passed through
(iii) CO2 is formed as a result of the reaction an aqueous solution of Sodium hydroxide it
between CaCO3 and HCl. Collect this gas in forms Sodium carbonate and Water.
four to five gas jars. The chemical equation of
48 Master Key Science & Technology (Term - II) (Std. IX)

Ans. 2NaOH + CO2 Na2CO3 + H2O and water. In these reaction 213 kcal/mol of
Aqueous Carbon Sodium Water heat is given out.
Sodium dioxide carbonate
hydroxide Ans. CH4 + 2O2 CO2 + 2H2O + heat
Methane Oxygen Carbon Water
(5) Carbon dioxide is passed through an aqueous
dioxide
solution of Sodium carbonate:
When carbon dioxide is passed through (10) Methane and Chlorine gases react with each
aqueous solution of Sodium carbonate it other.
forms Sodium bicarbonate. Methane and chlorine gases react with each
other at the temperature of 250ºC to 400ºC
Ans. Na2CO3 + H2O + CO2 2NaHCO3
Sodium Carbon Sodium
in presence of ultra voilet light and form
Water
carbonate dioxide bicarbonate mainly Methyl chloride (Chloromethane and
(6) Carbon dioxide is passed through freshly Hydrogen chloride)
prepared lime water for a short duration and This reaction is called Chlorination of methane.
then for longer duration: Light
Ans. CH4 + Cl2 CH3Cl + HCl
When Carbon dioxide is passed through Methane Chlorine Methyl Hydrogen
Chloride Chloride
freshly prepared lime water, it forms water
and white precipitate of Calcium carbonate (11) Production of methane gas in biogas plant.
because of which lime water turns milky. In biogas plant microbes act on the
Ans. Ca(OH)2 + CO2 H2O + CaCO3 biodegradable complex organic compounds
Calcium Carbon Water Calcium and produce organic acids.
hydroxide dioxide carbonate
(lime water) (white)
The methanogenic bacteria act on the organic
acids to produce Methane gas and Carbon
When Carbon dioxide is continuously passed dioxide gas.
through milky lime water, it forms Calcium
Ans. CH3COOH CH4 + CO2
bicarbonate which is soluble in water and
Organic acid Methane Carbon
therefore water once again turns colourless. (Acetic acid) dioxide
CaCO3 + H2O + CO2 Ca(HCO3)2 (12) Production of water gas:
Calcium Water Carbon Calcium
carbonate dioxide bicarbonate When super heated steam is passed over red
(Soluble) hot coke at high temperature it forms carbon
(7) Carbon dioxide gas is dissolved in water. monoxide gas and hydrogen gas.
Carbon dioxide gas is fairly soluble in water, This gaseous product of carbon monoxide gas
it dissolves in water under pressure to form and hydrogen gas together is called as water
Carbonic acid. gas.
Ans. CO2 + H2O H2CO3 Ans. C + H2O CO + H2
Carbon Water Carbonic Red hot Super heated Carbon
coke steam monoxide Hydrogen
dioxide acid
Water gas
(8) Sodium bicarbonate reacts with dilute
Sulphuric acid. (reaction in fire extinguisher): *Q.18. Can you recall?
When Sodium bicarbonate reacts with dilute (1) What is an element? What are the different
Sulphuric acid it forms Sodium sulphate, types of elements?
water and Carbon dioxide gas. Ans. A substance which cannot be decomposed into
Ans. 2NaHCO3 + H2SO4 Na2SO4 + 2H2O + 2CO2 simples substances by any physical or simple
Sodium Sulphuric Sodium Water Carbon chemical methods is called as an Element. An
bicarbonate acid sulphate dioxide
element is composed of atoms of only one
(9) Methane gas is burnt in air: kind. The different types of elements are:
Methane is highly inflammable it burns in Metals - Examples: Gold, Silver, etc.
air with a bluish flame and combines with Non-metals - Example: Carbon, Sulphur, etc.
oxygen present in air to form Carbon dioxide
Metalloids - Examples: Silicon, Antimony, etc.
Carbon : An Important Element 49

(2) What remains behind on complete them. This is because covalent bond is formed
combustion of any organic compound? by sharing of electrons. Therefore there is no
Ans. A black colour substance ‘Carbon’ remains change in number of electrons and protons
behind on complete combustion of any in these atoms and they remain electrically
organic compound. neutral.

(3) What type of element is carbon? Give some Covalent bonds occur when electrons are
information about it. shared between two atoms. A single covalent
bond is when only one pair of electrons is
Ans. Carbon is a non-metallic element. It is
shared between atoms. In this sharing the
available abundantly in the nature and occurs
atomic orbitals directly overlap between the
in free as well as combined state. Carbon in
nuclei of two atoms forming the strongest
free state is found as diamond and graphite
type of covalent bond called as sigma bond.
and in combined state it is present to the
Hence a single covalent bond between two
extent of approximately 0.27% in the form of
carbon atoms is strong and stable.
carbonate, coal, petroleum. In atmosphere,
the proportion of carbon in the form of carbon (2) In which of the solvents - water, kerosene and
dioxide is approximately 0.03 %. cooking oil does the coal powder dissolve?
Ans. Coal powder being covalently bonded,
*Q.19. Can you tell?
dissolves in organic solvents such as kerosene
(1) What is a compound? How are compounds and cooking oil but is insoluble in water.
formed?
(3) What inference will you draw about the
Ans. A compound is a substance formed when two solubility of carbon?
or more elements are chemically bonded with
Ans. Carbon is insoluble in water but soluble in
each other in definite proportion by weight.
organic solvents.
When atoms or two or more different
(4) Is the density of CO2 more or less than that
elements chemically react with each other in
of air?
a definite proportion by weight a compound
is formed. The properties of a compound Ans. Density is define as mass per unit volume of
are altogether different from its constituent a substance, expressed as kilograms per cubic
elements. Example: Pure water is a compound meter. At standard temperature and pressure,
made up of two elements Hydrogen and the density of air is 1.29 kg/m3. While that of
Oxygen. Hydrogen (H) atoms and oxygen carbon dioxide (CO2) is 1.79 kg/m3. Hence
(O) atoms have chemically reacted with density of CO2 is more than that of air.
each other in definite proportion to form a *Q.21. Activity based questions:
compound water (H2O). The proportion of
(1) Take some milk in an evaporating dish. Heat
hydrogen and oxygen in water by volume is
the evaporating dish on a bunsen burner.
2 : 1 and by weight is 1 : 8 respectively. The What remains behind at the bottom of an
properties of water are altogether different evaporating dish on complete evaporation
from the properties of its constituents elements of the milk?
hydrogen and oxygen.
Ans. On complete evaporation of milk, a black
*Q.20. Use your brain power! residue is left behind. This residue is of carbon.
(1) Does an electric charge form on atoms when (2) Take small samples of sugar, wool, dry
a covalent bond is formed between them? leaves, hair, seeds, split pulses and plastic
Why is a single bond between two carbon in separate test tubes. Heat each test tube
atoms strong and stable? and observe the changes taking place in the
Ans. No, electric charge is not formed on atoms substances.
when a covalent bond is formed between
50 Master Key Science & Technology (Term - II) (Std. IX)

What does the black substance in each test (i) With which gas in the air does the coal react
tube indicate? on igniting?
Ans. On heading the above samples, they get Ans. Coal reacts with oxygen gas present in the air.
charred and a black substance is left behind. (ii) What is the substance formed?
The black substance is carbon.
Ans. The substance formed is carbon dioxide.
(3) Apparatus : Coal, match box, moist litmus
(iii) What change takes place in the litmus paper?
paper, etc.
Ans. The moist blue litmus paper turns red.
Procedure : Ignite the coal. Hold the moist
(iv) Write down the chemical reaction taking place
blue litmus paper over the gas released on
in the above procedure.
igniting the coal. Note the observation.
Ans. Carbon combines with oxygen to form Carbon
dioxide
Moist blue litmus
C + O2 CO2
Carbon Oxygen Carbon dioxide

This CO2 combines with water present on

Coal
moist blue litmus paper to form Carbonic acid
which turns blue litmus to red.
CO2 + H2O H2CO3
Carbon Water Carbonic acid
dioxide

Fig. 13.8 Reaction of carbon with oxygen

vvv
Carbon : An Important Element 51

ASSIGNMENT - 13
Time : 1 Hr. Marks : 30

Q.1. (A) Fill in the blanks: (4)

(1) ............. is the essential element in all the organic compounds.
(2) The methanogenic bacteria act on the organic acids to produce ............. .
(3) At least one carbon bond in an unsaturated hydrocarbon is ............. .
(4) ............. is used to remove caffeine from coffee.
(B) Match the columns: (2)
Column ‘A’ Column ‘B’
(1) Ethyne (a) (CH3-CH = CH2)
(2) Propene (b) (HC º CH)
(3) Ethene (c) (CH3-C º CH)
(4) Propyne (d) (H2C = CH2)

Q.2. Answer the following in one or two sentence each: (Any four): (4)
(1) What is allotropy?
(2) Name the chemicals used in regular fire extinguisher.
(3) Name the organic solvents in which Fullerenes are soluble.
(4) How is carbon dioxide used in dramas and movies?
(5) What does biogas contain?
(B) Distinguish between: (4)
(1) Diamond and Graphite.
Q.3. (A) Give scientific reasons: (Any two): (4)
(1) Limewater turns milky when CO2 is passed through it.
(2) Biogas is an eco-friendly fuel.
(3) Graphite is not used in ornaments.

(B) Answer in brief: (Any two) (4)

(1) Give the properties of covalent compounds.
(2) Give the physical and chemical properties of carbon dioxide.
(3) Give the uses of methane.

Q.4. (A) Explain the following chemical reactions with the help of balanced
equation: (Any two) (4)
(1) Calcium carbonate reacts with dilute hydrochloric acid.
(2) Sodium bicarbonate reacts with dilute sulphuric acid.
(3) Methane gas and chlorine gas react with each other.
(B) Answer in detail: (Any one) (4)
(1) With the help of neat labelled diagram explain the laboratory preparation of Carbon dioxide gas.
(2) What are the different types of coal? What are their uses?
vvv
 14 Substances in Common Use

CONCEPT MAP

SUBSTANCES

Can be Can be Can be Can be Can be

ACIDS SALTS CHEMICAL RADIO BASES
strength SUBSTANCES IN DAY ACTIVE strength
represented by TO DAY LIFE SUBSTANCES represented by
pH range : pH < 7 Such as pH range : pH > 7
Such as

Sodium Sodium Calcium Sodium Crystalline

Chloride Bicarbonate Oxychloride Carbonate Salts
NaCl NaHCO3 CaOCl2 Na2CO3. H2O

Common Baking Bleaching Washing

Salt Soda Powder Soda

Food Colours Dye Artificial Deodrant Teflon Ceramic

and Essences Colours Some more
methods of Different
coating types

• Powder coating • Porcelain

• Anodizing • Bone China
• Advanced
Ceramics

* (4) The chemical name of Teflon is .................... .

MASTER KEY QUESTION SET - 14
(5) 25% of NaCl is known as .................... .
Q.1. (A) Fill in the blanks: (6) .................... gas is released when bleaching
* (1) The number of molecules of water of powder is added to water.
crystallization in washing soda is .................... . (7) Washing soda is .................... as it absorbs
* (2) The chemical name of baking soda is .................. moisture if left exposed to air.
* (3) is used
.................... in treatment of (8) .................... is used to make hard water soft.
hyperthyroidism. (9) Molecular formula for Alum is .................... .

(52)
Substances in Common Use 53

(10) .................... is used in blood test for diagnosing (3) .................... is known as chloride of lime.
anaemia. (a) Calcium carbonate
(11) High grade of .................... and .................... are (b) Sodium bicarbonate
used as raw material to manufacture bathing (c) Sodium chloride
soap. (d) Bleaching powder
(12) Pickles, jams and sauce contains small (4) Salt obtained from certain type of rock is
quantities of .................... and .................... . called .................... .
(13) Excessive consumption of foods with added (a) hard salt (b) rock salt
food colours leads to diseases like .................... . (c) stone salt (d) pure salt
(14) Melting point of Teflon is .................... . (5) The .................... % aqueous solution of salt is
called brine.
(15) Anodizing is done by .................... .
(a) 25 (b) 60 (c) 30 (d) 50
(16) The red blood cell count increases in the
(6) The molecular formula for baking soda is
disease .................... .
.................... .
(17) Magnesium sulphate (MgSO4.7H2O) is also
(a) Na2CO3 (b) NaHCO3
called .................... .
(c) Na2SO4 (d) NaNO3
(18) Sodium or potassium salts of higher fatty acid
(7) Chlorine gas is a strong .................... agent.
is called as .................... .
(a) reducing (b) oxidizing (c) neutral (d) acidic
(19) Molecular formula of sodium bicarbonate is
(8) Bleaching powder is .................... in colour.
.................... .
(a) brownish red (b) yellowish white
(20) Soap is .................... in nature.
(c) pinkish brown (d) greenish blue
(21) Molecular formula for magnesium bromide is
(9) Bleaching powder is also called .................... .
.................... .
(a) calcium oxygen chlorine
(22) Baking powder is .................... is nature.
(b) calcium oxychloride
(23) Sodium chloride is formed by a neutralization (c) calcium hydroxide
reaction between .................... and .................... . (d) calcium oxalate
Ans. (1) 10 (2) Sodium bicarbonate (3) Iodine -123 (10) NaHCO3 is also called as .................... .
(4) Polytetra fluoroethene (C2F4)n (5) Brine (a) sodium carbonate
(6) Chlorine (7) hygroscopic (8) Na2CO3 (b) sodium bicarbonate
(Washing soda) (9) K2SO4.Al2(SO4)3.24H2O (c) sodium carbon oxide
(10) Blue Vitriol (11) fats, oils (12) lead,mercury (d) sodium chloride
(13) ADHD (Attention Deficit Hyperactivity (11) Soap is .................... in nature.
Disorder) (14) 327°C (15) Electrolysis (16)
(a) acidic (b) basic
Polycythemia (17) Epsom salt (18) Soap (19)
(c) neutral (d) fuming
NaHCO3 (20) basic (21) MgBr2 (22) Basic (23)
(12) Molecular formula for magnesium bromide is
Sodium Hydroxide, Hydrochloric acid
.................... .
Q.2. Rewrite the following statements by
(a) MgBr (b) Mg2Br
selecting the correct options given below:
(c) Mg2Br2 (d) MgBr2
(1) Baking soda is .................... .
(13) Melting point of NaCl is .................... .
(a) non-metallic (b) metallic
(a) 400°C (b) 100°C
(c) acidic (d) basic
(c) 800°C (d) 600°C
(2) During electrolysis of NaCl in the fused state
(14) The molten state of NaCl is also called as
.................... is formed at cathode.
.................... .
(a) sodium (b) oxygen
(a) solid state (b) semi-solid
(c) oxalic acid (d) butyric acid (c) gaseous state (d) fused state
54 Master Key Science & Technology (Term - II) (Std. IX)

(15) Rock salt is .................... in colour. (11) Uses of sodium bicarbonate

(a) black (b) white Ans. To prepare breads, cakes and dhokla
(c) brown (d) blue (12) Constituents of baking powder.
(16) Strong odour in swimming pool is due to Ans. Baking soda and mild acid (tartaric acid)
.................... .
(13) Substance used to make hard water soft.
(a) chlorine gas (b) impurities
Ans. Washing soda is Na2CO3.10H2O.
(c) calcium carbonate (d) calcium hydroxide
(17) Substance used to make hard water soft is (14) Radioactive isotopes used in treatment of
.................... . bone cancer.
(a) Na2CO3.10H2O (b) Na2CO3.H2O Ans. Strontium - 89, strontium - 90, samarium - 153,
id radium - 223
(c) NaCO3.10H2O (d) NaCO3.H2O
(15) Strontium 89 and strontium 90 are used in
(18) The fixed number of molecules of water in
treatment of.
alum is .................... .
Ans. Bone cancer.
(a) 24 (b) 10 (c) 7 (d) 2
Ans. (1) basic (2) sodium (3) Bleaching powder (4) rock salt Q.4. *(A) Match the columns:
(5) 25 (6) NaHCO3 (7) Oxidising (8) yellowish white
Column ‘A’ Column ‘B’
(9) calcium oxychloride (10) sodium bicarbonate
(11) basic (12) MgBr2 (13) 800°C (14) fused state (15) (1) Saturated brine (a) Sodium metal freed
brown (16) chlorine gas (17) Na2CO3.10H2O (18) 24 (2) Fused NaCl (b) Basic salt
Q.3. Name the following: (3) CaOCl2 (c) Crystallization of salt
(1) Important salts found in sea water. (4) NaHCO3 (d) Oxidation of colour
Ans. Magnesium chloride
Potassium chloride Ans. (1 - c), (2 - a), (3 - d), (4 - b)
(2) Use in preparation of breads and cakes to (B) Match the columns:
make them soft.
Column ‘A’ Column ‘B’
Ans. Sodium bicarbonate
(3) Gas liberated when bleaching powder is (1) Barium chloride (a) 24H2O
added to CO2 gas. (2) Sodium sulphate (b) 7H2O
Ans. Chlorine (Cl2) gas. (3) Magnesium sulphate (c) 2H2O
(4) Salt used in refining petroleum (4) Alum (d) 10H2O
Ans. Sodium carbonate (Na2CO3)
Ans. (1 - c), (2 - d), (3 - b), (4 - a)
(5) Chemical formula of bleaching powder
Ans. CaOCl2 (C) Match the columns:
(6) The chemical formula of sodium hydrogen Column ‘A’ Column ‘B’
carbonate.
(1) Strontium - 90 (a) Brain tumour
Ans. NaHCO3
(2) Cobalt – 60 (b) Hyperthyroidism
(7) Nature of soap.
(3) Iodine - 131 (c) Polycythemia
Ans. Basic
(4) Phosphorus - 32 (d) Bone cancer
(8) Molecular formula for magnesium bromide
Ans. MgBr2 Ans. (1 - d), (2 - a), (3 - b), (4 - c)
(9) Melting point of NaCl Q.5. State whether true or false. If false rewrite the
Ans. 800°C correct statement:
(10) Two examples of Rock Salt (1) Bleaching powder is used in preparation of
Ans. Mineral halite and Himalayan rock salt. chloroform which is used as an anaesthetic.
Ans. True.
Substances in Common Use 55

(2) On addition of universal indicator the colour Ans. False, Bleaching powder available in market
of table salt changes to pink. is classified on the basis of percentage of
Ans. False, On addition of universal indicator the chlorine present in it.
colour of table salt changes to green. (19) The hard water becomes soft on adding baking
(3) Borax is Na2B4O7.9H2O. soda (NaHCO3)
Ans. False, Borax is Na2B4O7.10H2O Ans. False, Hard water becomes soft on adding
(4) Boron – 10 is used to cure bone cancer. washing soda (Na2CO3.10H2O)
Ans. False, Boron – 10 is used in treatment of brain Q.6. Select the odd man out:
tumour. (1) Sodium sulphate, Barium chloride,
(5) Clinical deo contains 20 to 25% of aluminium. Magnesium sulphate, bleaching powder.
Ans. True. Ans. Bleaching powder : All others are crystalline
(6) NaHCO3 is sodium carbonate. salt with water of crystallization while
bleaching powder is not.
Ans. False, NaHCO3 is sodium bicarbonate.
(2) Strontium – 89, Strontium – 90, Radium – 223,
(7) Soap is acidic in nature.
Iodine – 123.
Ans. False, Soap is basic in nature.
Ans. Iodine – 123 : It is used to cure hyperthyroidism
(8) Baking powder is neutral in nature. while others are used to cure bone cancer.
Ans. False, Baking powder is basic in nature. (3) Soap, Toothpaste, Baking soda, Curd.
(9) POP is crystalline in nature. Ans. Curd : It is acidic in nature while others are
Ans. False, POP is amorphous in nature. basic in nature.
(10) pH value of universal indicator is 0 – 7. (4) Na2CO3.10H2O, Na2SO4.10H2O, BaCl2.2H2O,
Ans. False, pH value of universal indicator is 0 – 14. CaOCl2
(11) Sodium chloride is formed by neutralization Ans. CaOCl2 : It is amorphous in nature while rest
reaction between sodium hydroxide and are crystalline in nature.
calcium carbonate. (5) Boron-10, Iodine – 131, Cobalt – 60, Iodine –
Ans. False, Sodium chloride is formed by a 123.
neutralization reaction between sodium Ans. Iodine – 123 : It is used in hyperthyroidism
hydroxide and hydrochloric acid. while rest are used in treatment of brain
(12) Boiling point of NaCl is 800°C. tumour.
Ans. False, Melting point of NaCl is 800°C. (6) Na2SO4, K3PO4, MgBr2, HCl.
(13) Molten state of NaCl is also called as solid Ans. HCl : Rest all are salt but HCl is an acid.
state.
Q.7. Write the correlated terms:
Ans. False, Molten state of NaCl is also called as
(1) Washing Powder : Basic : : Milk : .................... .
fused state.
(2) Na2SO4 : Sodium sulphate : : K2PO4 : .....................
(14) Mineral halite is an example of Rock Salt.
(3) CaOCl2 : Calcium Oxychloride : : NaHCO3 :
Ans. True.
.................... .
(15) Sodium bicarbonate is used to reduce acidity.
(4) Borax : 10H2O : : Alum : .................... .
Ans. True.
(5) Sodium Sulphate : Na2SO4.10H2O : :
(16) Bleaching powder is also called as chloride of
Magnesium Sulphate : .................... .
lime.
(6) Bathing soap : High grades fats and oils : :
Ans. True.
washing soap : .................... .
(17) Bleaching powder is obtained by reaction of
(7) Radium – 23 : Bone cancer : : Phosphorus – 32 :
chlorine gas with slaked lime.
.................... .
Ans. True.
(8) Iodine – 123 : Hyperthyroidism : : iodine – 131 :
(18) Bleaching powder available in market is .................... .
classified on the basis of colour.
56 Master Key Science & Technology (Term - II) (Std. IX)

(9) Clinical deo : 20-25% of aluminium : : (14) Baking Soda : Breads and Cakes : : Washing
Antiperspirant deo : .................... of aluminium Soda : .................... .
chlorohydrate. (15) Borax : (Na2B4O7.10H2O) : : Alum : .....................
(10) Sodium carbonate : Na2CO3 : : Sodium
bicarbonate : .................... . Ans. (1) Acidic (2) Potassium phosphate (3) Sodium
hydrogen carbonate (4) 24H2O (5) MgSO4.7H2O
(11) Curd : Acidic : : Soap : .................... .
(6) low grade fats and oils (7) Polycythemia (8)
(12) Calcium Carbonate : CaCO3 : : Magnesium
Tumour detection (9) 15% (10) NaHCO3 (11)
bromide : .................... .
basic (12) MgBr2 (13) Na2CO3.10H2O (14) hard
(13) Baking Soda : NaHCO3 : : Washing Soda : water soft (15) K2SO4.Al2(SO4)3.24H2O
.................... .

Q.8. Explain the following chemical reactions with the help of balanced equations :
(1) Sodium hydroxide reacts with dilute hydrochloric acid.
Ans. When sodium hydroxide reacts with dilute hydrochloric acid, it forms sodium chloride and water.
This is a neutralization reaction.
NaOH + HCl → NaCl + H2O
Sodium Hydrochloric Sodium water
hydroxide acid chloride (salt)
(2) When an electric current is passed through a saturated solution of sodium chloride (brine)
Ans. When an electric current is passed through a saturated solution of sodium chloride (brine) it is electrolysed
and hydrogen gas is released at the cathode while chlorine gas is released at the anode. Also, an important
basic compound NaOH is formed in the cell.
2NaCl + 2H O electric current
2
2NaOH + Cl ↑ + H↑ 2 2

Brine Sodium Chlorine Hydrogen

hydroxide
(3) Baking soda (sodium hydrogen carbonate) reacts with dilute hydrochloric acid.
Ans. When sodium bicarbonate (sodium hydrogen carbonate) reacts with dilute hydrochloric acid, it gives
sodium chloride, water and carbon dioxide gas is liberated.
NaHCO3(s) + HCl(aq) → NaCl(aq) + H2O(l) + CO2(g)
Sodium Hydrochloric Sodium Water Carbon
bicarbonate acid chloride dioxide
(4) Bleaching powder is exposed to air.
Ans. When bleaching powder is exposed to air, it undergoes slow decomposition due to the carbon dioxide in
air and chlorine gas is released.
CaOCl2 + CO2 → CaCO3 + Cl2 ↑
Bleaching Carbon Calcium Chlorine
powder dioxide (from air) carbonate
(5) When dry slaked lime reacts with chlorine gas.
Ans. When dry slaked lime reacts with chlorine gas, it gives bleaching powder.
Ca (OH)2 + Cl2 → CaOCl2 + H 2O
Slaked Chlorine Bleaching Water
lime powder
(6) Bleaching powder reacts with dilute sulphuric acid.
Ans. Dilute sulphuric acid reacts rapidly with bleaching powder to form calcium sulphate and release chlorine
Substances in Common Use 57

gas completely.
CaOCl2 + H2SO4 → CaSO4 + Cl2 ↑ + H2O
Bleaching Dilute sulphuric Calcium Chlorine Water
powder acid sulphate
 (7) Bleaching powder reacts with dilute hydrochloric acid.
Ans. Dilute hydrochloric acid reacts rapidly with bleaching powder to form calcium chloride and
release chlorine gas completely.
CaOCl2 + 2HCl → CaCl2 + Cl2 ↑ + H2O
Bleaching Dilute hydrochloric Calcium Chlorine Water
powder acid chloride
(8) Sodium carbonate reacts with magnesium chloride.
Ans. When sodium carbonate reacts with magnesium chloride it forms insoluble magnesium carbonate and
sodium chloride. This reaction is used to make hard water soft.
MgCl2(aq) + Na2CO3(s) → MgCO3(s) + 2 NaCl(s)
Magnesium Sodium Magnesium Sodium
chloride carbonate carbonate chloride
(9) Crystalline sodium carbonate is exposed to air.
Ans. When crystalline sodium carbonate is exposed to air it loses its water of crystallization readily and a
white powder is obtained. This powder is called washing soda.
Na2CO3.10H2O → Na2CO3.H2O
Crystalline White powder (washing soda)
Sodium carbonate
(10) Sodium carbonate reacts with sulphuric acid.
Ans. When sodium carbonate reacts with sulphuric acid it forms sodium sulphate, water and carbon dioxide
gas is liberated.
Na2CO3(s) + H2SO4 → Na2SO4 + H2O + CO2↑
Sodium Sulphuric Sodium Water Carbon
carbonate acid sulphate dioxide
Q.9. Answer the following questions in one or two (i) Blue vitriol is used in the blood test for
sentences each : diagnosing anaemia.
1
(1) What is brine? What happens when of this (ii) Bordeaux mixture which is a mixture of slaked
5
solution is evaporated? lime and blue vitriol is used as a fungicide on
Ans. The 25% aqueous solution of salt is called fruits like grapes and musk melon.
1
saturated brine. When of this solution is (4) What is radioactivity and what are radioactive
5
evaporated the dissolved salt gets crystallized substances?
and salt gets separated from the solution. Ans. Elements with a high atomic number such as
(2) What is baking soda? Give its chemical name uranium, thorium, radium have a property
and molecular formula. of spontaneously emitting invisible, highly
Ans. Baking soda is a white non-crystalline powder. penetrating and high energy radiation. This
Its chemical name is Sodium hydrogen property is called radioactivity. A substance
carbonate or Sodium bicarbonate and its having this property is called a radioactive
molecular formula is NaHCO3. substance.
(3) Give two uses of Blue vitriol. (5) What can you say about the uses of radioactive
isotopes?
Ans.
58 Master Key Science & Technology (Term - II) (Std. IX)

Ans. It is a misconception that radioactive elements without decomposing. Ceramic is brittle,

are used only for making an atom bomb. water resistant and an electrical insulator.
Radioactive isotopes are used in various (14) How is bone china made? How is it different
fields such as scientific research, agriculture, from porcelain?
industry, medicine, etc. Radioactive substances Ans. Bone china is made by adding some ash of
are used in two ways. animal bones in the mixture of china clay,
(i) By using the radiation alone. feldspar and fine silica while making porcelain.
(ii) By using the radioactive element itself. This ceramic is harder than porcelain.
(6) Give the uses of radioactive isotopes in (15) What compounds are used instead of clay for
Radiography. making advanced ceramic?
Ans. Radiography : Internal cracks and voids Ans. Oxides like Alumina (Al2O3), Zirconia (ZrO2)
in cast iron articles and iron solder can be Silica (SiO2) and some other compounds like
detected with the help of gamma rays. For this silicon carbide (SiC), boron carbide (B4C) are
purpose, isotopes like cobalt-60, iridium-192 used instead of clay for making advanced
are used in the radiography camera. This ceramic.
technique is used for detecting flaws in metal (16) What is sintering?
work. Ans. Advanced ceramics requires a temperature of
(7) Give the uses of radioactive isotopes in 1600 to 1800 °C and an oxygen free atmosphere
Ceramic articles. for firing. This process is called sintering.
Ans. Ceramic articles : Q.10. Distinguish between:
Luminous colours are used to decorate (1) Washing soda and Baking soda
ceramic tiles, utensils, plates, etc. Earlier Ans.
uranium oxide was used in these paints.
Washing soda Baking soda
(8) What is a Dye?
(i) It is sodium It is sodium bicarbonate
Ans. The coloured substance which on applying to carbonate. or sodium hydrogen
an article, imparts that colour to the article, is carbonate.
called a dye
(ii) Its molecular Its molecular formula is
(9) What is done to fix dye on the cloth ? formula is NaHCO3.
Ans. A mordant is to be used to fix the colour after Na2CO3.10H2O
dying a cloth. A mordant is a chemical binding (iii) It is a crystalline It is an amorphous
agent that adheres well to both the fibers and substance. powder.
the dye. (iv) It is used in It is used in bakery for
(10) What are used in artificial dyes ? manufacturing making cakes and bread
Ans. Petroleum products and minerals are used in soaps and lighter and spongy.
artificial dyes. detergent.
(11) What is Teflon? Give its chemical name. (2) Bathing soap and Washing soap
Ans. Teflon is the polymer of tetrafluoroethylene. Ans.
Its chemical name is polytetrafluoroethene Bathing soap Washing soap
(C2F4)n.
(i) High grade fats Low grade fats and
(12) What is powder coating? Why is it done? and oils are oils are used as the raw
Ans. Powder coating is a method of applying a layer used as the raw material.
harder than paint on the surface of plastic, material.
medium density fiber (MDF) board and iron (ii) Expensive Cheaper perfumes
object to make them attractive, durable and to perfumes added. added.
prevent rusting respectively. (iii) No free alkali Free alkali present for
(13) Give the properties of ceramics. content present to cleaning action.
Ans. Ceramics can withstand high temperatures prevent injuries to
skin.
Substances in Common Use 59

Q.11. Give scientific reasons: (4) Sodium carbonate is added to hard water to
(1) Baking soda is used while making cakes. make it soft.
Ans. Ans. The hardness of water is due to the presence
(i) Baking soda is chemically known as sodium of chlorides and sulphates of calcium and
bicarbonate. magnesium in it. Na2CO3 is added to it to soften
such water and make it suitable for use. The
(ii) On heating, sodium bicarbonate decomposes
reaction with Na2CO3 causes the formation of
to form sodium carbonate, water and carbon
insoluble carbonate salts of magnesium and
dioxide (CO2).
calcium thus making the water soft.
(iii) The carbon dioxide produced is released due
MgCl2(aq) + Na2CO3(s) → MgCO3(s) + 2NaCl(s)
to which the cake becomes soft and spongy.
(iv) Hence, baking soda is used to make cake Magnesium Sodium Magnesium Sodium
spongy and soft. chloride carbonate carbonate chloride

(2) Baking soda is used to reduce acidity in the (5) Alum is used in the process of water
stomach. purification.
Ans. Ans. Alum is used in the process of water purification
because of property of coagulation. The solid
(i) Baking soda is used as a medicine (antacid).
impurities in water come together, become
When it is taken, it undergoes hydrolysis
heavy and settle to the bottom. As a result, the
to give sodium hydroxide in the stomach.
water above becomes clear.
Thus sodium hydroxide neutralizes the
hydrochloric acid produced by gastric juice (6) Over consumption of artificial food colours
and gives relief to the patient from acidity. should be avoided?
(ii) NaHCO3 + H2O → NaOH + H2O + CO2 ↑ Ans. The over consumption of artificial food colours
Baking Sodium should be avoided because they can be
Soda hydroxide detrimental to health. Food colours added to
pickles, jam and sauce contain small quantities
(iii) NaOH + HCl → NaCl + H2O
of lead and mercury. These can be harmful
Sodium Hydrochloric Sodium
for those who consume these products on a
hydroxide acid chloride regular basis. Diseases like ADHD (Attention
(3) Tap water and water in swimming pool has a Deficit Hyperactivity Disorder) can affect
typical strong odour in the rainy season. children due to excessive consumption of
Ans. foods with added food colours.
(i) Tap water and water in swimming pool has a (7) Artificial colours in Rang Panchami should
typical strong odour in the rainy season, It is be used cautiously.
the odour of the chlorine gas used to destroy Ans. We regularly use artificial colours on Rang
the microbes in the water. Panchami. The red colour used on Rang
(ii) Chlorine gas is a strong oxidizing agent and Panchami is very dangerous. It contains a high
therefore, it has a strong disinfecting as well proportion of mercury in it. This poses risks
as bleaching action. Chlorine is inconvenient like blindness, skin cancer, asthma, itching of
to handle because of its gaseous state. Instead, the skin, permanent blocking of sweat pores
the solid bleaching powder which has the etc. Therefore, it is necessary that artificial
same effect is more convenient to use. colours are used cautiously.
(ii) Bleaching powder undergoes slow * (8) Bleaching powder has the odour of chlorine..
decomposition due to the carbon dioxide in Ans. Bleaching powder undergoes slow
air and chlorine gas is released. Bleaching decomposition due to the carbon dioxide in
powder gets its property because of this air and chlorine gas is released. Bleaching
release of chlorine gas. powder gets its property because of this
CaOCl2 + CO2 → CaCO3 + Cl2 ↑ release of chlorine gas.
Bleaching Carbon Calcium Chlorine CaOCl2 + CO2 → CaCO3 + Cl2 ↑
powder dioxide carbonate
60 Master Key Science & Technology (Term - II) (Std. IX)

* (9) The hard water of a well becomes soft on aluminium oxide is formed on the anode.
adding washing soda to it. Therefore aluminium article is used as an
Ans. The hard water from a well or a bore-well anode in the anodizing process.
becomes soft on adding washing soda and we (13) There are various brands of bleaching
come to know this from the lather formed on powder in the market.
it. The hardness of water is due to the presence Ans.
of chlorides and sulphates of calcium and
(i) When bleaching powder comes in contact
magnesium in it. Na2CO3 is added to it to soften
with air it reacts with carbon dioxide to form
such water and make it suitable for use. The
calcium carbonate and releases chlorine gas.
reaction with Na2CO3 causes the formation of
insoluble carbonate salts of magnesium and CaOCl2 + CO2 → CaCO3 + Cl2 ↑
calcium. (from air)
MgCl2 (aq) + Na2CO3 (s) → MgCO3(s) + 2 NaCl(s) (ii) This generated chlorine is known as “available
* (10) Soap forms a precipitate in hard water. chlorine.”

Ans. When soap is mixed with hard water, calcium (iii) On the basis of percentage of “available
and magnesium salts of fatty acids are chlorine” various brands of bleaching powder
formed. These being water insoluble they are available in the market.
form a precipitate and that is why lather is not * (14) When the radiation coming out from certain
formed. radioactive substance is passed through an
* (11) The particles of powder are given an electric electric field, marks are found at three places
charge while spraying them to form the on the photographic plate placed in its path.
powder coating. Ans.
Ans. Powder coating is a method of applying a (i) When the radiation coming out from certain
layer harder than paint on the surface of an radioactive substance is passed through an
iron object to prevent rusting. In this method, electric field, marks are found at three places
a polymer resin, a pigment and some other on the photographic plate placed in its path.
ingredients are melt mixed, cooled and This is because the radiation coming out from
ground into a uniform powder. This powder radioactive substance are of three types Alpha
is sprayed on the polished metal surface by rays, Beta rays and Gamma rays.
electrostatic spray deposition (ESD). In this (ii) The rays which get deviated slightly towards
method, the particles of the powder are given negatively charged plate are called alpha rays.
an electrostatic charge due to which a uniform They get deviated towards negatively charged
layer of the powder sticks to the metal surface. plate because they are made of positively
Then the object is heated in the over along charged particles called as alpha particles
with the coating. A chemical reaction occurs (He++).
in the layer, resulting in the formation of long (iii) The rays which get deviated substantially
cross-linked polymeric chains. towards the positively charged plate are
* (12) The aluminium article is used as an anode in called beta rays. They get deviated towards
the anodizing process. positively charged plate because they are
Ans. A protective layer is formed naturally on made of negatively charged particles called as
the surface of aluminium metal by reaction beta particles (e–).
with oxygen in air. In the anodizing process, (iv) The rays which do not deviate at all are
this layer is made of the desired thickness. called gamma rays. They are uncharged
Anodizing is done by electrolysis. Dilute electromagnetic radiation. Hence, marks are
Sulphuric acid is taken in the electrolytic cell found at three places on the photographic
and the aluminium article is dipped in it as plate.
the anode. When an electric current is passed, (For diagram refer Fig. 14 .1 from Q. 15(3))
hydrogen gas is released at the cathode
* (15) A certain type of ceramic tiles are fixed on
and oxygen gas at the anode. A reaction
the outer layer of a space shuttle.
with oxygen occurs and a layer of hydrated
Substances in Common Use 61

Ans. * (4) Where in the industrial field is radioactivity

(i) Each shuttle is covered by more than 24,000 of used?
the six- by six-inch advance ceramic tiles. This Ans. Industrial field
tiles withstand high temperatures without Radiography – Internal cracks and voids
decomposing. They are brittle , water resistant in cast iron articles and iron solder can be
and electrical insulator. Most of the tiles are detected with the help of gamma rays. For this
made of silica fibers, which are produced from purpose, isotopes like cobalt-60, iridium-192
high-grade sand (SiO2). are used in the radiography camera. This
(ii) Silica is an excellent insulator because it technique is used for detecting flaws in metal
transports heat slowly. When the outer portion work.
of a tile gets hot, the heat takes a long time to Measurement of thickness, density and
work its way down through the rest of the tile level : It is necessary to maintain the required
to the shuttle’s skin. The tiles keep the orbiter’s thickness in the manufacture of aluminium,
aluminum skin at 350 degrees or less. plastic, iron sheets of differing thickness.
(iii) The silica fibers are mixed with water and In the manufacturing process, a radioactive
chemicals, and the mixture is poured into substance is placed on one side and an
molds, which are zapped in microwave ovens instrument to measure radiation on the
at 2,350 degrees to fuse the silica fibers. Tiles other. The radiation read by the measuring
are too brittle to attach to the orbiter directly. instrument varies with the thickness of the
(iv) The shuttle’s skin contracts slightly while in sheet. Material inside a packing can also be
orbit, then expands during reentry. examined by the same technique.
(v) In addition, the stresses of launch and reentry Luminescent paint and radio luminescence:
cause the skin to flex and bend. Such motions The radioactive substances radium,
could easily crack the tiles or shake them off. promethium, tritium with some phosphor
To keep them in place, workers glue the tiles are used to make certain objects visible in the
to flexible felt-like pads, then glue the pads to dark, for example, the hands of a clock, and
the orbiter. certain other objects. Krypton-85 is used in
HID (High Intensity Discharge) lamps while
Q.12. Answer the following :
promethium-147 is used in portable X-ray
* (1) What is meant by radioactivity? units as the source of beta rays.
Ans. Elements with a high atomic number such as Use in Ceramic articles : Luminous colours
uranium, thorium, radium have a property are used to decorate ceramic tiles, utensils,
of spontaneously emitting invisible, highly plates, etc. Earlier uranium oxide was used in
penetrating and high energy radiation. This these paints.
property is called radioactivity. A substance
* (5) Write down properties of teflon.
having this property is called a radioactive
Ans. Properties of teflon :
substance.
(i) The atmosphere and chemical substances
* (2) When is said to be the nucleus unstable?
have no effect on Teflon.
Ans. It is the balance of protons and neutrons in a
(ii) Neither water nor oil will stick to Teflon coated
nucleus which determines whether a nucleus
articles.
will be stable or unstable. Too many neutrons
or protons upset this balance disrupting the (iii) High temperatures do not affect Teflon as its
binding energy from the strong nuclear forces melting point is 327 °C.
making the nucleus unstable. (iv) Teflon coated articles are easy to clean.
* (3) Which diseases are caused by artificial food * (6) What type of colours will you use to celebrate
colours ? ecofriendly Rang Panchami? Why?
Ans. Diseases like ADHD (Attention Deficit Ans. We regularly use artificial colours on Rang
Hyperactivity Disorder) can affect children Panchami. The red color used on Rang
due to excessive consumption of foods with Panchami is very dangerous. It contains a high
added food colours. proportion of mercury in it. This poses risks
62 Master Key Science & Technology (Term - II) (Std. IX)

like blindness, skin cancer, asthma, itching of pH value

the skin, permanent blocking of sweat pores (i) Neutral salts :
etc. Therefore, it is necessary to use eco-
Salt is neutral when its pH value is 7. Such a
friendly colours. Prepare colours for Rang
salt is made from a strong acid and a strong
Panchami from natural resources such as beet
base.
root, flowers of flame of forest, spinach, flame
tree (gulmohar) and protect your health by (ii) Acidic salts :
using these. The pH value of a salt made from a strong acid
* (7) Why has the use of methods like Teflon and a weak base is less than 7 and it is acidic.
coating become more common? (iii) Basic salts :
Ans. The use of methods like Teflon coating became The pH value of a salt made from a weak acid
more common because of following properties and strong base is more than 7 and it is basic.
of teflon: (3) Which is the most used salt? What is its
(i) The atmosphere, rain water and chemical chemical name? How is it formed?
substances have no effect on Teflon. Ans. Table salt, or common salt, which gives a salty
(ii) Neither water nor oil will stick to Teflon coated taste to food, is the most used of all salts. Its
articles. chemical name is Sodium chloride. Sodium
(iii) High temperatures do not affect Teflon as its chloride is formed by a neutralization reaction
melting point is 327 °C. between Sodium hydroxide and Hydrochloric
acid.
(iv) Teflon coated articles are easy to clean.
NaOH + HCl → NaCl + H2O
(v) Teflon is a poor conductor of electricity.
Sodium Hydrochloric Sodium water
* (8) Write the chemical formula of bleaching
hydroxide acid chloride (salt)
powder, common salt, baking soda and
washing soda. This is a neutral salt and the pH value of its
aqueous solution is 7.
Ans. Bleaching powder - CaOCl2
(4) Give the properties and uses of Sodium
Common salt - NaCl
bicarbonate.
Baking soda - NaHCO3
Ans. Properties and uses of sodium bicarbonate
Washing soda – Na2CO3.10 H2O
(i) NaHCO3 reacts with moist litmus paper and
Q.13. Answer in brief: red litmus turns blue which means that it is
basic in nature.
(1) What are salts? Give their source.
(ii) It is used to make bread, cake, dhokla.
Ans. The ionic compounds which do not contain
H+ and OH– ions and contain only one kind (iii) Being basic in nature it is used to reduce
of cation and anion are called simple salts. For acidity in the stomach.
example, Na2SO4, K3PO4, CaCl2. the sea is said (iv) NaHCO3 is used to make the active substance
to be a rich source of salts of various elements CO2 in the fire extinguisher.
such as chlorine, sodium, magnesium, (v) Baking soda is used to clean an oven.
potassium, calcium, bromine.
(5) How is bleaching powder obtained?
The important salts found in sea water
Ans. Bleaching powder is obtained by the reaction
(i) Sodium chloride of chlorine gas with slaked lime.
(ii) Magnesium chloride
Ca(OH)2 + Cl2 → CaOCl2 + H2O
(iii) Magnesium sulphate
(iv) Potassium chloride Slaked Chlorine Bleaching Water
(v) Calcium carbonate lime powder
(vi) Magnesium bromide (6) How is hard water from well converted to
(2) Which are the three kinds of salts depending soft water?
on their pH value? How are they formed? Ans. The hard water from a well or a bore-well
Ans. The three kinds of salts depending on their becomes soft on adding washing soda and we
Substances in Common Use 63

come to know this from the lather formed on sodium or potassium salts of carboxylic acids
it. The hardness of water is due to the presence (fatty acids) are formed. These salts are called
of chlorides and sulphates of calcium and soap. When soap is mixed with hard water
magnesium in it. Na2CO3 is added to it to soften calcium and magnesium salts of fatty acids
such water and make it suitable for use. The are formed. These being water insoluble they
reaction with Na2CO3 causes the formation of form a precipitate and that is why lather is not
insoluble carbonate salts of magnesium and formed.
calcium. (11) Give the uses of radioactive isotopes in
MgCl2(aq) + Na2CO3(s) → MgCO3(s) + 2NaCl(s) measurement of thickness, density and level.
Magnesium Sodium Magnesium Sodium Ans. Measurement of thickness, density and
chloride carbonate carbonate chloride level:
(7) How is washing soda obtained from sodium It is necessary to maintain the required
carbonate? thickness in the manufacture of aluminium,
Ans. Sodium carbonate is a water soluble salt of plastic, iron sheets of differing thickness.
sodium. Crystalline sodium carbonate, on In the manufacturing process, a radioactive
keeping, loses its water of crystallization substance is placed on one side and an
readily and a white powder is obtained. This instrument to measure radiation on the
powder is called washing soda. other. The radiation read by the measuring
instrument varies with the thickness of the
Na2CO3.10H2O → Na2CO3.H2O
sheet. Material inside a packing can also be
Crystalline White powder examined by the same technique.
Sodium carbonate (washing soda)
(12) Give the uses of radioactive isotopes in
(8) Give the properties and uses of Washing Luminescent paint and radioluminescence.
soda.
Ans. Luminescent paint and radioluminescence:
Ans. Properties and uses of washing soda :
The radioactive substances radium,
(i) Washing soda is a whitish and odourless promethium, tritium with some phosphor
powder at room temperature. are used to make certain objects visible in the
(ii) Litmus has a blue colour in its aqueous dark, for example, the hands of a clock, and
solution. certain other objects. Krypton-85 is used in
(iii) It is hygroscopic, that is, it absorbs moisture if HID (High Intensity Discharge) lamps while
left exposed to air. promethium-147 is used in portable X-ray
(iv) It is used mainly for washing clothes. units as the source of beta rays.
(v) Sodium carbonate is used in the glass and (13) Give the uses of radioactive isotopes in Field
paper industry and also in refining of petrol. of agriculture.
(9) Name some substances in our daily use Ans. Field of agriculture:
which contain water of crystallization. (i) The genes and chromosomes that give
Ans. seeds properties like fast growth, higher
productivity, etc. can be modified by means of
(i) Alum (Potash alum - K2SO4.Al2(SO4)3.24H2O)
radiation.
(ii) Borax (Na2B4O7.10H2O)
(ii) The radioactive isotope cobalt-60 is used for
(iii) Epsom salt food preservation.
(Magnesium sulphate MgSO4.7H2O)
(iii) Onions, potatoes are irradiated with gamma
(iv) Barium chloride (BaCl2.2H2O) rays from cobalt-60 to prevent their sprouting.
(v) Sodium sulphate (iv) Strontium-90 is used as a tracer in the research
(Glauber’s salt Na2SO4.10 H2O) on various crops.
(10) How is soap prepared? Why it does not form (14) What are the harmful effects of artificial food
lather with hard water? colours?
Ans. When oil or animal fat is boiled with an aqueous Ans.
solution of sodium or potassium hydroxide,
(i) Food colours added to pickles, jam and sauce
64 Master Key Science & Technology (Term - II) (Std. IX)

contain small quantities of lead and mercury. without our knowledge.

These can be harmful for those who consume (ii) There is a possibility of various skin disorders
these products on a regular basis. and also skin cancer due to the aluminium
(ii) Diseases like ADHD (Attention Deficit chlorohydrates.
Hyperactivity Disorder) can affect children (20) Give the properties of teflon.
due to excessive consumption of foods with Ans. Properties of teflon :
added food colours.
(i) The atmosphere and chemical substances
(15) Which is the main source of colour for have no effect on Teflon.
preparing a natural dye ?
(ii) Neither water nor oil will stick to Teflon coated
Ans. Plants are the main source of colour for articles.
preparing a natural dye. Roots, leaves, flowers,
(iii) High temperatures do not affect Teflon as its
bark, fruits, seeds, fungus and pistil are used
melting point is 327 °C.
for making dyes. In Kashmir a very good dye
is made from saffron, which is used to dye (iv) Teflon coated articles are easy to clean.
fibers from which saris, shawls and dresses (21) Give the uses of teflon.
are made. These are very costly. The use of Ans. Uses of teflon :
henna leaves to colour hair is safe for health. (i) Teflon is a poor conductor of electricity.
(16) Give the uses of dyes. Therefore, Teflon cladded wires and parts
Ans. Uses of dyes : are used in high technology electronics
(i) They are used for colouring cloth and hair. instruments.
(ii) Fluorescent colours are used to make street (ii) It is used for making non-stick kitchenware.
boards that are visible at night. (iii) The coloured metal sheets of two-wheelers
(iii) Dyes are used to polish leather shoes, purses and four-wheelers are given a Teflon coating
and chappals. to protect them from damage due to high
temperature and rain.
(17) What are the adverse effects of dyes?
(22) What is ceramic? Give examples.
Ans. Adverse effects dyes :
Ans.
(i) Dyeing hair can have adverse effects like hair
fall, damage to hair texture, burning of skin, (i) Ceramic is a heat resistant substance formed
adverse effect on eyes, etc. by kneading an inorganic substance in water
and then shaping it and hardening it by
(ii) Lipstick contains a dye named carmine. It does
heating.
not affect lips but causes stomach disorders.
(ii) Pots made by a potter, Mangalore roofing tiles,
(iii) Excessive use of plants for making natural dyes
construction bricks, pottery, terracotta articles
results in deterioration of the environment.
are some examples of common ceramic articles
(18) How are artificial colours harmful to us? that we see around.
Ans. We regularly use artificial colours on Rang (23) How is a ceramic article made?
Panchami. The red colour used on Rang
Ans.
Panchami is very dangerous. It contains a high
proportion of mercury in it. This poses risks (i) When clay is kneaded in water, shaped and
like blindness, skin cancer, asthma, itching of then fired in a kiln at a temperature of 1000 to
the skin, permanent blocking of sweat pores 1150°C, a porous ceramic is formed.
etc. Therefore, it is necessary that artificial (ii) To overcome the porosity the fired object is
colours are used cautiously. covered with finely ground glass powder
(19) What are the harmful effects of deodorant? suspended in water (glaze) and is then fired
again. As a result, the surface of the ceramic
Ans.
becomes shiny and its porosity disappears.
(i) Aluminium – Zirconium compounds are the
(24) What is porcelain? How is it made?
most harmful chemicals in the deodorant.
Disorders like headache, asthma, respiratory Ans.
disorders, heart disease are likely to occur (i) Porcelain is a hard, translucent and white
Substances in Common Use 65

coloured ceramic. It is made by using the (v) Sodium sulphate

white clay called kaolin, found in China. Glass, (Glauber’s salt Na2SO4.10 H2O)
granite and the mineral feldspar is mixed with (vi) Blue vitriol (Copper Sulphate - CuSO4.5H2O)
kaolin and kneaded with water.
Uses of these salts are as given below:
(ii) The resulting mixture is shaped and fired in
(i) Alum (Potash alum – K2SO4.Al2(SO4)3.24H2O)
a kiln at a temperature of 1200 to 1450 °C. On
firing again after glazing, beautiful articles of (a) Alum is used in the process of water
porcelain are obtained. purification. Because of the property of
coagulation, the solid impurities in water
(25) Give the uses of ceramics.
come together, become heavy and settle
Ans. to the bottom. As a result, the water above
(i) Ceramics can withstand high temperatures becomes clear.
without decomposing. Ceramic is brittle, (b) Alum powder, found in the spice section
water resistant and an electrical insulator. of many grocery stores, may be used
(ii) Therefore, it is used in electrical instruments, in picking recipes as a preservative to
for coating the interior of a kiln, the outer maintain fruit and vegetable crispness.
surfaces of ships and blades of jet engines. A (c) Alum is used as the acidic component of
certain type of ceramic tiles are fixed on the some commercial baking powders.
outer layer of a space shuttle. Some types of
(d) Alum has been used as an after shave
ceramics are used as superconductors.
treatment.
* (26) Write about artificial food colours, the
(ii) Borax (Na2B4O7.10H2O)
substances used in them and their harmful
effects. (a) Borax today is used for many cleaning
purposes.
Ans. Food colours are mixed in most soft drinks
and foodstuffs available in the market. These (b) It is used to make homemade laundry
food colours are in the form of powders, gels detergent.
and pastes. Food colours are used in domestic (c) It is added as a cleaning boost to any other
as well as commercial products. Certain detergent.
colours and essences are added to ice cream, (d) It even keeps ants and other pests away.
ice candies, sauce, fruit juices, cold drinks, (iii) Epsom salt (Magnesium sulphate MgSO4.7H2O)
pickles, jams and jelly. Food colours are often
(a) As a relaxing magnesium bath soak.
found to be added to packaged meat (chicken,
mutton), chilli powder, turmeric, sweets and (b) To grow better vegetables – Add a
other similar substances so as to give them tablespoon of Epsom salt to the soil below
a good colour. Tetrazene, sunset yellow are a vegetable plant to boost growth.
artificial food colours used extensively. (iv) Barium chloride (BaCl2.2H2O)
* (27) What is meant by water of crystallization? (a) In industry, Barium chloride is mainly
Give examples of salts with water of used in the purification of brine solution
crystallization, and their uses. in caustic chlorine plants.
Ans. The exact number of water molecules which (b) It is also used in the manufacture of heat
are chemically bonded to a molecule of a salt treatment salts.
within a hydrated crystalline compound is (c) It is used in hardening of steel.
called as water of crystallization. (d) It is used in the manufacture of pigments.
Some substances in our daily use which (v) Sodium sulphate (Glauber’s salt Na2SO4.10H2O)
contain water of crystallization
(a) In the laboratory, anhydrous sodium
(i) Alum (Potash alum - K2SO4.Al2(SO4)3.24H2O ) sulphate is widely used as an inert drying
(ii) Borax (Na2B4O7.10H2O) agent, for removing traces of water from
(iii) Epsom salt (Magnesium sulphate MgSO4.7H2O) organic solutions.
(iv) Barium chloride (BaCl2.2H2O) (b) Glauber’s salt, the decahydrate, is used as
a laxative.
66 Master Key Science & Technology (Term - II) (Std. IX)

(vi) Blue vitriol (Copper sulphate CuSO4.5H2O) good colour. Food colours are natural as well
(a) Blue vitriol is used in the blood test for as artificial. The food colours prepared from
diagnosing anaemia. seeds, beetroot, flowers and fruit concentrate
are natural. Tetrazene, sunset yellow are
(b) Slaked lime is used with blue vitriol in
artificial food colours used extensively.
the Bordeaux mixture which is used as a
However, over-consumption of artificial
fungicide on fruits like grapes and musk
food colours can be detrimental to health.
melon.
Therefore, usage of natural food colours is
(28) Write briefly about the methods of always good.
electrolysis of sodium chloride.
(3) Anodizing.
Ans.
Ans. A protective layer is formed naturally on the
(i) When an electric current is passed through a surface of aluminium metal by reaction with
saturated solution of sodium chloride (brine) oxygen in air. In the anodizing process, this
it is electrolysed and hydrogen gas is released layer can be made of the desired thickness.
at the cathode while chlorine gas is released at
Anodizing is done by electrolysis. Dilute
the anode. This method is used for production
Sulphuric acid is taken in the electrolytic cell
of chlorine gas. In this method an important
and the aluminium article is dipped in it as
basic compound NaOH is formed in the cell.
the anode. When an electric current is passed
2NaCl + 2H2O → 2NaOH + Cl2 ↑ + H2↑ hydrogen gas is released at the cathode
(ii) When salt is heated to a high temperature and oxygen gas at the anode. A reaction
(about 800 °C), it melts. This is called the fused with oxygen occurs and a layer of hydrated
state of the salt. aluminium oxide is formed on the anode, i.e.
(iii) When fused salt is electrolysed, chlorine gas the aluminium article. This layer can be made
is released at the anode and liquid sodium attractive by adding colour in the cell during
metal, at the cathode. electrolysis.

Q.14. Write short notes on : Q.15. Answer in detail:

(1) Chernobyl disaster. (1) Give the properties and uses of Sodium
Ans. Chernobyl disaster : On 26th April 1986 the chloride.
graphite reactor in the Chernobyl atomic Ans. Properties and uses of sodium chloride:
power plant exploded, and suddenly the (i) Common salt is a colourless and crystalline
radioactive isotopes and radiation came ionic compound. There is no water of
out. Due to this episode radioactive isotopes crystallization in its crystalline structure.
entered the human body through water and (ii) It is a neutral salt, salty in taste.
land and caused genetic disorders. These
(iii) This compound is used for the production of
got carried further into the next generation.
salts like Na2CO3, NaHCO3.
Thyroid disorders increased in children as well
as adults. As a result, the incidence of throat (iv) When an electric current is passed through a
diseases is greater there than in other places. saturated solution of sodium chloride (brine)
it is electrolysed and hydrogen gas is released
(2) Food colours.
at the cathode while chlorine gas is released at
Ans. Food colours are mixed in most soft drinks the anode. This method is used for production
and foodstuffs available in the market. These of chlorine gas. In this method an important
food colours are in the form of powders, gels basic compound NaOH is formed in the cell.
and pastes. Food colours are used in domestic
2NaCl + 2H2O → 2NaOH + Cl2↑ + H2↑
as well as commercial products. Certain
colours and essences are added to ice cream, (v) When salt is heated to a high temperature
ice candies, sauce, fruit juices, cold drinks, (about 800 °C), it melts. This is called the fused
pickles, jams and jelly. Food colours are often state of the salt.
found to be added to packaged meat (chicken, (vi) When fused salt is electrolysed, chlorine gas
mutton), chilli powder, turmeric, sweets and is released at the anode and liquid sodium
other similar substances so as to give them a metal, at the cathode.
Substances in Common Use 67

(2) Give the properties and uses of Bleaching (v) It is used for bleaching of cloth.
Powder. (vi) It is used for disinfection by the road side and
Ans. Properties and uses bleaching powder: garbage sites.
(i) Bleaching powder is a yellowish white (vii) Dilute sulphuric acid and dilute hydrochloric
coloured solid substance. acid react rapidly with bleaching powder to
(ii) Its chemical name is Calcium oxychloride. release chlorine gas completely.
(iii) It has a strong odour of chlorine gas. CaOCl2 + H2SO4 → CaSO4 + Cl2 ↑ + H2O
(iv) It is used for disinfection of drinking water (viii) Calcium oxychloride reacts slowly with
at the water works and the water in the carbon dioxide to form calcium carbonate and
swimming pool. chlorine.

(3) Explain with neat labelled diagram the nature of radioactive radiation.
Ans.

Lead block
b rays
(+)

g rays

a rays
(–)
Slit
ZnS coated
Radioactive substance Electrically photographic plate
charged plates
14.1 Alpha, beta and gamma rays

(i) When radioactive radiations are allowed (iv) One type of radiation deviated slightly
to pass through two oppositely charged towards the negatively charged plate,
plates they get separated. This method while the second type of radiation deviated
was introduced by Rutherford in 1902. substantially towards the positively charged
(ii) Rutherford and Willard studied the radiation plate. However, the third type of radiation did
emitted by radioactive substances. For not deviate at all in the electrical field.
this purpose, the rays were allowed to (v) The rays which deviated slightly toward
pass through an electrical field and a negatively charged plate are called alpha rays,
photographic plate was held in their path. those which deviate substantially towards the
(iii) It was found that the radiation was divided positively charged plate are called beta rays
into three types. and those which do not deviate at all are called
gamma rays.
(4) Give the characteristics of alpha, beta and gamma rays.
Ans. Characteristics of alpha, beta and gamma rays are as given in the table.
Sr. No. Properties Alpha rays (a) Beta rays (b) Gamma rays (g)
(i) Nature Current of alpha Current of beta (e–) particles Electromagnetic
(He++) particles radiation
(ii) Mass 4.0028 u 0.000548 u No mass
(iii) Charge +2 –1 Electrically neutral
68 Master Key Science & Technology (Term - II) (Std. IX)

(iv) Velocity 1 / 5 to 1/ 20 times the 1/5 to 9/10 times the velocity Same as the velocity of
velocity of light of light light
(v) Deviation in the Attracted towards Attracted towards Not deviated
electric field negatively charged positively charged plate
plate
(vi) Penetrating Can penetrate an Can penetrate an Can penetrate 15 cm
power aluminium sheet of aluminium sheet of thick lead screen which
thickness < 0.02 mm thickness 2 mm, which is is 10,000 times the
100 times the penetration of penetration of alpha
alpha particles. particles
(vii) Ionization power Very high Low Very Low
(viii) Power to produce Very high Very low Low
fluorescence

(5) Give the uses of radioactive isotopes in enter the human body.
Medical science. (vi) The radioactive paint on the watch can cause
Ans. Medical science: cancer.
(i) Polycythemia : The red blood cell count (vii) The radioactive isotopes strontium-90 can
increases in the disease polycythemia. enter the body through plants, fruits, flowers,
Phosphorus- 32 is used in its treatment. cereals, milk, etc. and cause diseases like bone
(ii) Bone cancer : Strontium-89, strontium-90, cancer, leukemia.
samarium-153 and radium-223 are used in the (7) Why are deodorant used? Give their types
treatment of bone cancer. and content.
(iii) Hyperthyroidism : Enlargement of thyroid Ans.
gland, weight loss in spite of appetite, insomnia (i) Body odour is caused by the bacterial
are the symptoms of hyperthyroidism. It decomposition of the sweat. A deodorant is
occurs due to overproduction of hormones by used to prevent this odour.
the thyroid gland. Iodine-123 is used in the (ii) Deodorants contain parabens (methyl, ethyl,
treatment of hyperthyroidism. propyl, benzyl and butyl) and also alcohol in
(iv) Tumour detection : Boron-10, iodine-131, large proportions. Aluminium compounds
cobalt-60 are used in treatment of brain and silica are also used.
tumour, while arsenic-74 is used in detection (iii) Types of deodorants are :
of small tumours in the body.
(a) Ordinary deo : It contains a smaller
(6) What are the hazards of radioactive proportion of aluminium. It decreases the
substances and radiation? odour of the sweat.
Ans. (b) Antiperspirant deo : This decreases the
(i) The central nervous system is affected by extent of sweating. It contains about 15%
radioactive radiations. of aluminium chlorohydrate. It clogs the
(ii) Hereditary defects are generated by sweat pores on the skin.
bombardment of radiation on D.N.A in the (c) Clinical deo : Some people sweat heavily
body. and it has harmful effects on the skin.
(iii) Radioactive radiation can penetrate the skin, Clinical deo is meant for such people. It
and causes diseases like skin cancer, leukemia. contain 20 to 25% aluminium. It is used
(iv) The radiative pollutants created due to during the night.
explosions enter the body through air and it is (8) Explain how powder coating is done.
difficult to control them. Ans.
(v) The radioactive pollutants released in the sea (i) Powder coating is a method of applying a
enter the bodies of fishes and through them layer harder than paint on the surface of an
Substances in Common Use 69

iron object to prevent rusting. other. The radiation read by the measuring
(ii) In this method, a polymer resin, a pigment instrument varies with the thickness of the
and some other ingredients are melt, mixed, sheet. Material inside a packing can also be
cooled and ground into a uniform powder. examined by the same technique.
(iii) This powder is sprayed on the polished metal Luminescent paint and radioluminescence:
surface by electrostatic spray deposition The radioactive substances radium,
(ESD). promethium, tritium with some phosphor
are used to make certain objects visible in the
(iv) In this method, the particles of the powder
dark, for example, the hands of a clock, and
are given an electrostatic charge due to which
certain other objects. Krypton-85 is used in
a uniform layer of the powder sticks to the
HID (High Intensity Discharge) lamps while
metal surface.
promethium-147 is used in portable X-ray
(v) Then the object is heated in the oven along units as the source of beta rays.
with the coating.
Use in Ceramic articles – Luminous colours
(vi) A chemical reaction occurs in the layer, are used to decorate ceramic tiles, utensils,
resulting in the formation of long cross-linked plates, etc. Earlier uranium oxide was used in
polymeric chains. This powder coating is these paints.
highly durable, hard and attractive. Powder
(b) Field of agriculture :
coating can be done on plastic and medium
density fibre (MDF) board in day to day use (1) The genes and chromosomes that give
as well. seeds properties like fast growth, higher
productivity, etc. can be modified by
* (9) Write the uses of :
means of radiation.
(i) Anodizing.
(2) The radioactive isotope cobalt-60 is used
(ii) Powder coating for food preservation.
(iii) Radioactive substances (3) Onions, potatoes are irradiated with
(iv) Ceramic gamma rays from cobalt-60 to prevent
Ans. their sprouting.
(i) Anodizing : Anodizing is done on anodized (4) Strontium-90 is used as a tracer in the
cooking utensils like griddles and cookers. research on various crops.
(ii) Powder coating : Powder coating is done (c) Medical science :
on Iron objects to prevent rusting. Also, on (1) Polycythemia : The red blood cell count
Plastic and Medium density fibre (MDF) increases in the disease polycythemia.
board, to make them highly durable, hard and Phosphorus- 32 is used in its treatment.
attractive.
(2) Bone cancer : Strontium-89, strontium-90,
(iii) Radioactive substances : samarium-153 and radium-223 are used in
(a) Industrial field : the treatment of bone cancer.
Industrial Radiography : Internal cracks and (3) Hyperthyroidism : Enlargement of
voids in cast iron articles and iron solder can be thyroid gland, weight loss in spite of
detected with the help of gamma rays. For this appetite, insomnia are the symptoms
purpose, isotopes like cobalt-60, iridium-192 are of hyperthyroidism. It occurs due to
used in the radiography camera. This technique overproduction of hormones by the
is used for detecting flaws in metal work. thyroid gland. Iodine-123 is used in the
Measurement of thickness, density and treatment of hyperthyroidism .
level : It is necessary to maintain the required (4) Tumour detection : Boron-10, iodine-131,
thickness in the manufacture of aluminium, cobalt-60 are used in treatment of brain
plastic, iron sheets of differing thickness. tumour, while arsenic-74 is used in
In the manufacturing process, a radioactive detection of small tumours in the body.
substance is placed on one side and an (iv) Ceramic : Pots made by a potter, Mangalore
instrument to measure radiation on the roofing tiles, construction bricks, pottery,
70 Master Key Science & Technology (Term - II) (Std. IX)

terracotta articles are some examples of most harmful chemicals in the deodorant.
common ceramic articles that we see around. Disorders like headache, asthma, respiratory
* (10) Write the harmful effects: disorders, heart disease are likely to occur
without our knowledge.
(i) Artificial dye
(b) There is a possibility of various skin disorders
(ii) Artificial food colour
and also skin cancer due to the aluminium
(iii) Radioactive substances chlorohydrates.
(iv) Deodorant
* (11) Explain what you see in the following picture
Ans.
Ans.
(i) Artificial dye :
(a) Dyeing hair can have adverse effects like hair
fall, damage to hair texture, burning of skin,
adverse effect on eyes, etc.
(b) Lipstick contains a dye named carmine. It does
not affect lips but causes stomach disorders.
(c) Excessive use of plants for making natural dyes
results in deterioration of the environment.
(ii) Artificial food colour :
(a) Food colours added to pickles, jam and sauce 14.2 Powder coating
contain small quantities of lead and mercury. This pictures shows powder coating of the
These can be harmful for those who consume given object. Powder coating is a method of
these products on a regular basis. applying a layer harder than paint on the
(b) Diseases like ADHD (Attention Deficit surface of an iron object to prevent rusting.
Hyperactivity Disorder) can affect children In this method, a polymer resin, a pigment
due to excessive consumption of foods with and some other ingredients are melt mixed,
added food colours. cooled and ground into a uniform powder.
(iii) Radioactive substances : This powder is sprayed on the polished metal
(a) The central nervous system is affected by surface by electrostatic spray deposition
radioactive radiations. (ESD). In this method, the particles of the
(b) Hereditary defects are generated by powder are given an electrostatic charge due
bombardment of radiation on D.N.A in the to which a uniform layer of the powder sticks
body. to the metal surface. Then the object is heated
in the over along with the coating. A chemical
(c) Radioactive radiation can penetrate the skin,
reaction occurs in the layer, resulting in the
and causes diseases like skin cancer, leukemia.
formation of long cross-linked polymeric
(d) The radioactive pollutants created due to chains. This powder coating is highly durable,
explosions enter the body through air and it is hard and attractive. Powder coating can be
difficult to control them. done on plastic and medium density fibre
(e) The radioactive pollutants released in the sea (MDF) board in day to day use as well.
enter the bodies of fishes and through them
*Q.16. Can you recall?
enter the human body.
(1) What are the important substances that we
(f) The radioactive paint on the watch can cause
use in day to day life? For what purposes do
cancer.
we use them?
(g) The radioactive isotopes strontium-90 can
Ans. Some of the substances we use in our day to
enter the body through plants, fruits, flowers,
day life and the purpose of using them are as
cereals, milk, etc. and cause diseases like bone
follows :
cancer, leukemia.
Toothpaste : for cleaning teeth and
(iv) Deodorant :
maintaining hygienic conditions of mouth.
(a) Aluminium – Zirconium compounds are the
Substances in Common Use 71

Soap : for bathing and maintaining hygienic Sodium hydroxide (NaOH)

conditions of body. Salt (Sodium chloride NaCl)
Natural and artificial fibers : we wear them Apparatus : 500 ml glass beaker
as clothes to protect our body and many other
Burner
purposes.
Flat glass tray
Washing powder : for cleaning clothes.
Knife
Vegetables, fruits and food grains : they
provide us with necessary vitamins, minerals Soaps are essential to personal and public
and carbohydrates required for proper health. They safely remove germs, soils
functioning of body. and other contaminants and help us to stay
healthy and make our surroundings more
Water : very important for our survival and
pleasant. Soaps are made from fats and oils
many other functions of day to day life.
or their fatty acids.
Metals : for making buildings, bridges, roads,
Take about 20 ml of any vegetable oil (coconut
vehicles, trains, ships, airplanes, utensils etc.
oil, castor oil, soybean oil etc.) in a beaker. Put
Acids, bases and salts : used for various about 30 – 35 ml of NaOH in it and heat and
purposes, for example. Sodium chloride stir the mixture till a paste is formed. Now add
which is used as common salt, a very necessary a little salt. Stir again and allow the mixture to
ingredient of our daily food without which cool in a flat glass tray, on cooling it solidifies.
our food is tasteless. Take a knife and cut it in soap bars as per the
(2) How are the various substances in day to size required.
day use classified from the scientific point of
*Q.17. Can you tell?
view?
(1) What are salts?
Ans. The various substances in day to day use are
classified from the scientific point of view as Ans. The ionic compounds which do not contain
elements, compounds, mixtures, metals, non- H+ and OH– ions and contain only one kind
metals, acids, bases and salts. of cation and anion are called simple salts. For
example, Na2SO4, K3PO4, CaCl2.
(3) What are detergents?
Inorganic substances occur naturally in the
Ans. Detergent is a water-soluble cleansing agent
form of salts rather than acids or bases. The
which combines with impurities and dirt to
ionic compounds which do not contain H+
make them more soluble, and differs from
and OH– ions and contain only one kind of
soap in not forming a scum with the salts in
cation and anion are called simple salts. For
hard water.
example, Na2SO4, K3PO4, CaCl2. The sea is said
Today, detergents are more likely to be a to be a rich source of salts. In fact, the sea is a
mixture of synthetic chemicals and additives rich source of several salts of various elements
cooked up in a huge chemical plant and, such as chlorine, sodium, magnesium,
unlike traditional soap, they’re generally potassium, calcium, bromine. The important
liquids rather than solids. salts found in sea water are Sodium chloride,
Detergents are used in everything from hair Magnesium chloride, Magnesium sulphate,
shampoo and clothes, washing powder to Potassium chloride, Calcium carbonate and
shaving foam and stain removers. The most Magnesium bromide.
important ingredients in detergents are (2) What is the strip shown below? What is it
chemicals called surfactants – a word made used for?
from bits of the words surface active agents.
(2) What is the strip shown below? What is it
(4) Which chemicals and apparatus will you use used for?
in the laboratory for making soap?
Ans. For making soap in laboratory following
(Note: The above strip is in black and white.
chemicals and apparatus are used :
For coloured strip please refer to Textbook
Chemicals : Vegetable oil (coconut oil, castor Page No. 151)
oil, soya bean oil etc.)
72 Master Key Science & Technology (Term - II) (Std. IX)

Ans. The strip shown is pH metre scale it is used to colour or pH value 7 indicates the substances
determined pH of solutions. are neutral.
* (3) How is it determined whether a substance is (4) A sweets shop looks attractive because of
acidic, basic or neutral? the colourful sweets displayed there. Which
Ans. In the pH scale, the pH of solutions varies colours are used in these substances?
from 0 to 14 in accordance with the strength of Ans. Food colours and essences are used in sweets
the acids or base. The pH scale shows different to make them colourful and tasty. These food
colours at different values of pH. Colour from colour are in the form of powders, gels and
dark red to yellow or from pH value 0 to 6 pastes. Food colours are natural as well as
indicates the substances are acidic. Colour artificial. The food colours prepared from
from light blue to violet or from pH value 8 seeds, beetroot, flowers and fruit concentrate
to 14 indicates the substances are basic. Green are natural. Tetrazene, sunset yellow are
artificial food colours used extensively.
(5) Make a list of substances in day to day use in accordance with their pH value (0 to 14).
Ans.
Original colour Colour on addition of
Substances pH value Nature
(of the solution) universal indicator
Kokam extract Pink Orange 4.5 Acidic
Palak extract Green Light green 9.5 Basic
Aerated drink Brown Greenish yellow 6.0 Acidic
Tomato juice Red Orange 4.1 Acidic
Dilute HNO3 Colourless Orange red 3 Acidic
Dilute KOH Colourless Violet 13 Basic
Prepared tea Brown Orange yellow 6 Acidic
Ginger juice +
Brown Yellow 5.5 Acidic
Honey
Butter milk White Greenish yellow 6.5 Acidic
(6) A doctor gives you medicines when you fall (7) What problems do you get after playing
ill. What are the medicines made from? colours on Rang Panchami? Why?
Ans. Long before pure chemicals were manufactured Ans. After playing colours on Rang Panchami we
in labs, people used plants for medicine. may get problems such as risks of blindness,
There are over a hundred active ingredients skin cancer, asthma, itching of the skin,
derived from plants for use as drugs and permanent blocking of sweat pores etc. This
medicines. The emergence of synthetic is because the colours used in rang panchami
chemistry in the 1800s opened up new specially the red colour is very dangerous. It
avenues for scientific research into drugs. contains a high proportion of mercury in it.
Many chemists tried to isolate medically (8) Which colours will you use to prevent the
active ingredients in plants (for instance the occurrence of these problems?
important malaria remedy quinine), and Ans. To prevent this problem instead of using
subsequently tried to make those substances in artificial colours natural colours should be
the laboratory in order to become independent used.
of plant supplies. At the same time, a new Natural colours are prepared from natural
industry developed as scientists developed resources such as beet root, flowers of flame
processes to synthesise new chemicals on of forest, spinach, flame tree (gulmohar).
a large scale. New production methods
(9) What problem do you have on painting the
developed in the late 1800s and early 1900s
house and furniture?
made it easier to standardise, package and
transport medicines. Ans. On painting the house and furniture with
artificial colours which are dangerous, we may
Substances in Common Use 73

get problems such as risks of blindness, skin of which it is used in nonstick cookware.
cancer, asthma, itching of the skin, permanent (i) The atmosphere and chemical substances
blocking of sweat pores etc. This is because the have no effect on Teflon.
colours contain a high proportion of mercury
(ii) Neither water nor oil will stick to Teflon coated
in it.
non-stickware.
(10) What is the property of Teflon because of
(iii) High temperatures do not affect Teflon as its
which it is used in non-stickware ?
melting point is 327 °C.
Ans. Following are the properties of teflon because
(iv) Teflon coated nonstick ware are easy to clean.

*Q.17. Activity based question:

(1) Prepare saturated solutions of given salts and put 2-3 drops of the universal indicator in them and note
your observations in the table below:
Salt Original colour Colour on pH value Nature
(of the solution) addition of
universal
indicator
Table salt Colorless Green 7 Neutral
Soap
Washing soda
Baking soda
Baking powder
POP
Ans.
Salt Original colour Colour on pH value Nature
(of the solution) addition of
universal
indicator
Table salt Colorless Green 7 Neutral
Soap White Blue 9 Alkaline (mildly)
Washing soda White Dark blue 11 Alkaline (strong)
Baking soda White Dark green 8 Alkaline (slightly)
Baking powder White Dark green 8.5 Alkaline (slightly)
POP White Green 7 Neutral

(2) What are the constituents of baking powder?

(3) Take a piece of coloured cloth. Put some
Where is the baking powder used?
saturated solution of bleaching powder on
Ans. a small part and observe what changes take
(i) Baking powder consist of 30% sodium place in the colour of the cloth.
bicarbonate, 5-12% monocalcium phosphate Ans. When bleaching powder is added to a piece
and 21-26% sodium aluminium sulphate. of coloured cloth, the fabric looses its colour
(ii) Baking powder is a leavening agent and is due to the oxidising reaction of the chlorine
used for increasing the volume and lightening present in the bleaching powder.
the texture of baked goods.

vvv
74 Master Key Science & Technology (Term - II) (Std. IX)

ASSIGNMENT - 14
Time : 1 Hr. Marks : 30

Q.1. (A) Fill in the blanks: (4)

(1) Soap is ................. in nature.
(2) Rock salt is ................. in colour.
(3) ................. is used in treatment of hyperthyroidism.
(4) Excessive consumption of foods with added food colours leads to diseases like ................. .
(B) Match the column: (2)
Column ‘A’ Column ‘B’
(1) Saturated brine (a) sodium metal freed
(2) Fused NaCl (b) basic salt
(3) CaOCl2 (c) crystallization of salt
(4) NaHCO3 (d) oxidation of colour

Q.2. (A) Answer the following in one or two sentences each: (Any four) (4)
(1) Give two uses of Blue vitriol.
(2) How is bone china made? How is it different from porcelain?
(3) What is Teflon? Give it’s chemical name.
(4) What is radioactivity and what are radioactive substances?
(5) What type of colours will you use to celebrate eco-friendly Rang Panchami? Why?
(B) Distinguish between: (4)
(1) Washing soda and Baking soda.
Q.3. (A) Give scientific reasons: (Any two) (4)
(1) Bleaching powder has the odour of chlorine.
(2) Alum is used in the process of water purification.
(3) The hard water of a well becomes soft on adding washing soda to it.
(B) Answer in brief: (Any two) (4)
(1) How is bleaching powder obtained?
(2) How is washing soda obtained from sodium carbonate?
(3) Give the uses of radioactive isotopes in field of agriculture.
Q.4. (A) Explain the following chemical reactions with the help of balanced equation: (Any two) (4)
(1) Sodium carbonate reacts with sulphuric acid.
(2) Bleaching powder reacts with dilute hydrochloric acid.
(3) When an electric current is passed through a saturated solution of sodium chloride (brine).
(B) Answer in detail: (Any one) (4)
(1) Give the characteristics of alpha, beta and gamma rays.
(2) Explain how powder coating is done.
vvv
15 Life Processes in Living Organisms

Points to Remember:
• By the process of transportation, a substance synthesized or absorbed in one part of the body
reaches another.
• Plants need inorganic substances like nitrogen, phosphorus, magnesium, manganese, sodium
etc. Soil is the nearest and richest source of these substances. Roots of plants absorb these
substances from the soil and transport them.
• There are specific types of conducting tissues in plants to perform these functions. The xylem
conducts water whereas the phloem conducts food.
All parts of the plant are connected with these conducting tissues.
• In shrubs, small plants and trees, transport of water takes place through root pressure.
• Transpiration helps in absorption of water and minerals and distribution to all parts of the
plant whereas root pressure performs the role of pushing the water up during night time.
• The food produced in the leaves is transported to each cell in the plant body. This process
is called translocation. It is carried out in both the upward and downward direction by the
phloem by using energy from ATP.
• Removal of waste or harmful substances from the body is called excretion.
• In plants most of the waste products are stored in vacuoles of leaf-cells, flowers, fruits and
bark of the stem. Some waste materials are stored in old and worn out xylem in the form of
resin and gum.
• Some waste materials of plants are useful to humans, for example, gum, resin, latex of rubber,
etc.
• The human excretory system consists of a pair of kidneys, a pair of ureters, the urinary bladder
and the urethra. Urine is formed by the kidneys by separating the waste and unwanted excess
substances from the blood.
• The functional unit of the kidney that performs the basic function of filtration is called a
nephron.
• Systematic regulation of different processes is called control and bringing about the different
processes in the proper sequence is called co-ordination.
• Proper co-ordination between various systems of an organism helps to maintain a state of
equilibrium called homeostasis which is necessary for trhe optimal efficiency of the body.
• Co-ordination in plants is brought about by movements in the form of responses given to
stimuli.
• There are two types of movements in plants – Movements which are related to growth are
called growth relevant movements and movements which do not result in growth of the
plant are called growth irrelevant movements.
• Co-ordination in human being is brought about by nervous control and chemical control.

(75)
76 Master Key Science & Technology (Term - II) (Std. IX)

• Neurons are the structural and functional units of the nervous system.
• Nerve cells and neuroglial cells together form nerves.
• According to their functions, neurons are classified as sensory neurons, motor neurons and
association neurons.
• The human nervous system is divided into three parts – Central nervous system, peripheral
nervous system and autonomic nervous system.
• The central nervous system is made up of brain and spinal cord.
• The human brain is made up of three parts – Cerebrum, cerebellum and medulla oblongata.
• The peripheral nervous system consists of the nerves originating from the central nervous
system. They are of two types – Cranial nerves and spinal nerves.
• Autonomic nervous system consists of the nerves of the involuntary organs like the heart,
stomach, lungs, etc. It is not under the control of our will.
• An immediate and involuntary response given to a stimulus from the environment is called
a reflex action. Reflex actions are co-ordinated by spinal cord.
• Chemical control is brought about by hormones secreted by the endocrine glands.
• Endocrine glands along with the nervous system are responsible for the control and co-
ordination in our body. These two systems help each other and integrate the various activities
in the body.
• A marked difference between the two is that the nerve impulses are fast but short lived
whereas the action of hormones is very slow but long lasting.

(9) Each nephron has a cup-like, thin-walled

MASTER KEY QUESTION SET - 15 upper part called the .................... .
Q.1. (A) Fill in the blanks: (10) The network of capillaries in the Bowman’s
(1) By the process of .................... a substance either capsule is called a .................... .
synthesised or absorbed in one part of the (11) Everyday about .................... urine is formed.
body reaches another. (12) The process of separating the nitrogenous
(2) The .................... conducts water whereas the waste from blood with the help of a machine
.................... conducts food. is called .................... .
(3) Plants give out water in the form of vapour (13) Bringing about the different processes in the
through the .................... on their leaves. proper sequence is called .................... .
(4) The opening and closing of stomata is (14) Proper co-ordination between various systems
controlled by the .................... . of an organism helps to maintain a state of
(5) Energy required for translocation of food is equilibrium called .................... .
obtained from .................... . (15) Movement or growth of any part of the plant
(6) In plants, some waste materials are stored in response to an external stimulus is called
in old and worn out xylem in the form of .................... .
.................... . (16) .................... of climbers are sensitive to touch.
(7) In some plants, waste materials are present in (17) A hormone called .................... produced in the
the form of crystals of calcium oxalate called apical part of the shoot helps in enlargement
as .................... of cells.
(8) The functional unit of kidney that performs (18) .................... are the structural and functional
the basic function of filtration is called a units of the nervous system.
....................
Life Processes in Living Organisms 77

(19) The cells that support the nerve cells and help * (B) Complete the paragraph:
in their functioning are called .................... . The milk was on the stove. Rasika was
(20) Nerve cells and neurological cells together engrossed watching television. She smelled
form the .................... . something burning. She ran towards the
(21) The minute space between two adjacent kitchen. The milk was boiling over. She
neurons is called .................... . held the vessel with her bare hands but,
(22) Plants use .................... for transfer of information screaming, she let it go at once. This activity
from one place to another. was controlled by .................... cells. Special
ends of .................... in these cells collected the
(23) Control and co-ordination is brought about
information, from where it was transferred to
with a special type of cells called .................... .
the .................... and then towards the terminal
(24) Neurons that conduct impulses from the brain end of the .................... The chemicals produced
or spinal cord to effector organs like muscles
at the terminal end passed through the minute
or glands are called .................... .
space i.e. .................... In this way, ....................
(25) The central nervous system consists of the were conducted in the body and the process of
.................... and .................... . .................... was completed by conducting the
(26) Cavities present in various parts of the brain impulses from .................... to ....................
are called .................... . Ans. nerve, dendrite, cell body, axon, synapse, impulses,
(27) The long tubular cavity of the spinal cord is reflex action, nerve, muscle cell.
called .................... .
Q.2. Select the correct option and complete the
(28) In the space between the delicate central
statements:
nervous system and its bony covering are the
protective layers called the .................... . (1) .................... occurs through stomata.

(29) .................... supplies nutrients to the central (a) Translocation (b) Perspiration
nervous system and protects it from shock. (c) Transpiration (d) Conduction
(30) The two cerebral hemispheres are joined with (2) .................... performs the important role of
each other with the help of tough fibres and pushing the water up during the night time.
.................... . (a) Translocation (b) Root pressure
(31) The thread - like fibrous structure at the end of (c) Transpiration pull (d) None of these
spinal cord is called .................... .
(3) The transport of food produced in leaves to
(32) Hormones are secreted by .................... . each cell in the plant body is called ....................
(33) Movement shown by plants in rensponse (a) transpiration (b) root pressure
to specific chemical is called ....................
(c) translocation (d) ascent of sap
movement.
(4) In plants, gaseous substances are given out by
Ans. (1) transportation (2) xylem, phloem (3) stomata
....................
(4) guard cells (5) ATP (6) resin and gum
(7) raphides (8) nephron (9) bowman’s capsule (a) root pressure (b) osmosis
(10) glomerulus (11) 1 to 1.9 litres (12) dialysis (c) diffusion (d) translocation
(13) co-ordination (14) homeostasis (15) tropism (5) Each kidney has approximately ....................
or tropic movement (16) Tendrils (17) auxin nephrons.
(18) Neurons (19) neuroglia (20) nerves (a) 1 lakh (b) 10,000
(21) synapse (22) electro-chemical
(c) 10 lakh (d) 50 lakh
impulse (23) neurons (24) motor neurons
(25) brain, spinal cord (26) ventricles (6) Kidneys filter blood about .................... times
(27) central canal (28) meninges (29) Cerebrospinal every day.
fluid (30) nerve tracts (31) filum terminale (a) 100 (b) 200
(32) endocrine glands (33) chemotropic (c) 300 (d) 400
78 Master Key Science & Technology (Term - II) (Std. IX)

(7) About .................... of blood is sent through the (18) Control of voluntary movements is done by
dialysis machine at one time. ....................
(a) 500 ml (b) 5 l (a) cerebrum (b) cerebellum
(c) 200 ml (d) 400 ml (c) medulla oblongala (d) spinal cord
(8) The movement of plant towards the source of (19) Co-ordination of voluntary movements is
light is called .................... movement. done by ....................
(a) chemotropic (b) hydrotropic (a) cerebrum (b) cerebellum
(c) phototropic (d) gravitropic (c) medulla oblongata (d) spinal cord
(9) The movement of root system towards stimulus (20) Control of involuntary activities like the
of gravity is called ....................movement. beating of the heart, blood circulation,
(a) phototropic (b) gravitropic breathing etc. are controlled by ....................
(c) hydrotropic (d) chemotropic (a) spinal cord (b) cerebrum
(10) The movement of root system towards stimulus (c) cerebellum
of water is called ....................movement.
(d) medulla oblongate
(a) phototropic (b) gravitropic
(21) The function of cerebrum is .................... .
(c) hydrotropic (d) chemiotropic
(a) control of voluntary movements
(11) Hormone .................... helps in stem elongation.
(b) co-ordination of voluntary movements
(a) auxin (b) gibberellin
(c) control of involuntary activities
(c) cytokinin (d) abscisic acid
(d) maintaining the body balance
(12) Hormone .................... helps in cell division.
(a) auxin (b) gibberellin (22) The function of cerebellum is ....................

(c) cytokinin (d) abscisic acid (a) control of voluntary movements

(13) The hormone .................... is effective in (b) maintaining the body balance
prevention and retardation of growth, leaf (c) control of involuntary activities
wilting, etc. (d) co-ordination of voluntary movements
(a) auxin (b) cytokinin (23) Hormone .................... stimulates the liver to
(c) gibberellin (d) abscisic acid convert excess blood glucose into glycogen.
(14) .................... neurons conduct impulses from (a) glucagon (b) insulin
the sensory organs to the brain and the spinal (c) somatostatin
cord.
(d) pancreatic polypeptide
(a) Sensory (b) Motor
(24) Hormone .................... controls behaviour
(c) Association (d) All of these
during crisis and emotional situation.
(15) The brain of an adult human weighs about
(a) thyroxine (b) parathormone
....................
(c) adrenalin and nor adrenalin
(a) 500 - 600 grams (b) 2 - 3 kilograms
(c) 1300 - 1400 grams (d) 1500 - 1600 grams (d) somatostatin

(16) .................... is the largest part of the brain. (25) .................... controls menstrual cycle and
ovulation.
(a) Cerebrum (b) Cerebellum
(a) Prolactin (b) Oxytocin
(c) Medulla oblongata (d) Spinal cord
(c) Lutenizing hormone (d) Progesterone
(17) There are two triangular swollen structure
called .................... on the upper side of the (26) .................... stimulates growth of secondary
medulla oblongata. sexual characteristics in men.
(a) ventricles (b) meninges (a) Thymosin (b) Testosterone
(c) pyramids (d) pons (c) Oestrogen (d) Thyroxine
Life Processes in Living Organisms 79

(27) Insulin is secreted by the .................... of the (C)

pancreas. Column ‘A’ Column ‘B’
(a) alpha cells (b) beta cells
(1) Cerebrum (a) Control of involuntary
(c) delta cells (d) F cells activities
(2) Cerebelleum
Ans. (1) Transpiration (2) Root pressure (3) translocation (b) Decision - making,
(3) Medulla
(4) diffusion (5) 10 lakh (6) 400 (7) 500 ml oblongata memory and intellectual
(8) phototropic (9) gravitropic (10) hydrotropic activities.
(4) Spinal cord
(11) gibberellin (12) cytokinin (13) abscisic acid (c) Centre for co-ordination
(14) Sensory (15) 1300 - 1400 grams (16) Cerebrum of reflex actions
(17) pyramids (18) cerebrum (19) cerebellum (d) Maintaining body’s
(20) medulla oblongata (21) control of voluntary balance
movements (22) maintaining the body balance
(23) glucagon (24) adrenalin and nor adrenalin Ans. (1 – b), (2 – d), (3 – a), (4 – c).
(25) Lutenizing hormone (26) Testosterone
Q.4. State whether true or false: If false rewrite
(27) beta cells
the correct statement.
Q.3. *(A) Match the columns: (1) Plants need less energy as compared to
animals.
Column ‘A’ Column ‘B’
Ans. True.
(1) Growth of pollen (a) Gravitropic (2) Xylem conducts food whereas phloem
tube towards movement conducts water.
ovules (b) Chemotropic Ans. False, Xylem conducts water whereas phloem
(2) Growth of shoot movement conducts food.
system (c) Phototropic (3) The loss of water from the plants is known as
(3) Growth of root movement translocation.
system (d) Growth-irrelevant Ans. False, The loss of water from the plants is
(4) Growth towards movement known as transpiration.
water (e) Hydrotropic (4) Calcium oxalate crystals present in some
plants are called resins.
movement
Ans. False, Calcium oxalate crystals present in
Ans. (1 – b), (2 – c), (3 – a), (4 – e). some plants are called raphides.
(5) Root pressure helps to push the water up in
(B)
plants during night time.
Column ‘A’ Column ‘B’ Ans. True.
(1) Gibberellins (a) enlargement of (6) Translocation is carried out by phloem in
(2) Cytokinins cells downward direction.
(3) Abscisic acid (b) helps in stem Ans. False, Translocation is carried out by phloem
elogation in both upward and downward direction.
(4) Auxin
(c) cell division (7) In unicellular organisms, waste materials are
directly eliminated across the cell surface.
(d) wilting of leaf
Ans. True.
Ans. (1 – b), (2 – c), (3 – d), (4 – a). (8) Urea is produced in the liver.
Ans. True.
(9) Systematic regulation of different processes is
called co-ordination.
Ans. False, Systematic regulation of different
processes is called control.
80 Master Key Science & Technology (Term - II) (Std. IX)

(10) A hormone auxin produced in the apical part (20) Thyroid stimulating hormone is secreted by
of the shoot helps in enlargement of cells. the pituitary gland.
Ans. True. Ans. True
(11) Gibberellin helps in prevention and retardation (21) The hormone thymosin is secreted by the
of growth, leaf wilting etc. thyroid gland.
Ans. False, Abscisic acid helps in prevention and Ans. False, The hormone thymosin is secreted by
retardation of growth, leaf wilting etc. the thymus gland.
(12) The movement shown by venus fly trap (22) Parathormone controls metabolism of calcium
while trapping an insect is a growth relevant and phosphorns.
movement. Ans. True
Ans. False, The movement shown by venus fly trap (23) The right kidney is slightly lower than the left
while trapping an insect is a growth irrelevant kidney.
movement.
Ans. True
(13) The lotus flower opens during night time
while that of tuberose (polyanthus) opens Q.5. Select the odd man out:
during day time. (1) Skin, Brain, Kidneys, Lungs.
Ans. False, The lotus flower opens during day time Ans. Brain. It is a controlling organ whereas the
while that of tuberose (polyanthus) opens others are excretory organs.
during night time. (2) Gum, Resin, Urea, Latex
(14) Sensory neurons conduct impulses from the Ans. Urea. It is an excretory product of animals
brain and the spinal cord to effector organs whereas the others are excretory products of
like muscles or glands. plants.
Ans. False, Sensory neurons conduct impulses (3) Gibberllin, Auxin, Thyroxine, Cytokinin.
from the sensory organs to the brain and the
Ans. Thyroxine. It is a hormone in animals whereas
spinal cord.
the others are hormones in plants.
(15) There are 31 pairs of cranial nerves.
(4) Dendrite, Cell body, Axon, Synapse.
Ans. False, There are 12 pairs of cranial nerves.
Ans. Synapse. It is a minute space between two
(16) Activities like heart beat, blood circulation, adjacent neurons whereas the others are parts
breathing, sneezing, etc. are controlled by of the neuron.
cerebellum.
(5) Thyroxine, Calcitonin, Insulin, Auxin.
Ans. False, Activities like heart beat, blood
Ans. Auxin. It is a plant hormone whereas the
circulation, breathing, sneezing, etc. are
others are hormones in human beings.
controlled by cerebellum.
(17) Spinal nerves are associated with head, thorax Q.6. Complete the Analogy:
and abdomen. (1) Water : Xylem : : Food : .................... .
Ans. False, Spinal nerves are associated with arms, Ans. Phloem.
legs, skin and some other parts of the body. (2) Movement of root system : gravitropic : :
(18) Nerve impulses are slow and long lasting movement of shoot system : .................... .
whereas action of hormones is fast and short Ans. Phototropic
lived.
(3) Brain : Cranial Cavity : : Spinal Cord :
Ans. False, Nerve impulses are fast and short lived .................... .
whereas action of hormones is slow and long
Ans. Vertebral column
lasting.
(4) Cavities of the brain : ventricles : : Cavities of
(19) Reflex actions area controlled by cerebellum.
the spinal cord : .................... .
Ans. False, Reflex actions are controlled by spinal
Ans. Central canal
cord.
Life Processes in Living Organisms 81

(5) Involuntary activities : medulla oblongata : :

(ii) Waste substances are Most of the waste
Balance of the body : .................... .
generall y eliminated out substances are
Ans. Cerebellum
of the body. stored in the
(6) Stem elongation: Gibberellin : : Cell division : leaves, flowers,
.................... . fruits and bark of
Ans. Cytokinin the stem.
(7) Control of voluntary movements : cerebrum
(iii) The excretory products The excretory
: : co-ordination of voluntary movements :
are urea, uric acid, products are gum,
.................... .
ammonia etc. resin, latex of
Ans. Cerebellum rubber etc.
(8) Converts glucose to glycogen : Insulin : :
converts glycogen to glucose : .................... . (2) Nervous control and Chemical control
Ans. Glucagon Ans.
(9) Secondary sexual characters in males : Nervous Control Chemical Control
Testosterone : : secondary sexual characters in
(i) Nervous control is Chemical control is
females : .................... .
brought about by brought about by
Ans. Oestrogen.
special types of cells chemical substances
Q.7. Define: called neurons. called hormones.
(1) Transportation
(ii) It involves the It involves the
Ans. The process by which, a substance either nervous system i.e., endocrine glands.
synthesized or absorbed in one part of the body brain, spinal cord and
reaches another is called as transportation. nerves.
(2) Control
Ans. Systematic regulation of different processes is (iii) Nerve impulses are Action of hormones
called as control. fast and short lived. is very slow and long
lasting.
(3) Coordination
Ans. Bringing about the different processes in the (3) Growth relevant movements and growth
proper sequence is called as co-ordination. irrelevant movements
(4) Tropism or Tropic movement Ans.
Ans. Movement or growth of any part of the plant Growth relevant Growth irrelevant
in response to an external stimulus is called as movements movements
tropism or tropic movement.
(i) Growth relevant Growth irrelevant
(5) Excretion
movements result in movements do not
Ans. Removal of waste or harmful substances from growth of the plants. result in growth of the
the body is called excretion. plants.
Q.8. Distinguish between: (ii) They are also called as They are also called as
* (1) Excretory system of plants and animals. tropic movements. nastic movements.
Ans.
(iii) They are in response They are generally in
Excretory system of Excretory system
to stimulus of light, response to stimulus
humans of plants
water, gravity, of touch.
(i) In humans, the excretory In plants, there is chemicals, etc.
system carries out the no special system
function of removal of or organ for
waste from the body. excretion.
82 Master Key Science & Technology (Term - II) (Std. IX)

(ii) Plants use electro-chemical impulses for

(iv) Examples : Bending Example : Closing of
transfer of information from one place to
of stem towards light, leaflets of Mimosa
another.
movement of roots plant, closing of
towards gravity and Venus fly trap, etc. (iii) Plant cells change their shape by increasing
water, etc. or decreasing their water content and thereby
bring about the movements of plants.
(4) Cerebrum and Cerebellum (iv) Hence, in plants like touch-me-not (Mimosa)
Ans. movement also occurs at the places other than
Cerebrum Cerebellum where it has been touched.
(3) Endocrine glands are also called ductless
(i) It is the largest part of It is the smaller part glands.
the brain. of the brain.
Ans.
(ii) It occupies two thirds It is situated below (i) Hormones are secreted by endocrine glands.
of the brain. the cerebrum at the
(ii) These glands do not have any arrangement of
back of the cranial
their own to store or carry their secretions.
cavity.
(iii) Hence, as soon as hormones are produced,
(iii) Its surface has deep, Its surface shows they are directly released into the blood
irregular ridges and shallow grooves circulation.
grooves which are instead of (iv) Thus, though these endocrine glands are
called convolutions. convolutions. present at specific locations in our body, their
(iv) It controls voluntary It co-ordinates secretions reach all parts of the body via blood.
movements, voluntary (v) Therefore, endocrine glands are also called
concentration, movements and ductless glands.
planning, decision- maintains the body’s
making, memory, balance. Q.10. Write Short Notes:
intelligence and * (1) Root Pressure
intellectual activities. Ans.
(i) Root cells are in contact with water and
Q.9. Give scientific reasons:
minerals in the soil.
(1) It is necessary to remove harmful and waste
(ii) Water and minerals enter the cells of the root
substances from the body.
surface due to difference in concentration. As
Ans. a result, these cells become turgid.
(i) Many harmful and waste substances like urea, (iii) This is called root pressure.
uric acid, ammonia, etc. are produced in living
(iv) Under the effect of this pressure, water and
organisms.
minerals reach the xylem of the roots and to
(ii) If these substances accumulate is the body or reduce this difference in concentration they
are retained in the body for long, it can lead to are continuously pushed forward.
serious harm or even death.
(v) As a result of this continuous movement, a
(iii) Hence, it is necessary to remove such harmful water column is formed, which is continuously
and waste substances from the body. pushed ahead.
(2) In plants like touch-me-not (Mimosa), (vi) This pressure, is sufficient to lift the water up
movement also occurs at the places other in shrubs, small plants and small trees.
than where it has been touched.
* (2) Transpiration
Ans.
(i) Plants give out water in the form of water
(i) In plants like touch-me-not (Mimosa), the vapour through the stomata on their leaves.
information about the touch is relayed within This is known as transpiration.
the plant from one place to another.
(ii) Two cells called guard cells are present around
Life Processes in Living Organisms 83

the stomata. They control the opening and Human brain is made up of following parts:
closing of stomata. (1) Cerebrum :
(iii) Water is released into the atmosphere by (i) This is the largest part of the brain and
leaves through the process of evaporation. consists of two cerebral hemispheres. These
(iv) As a result, water in the epidermal layer of the hemispheres are joined with each other with
leaf decreases. the help of tough fibres and nerve tracts.
(v) Water is brought up to the leaves through the (ii) The cerebrum occupies two-thirds of the brain.
xylem to compensate for the lost water. Hence, it is also called as large brain.
(vi) Transpiration helps in absorption of water and (iii) Its surface has deep, irregular ridges and
minerals and distribution to all parts of the grooves which are called convolutions,
plant. convolution increases the surface area of the
* (3) Nerve cell : cerebrum and therefore a large number of
nerve cells can be accommodated.
(i) Nerve cells also called as neurons are special
types of cells which conduct impulses from (2) Cerebellum :
one place to another in the body. (i) This is the smaller part of the brain situated
(ii) Neurons are the structural and functional below the cerebrum at the back of the cranial
units of the nervous system. cavity.
(iii) Nerve cells, the largest cell in the human body, (ii) Its surface shows shallow grooves instead of
may measure upto a few metres in length. deep convolutions.
(iv) Nerve cells have the ability to generate and (3) Medulla Oblongata :
conduct electrochemical impulse. (i) This is the hind-most part of the brain.
(v) The cells that support the nerve cells and (ii) There are two triangular swollen structures
help in their functioning are called neuroglia. called pyramids on the upper side of medulla
Nerve cells and neuroglial cells together form oblongata.
nerves. (iii) The medulla oblogata continues downwards
* (4) Human Brain: the spinal cord.
(i) The brain is the main controlling part of the * (5) Reflex action:
nervous system and is safely located in the (i) An immediate and involuntary response
cranial cavity. given to a stimulus from the environment is
(ii) The brain is covered by protective layers called called a reflex action.
the Meninges. (ii) Sometimes we react to an incident without
(iii) Cavities present in various parts of the brain any thinking on our part or control over the
are called ventricles. reaction.
(iv) The ventricles are filled with cerebrospinal (iii) This is a response given to a certain stimulus
fluid. This fluid supplies nutrients to the brain from the surroundings.
and also protects it from shock. (iv) In such situations, proper control and
(v) The brain of an adult human weighs about 1300 co-ordination is achieved even without
- 1400 grams and consists of approximately intervention of the brain.
100 million neurons. (v) For example, when our hand touches a hot
(vi) The left side of our brain controls the right object, the receptor in the skin detects the
side of our body and right side of our brain stimulus. The sensory neuron sends the
control left side of the body. impulse to the relay neuron in the spinal cord.
(v) In addition, the left side of the brain controls The impulses are then sent to motor neurons
our speech and conversation, writing, logical which cause the muscles of the hand to
thinking etc., whereas the right side controls contract and move away from the hot object.
artistic abilities. (vi) Spinal cord is the centre of co-ordination for
reflex actions.
84 Master Key Science & Technology (Term - II) (Std. IX)

(6) Spinal cord: (4) Prolactin Stimulates milk

(i) The spinal cord is the part of the central production.
nervous system and it is held within the
(5) Follicle stimulating Controls growth of
vertebral column.
hormone gonads.
(ii) It is slightly thick but gradually tapers towards
the end. (6) Luteinizing Controls menstrual cycle
(iii) There is a thread like fibrous structure at its hormone and ovulation.
end. It is called the film terminale. (7) Oxytocin Contracts uterus during
(iv) The long tubular cavity of the spinal cord parturition.
is called the central canal. It is filled with (8) Antidiuretic Regulates water-level in
cerebrospinal fluid.
hormone the body.
(v) The spinal cord conducts impulses from the
skin towards the brain and form the brain to * (2) Thyroid
the muscles and glands. Ans.
(vi) It functions as a centre of co-ordination of Hormone Function
reflex actions.
(1) Thyroxine Controls growth of body and
(7) Dialysis: metabolic activities.
(i) The efficiency of kidneys can be adversely
affected by injury, infection or decreased blood (2) Calcitonin Controls calcium metabolism
supply. and calcium level in blood.
(ii) If this happens, excess of toxic substances * (3) Adrenal
accumulates in the body and it can lead to Ans.
death.
Hormone Function
(iii) If kidneys fail, nitrogenous wastes are
separated from the blood with the help of a (1) Adrenalin and Controls behaviour during
man-made machine. nor-adrenalin crisis and emotional situation.
(iv) The process of separating the nitrogenous
waste from the blood with the help of this
(2) Corticosteroid Maintains balance of Na+ and
machine is called dialysis.
K+ and stimulates metabolism.
(v) About 500 ml of blood is sent at one time
through this machine. Purified blood is
* (4) Thymus
reinfused into the body of the patient.
Ans.
Q.11. Name the hormones of the following
Hormone Function
endocrine glands and the function of each:
* (1) Pituitary: (1) Thymosin Control the cells which give
rise to immunity.
Ans.
Hormone Function * (5) Testis

(1) Growth hormone Stimulates growth of Ans.

bones. Hormone Function
(2) Adrenocorticotropic Stimulates adrenal (1) Testosterone Stimulates growth
hormone gland. of secondary sexual
(3) Thyroid stimulating Stimulates thyroid characteristics like beard,
hormone gland. mustache, hoarse voice etc. in
men.
Life Processes in Living Organisms 85

* (6) Ovary Q.12. Draw neat and labelled diagrams:

Ans. * (1) Human endocrine glands
Hormone Function Ans.

(1) Oestrogen Stimulates growth of Hypothalamus

endometrium. Pineal gland

Stimulates growth Pituitary gland
of secondary sexual Thyroid
characteristics in women. gland and
Parathyroid
gland
(2) Progesterone Prepares the endometrium
for conception and maintains Thymus
pregnancy.
Adrenal
glands
(7) Parathyroid
Ans.
Ovary
Hormone Function
Testis
(1) Parathormone Controls metabolism of Fig 15.1 - Endocrine glands
calcium and phosphorus * (2) Human Brain
Ans.
(8) Pancreas Convolutions of the cerebrum
Ans.
Hormone Function
(1) Glucagon Stimulates liver to convert
glycogen into glucose.

Stimulates liver to convert

(2) Insulin excess blood glucose into Pons
Cerebellum
glycogen. Spinal cord Medulla oblongata
(3) Somatostatin Controls levels of insulin and Fig 15.2 - Structure of Brain
glucagon. * (3) Nephron
(4) Pancreatic Controls movement of Ans.
Polypeptide intestine and thereby glucose
Bowman’s Distal
Proximal capsule convoluted tubule
absorption. convoluted Glomerulus
tubule
Controls secretion of
pancreatic juice.

Cortex

Medulla

Loop of
Henle
Collecting
duct
Kidney to ureter

Fig 15.3 - Nephron

86 Master Key Science & Technology (Term - II) (Std. IX)

* (4) Nerve cell (7) Reflex action

Ans. Ans.
Dendrites Receptor in skin Association
neuron
Nucleus
Stimulus
Cell body
Sensory
neuron
Axon spinal
cord
Muscles motor
Schwann’s cell neuron

Myelin sheath
Node of Ranvier

Axon terminal Fig. 15.7 Reflex action

Fig. 15.3 Nerve cell

Q.13. Answer the following:
* (5) Human excretory system * (1) How does excretion occur in human being?
Ans. Ans.
Adrenal gland (i) Removal of wastes from the body is very
Inferior vena cava important and it is the excretory system that
Renal artery carries out this function.
(ii) The human excretory system consists of a
Renal pelvis Renal vein
pair of kidneys, a pair of ureters, the urinary
Kidney bladder and the urethra. Urine is formed
Medulla
Abdominal
by the kidneys by separating the waste and
aorta unwanted excess substances from the blood.
Cortex
(iii) The functional unit of the kidney that
Ureter performs the basic function of filtration is
called a nephron. The urea produced in the
Bladder liver comes into the blood.
Urethra
(iv) When the urea-containing blood comes into
Fig. 15.4 Excretory system and kidneys the glomerulus, it is filtered through capillaries
and urea and other similar substances are
(6) Vertical Section of Kidney
separated from it.
Ans.
(v) Water molecules and small molecules of some
Cortex
Renal capsule other substances can cross the semipermeable
Renal pyramid membrane of Bowman’s capsule.
(vi) The solution accumulated in the cavity of
Bowman’s capsule passes into the tubular part
Renal artery of the nephron. Here, molecules of water and
some other useful substances are reabsorbed
Renal vein
into the blood.
(vii) Urine is formed from the remaining solution
which is full of waste materials. The urine
is carried by the ureters and stored in the
Renal calyx urinary bladder. Afterwards, urine is given
Ureter
out through the urethra.
Fig. 15.6 Kidneys
Life Processes in Living Organisms 87

* (2) How is excretion in plants useful to human (6) How are nerve impulses conducted in the
beings? body?
Ans. Ans.
(i) Plants give out oxygen during photosynthesis (i) Special types of cells which conduct impulses
by diffusion which is useful to human beings from one place to another in the body are
for respiration. called neurons. Nerve cells have the ability
(ii) Some waste materials of plants for example, to generate and conduct electro-chemical
gum, resin, latex of rubber, etc. are useful to impulses.
humans. (ii) The cells that support the nerve cells and help
(3) What are growth-irrelevant movements? in their functioning are called neuroglia.
Give examples. (iii) All the information about our surroundings
Ans. is collected by the ends or dendrites of the
neuron.
(i) Some specific movements of the plants do not
lead to the plant growth. Such movements are (iv) The chemical process begins at those ends
called growth-irrelevant movements. and electric impulses are generated which are
conducted from the dendrites to the cell body,
(ii) In the plant called venus fly trap, there is a
from the cell body to the axon and from the
trap that appears and smells like flowers and
axon to its terminal.
deceives insects. When an insect visits the
flower-like trap, the trap closes up and the (v) There impulses are then to be transferred from
trapped insect is digested by the plant. this nerve cell to the next.
(iii) Fibrils present on the leaves of the insectivorous (vi) Now the impulse that reaches the terminal of
plant Drosera, bend inward as soon as an an axon, stimulates the nerve cell to secrete
insect lands on the leaves and surround the certain chemicals.
insects from all sides. (vii) These chemicals pass through a minute space,
(iv) In Balsam, the ripened fruit dehisus (bursts- called the synapse, between two adjacent
open) at the right time to disperse the seeds. neurons and generate the impulses in the
dendrites of the next neuron.
(4) Name the plant hormones and state their
functions. (vii) In this way, impulses are conducted in the
body and these impulses are finally conveyed
Ans.
by nerve cells to muscles cells or glands.
(i) Auxin : Produced in the apical part of the
(7) Which are the different types of nerve cells
shoot. Helps in enlargement of cells.
or neurons? OR
(ii) Gibberellins : Help in stem elongation.
How are nerve cells classified according to
(iii) Cytokinins : Help in cell division.
their function?
(iv) Abscisic acid : Effective in prevention and
Ans. According to their function, nerve cells are
retardation of growth, leaf wilting, etc.
classified into three types:
(5) How do plants bring about movements in
(i) Sensory neurons : They conduct impulses
them?
from the sensory organs to the brain and the
Ans. spinal cord.
(i) Plants use electro-chemical impulses for (ii) Motor neurons : They conduct impulses from
transfer of information from one place to the brain or spinal cord to effector organs like
another. muscles or glands.
(ii) Plant cells change their shape by increasing (iii) Association neurons : Association neurons
or decreasing their water content and thereby perform the function of integration in the
bring about the movement of plants. nervous system.
88 Master Key Science & Technology (Term - II) (Std. IX)

(8) What are the different parts of the human (ii) They are associated with various parts in the
nervous system? head.
Ans. The human nervous system can be divided (iii) There are 12 pairs of cranial nerves.
into the following three parts. (2) Spinal nerves:
(i) Central nervous system (CNS) : It consists of (i) Nerves originating from the spinal cord are
the brain and the spinal cord. It controls and called spinal nerves.
regulates all activities of the body.
(ii) They are associated with arms, legs, skin and
(ii) Peripheral nervous system (PNS) : The some other parts of the body.
peripheral nervous system consists of the
(iii) There are 31 pairs of spinal nerves.
nerves originating from the central nervous
system with connect the central nervous (11) How do plants get rid of their excretory
system with all parts of the body. They are of products?
two types cranial nerves and spinal nerves. Ans.
(iii) Autonomic nervous system (ANS) : The (i) Excretion is a simpler process in plants. There
autonomous nervous system consists of the is no special organ or system for excretion in
nerves of involuntary organs like the heart, plants.
lungs, stomach etc. It is not under the control (ii) Gases are given out by diffusion.
of our will. (iii) Most of the waste substances of plants are
(9) Describe the structure of the central nervous stored in vacuoles of leaf-cells and in flowers,
system. fruits and the bark of the stem. After some
Ans. time these parts fall off.
(i) The central nervous system consists of the (iv) Some other waste materials are stored in old
brain and spinal card. and worn out xylem in the form of resin and
(ii) The organization of the brain is extremely gum.
delicate and highly evolved. (v) Some waste materials are also given out
(iii) The brain is the main controlling part of the through roots in the surrounding soil.
nervous system and is safely located in the Q.14. Answer in brief:
cranial cavity. The spinal cord is protected by
* (1) Explain chemical co-ordination in humans
the vertebral column.
and give the names and functions of some
(iv) In the space between the delicate central
hormones.
nervous system and its bony covering are the
Ans. Chemical co-ordination in humans :
protective layers called the meninges.
(i) In humans chemical co-ordination is brought
(v) Cavities present in various parts of the brain
are called ventricles whereas the long tubular about with the help of certain chemical
cavity of the spinal cord is called the central substances called hormones.
canal. (ii) Hormones are secreted by endocrine glands.
(vi) The ventricles, central canal and spaces These glands are also called ductless glands.
between the meninges are filled with (iii) These glands do not have any arrangement
cerebrospinal fluid. of their own to either store or carry their
(vii) This fluid supplies nutrients to the central secretions. So, the hormones are directly
nervous system and protects it from shock. released into the blood circulation.
(10) Which are the two types of peripheral nerves? (iv) Though the endocrine glands are present at
specific locations in our body, their secretions
Ans. Peripheral nerves are of two types:
reach all parts of the body via the blood.
(1) Cranial nerves:
(v) Endocrine glands along with the nervous
(i) Nerves originating from the brain are called systems are responsible for control and co-
cranial nerves. ordination in our body.
Life Processes in Living Organisms 89

These two systems help each other to control (v) Examples of growth relevant movements are :
and integrate the various activities of the body. The shoot system of any plant responds to the
(vi) A marked difference between these two light stimulus i.e., it grows towards the source
systems is that nerve impulses are fast but of light. This is called phototropic movement.
short lived whereas the action of hormones is (vi) The root system of plants responds to stimuli
very slow but long lasting. like gravitation and water. These responses are
(vii) It is very important that hormones are called gravitropic movement and hydrotropic
secreted only in the required quantity and movement respectively.
there is a special mechanism which controls (vii) Movement shown by plants in response
the quantity and timing of hormone secretion. to specific chemicals is called chemotropic
(viii) For example, whenever there is an increase movement. For example, the growth of the
in blood glucose level, certain cells in the pollen tube towards the ovule.
pancreas get stimulated and as a response, (viii) Some specific movements of the plants do not
they release a greater quantity of insulin thus lead to the plant growth. Such movements
bringing down the sugar level to normal. are called growth-irrelevant movements. As a
Names and functions of some hormones: response to changes in the surroundings, plant
hormones bring about various movements in
Hormone Function
plants.
(1) Growth hormone Stimulates growth of (ix) Examples of growth irrelevant movements are
bones. closing of leaflets of touch-me-not (Mimosa)
(2) Luteinizing Controls menstrual cycle plant on touch. In the plant called venus fly
hormone and ovulation. trap, when an insect visit the flower like trap,
(3) Thyroxine Controls growth of body the trap closes up and the trapped insect is
and metabolic activities. digested by the plant.
(x) The lotus flower opens during day-time while
(4) Insulin Stimulates liver to
that of the tuberose opens at night.
convert excess blood
glucose to glycogen. (xi) In plants like touch-me-not (Mimosa),
movement also occurs at places other than
(5) Testosterone Stimulates growth
where it has been touched. Hence, we can
of secondary sexual
infer that the information about the touch
characters like beard,
must have been released within the plant from
mustache, hoarse voice,
one place to another.
etc. in men.
(xii) Plants use electrochemical impulses for
* (2) Explain co-ordination is plants with the help transfer of information from one place to
of suitable examples. another. Plant cells change their shape by
Ans. increasing or decreasing the water content and
(i) Plants do not have systems like the nervous thereby bring about the movements of plants.
system or muscular system. * (3) What is meant by co-ordination?
(ii) In plants, movements are mainly in the form Ans.
of responses given to the stimuli. (i) Several different organ systems function in
(iii) Plants show two types of movements - growth multicellular organisms.
relevant movements and growth irrelevant (ii) Their life goes on smoothly if there is co-
movements. ordination between different organ systems or
(iv) Movement or growth of any part of the plant organs and the stimuli in the surrounding.
in response to an external stimulus is called (iii) Depending upon this, we can say that
tropism or tropic movement. systematic regulation of different processes
90 Master Key Science & Technology (Term - II) (Std. IX)

can be called control and bringing about the (ix) Due to the increased pressure, food is pushed
different processes in the proper sequence is into the neighbouring cells where the pressure
called co-ordination. is low.
(iv) If any activity in the body is to be completed (x) This process helps the phloem to transport the
successfully, proper co-ordination between materials as per the need of the plant.
different systems, and organs participating at (5) Explain how food and other substances are
different steps of that activity is necessary. transported in plants? OR
(v) If due to lack of co-ordination, there is Explain translocation in plants.
confusion at any step, the activity may not get
Ans.
completed. There should be no randomness at
(i) The food produced in leaves is transported to
any step.
each cell in the plant body.
(vi) There should be proper co-ordination between
(ii) Excess food, except amino acids, is stored in
internal activities of the body resulting from
roots, fruits and seeds. This process is called
various factors like body temperature, water-
translocation of materials.
level, enzyme-level, etc. or stimuli arising in
the surrounding environment. (iii) It is carried out in both the upward and
downward directions by the phloem.
(vii) Proper co-ordination between various
systems of an organism helps to maintain a (iv) Translocation is not a simple process, it
state of equilibrium called homeostasis which requires energy. This energy is obtained from
is necessary for the optimal efficiency of the ATP.
body. (v) Whenever food material like sucrose is
* (4) Describe the transportation system of plants. transported towards a part of a plant via
the phloem with the help of ATP, the water
Ans.
concentration decreases in the part. As a
(i) Plants have two types of conducting tissues
result, water enters the cell by the process of
i.e., xylem which conducts water and phloem
diffusion.
which conducts food.
(vi) The pressure on the cell wall increases due to
(ii) During transpiration, water is released into
increase in cellular contents.
the atmosphere.
(vii) Due to the increase pressure, food is pushed
(iii) As a result, water level is the epidermal layer
into the neighbouring cells where the pressure
of the leaf decreases.
is low.
(iv) Water is brought up to the leaves through the
(viii) This process helps the phloem to transport the
xylem so as to compensate for the lost water.
materials as per the need of the plant. During
(v) Transpiration helps in absorption of water flowering season, the sugar stored in roots or
and minerals and distribution to all parts of stem is transported towards the floral buds to
the plant whereas root pressure preforms the make them open and blossom.
important role of pushing the water up at
(6) What is tropic movement? Describe the
night time.
different types of tropic movements.
(vi) The food produced by leaves is transported to
OR
each cell of the plant through phloem.
What are growth relevant movements?
(vii) When the food material like sucrose, is
Describe the different types of growth
transported towards a part of the plant through
relevant movements.
phloem, using ATP, the water concentration in
Ans. Movement or growth of any part of the plant
that part decreases.
in response to an external stimulus is called
(viii) As a result, water enters the cell by diffusion.
tropic movement or tropism.
The pressure on the cell wall increases due to
The different types of tropic movements are:
increase in the cellular contents.
Life Processes in Living Organisms 91

(i) Phototropic movement : The shoot system Q.15. Can you recall?
of any plant responds to the light stimulus. (1) How do the digestive system and respiratory
i.e., it grows towards the source of light. The system work ?
movement shown by plants towards the source Ans. Digestive system:
of light is called phototropic movement.
(i) The digestive system is responsible for
(ii) Gravitropic movement : The root system of digestion of food. i.e. breaking down complex
plants responds to stimulus of gravity. This is insoluble food into simpler soluble form.
called gravitropic movement.
(ii) The digestive system is made up of alimentary
(iii) Hydrotropic movement : The root system of canal and digestive glands.
plants responds to the stimulus of water. This
(iii) The alimentary canal is a long and muscular
is called hydrotropic movement.
tube of varying diameter which extends from
(iv) Chemotropic movement : Movement shown the mouth to the anus. The digestive glands
by plants in response to specific chemicals is associated with alimentary canal are salivary
called chemotropic movement. For example, glands, gastric glands, liver and pancreas.
the growth of the pollen tube towards the
(iv) The process of digestion includes various
ovule.
stages wherein the food passes through the
All the above-mentioned movement of plants different organs of the alimentary canal and
are related with growth, hence are called there it is digested part by part with the help of
growth relevant movement. various enzymes secreted from the digestive
(7) State the functions of different parts of the glands.
brain. (v) After the food is digested, the important
Ans. nutrients are absorbed into the blood and the
undigested food and residue of digested food
Parts of the is removed out of the body through the anus.
Functions
Brain
Respiratory sytem:
Cerebrum Control of voluntary movements, (i) Respiration is the process of release of energy
concentration, planning, decision- form the assimilated food.
making, memory, intelligence, and (ii) The respiratory system consists of nose,
intellectual activities. pharynx, larynx, trachea, bronchi and lungs
(alveoli).
Cerebellum (1) Co-ordination of voluntary
(iii) Oxygen enters our body through breathing.
movements.
This oxygen is taken to the cells and with the
(2) Maintaining the body’s balance. help of oxygen, food is oxidized into the cells
to release energy in the form of ATP.
Medulla Control of involuntary activities
oblongata like the beating of the heart, blood (iv) During this process, carbon dioxide and water
circulation, breathing, sneezing, vapour are given out as by - products which
coughing, salivation, etc. are given out during breathing.
Thus, the digestive and respiratory systems
Spinal cord (1) Conduction of impulses from work in co-ordination with each other to
the skin towards the brain. produce energy from food.

(2) Conduction of impulses from (2) Previously you have performed the activity
of observing a branch covered in a plastic
brain to muscles and glands.
bag. What did you observe in that activity?
(3) Functions as centre of co-
Ans.
ordination of reflex actions.
(i) When a branch is covered in a plastic bag,
we observe that small droplets of water
92 Master Key Science & Technology (Term - II) (Std. IX)

accumulate on the inner side of the plastic (iii) If we are distracted with other activities while
bag. eating, it can cause us to bite our tongue or
(ii) This shows that leaves release water in the finger.
form of vapour through the stomata during (iv) Thus, due to lack of co-ordination sometimes
transpiration. These vapours get condense to while eating, we bite our own finger or tongue
form water droplets and accumulate inside by mistake.
the bag. (5) Sometimes, we choke while eating in a hurry.
Q.16. Think about it: Ans.
(1) Why do we eat fruits and vegetables? Do the (i) There is an elastic flap at the starting of the
plants also need minerals like we do? wind-pipe called epiglottis which opens
whenever we breathe in air and closes to
Ans.
prevent the entry of food into the respiratory
(i) We eat fruits and vegetables to get nutrients
system.
like carbohydrates, vitamins, minerals and
(ii) While eating in hurry, due to lack of co-
fibers. These nutrients are important for the
ordination, the epiglottis opens to take in air
proper functioning of the body .
but food too enters in causing us to choke.
(ii) Plants too need minerals for their growth and
(6) An injury to the medulla oblongata can lead
development.
to death. Why?
(2) From where do plants get inorganic
Ans.
substances other than carbon dioxide and
oxygen? (i) The medulla oblongata controls involuntary
activities like the beating of the heart, blood
Ans. Plants get inorganic substances like nitrogen,
circulation, breathing etc.
phosphorus, magnesium, manganese, sodium
etc. from the soil. Soil is the nearest and richest (ii) An injury to the medulla oblongata will stop
source of these elements. these activities leading to death.
(3) At least a small quantity of garbage or waste (7) You may have seen how a drunken person
is produced every day in each house. What struggles to maintain his body balance. An
will happen if you keep this garbage for excess of alcohol in the body causes one to
many days in your house? lose control over it. Why does this happen?
Find out the reason with help of the internet.
Ans.
Ans.
(i) If we keep this garbage for many days in our
house, it will start decaying due to the growth (i) Cerebellum co-ordinates voluntary
of decomposers like fungi and bacteria. movements and maintains balance of the
body.
(ii) This will result in foul odour and will also
lead to spread of diseases. (ii) An excess of alcohol causes dysfunctioning of
the cerebellum.
(4) Sometimes, while eating we bite our own
finger or tongue by mistake. (iii) It results in primary loss of co-ordinated
movements and loss of balance.
Ans.
(i) Sometimes, while eating we over-fill our Q.17. Can you tell?
mouth causing the bite to misalign, thus we (1) Why does this happen?
bite our own finger or tongue by mistake.
(a) Leaves of plants fall off in a particular season.
(ii) If we are dehydrated, the muscles of the mouth
Ans.
and tongue do not function properly causing
(i) Plants lose water through their leaves by
us to bite our own tongue.
transpiration. So some plants shed their leaves
Life Processes in Living Organisms 93

in dry season to reduce transpiration and (v) The skin helps to perceive the sensation of
conserve water. touch, pain, pressure etc.
(ii) In plants, the waste substances are stored in (vi) Some insects also possess antennae for sensing
the vacuoles of leaf-cells which are then shed the changes in the environment.
along with the leaves in a specific season. (4) Where are the gustatory and olfactory nerves
(b) Fruits, flowers fall off after a certain period to be found?
of time. Ans.
Ans. (i) Gustatory nerves are concerned with sense of
(i) In plants, waste substances are stored in the taste whereas olfactory nerves are concerned
vacuoles of fruits and flowers. So, they fall off with the sense of smell.
after some time to excrete these wastes. (ii) Gustatory nerves are found in the tongue from
(ii) Also, when fruits and flowers mature, the where they carry impulses to the gustatory
supply of nutrients to mature fruits and cortex in the brain, whereas the olfactory
flowers is blocked. This causes abscission in nerves are found in the nasal passage from
that part of the plant leading to its detachment where they carry impulses to the olfactory
from the plant body and falling off. lobes in the brain.
(c) Substances like resin, gum, etc. are given out
Q.18. Use your brain power:
of the plant body.
(1) As compared to the monsoons and winter a
Ans.
very small quantity of urine is produced in
(i) Resin, gum etc. are the waste products of the summer season. Why is it so?
plants. They are given out after some time as a
Ans. In summer, we sweat more due to excess
process of excretion in plants.
heat. So, the body tries to conserve water by
(ii) Many plants, particularly, woody plants reducing urine formation. This is to prevent
produce resin and gum in response to dehydration.
injury. These resin and gum act as bandage
(2) In adults, the process of urination is under
protecting the plants from invading insects
their control but not in infants. Why is it so?
and pathogens.
Ans.
(2) Which waste products are produced in our
(i) In adults, the muscles of the bladder are
body through metabolic activities?
under the voluntary control. So the process of
Ans. The waste products formed in our body
urination is under control.
through metabolic activities are urea, uric
(ii) In infants, the bladder muscles are not mature
acid, ammonia, carbon dioxide etc.
until about two years of age. So, the process of
(3) Which are the sensory organs of an organism?
urination is not under control.
What is their function?
Ans. Q.19. Observe:
(i) Sensory organs of an organism are eyes, ears, (1) Observe your mother while she cuts
tongue, skin and nose. elephant’s foot (Amorphophallus) or arum
leaves. Your hands may also begin to itch
(ii) The eyes helps the organism to perceive the
if you try to cut these leaves. Why does this
sensation of light to see the objects around it.
happen? Try to find out. Ask your mother
(iii) The ears help the organism to perceive the
what she does to prevent the itching.
sensation of sound and also perceive the
Ans.
sensation of pressure.
(i) In some plants like elephant foot
(iv) The tongue helps to perceive different tastes
(Amorphophallus) or arum, waste materials
and also in chewing the food.
94 Master Key Science & Technology (Term - II) (Std. IX)

are in the form of crystals of calcium oxalate. (ii) This can be prevented by applying tartaric
They are called raphides. As they are needle- acid (tamarind) or citric acid (lemon) on the
shaped, they prickle and cause irritation of the hands while cutting these vegetables as the
skin leading to itching. acids dissolve the crystals of calcium oxalate.
(2) Observe the following figures carefully.

A B C
Pollen grains sun Tendrils

Pollen tube

Ovule

Plantlet bent
Ovary towards the sun

Pollen tube growing towards the ovule Phototropic response Thigmotropic response

Fig. 15.8 Co-ordination in plants

Ans.
Observations:
(i) Figure A shows chemotropic movement. (iii) Figure C shows thigmotropic movement.
Pollen tube grows towards the ovule in Tendrils of climbers are sensitive to touch.
response to specific chemicals released by the When they come in contact with an object,
ovule. they entwine around the object and cling to it.
(ii) Figure B shows phototropic movement. Shoot (iv) All the above movements are related to
grows towards the sun in response to stimulus growth. Hence they are called growth relevant
of light. movements.
(3) Observe the pictures carefully and think about them.

(A) Touch-me-not (B) Venus fly trap (C) Lotus (D) Balsam
Fig. 15.9 Various plants
Ans. visits that flower-like trap, the trap closes up
(i) Figure A shows touch-me-not (Mimosa) plant. and the trapped insect is digested by the plant.
In this plant, the leaflets close in response to (iii) Figure C shows lotus plant. The lotus flower
stimulus of touch. opens during day-time.
(ii) Figure B shows Venus fly trap. In this plant, (iv) Figure D shows Balsam plant. In this plant,
there is a trap that appears and smells like a the ripened fruit dehisces (bursts-open) at the
flower and deceives the insect. When an insect night time to disperse the seeds.
Life Processes in Living Organisms 95

(4) As you watch the match being played on (vi) At 7, where has the impulse reached? What is
your school ground, you will see the control its effect?
and co-ordination among the movements of Ans. At 7, the impulse has reached the muscles of
the players. Make a list of all such different the hand. As a result, the muscles contract and
actions. the hand is withdrawn instantly in response to
Ans. In an inter-house basketball match, control the stimulus of heat.
and co-ordination is seen in dodging the ball, (6) Sketch and label Fig. 15.10
jumping, running, passing it to the team mates Ans. For diagram refer question no 19 (6)
and dribbling the ball. Do the labelling as follows:
(5) Observe the figure carefully and as per the 1 – Stimulus
numbers in that figure, answer the following
2 – Hand is withdrawn
questions.
3 – Sensory neuron
2
4 4 – Association neuron
1
5 – Spinal cord
6 – Motor neuron
7 – Muscles
3 5
Q.20. Activity based questions:
7 6
(1) Take a small plant like balsam or tuberose
with its roots intact. Wash and clean its roots.
As shown in the fig, keep it in the water
containing a stain like safranin or eosin.
Observe the stem and the veins of the leaves
Fig. 15.10 Reflex action after 2-3 hours.
(i) What is happening at 1 and 2?
Ans. At 1 stimulus of heat is received by thermo-
Veins (turned red)
receptors in the skin. At 2, the hand is
withdrawn instantly.
(ii) Which nerve carried the impulse to the point Stem
marked 3? In which direction is it conducting
the impulse? Stand
Ans. Sensory nerve carried the impulse to the point
marked 3. The impulse is conducted from the
skin towards the spinal cord.
Beaker
(iii) Which is the nerve shown by 4?
Ans. The nerve shown by 4 is association neuron. It Eosin solution
is present in the gray matter of the spinal cord.
It receives the sensory impulse, interprets it
and generates impulse.
(iv) Which is the organ marked as 5?
Fig. 15.11 Root pressure
Ans. Spinal cord.
Ans.
(v) At 6, which nerve is conducting the response
impulse? (i) The stem and veins of the leaves appear
pinkish in colour.
Ans. Motor nerve.
(ii) Due to the root pressure generated, eosin
solution is continuously pushed upward. As
96 Master Key Science & Technology (Term - II) (Std. IX)

a result water reaches xylem and the water Ans. The xylem elements appear pinkish as the
column is pushed forward. eosin solution is conducted upwards through
(1) Take a transverse section of the stem of a the xylem. From this we infer that xylem
plant and observe the stained xylem under a is responsible for conduction of water and
compound microscope. minerals in the plant.
vvv

ASSIGNMENT - 15
Time : 1 Hr. Marks : 30

Q. 1 (A) Fill in the blanks: (2)

(1) In some plants, waste materials are present in the form of crystals of calcium oxalate called as
................. .
(2) The thread-like fibrous structure at the end of spinal cord is called ................. .
(B) Match the columns: (2)

Column 'A' Column 'B'

(1) Growth of pollen tube (a) Gravitropic movement
towards ovule
(2) Growth of shoot system (b) Chemotropic movement
(3) Growth of root system (c) Phototropic movement
(4) Growth towards water (d) Growth-irrelevant movement
(e) Hydrotropic movement

Q. 2 Answer the following questions. (10)

(1) Distinguish between excretory system of plants and excretory system of animals.
(2) Write a short note on root pressure.
(3) Write a short note on Reflex action.
(4) Name the hormones of adrenal gland and their functions.
(5) Draw a neat labelled diagram of human brain.
Q. 3 Answer the following questions. (6)
(1) State the functions of different parts of the brain.
(2) How are nerve cells classified according to their functions?
(3) What is meant by co-ordination?
Q. 4 Answer the following questions. (10)
(1) How does excretion occur in human beings.
(2) Explain co-ordination in plants with help of suitable examples.
vvv
16 Heredity and Variation
Points to Remember:
• The branch of biology which studies the transfer of characteristics of organisms from one
generation to the next, and genes in particular, is called genetics.
• Organisms reproduced through sexual reproduction show minor variations. However,
offsprings produced through sexual reproduction, show comparatively greater variations.
• Transfer of characteristics from parents to offsprings is called heredity.
• The structure in the nucleus of the cells that carries the hereditary characteristics is called the
chromosome.
• Each chromosome is made up of DNA
• Depending upon the position of the centromere, there are four types of chromosomes –
metacentric, sub-metacentric, acrocentric and telocentric
• If the chromosome pair consists of similar chromosomes by shape and organization they are
called homologous chromosomes and if they are not similar they are called heterologous
chromosomes.
• DNA was discovered by the Swiss biochemist Frederick Miescher in 1869. In 1953, Watson
and Crick proposed the double helix model of DNA.
• DNA control the functioning, growth and division (reproduction) of the cell and are therefore
called ‘Master molecules’.
• Segments of DNA molecule are called genes. Genes control the structure and function of
the cells and of the body. Also, they transmit the hereditary characteristics from parents to
offsprings.
• DNA fingerprinting is the process of identifying the sequence of the genes in the DNA of a
person i.e. the genome of the person.
• RNA is the second important nucleic acid of the cell. According to function, there are three
types of RNA – rRNA, mRNA and tRNA. RNA help in protein synthesis.
• Principles of heredity are based upon the fact that genetic material is transferred in equal
quantity from parents to progeny.
• Mendel carried out research in this direction and put forth the principles of heredity
responsible for such inheritance.
• Mendel’s monohybrid and dihybrid cross were based upon the visible characteristics of the
pea plant (Pisum sativum).
• Disorders occurring due to abnormality in chromosomes and mutations in genes are called
genetic disorders.
• Chromosomal disorders – Down syndrome, Turner syndrome, Klinefelter syndrome.

(97)
98 Master Key Science & Technology (Term - II) (Std. IX)

• Monogenic disorders are caused due to mutation in a single gene into a defective one .
Examples – Hutchinson’s disease, Tay-Sachs disease, galactosaemia, phenylketonuria, sickle
cell anaemia, cystic fibrosis, albinism, haemophilia, night blindness etc.
• Mitochondrial disorders are caused due to mutation in mitochondrial DNA. Example – Leber
hereditary optic neuropathy.
• Polygenic disorders are caused due to complex interaction between environment, life style
and defects in several genes. Examples – cleft lip, cleft palate, constricted stomach, spina
bifida, diabetes, blood pressure, heart disorders, asthma, obesity etc.
• Tobacco consumption leads to shortening of life, bronchitis, cancer of the lungs, mouth,
larynx, pharynx, pancreas, urinary bladder, lips or tongue.

(5) The constricted region on each chromosome is

MASTER KEY QUESTION SET - 16 called .
Q.1. (A) Complete the following sentences by (6) If the chromosome pair consists of similar
choosing the appropriate word from the chromosomes by shape and organisation,
bracket: they are called .
(Inheritance, sexual reproduction, asexual (7) DNA molecules are called .
reproduction, chromosomes, DNA, RNA, gene) (8) Each strand in the DNA is made up of many
*(1) Hereditary characters are transferred from small molecules known as .
parents to offsprings by hence they (9) Purines present in DNA are and
are said to be structural and functional units .
to heredity. (10) Pyrimidines present in DNA are and
*(2) Organisms produced by show minor .
variations. (11) The process where the sequence of the genes
*(3) The component which is in the nuclei of cells in the DNA of a person is identified is called
and carries the hereditary characteristics is .
called . (12) The RNA molecule that carries the information
*(4) Chromosomes are mainly made up of of protein synthesis from genes to ribosomes
. in the cytoplasm is called .
*(5) Organisms produced through show (13) studied the inheritance of
major variations. characteristics of pea plant.
Ans. (1) gene (2) asexual reproduction (3) chromosomes (14) means external appearance or visible
(4) DNA (5) sexual reproduction characteristics of an organism.
(B) Fill in the blanks: (15) means the pairs of genes responsible
(1) The branch of biology which studies the for the visible characteristics.
transfer of characteristics of organisms from (16) Disorders occurring due to abnormalities in
one generation to the next, and genes in chromosomes and mutations in genes are
particular, is called . called .
(2) Transfer of characteristics from parents to (17) Human beings have chromosomes
offsprings is called . in pairs.
(3) The segment of DNA which contains all the (18) Chromosomes in women are represented as
necessary information for synthesis of a and in men as .
particular protein is called .
(19) arises due to trisomy of 21st pair of
(4) Chromosomes can be seen clearly during chromosomes.
.
Heredity and Variation 99

(20) is the most prominent characteristic (3) The chromosome in which the centromere
of Down syndrome. is exactly at the mid-point is called
(21) Disorders occurring due to mutation in any chromosome.
single gene into a defective one are called (a) sub-metacentric (b) metacentric
. (c) acrocentric (d) telocentric
(22) In , the body cannot produce melanin. (4) The chromosome in which the centromere
(23) Normal haemoglobin has as the 6th is somewhere near the mid-point is called
amino acid in its molecular structure. chromosome.
(24) Sickle-cell anaemia occurs when the 6th (a) metacentric (b) acrocentric
amino acid glutamic acid in the haemoglobin
(c) sub-metacentric (d) telocentric
is replaced by .
(5) The chromosome in which the centromere
(25) A person suffering from sickle cell anaemia
is near one end of the chromosome is called
should take a tablet of daily.
chromosome.
(26) Harmful effects of smoking are due to the
present in tobacco. (a) metacentric (b) acrocentric
(27) The confirmatory diagnostic test for (c) sub-metacentric (d) telocentric
sickle-cell anaemia is performed at rural and (6) Sex chromosomes are called .
sub-district hospitals. (a) homologous chromosomes
(28) Homologous chromosomes are called (b) autosomes
.
(c) allosomes
(29) The molecule of RNA which according to the
message of the mRNA carries the amino acid (d) metacentric chromosomes
up to the ribosomes is called . (7) Which of the following is absent in RNA?
(30) The scientific name of pea plant is . .
Ans. (1) genetics (2) heredity (3) gene (4) cell (a) Adenine (b) Uracil
division (5)primary constriction or centromere (c) Cytosine (d) Thymine
(6) homologous chromosomes (7) master (8) DNA was discovered by .
molecules (8) nucleotide (9) adenine
(a) Watson and Crick
and guanine (10) cytosine and thymine
(11) DNA fingerprinting (12) messenger (b) Frederick Miescher
RNA (mRNA) (13) Gregor Johann Mendel (c) Gregor Johann Mendel
(14) phenotype (15) genotype (16) genetic (d) Robert Brown
disorders (17) 46, 23 (18) 44+XX, 44+XY (9) The double helix model of DNA was produced
(19) Down Syndrome (20) Mental retardation by .
(21) monogenic disorders (22) Albinism
(a) Watson and Crick
(23) glutamic acid (24) valine (25) folic acid
(26) nicotine (27) Electrophoresis (28) autosomes (b) Frederick Miescher
(29) transfer RNA (tRNA) (30) Pisum sativum (c) Gregor Johann Mendel
Q.2. Rewrite the following statements by (d) Robert Hooke
selecting the correct options given below: (10) The molecule of RNA which is a component of
(1) The similarities and differences are all the the ribosome organelle is called a .
effect of . (a) mRNA (b) tRNA
(a) heredity (b) fertilization (c) rRNA (d) DNA
(c) evolution (d) natural selection (11) is a recessive character of pea plant.
(2) Each chromosome appears midway (a) Round shape of seeds
during cell division.
(b) White colour of flowers
(a) circular (b) rod-shaped
(c) Green colour of pods
(c) dumbell-shaped (d) bottle-shaped
(d) Inflated shape of pods
100 Master Key Science & Technology (Term - II) (Std. IX)

(12) is a dominant character of pea plant. (19) If one parent is carrier and one parent is
(a) Dwarf height a sufferer of sickle-cell anaemia, then the
progenies will be .
(b) Yellow colour of pod
(a) 50% normal and 50% carrier
(c) Yellow colour of seeds
(b) all sufferers
(d) Terminal position of flower
(c) 50% carrier and 50% sufferer
(13) is a dominant character in human
beings. (d) all carrier
(a) Non-rolling tongue (20) is a mitochondrial disorder.
(b) Attached ear lobe (a) Down syndrome
(c) Absence of hair on arms (b) Cleft palate
(d) Free ear lobe (c) Spina bifida
(14) is a recessive character in human (d) Leber hereditary optic neuropathy
beings. (21) is a monogenic disorder.
(a) Absence of hair on arms (a) Haemophilia (b) Cleft palate
(b) Black and curly hair (c) Diabetes (d) Spina bifida
(c) Free earlobe Ans. (1) heredity (2) dumbell-shaped (3) metacentric
(d) Presence of hair on arms (4) sub-metacentric (5) telocentric (6) allosomes
(7) Thymine (8) Frederick Miescher (9) Watson
(15) In a monohybrid cross, the phenotypic ratio of
and Crick (10) rRNA (11) White colour of flowers
F2 generation is .
(12) Yellow colour of seeds (13) Free ear lobe
(a) 1 tall : 3 dwarf (b) 2 tall : 2 dwarf
(14) Absence of hair on arms (15) 3 tall:1
(c) 3 tall : 1 dwarf (d) 3 tall : 2 dwarf dwarf (16) Turner syndrome (17) all carrier
(16) arises due to either inheritance of (18) 50% normal and 50% carrier (19)
only X chromosome from parents or due 50% carrier and 50% sufferer (20) Leber
to inactivation of the gender-related part of hereditary optic neuropathy (21) Haemophilia
X-chromosomes.
Q.3. (A) How are the items in groups A, B and C
(a) Down syndrome inter-related?
(b) Turner syndrome
A B C
(c) Klinefelter syndrome
(d) Albinism Leber hereditary 44 + XXY Pale skin,
optic neuropathy white hairs
(17) Progenies of normal man and sufferer woman
for sickle-cell anaemia will be . Diabetes 45 + X Men are
(a) all normal sterile
(b) 25% normal and 75% sufferer Albinism Mitochondrial Women are
(c) all carrier disorder sterile
(d) all sufferer Turner syndrome Polygenic This disorder
(18) If one parent is normal and one parent is carrier disorder arises during
of sickle-cell anaemia, then the progenies will development
be . of zygote
(a) all normal
Klinefelter Monogenic Effect on
(b) 50% normal and 50% carrier disorder blood-glucose
Syndrome
(c) 50% carrier and 50% sufferer level.
(d) all carrier
Heredity and Variation 101

Ans. Q.4. State whether the following statements are

true or false. If false, rewrite the correct
A B C
statement:
Leber hereditary Mitochondrial This disorder (1) Offsprings produced through asexual
optic neuropathy disorder arises during
reproduction show greater variations as
development
compared to those produced through sexual
of zygote
reproduction.
Diabetes Polygenic Effect on Ans. False. Offsprings produced through asexual
disorder blood-glucose reproduction show minor variations as
level. compared to those produced through sexual
Albinism Monogenic Pale skin, reproduction.
disorder white hairs (2) Information necessary for protein synthesis
Turner syndrome 44 + X Women are is stored in the RNA.
sterile Ans. False. Information necessary for protein
synthesis is stored in the DNA.
Klinefelter 44 + XXY Men are
sterile (3) The quantity of growth hormone produced
Syndrome
by a plant depends upon the efficiency of the
(B) Match the columns: concerned enzyme.
(1) Column `A' Column `B' Ans. True.
(4) The chromosome in which the centromere is
Organism Chromosome Number exactly at the mid-point is called telocentric
chromosome.
(1) Crab (a) 48
Ans. False, The chromosome in which the
(2) Potato (b) 04 centromere is exactly at the mid-point is called
metacentric chromosome.
(3) Frog (c) 200
(5) RNA molecules are called master molecules.
(4) Roundworm (d) 26 Ans. False. DNA molecules are called master
molecules.
Ans. (1 - c), (2 - a), (3 - d), (4 - b)
(6) The pair of sex chromosomes is called
(2) Column `A' Column `B' autosomes.
Ans. False. The pair of sex chromosomes is called
(1) Yellow and wrinkled (a) yyrr
allosomes.
(2) Green and round (b) YyRr (7) In DNA, Adenine always pairs with thymine
and cytosine always pairs with guanine.
(3) Yellow and round (c) YYrr
Ans. True.
(4) Green and wrinkled (d) yyRr (8) In humans there are 23 pairs of autosomes
Ans. (1 - c), (2 - d), (3 - b), (4 - a) and one pair of allosomes.
Ans. False. In humans, there are 22 pairs of
(3) Column `A' Column `B' autosomes and one pair of allosomes.
(1) Tay-Sachs disease (a) multifactorial (9) The phenotypic and genotypic ratios are not
disorder same.
(2) Diabetes (b) destruction of Ans. True.
erythrocytes (10) Phenotype means the pairs of genes
(3) Sickle-cell anaemia (c) absence of melanin responsible for the visible characteristics of
organisms.
(4) Albinism (d) monogenic disorder
Ans. False. Phentotype means external appearance
Ans. (1 - d), (2 - a), (3 - b), (4 - c) of visible characteristics of organisms.
102 Master Key Science & Technology (Term - II) (Std. IX)

(11) During gamete formation, in P1 generation (5) Attached ear lobes, brown and straight hair,
the pair of gametes separate independently. non-rolling tongue, presence of hair on arms.
Ans. True. Ans. Presence of hair on arms. It is a dominant
(12) Down syndrome is caused due to monosomy characteristic of human beings whereas the
of X chromosome. others are recessive characters.
Ans. False. Down syndrome is caused due to (6) Cystic fibrosis, Albinism, Spina bifida,
trisomy of 21st chromosome. Sickle-cell anaemia.
(13) In Klinefelter syndrome, women are sterile. Ans. Spina bifida. It is a polygenic disorder
Ans. False. In Klinefelter syndrome, men are whereas the others are monogenic disorders.
sterile as this disorder arises in men due to (7) Hutchinson’s disease, phenylketonuria,
abnormality in sex chromosome. nightblindness, Leber hereditary optic
(14) If the father and mother are both sufferers neuropathy
or carriers of sickle-cell anaemia, their Ans. Leber hereditary optic neuropathy. It is a
offsprings are likely to suffer from this mitochondrial disorder whereas the others
disease. are monogenic disorders.
Ans. True. Q.6. Complete the analogy:
(15) During fertilization, mitochondria is *(1) 44 + X : Turner syndrome : : 44 + XXY :
contributed by the sperm cell and egg
cell(ovum). *(2) 3 :1 : Monohybrid : : 9 : 3 : 3 : 1 :

Ans. False. During fertilization, mitochondria is *(3) Women : Turner syndrome : : Men :
contributed by the egg cell (ovum) alone. (4) Tall plant : Phenotype : : Tt :
(16) Polygenic disorders strictly follow Mendel’s (5) Dominant trait : Axial position of flower : :
principles of heredity. Recessive trait :
Ans. False. Polygenic disorders do not strictly (6) Women : 44 + XX : : Men :
follow Mendel’s principles of heredity. (7) Adenine and Guanine : Purine : : Cytosine and
(17) Genetic material is transferred in equal Thymine :
quantity from parents to progeny. Ans. (1) Klinefelter syndrome (2) Dihybrid
Ans. True. (3) Klinefelter syndrome (4) Genotype
Q.5. Find the odd man out: (5) Terminal position of flower (6) 44 + XY
(7) Pyrimidine
(1) Adenine, thymine, cytosine, uracil
Ans. Adenine. It is a purine whereas the others are Q.7. Distinguish between:
pyrimidines. (1) DNA and RNA
(2) Axillary flower, green pod, green seed, DNA RNA
Inflated pod
(1) In DNA, the (1) In RNA, the sugar
Ans. Green seed. It is a recessive character of sugar present is present is ribose.
pea plant whereas the others are dominant deoxyribose.
characters.
(2) In DNA, the (2) In RNA, the
(3) Constricted pod, purple flower, Axillary nitrogen bases are nitrogen base
flower, Yellow seeds. adenine, guanine, thymine is replaced
Ans. Constricted pod. It is a recessive character of cytosine and by uracil.
pea plant whereas the others are dominant thymine.
characters.
(3) DNA is double (3) RNA is single
(4) Green seeds, wrinkled seeds, terminal stranded. stranded.
flower, Green pod.
(4) DNA carries (4) RNA helps in
Ans. Green pod. It is a dominant character of h e r e d i t a r y protein synthesis
pea plant whereas the others are recessive information
characters.
Heredity and Variation 103

*(2) Monohybrid and Dihybrid Cross (ii) The genes responsible for any particular
character are present in pairs.
Monohybrid cross Dihybrid cross
(iii) Though, there are two genes, the phenotype
(1) Cross involving (1) Cross involving
depends on the presence of the dominant
a single pair two pairs
gene. e.g. Genotype for tall height of the plant
of contrasting of contrasting
is TT or Tt.
characters is called characters is called
(iv) Therefore, phenotypic and genotypic ratios
monohybrid cross. dihybrid cross.
are different.
(2) F1 plants of (b) F1 plants of (3) A carrier or sufferer of sickle-cell anaemia
monohybrid cross dihybrid cross should avoid marriage with another carrier
produce two types produce four types or sufferer.
of gametes. of gametes. Ans.
(3) Monohybrid cross (d) Dihybrid cross has (i) Sickle-cell anaemia is a hereditary disease
has a phenotypic a phenotypic ratio caused due to mutation of a single gene.
ratio of 3 : 1 in F2 of 9 : 3 : 3 : 1 in F2 (ii) It is a monogenic disorder that occurs due to
generation. generation. changes in a gene during conception,
(3) Turner syndrome and Klinefelter syndrome. (iii) If father and mother both are sufferers or
carriers of sickle-cell anaemia, their offsprings
Turner syndrome Klienefelter syndrome are likely to suffer from the disease.
(1) Disorder of sex (1) Disorder of (iv) Therefore, a carrier or sufferer of sickle-cell
chromosomes sex chromosomes anaemia should avoid marriage with another
resulting in 44 + X resulting in carrier or sufferer.
condition. 44 + XXY condition. (4) Mitochondrial disorders are inherited from
(2) Seen in women (2) Seen in men. the mother only.
Ans.
(3) Women suffering (3) Men suffering from (i) Mitochondrial DNA becomes defective due to
from this syndrome this syndrome are mutation.
are sexually sterile. sexually sterile. (ii) During fertilization, mitochondria are
(4) There is presence of (4) There is presence contributed by the egg cell (ovum) alone.
total 45 chromosomes of total 47 (iii) Hence, mitochondrial disorders are inherited
instead of 46. chromosomes from the mother only.
instead of 46. (5) Tobacco smoking causes cancer.
Q.8. Give scientific reasons: Ans.
(1) DNA molecules are called as ‘Master (i) Tobacco smoke contains harmful chemicals
molecules’. like pyridine, ammonia, aldehyde furfural,
Ans. carbon monoxide, nicotine, sulphur dioxide
(i) Molecules of DNA are present in all organisms etc.
from viruses and bacteria to human beings. (ii) They cause uncontrolled cell division.
(ii) These molecules control the functioning, (iii) Tobacco smoke is full of minute carbon
growth and division (reproduction) of the cell.
particles which cause normal tissue lining of
(iii) Genes present in the DNA are also responsible the lung to transform into thickened black
for transfer of hereditary characteristics from tissue. This leads to cancer.
parents to offsprings.
(iv) Therefore, tobacco smoking causes cancer.
(iv) Therefore, DNA molecules are called as
Q.9. Write short notes on:
‘Master molecules’.
(2) Phentoypic and genotypic ratios are different. *(1) Down syndrome:
Ans. Ans.
(i) Phenotype means external appearance or (i) Down syndrome is the disorder arising due to
visible characteristics of organisms whereas chromosomal abnormality.
the genotype is the pairs of genes responsible (ii) This is the first discovered and described
for the visible characteristics. chromosomal disorder in human beings.
104 Master Key Science & Technology (Term - II) (Std. IX)

(iii) This disorder i s characterized by the presence (v) Symptoms of sickle-cell anaemia are swelling
of 47 chromosomes. It is described as the of legs and hands, pain in joints, severe
trisomy of the 21st pair. general body aches, frequent cold and cough,
(iv) Infants with this disorder have one extra constant low grade fever, exhaustion, pale
chromosome with the 21st pair in every face, low haemoglobin count.
cell of the body. Therefore, they have 47 (vi) A person suffering from sickle-cell anaemia
chromosomes instead of 46. should take a tablet of folic acid daily.
(v) Children suffering from Down syndrome (4) Albinism
are usually mentally retarded and have a Ans.
short lifespan. Mental retardation is the most (i) Albinism is a monogenic disorder.
prominent characteristic. (ii) Our eyes, skin and hair have colour due to the
(vi) Other symptoms include short height, short brown pigment melanin. In this disease, the
wide neck, flat nose, short fingers, scanty hair, body cannot produce melanin.
single horizontal crease on palm and a life (iii) The skin becomes pale, hair are white and eyes
expectancy of about 16-20 years. are usually pink due to absence of melanin
pigment in the retina and sclera.
*(2) Monogenic disorders
Ans. (5) Polygenic disorders.
(i) Disorders occurring due to mutation in any Ans.
single gene into a defective one are called (i) Polygenic disorders are caused due to
monogenic disorders. mutations in more than one gene.
(ii) In most such cases, their severity increases
(ii) Approximately 4000 disorders of this type are
due to effects of environmental factors on the
now known.
foetus.
(iii) Due to abnormal genes, their products are
(iii) Common examples of such disorders are cleft
either produced in insufficient quantity or not
lip, cleft palate, constricted stomach, spina
produced at all. bifida ( a defect of the spinal cord) etc. Besides,
(iv) It causes abnormal metabolism and may lead diabetes, blood pressure, heart disorders,
to death at a tender age. asthma and obesity are also polygenic
(v) Examples of monogenic disorders are disorders.
Hutchinson’s disease, Tay-Sachs disease, (iv) Polygenic disorders do not strictly follow
galactosaemia, phenylketonuria, sickle Mendel’s principles of heredity.
cell anaemia, cyctic fibrosis, albinism, (v) These disorders arise from a complex
haemophilia, night blindness etc. interaction between environment, life style
*(3) Sickle-cell anaemia: Symptoms and and defects in several genes.
treatment. Q.10. Draw neat and labelled diagrams of the
Ans. following:
(i) Sickle-cell anaemia is a hereditary disease (1) Structure of chromosome
caused due to mutation in a single gene. It is a
Ans. Arms of
monogenic disorder.
(ii) Normal haemoglobin has glutamic acid as chromosomes
the 6th amino acid in its molecular structure.
However, if it is replaced by valine, the p Arm
shape/structure of the haemoglobin molecule
changes.
(iii) Due to this, the erythrocytes (RBCs) which are Centromere
normally biconcave become sickle-shaped.
This condition is called sickle-cell anaemia.
The oxygen carrying capacity of haemoglobin
in such individuals is very low. q Arm
(iv) In this condition, clumping and thereby
destruction of erythrocytes occurs most often.
As a result, blood vessels are obstructed and (DNA)
the circulatory sytem, brain, lungs, kidneys,
etc. are damaged.
Heredity and Variation 105

(2) Types of Chromosomes Q.11. Answer the following questions:

Ans. (1) What are the main objectives of National
Health Mission?
Arm
Ans. The main objectives of National Health
Mission are:
Centromere
(i) Strengthening of the rural and urban health
facilities.
Metacentric Sub-metacentric (ii) Controlling various diseases and illnesses.
(iii) Increasing public awareness about health.
(iv) Offering financial assistance to patients
through various schemes.
(2) Which were the seven pairs of contrasting
characteristics studied by Mendel in pea
plant?
Acrocentric Telocentric Ans. The seven pairs of contrasting characters
studied by Mendel in pea plant were as
follows:
(3) Structure of DNA Characters Dominant Recessive
Ans. (i) Shape of the Round (R) Wrinkled (r)
seed
(ii) Colour of the Yellow (Y) Green (y)
Adenine Thymine
seed
Pair of nitrogenous (iii) Colour of the Purple (C) White (c)
bases (nucleotides)
flower
Guanine Cytosine
(iv) Shape of pod Inflated (I) Constricted (i)
Rails of the DNA
made up of sugar (v) Colour of Green (G) Yellow (g)
and phosphoric pod
acid
(vi) Position of Axillary (A) Terminal (a)
flower
(4) Types of RNA
(vii) Height of the Tall (T) Dwarf (t)
Ans.
mRNA plant
(3) Name some dominant and recessive
characteristics seen in human beings.
Ans. Some dominant and recessive characteristics
of human beings.

Dominant Recessive
Rolling tongue Non-rolling tongue
rRNA Presence of hair on arms Absence of hairs on arms
Black and curly hair Brown and straight hair
Free earlobe Attached earlobe
(4) What is Turner syndrome?
Ans.
(i) Turner syndrome is a disorder arising
in women due to abnormality in sex
tRNA chromosomes.
(ii) Turner syndrome arises due to either
106 Master Key Science & Technology (Term - II) (Std. IX)

inheritance of only one X chromosome from (ii) Genetic disorders are transmitted from
parents or due to inactivation of the gender- parents to offsprings only and they are non-
related part of X-chromosomes. contagious, i.e., they do not spread from one
(iii) Instead of the normal 44 + XX condition, person to another through contact.
women suffering from Turner syndrome *(9) Why is it necessary for people to have their
show a 44 + X condition. blood examined before marriage?
(iv) Such women are sterile i.e. unable to have Ans.
children due to improper growth of the (i) If people have their blood examined before
reproductive organs. marriage, the partners will know about the
(5) What is Klinefelter syndrome? possible genetic diseases that their children
Ans. might inherit. So they may decide not to have
(i) Klinefelter syndrome is a disorder arising in children or not to get married.
men due to abnormalities in sex chromosomes. (ii) Blood tests before marriage are also done
(ii) In this disorder, men have one extra X to check for any contagious disease in the
chromosome, hence their chromosomal partners. This will help to protect the partners
condition becomes 44 + XXY. from contagious disease like STDs.
(iii) Such men are usually sterile because their Q.12. Answer in brief:
reproductive organs are not well developed. *(1) Explain Mendel’s monohybrid progeny with
(6) How is the diagnosis for sickle-cell anaemia the help of any one cross.
made? Ans.
Ans. (i) Mendel brought about a cross between two
(i) Under the National Health Mission scheme, pea plants with only pair of contrasting
the ‘Solubility Test’ for diagnosis of sickle-cell characters. This type of cross is called a
anaemia is available at all district hospitals. monohybrid cross.
(ii) Similarly, the confirmatory diagnostic test – (ii) Tall pea plants and dwarf pea plants were used
‘Electrophoresis’ is performed at rural and in this cross. Hence this is parent generation
sub-district hospitals. (P1).
(7) What are the effects of tobacco consumption?
Ans. Mendel’s experiment of the Monohybrid Cross
(i) Smoking of cigarettes and bidis adversely Parental Generation (P1)
affects the process of digestion. Phenotype: Tall Dwarf
(ii) It causes a burning sensation in the throat and Genotype: TT tt
cough. Gametes: T t
(iii) Excessive smoking causes instability and
trembling of fingers. First Filial
(iv) It causes dry cough which leads to
Generation (F1) Tt
sleeplessness.
Phenotype: Tall
(v) Tobacco consumption can lead to shortening
of life span, chronic bronchitis, pericarditis, Parental Generation (P2) Selfing in F1
cancer of the lungs, mouth, larynx (voice box), Phenotype: Tall Tall
pharynx , urinary bladder, lips or tongue. Genotype: Tt Tt
(vi) The nicotine present in tobacco affects the Gametes: T and t T and t
central and peripheral nervous system. Arteries
Male gamete
become hard i.e. it causes arteriosclerosis and Second Filial T t
hypertension. Generation (F2) Female gamete
*(8) Is it right to avoid living with a person T TT (Tall) Tt (Tall)
suffering from a genetic disorder? t Tt (Tall) tt (Dwarf)
Ans.
(i) No, it is not right to avoid living with a person (iii) All the plants produced in F1 generation are
suffering from a genetic disorder. tall, having genotype Tt. This indicates that
Heredity and Variation 107

the gene responsible for tallness in pea plants (iv) When F1 plants are self pollinated, they
is dominant over the gene responsible for produce four types of gamates - RY, Ry, rY, ry.
dwarfness. (v) F2 plants formed by the fusion of four types
(iv) When F1 plants are self pollinated they of male gametes and four types of female
produce second filial generation (F2). gametes, had phenotypes such as round
(v) In F2 generation both tall and dwarf plants yellow, wrinkled yellow, round green and
appeared in the ratio 3 : 1. wrinkled green.
(vi) Also, F2 generation showed nine different
(vi) Thus, the genotypic ratio of F2 generation is
types of genotypes such as RRYY, RRYy, RRyy,
3 (Tall) : 1 (Dwarf) and the genotypic ratio is
RrYY, RrYy, Rryy, rrYY, rrYy, rryy.
1 TT : 2 Tt : 1 tt.
(vii) Phenotypic ratio of dihybrid cross is
(2) Explain Mendel’s dihybrid ratio with the 9 : 3 : 3 : 1
help of any one cross.
Round Wrinkled Round wrinkled
Ans. Yellow Yellow Green Green
(i) In dihybrid cross, Mendel considered two (viii) The genotypic ratio of dihybrid cross is
pairs of contrasting characters.
1 : 2 : 1 : 2 4 :
(ii) He made a cross between a pea plant producing
RRYY RRYy Rryy RrYY RrYy
rounded and yellow couloured seeds and a
pea plant with wrinkled and green coloured 2 : 1 : 2 : 1
seeds. Rryy rryy rrYy rryy
Mendel’s experiment of the Monohybrid Cross
*(3) What is meant by chromosome? Explain its
Parental Generation (P1) types.
Phenotype: Rounded-yellow seeds Wrinkled-green seeds Ans.
Genotype: RRYY rryy (i) The structure in the nucleus of cells that
Gametes: RY ry carries the hereditary characteristics is called
the chromosome.
First Filial (ii) It is made up mainly of nucleic acids and
Generation (F1) RrYy proteins.
Phenotype: (Rounded-yellow seeds) (iii) Depending upon the position of centromere,
Parental Generation (P2) Selfing in F1 there are four types of chromosomes.
Phenotype: Rounded-yellow seeds Rounded-yellow seeds
Genotype: RrYy RrYy
Arm

Gametes: RY, Ry, rY, ry RY, Ry, rY, ry

Centromere
Second Filial
Generation (F2)
Male gamete Metacentric Sub-metacentric
RY Ry rY ry
Female gamete
RY RRYY RRYy RrYY RrYy
Ry RRYy RRyy RrYy Rryy
rY RrYY RrYy rrYY rrYy
ry RrYy Rryy rrYy rryy
(iii) All the plants produced in F1 generation had Acrocentric Telocentric
rounded yellow seeds. This is because in pea
plants, round shape of seed is dominant over (a) Metacentric: The centromere is exactly at
wrinkled shape and yellow colour of seed is the mid-point in this chromosome, and
dominant over green colour. therefore it looks like the English letter
108 Master Key Science & Technology (Term - II) (Std. IX)

‘V’. The arms of this chromosome are guanine, cytosine and thymine. Adenine and
equal in length. guanine are called as purines while cytosine
and thymine are called as pyrimidines.
(b) Sub-metacentic: The centromere is
somewhere near the mid-point in this (vi) Nucleotides are arranged like a chain in the
chromosome which therefore looks like DNA.
the English letter ‘L’. One arm is slightly (vii) The two threads (strands) of the DNA are
shorter than the other. comparable to the two rails of the ladder
and each rail is made up of alternately joined
(c) Acrocentric: The centromere is near one
molecules of sugar and phosphoric acid.
end of this chromosome which therefore
looks like the English letter ‘j’. One arm is (viii) Each rung of the ladder is a pair of nitrogenous
much smaller than the other. bases joined by hydrogen bonds. Adenine
always pairs with thymine and cytosine
(d) Telocentric: The centromere is right at always pairs with guanine
the end of this chromosome making the
*(5) Express your opinion about the use of DNA
chromosome look like the English letter
fingerprinting.
‘i’. This chromosome consists of only one
arm. Ans.
(i) DNA fingerprinting is the technique in
*(4) Describe the structure of DNA molecule.
which the sequence of the genes in the DNA
Ans.
of a person. i.e., the genome of the person is
identified.
C G
A T (ii) This technique is useful to identify the lineage
C G and to identify criminals because it is unique
G C to every person.
T A
(iii) It is also useful to identify paternity and
C G
T A
maternity disputes etc.
3.4 nm (iv) This technique was developed by Professor of
A T
genetics Sir Alec Jeffreys.
G C
T A (v) A common method of collecting a reference
C G
sample, in the use of a buccal swab. If this is
not available, blood or saliva or hair sample
0.34 nm
G C may be used.
(vi) Just like your actual fingerprint, your DNA
A T
C G
fingerprint is something that you are born
2 nm with. It is unique to you.
(vii) DNA fingerprint is very useful in forensic
(i) In 1953, Watson and Crick proposed a model science.
of the DNA molecule. *(6) Explain the structure, function and types of
(ii) As per their model, two parallel threads RNA.
(strands) of nucleotides are coiled around Ans.
each other to form a double helix structure. (i) Ribonucleic acid (RNA) is an important
This structure can be compared with a coiled nucleic acid of the cell.
and flexible ladder.
(ii) RNA is made up of ribose sugar, phosphate
(iii) Each strand of DNA is made up of many small molecules and four types of nitrogenous bases
molecules known as nucleotide. adenine, guanine, cytosine and uracil.
(iv) Each nucleotide is made up of a molecule of (iii) The nucleotide i.e., smallest unit of the
nitrogen base and phosphoric acid joined to a chain of the RNA molecule is formed by the
molecule of sugar. combination of a ribose sugar, phosphate
(v) There are four types of nitrogen bases-adenine, molecule and one of the nitrogen bases.
Heredity and Variation 109

(iv) Large numbers of nucleotides are bonded (b) Messenger RNA (mRNA): It carries
together to form the macromolecule of RNA. the information for protein synthesis
(v) RNA performs the function of protein from genes (i.e. DNA segment in the cell
synthesis. nucleus) to ribosomes (in the cytoplasm)
(vi) According to function, there are three types of which produce the proteins.
RNA:
(c) Transfer RNA (tRNA): It carries the
(a) Ribosomal RNA (rRNA): It is the
amino acid up to the ribosomes as per the
component of cellular organelle ribosome.
message of the mRNA.
Ribosomes perform the function of
protein synthesis.
*Q.13. Complete the tree diagram below based on the type of hereditary disorders.:

Ans.
Hereditary Disorders

Chromosomal Monogenic Mitochondrial Polygenic

Abnormalities Disorders disorder Disorders
Down syndrome, Albinism, sickle cell anaemia, Leber hereditary Spina bifida (defect of
Turner syndrome, Phenylketonuria, optic neuropathy spinal cord), diabetes, blood
Klinefelter syndrome Hutchinson’s pressure, heart disorders,
disease, Tay-Sachs disease, asthma, obesity, cleft lip, cleft
galactosaemia, cystic fibrosis, palate, constricted
haemophilia, stomach.
night blindness
Q.14. Think about it.
*(1) Do all boys and girls of your class look alike?
Ans. No, all the boys and girls of my class do not look alike. There is a lot of variation among them.
*(2) Think about the following characteristics and note similarities and differences.
Sr. No. Personal characteristics Own Grandfather Grandmother Father Mother

(1) Colour of skin

(2) Shape of face (Round / Oblong)
(3) Height
(4) Colour of eyes
(5) Orientation of thumb
Ans. Students are expected to do this activity on their own.

Q.15. Can you tell? (iii) To understand how a specific trait is expressed,
*(1) How do specific traits or characteristics let us consider plant height as an example.
appear in organisms? (iv) We know that there are growth hormones in
Ans. plants. Increase in height of plants depends
(i) Information necessary for synthesis of a upon the quantity of growth hormones.
particular protein is stored in the DNA. (v) The quantity of growth hormone produced
(ii) The segment of DNA which contains all the by a plant depends upon the efficiency of the
information for synthesis of a particular concerned enzyme.
protein is called a gene for that protein. (vi) Efficient enzymes produce a greater quantity
110 Master Key Science & Technology (Term - II) (Std. IX)

of the hormone due to which the height of the *(4) Why did the characteristic of the Rounded-
plant increases. However, if the enzymes are Yellow seeds alone appear in the F1
less efficient, a smaller quantity of hormone is generation but not the characteristic of the
produced leading to a stunting of the plant. wrinkled-green seeds?
(vii) Thus, the expression of traits is controlled by Ans. Rounded-Yellow seeds is a dominant
the genes . characteristic whereas wrinkled-green seeds
Q.16. Use your brain power! is a recessive characteristic. Therefore only
the characteristic of Rounded-Yellow seeds
*(1) Phenotypic ratio:
appeared in the F1 generation.
(i) Round-Yellow (ii) Wrinkled-Yellow
Q.17. Observe:
(iii) Round-Green (iv) Wrinkled-Green
*(1) Carefully observe your classmate’s earlobes.
Ans. Ans.
(i) Round-Yellow: 9 (ii) Wrinkled-Yellow: 3 (i) Most of the classmates have free earlobes
(iii) Round-Green: 3 (iv) Wrinkled-Green: 1 while very few have attached ear lobes.
Phenotypic ratio: 9 : 3 : 3 : 1 (ii) This shows that in humans free earlobes is
(2) Genotypic ratio: a dominant characteristic whereas attached
(i) RRYY (ii) RRYy (iii) RRyy earlobe is a recessive characteristic.
(iv) RrYY (v) RrYy (vi) Rryy *(2) Irrespective of all of us being humans, what
(vii) rrYY (viii) rrYy (ix) rryy difference do you notice in our skin colour?
Ans.
Ans.
(i) Irrespective of all of us being humans, there
(i) RRYY - 1 (ii) RRYy – 2 (iii) RRyy – 1 is a lot of variation in our skin colour. Some
(iv) RrYY – 2 (v) RrYy – 4 (vi) Rryy – 2 people are light-skinned while some are dark-
(vii) rrYY – 1 (viii) rrYy – 2 (ix) rryy – 1 skinned.
Genotypic ratio: 1 : 2 : 1 : 2 : 4 : 2 : 1 : 2 : 1 (ii) The difference in skin colour is due to the gene
*(3) Show the monohybrid cross between (RR) responsible for production of the pigment
and (rr) and write the phenotypic and melanin.
genotypic ratio of F2 generation. *(3) All of you are in std. IX. Why then are some
students tall and some short?
Ans. Parental Generation (P1)
Ans. Our height is decided by genes. People who
Phenotype: Round Seeds Wrinkled Seeds are tall have genes for tall height whereas
Genotype RR rr people who are short have genes for short
Gametes R r height and hence the variation.
Q.18. Find out.
First Filial Rr *(1) Number of chromosomes in different
Generation (F1) organisms.
Ans.
Phenotype: Round Seeds
Organism No. of Chromosomes
Parental Generation (P2) Selfing in F1
Crab 200
Phenotype: Round Seeds Round Seeds
Maize 20
Genotype: Rr Rr
Gametes: R and r R and r Frog 26
Second Filial Generation (F2) Roundworm 04
Male gamete
R r Potato 48
Female gamete Human 46
R RR (Round) Rr (Round Dog 78
r Rr (Round) rr (Wrinkled) Elephant 56
Phenotypic ratio : 3 Round : 1 Wrinkled Fruit fly 08
Genotypic ratio : 1 RR : 2 Rr : 1 rr Mango 40
Heredity and Variation 111

ASSIGNMENT - 16
Time : 1 Hr. Marks : 30

Q.1. (A) Fill in the blanks: (2)

(1) Hereditary characters are transferred from parents to offsprings by hence they are said to
be the structural and functional units of heredity.
(2) The constricted region on each chromosome is called .
(B) Match the column: (2)
A B C
Leber hereditary 44 + XXY Pale skin,
optic neuropathy white hairs
Diabetes 45 + X Men are
sterile
Albinism Mitochondrial Women are
disorder sterile
Turner syndrome Polygenic This disorder
disorder arises during
development
of zygote
Monogenic Effect on
disorder blood-glucose
level.

(C) Complete the analogy: (1)

(1) 44+X : Turner syndrome : : 44+XXY : .
Q.2. Answer the following questions: (9)
(1) DNA molecules are called Master molecules – Give reason.
(2) Write short note on Down syndrome.
(3) Write short note on monogenic disorders.
Q.3. Answer the following questions: (Any 2) (6)
(1) What are the effects of tobacco consumption?
(2) What is sickle-cell anaemia? Write its symptoms and treatment.
(3) Describe the structure of DNA molecule.
(4) Explain the structure, function and types of RNA.
Q.4. Answer the following: (10)
(1) Explain Mendel’s monohybrid progeny with the help of any one cross.
(2) What is meant by chromosomes? Explain its types.

vvv
17 Introduction to Biotechnology

Points to Remember:
• A group of cells having the same origin, same structure and same function is called tissue.
• Tissues are basically classified into two types – Simple tissues and complex tissues.
• Simple tissues are made up of only one type of cells .Example – Epithelial tissue of animals
and Meristematic tissue of plants.
• Complex tissues are made up of more than one type of cells. Example – Blood of animals,
xylem and phloem of plants.
• Plants and animals have different types of tissues to perform the necessary functions.
• Animal tissues:
- Animal tissues are of four types – Epithelial tissue, connective tissue, muscular tissue,
nervous tissue.
- Protective coverings in the animal body are called epithelial tissues. Cells in this tissue are
closely packed and form continuous layers.
- The skin, mucous layer of the mouth cavity, inner surface of blood vessels, walls of the
alveoli, etc. are made up of epithelial tissues.
- The different types of epithelial tissues are Squamous epithelium, Stratified squamous
epithelium, Glandular epithelium, Columnar epithelium, Ciliated epithelium, Cuboidal
epithelium.
- Tissues which join different parts of the body are called connective tissues. The different
types of connective tissues are blood, lymph, areolar tissue, adipose tissue, cartilage, bones,
tendons and ligaments.
- Muscular tissues are made up of long cells called muscle fibres. The different types of
muscular tissues are striated muscles, non-striated muscles and cardiac muscles.
- Nervous tissue enables us to respond to stimuli like touch, sound, odour, colour,etc.
• Plants tissues:
- Plant tissues are of two types – Meristematic tissue and Permanent tissue.
- Meristematic tissue is present in specific parts of a plant where growth occurs.
- Meristematic tissues are of three types – Apical meristem, intercalary meristem and lateral
meristem.
- After their growth is complete, new cells formed by division of meristematic tissue lose
their ability to divide and start to perform a specific function at specific place. Thus, they
permanently acquire a specific structure, shape and location and perform a specific function.
This is called as differentiation and permanent tissues are formed from these differentiated
cells.
- There are two types of permanent tissues – simple permanent and complex permanent
tissue.
- Simple permanent tissues are made up of only one type of cells. According to function

(112)
Introduction to Biotechnology 113

they are of following types – Parenchyma, collenchyma, sclerenchyma, chlorenchyma and

aerenchyma.
- Complex permanent tissues are made up of more than one type of cells. They are xylem and
phloem.
• The techniques of bringing about improvements in living organisms by artificial genetic
changes and by hybridization for the welfare of human beings is called biotechnology. It
includes the techniques of genetic engineering and tissue culture.
• Ex vivo growth of cells or tissues in an aseptic and nutrient-rich medium is called tissue
culture.
• Genetically modified crops (GM crops) are being produced by introducing changes in DNA
of natural crops. Normally such varieties are not found in nature. Different useful characters
are introduced in such varieties.
• Biotechnology has various applications in the field of floriculture, nurseries and forestry.
• Plantlets of flowering, medicinal, ornamental, vegetable plants and fruit trees can be
produced on a large scale by the tissue culture technique. If sufficient land is available, the
emerging field of agri-tourism would be a good business.
• The businesses that are complementary to agriculture and generate supplementary income
for the farmers are known as agro-complimentary occupations.
• Agro-complimentary occupations include animal husbandry, poultry farming, sericulture,
apiculture, fisheries, pearl culture, etc.
• Animal husbandry involves rearing of cattle for milk production and using cattle as help in
farming operations.
• Poultry-farming is the rearing of chickens for eggs and meat. Chickens reared for eggs are
called layers whereas the chickens reared for meat are called broilers.
• Sericulture is the rearing of silkworms (moths) for silk production.

of cells.
MASTER KEY QUESTION SET - 17
(9) performs the function of secretion of
Q.1. (A) Fill in the blanks: sweat, oil, mucus, etc.
(1) We can perform movements due to contraction (10) epithelium bears minute hair-like
and relaxation of . processes.
(2) In , most of the tissues are of the type (11) is the fluid oozed out of blood
that give support. capillaries, contains leucocytes and liquid
ground substance.
(3) Most of the tissues of are made up of
living cells. (12) The cells of tissue are filled with fat
droplets.
(4) Blood is a type of tissue.
(13) lubricates the surface of bones, gives
(5) Cells in tissue are closely packed
support and shape to organs.
and form continuous layers.
(14) Muscular tissues are made up of long cells
(6) Any material that enters the body first
called .
encounters tissue.
(15) are cylindrical, uninucleate and
(7) Cells of epithelial tissue are separated from
branched.
the cells of the other underlying tissues by a
. (16) tissue enables us to respond to
stimuli.
(8) In epithelium, there are many layers
114 Master Key Science & Technology (Term - II) (Std. IX)

(17) Numerous, small, branched fibres arising (30) layers (31) broilers (32) Bombyx mori
from the cell body of the nerve cell are called (33) mulberry (34) tissue (35) differentiation
.
Q.2. Rewrite the following statements by
(18) To bring about plant growth is the main selecting the correct options given below:
function of tissue.
(1) Protective coverings in the animal body are
(19) increases girth (diameter) of root called tissues.
and stem.
(a) meristematic (b) muscular
(20) helps in support, storage of food (c) epithelial (d) bone
and filling vacant spaces in plants.
(2) Epithelial tissue is present in .
(21) gives support and flexibility to
(a) skin
various parts of the plant.
(b) inner surface of blood vessels
(22) The cell wall of sclerenchyma cells contain
(c) walls of the alveoli
.
(d) all of these
(23) Some cells in the body of living organisms
are that is if provided a proper (3) helps in selective transport of substances.
environment, a new organism can grow from (a) Squamous epithelium
these cells. (b) Stratified epithelium
(24) Biotechnology includes the techniques of (c) Cuboidal epithelium
and . (d) Columnar epithelium
(25) Ex vivo growth of cells or tissues in an aseptic (4) helps in secretion of digestive juice,
and nutrient-rich medium is called . absorption of nutrients.
(26) crops are being produced by (a) Glandular epithelium
introducing changes in DNA of natural crops.
(b) Columnar epithelium
(27) is an example of genetically modified
(c) Cuboidal epithelium
rice crop.
(d) Ciliated epithelium
(28) The epidermis of stem and leaves is covered
by a waxy layer of . (5) epithelium is present in the inner
surface of respiratory tract.
(29) Genetically modified cotton is called .
(a) Stratified (b) Columnar
(30) Chickens raised for eggs are called .
(c) Ciliated (d) Cuboidal
(31) Chickens raised for meat are called .
(6) supports internal organs.
(32) is the most commonly used variety
of silkworm for sericulture. (a) Areolar tissue (b) Adipose tissue

(33) Larvae of silkworm feed on leaves. (c) Lymph (d) Tendon

(34) A group of cells having the same origin, same (7) tissue helps in insulation, supply of
structure and same function is called . energy, storage of fats.

(35) When cells acquire a specific structure, shape (a) Areolar tissue (b) Adipose tissue
and location and perform a specific function, (c) Muscular tissue (d) Epithelial tissue
it is called . (8) Bones consist of osteocytes embedded in solid
Ans. (1) muscles (2) plants (3) animals (4) connective ground substance made up of .
(5) epithelial (6) epithelial (7) fibrous membrane (a) calcium bicarbonate
(8) stratified (9) glandular epithelium (10) Ciliated (b) calcium carbonate
(11) Lymph (12) Adipose (13) Cartilage (14)
(c) calcium phosphate
muscle fibres (15) Cardiac muscles (16) Nervous
(17) dendrites (18) meristematic (19) Lateral (d) calcium sulphate
meristem (20) Parenchyma (21) Collenchyma (9) connect muscles to bones.
(22) lignin (23) totipotent (24) genetic engineering, (a) Ligaments (b) Tendons
tissue culture (25) tissue culture (26) Genetically (c) Cartilage (d) Nerves
modified (27) Golden rice (28) cuticle (29) BT cotton
Introduction to Biotechnology 115

(10) join two bones to each other. (22) Cuboidal epithelium is found in .
(a) Cartilage (b) Tendons (a) inner surface of mouth, blood vessels
(c) Ligaments (d) Muscles (b) inner layer of skin
(11) meristem increases the length of (c) tubules of kidney, salivary gland
root and stem. (d) inner surface of respiratory tract
(a) Intercalary (b) Apical (23) Which of the following is an exotic variety of
(c) Lateral (d) Permanent cow?
(12) helps in growth of branches, formation (a) Plymouth Rock
of leaves and flowers. (b) New Hampshire
(a) Lateral meristem (b) Apical meristem (c) Black Rock
(c) Intercalary meristem (d) Xylem (d) Brown Swiss
(13) tissue is present in the hard coat of Ans. (1) epithelial (2) all of these (3) Squamous
seeds, outer covering of coconut. epithelium (4) Columnar epithelium (5) Ciliated
(a) Parenchyma (b) Xylem (6) Areolar tissue (7) Adipose tissue (8) calcium
phosphate (9) Tendons (10) Ligaments (11) Apical
(c) Collenchyma (d) Sclerenchyma
(12) Intercalary meristem (13) Sclerenchyma (14)
(14) The cells of tissue are dead. Sclerenchyma (15) Frederick Campion Steward
(a) Parenchyma (b) Collenchyma (16) MON 810 (17) Holstein (18) Leghorn (19)
(c) Sclerenchyma (d) All of these Aseel (20) Cochin (21) in nose, ear, larynx,trachea
(15) showed that cells and tissues can be (22) tubules of kidney, salivary gland (23) Brown
grown ex vivo. Swiss
(a) Frederick Campion Steward Q.3. Name the following:
(b) Gregor Johann Mendel * (1) Tissue lining inner surface of the mouth.
(c) Frederick Miescher Ans. Squamous epithelium.
(d) Robert Brown * (2) Tissue joining muscles and bones.
(16) is an example of genetically modified Ans. Tendon
maize.
* (3) Tissue responsible for increasing the height
(a) Vaishali (b) Vistive Gold of plants.
(c) MON 810 (d) Amflora
Ans. Apical meristem.
(17) is an exotic variety of cow.
* (4) Tissue responsible for increasing the girth of
(a) Holstein (b) Gir stem.
(c) Sahiwal (d) Dangi Ans. Lateral meristem.
(18) is a layer chicken. (5) Tissue responsible for growth of branches,
(a) Brahma (b) Leghorn formation of leaves and flowers.
(c) Cochin (d) Aseel Ans. Intercalary meristem.
(19) is a broiler chicken. (6) Tissue that helps in insulation, supply of
(a) Leghorn (b) Lehman energy, storage of fats.
(c) Aseel (d) Minorca Ans. Adipose tissue.
(20) is a broiler chicken. (7) Tissue present in outer layer of skin.
(a) Minroca (b) Ancona Ans. Glandular epithelium.
(c) Leghorn (d) Cochin (8) Tissue present in nose, ear, larynx, trachea.
(21) Cartilage is found . Ans. Cartilage.
(a) all around the cells in body (9) Dead cells in xylem.
(b) in nose, ear, larynx, trachea Ans. Tracheids, vessels and xylem fibres.
(c) between the muscles and skin (10) Living cells in xylem.
(d) around the blood vessels Ans. Xylem parenchyma.
116 Master Key Science & Technology (Term - II) (Std. IX)

(11) Living cells in phloem. Q.5. State whether the following statements are
Ans. Sieve tubes, companion cells, phloem true or false and if false, rewrite the correct
parenchyma. statement:
(12) Dead cells in phloem. * (1) Simple squamous epithelium is present in
respiratory tract.
Ans. Phloem fibres.
Ans. False. Ciliated columnar epithelium is present
(13) GM crops.
in respiratory tract.
Ans. BT cotton, Amflora, Golden Rice.
* (2) Glandular epithelium is present in kidneys.
(14) Local Indian varieties of cow.
Ans. False. Cuboidal epithelium is present in
Ans. Sahiwal, Sindhi, Lal kandhari, Devni, Khillari, kidneys.
Dangi.
* (3) Chlorenchyma helps the plant to float in
(15) Exotic varieties of cow. water.
Ans. Jersey, Brown swiss, Holstein. Ans. False. Aerenchyma helps the plant to float in
(16) Layers. water.
Ans. Leghorn, Minorca, Ancona, Lehman. * (4) Striated muscles are also called involuntary
(17) Broilers. muscles.
Ans. Brahma, Long, Cochin, Aseel. Ans. False. Striated muscles are also called
(18) Chickens reared for both eggs and meat. voluntary muscles.
Ans. Rhode Island Red, New Hampshire, Plymouth * (5) Chloroplast is present in permanent tissues.
Rock, Black Rock. Ans. False. Chlorenchyma is present in
chlorenchyma tissue.
Q.4. Match the columns:
(6) Lateral meristem increase girth(diameter) of
(1) Column ’A’ Column ’B’ the root and stem.
(1) Squamous (a) Secretion of digestive Ans. True.
epithelium juice (7) Due to use of seeds of GM crops there is
(2) Cuboidal (b) Selective transport of decrease in nutritive value and increase in
epithelium substances loss of crops.
(3) Columnar (c) Protection of organs Ans. False. Due to use of seeds of GM crops there is
epithelium improvement in nutritive value and decrease
(4) Stratified (d) Secretion of saliva in loss of crops.
epithelium (8) In a bioreactor, cells can be grown in a
Ans. (1 - b), (2 - d), (3 - a), (4 - c) more nutritive medium and protected from
pathogens.
(2) Column ’A’ Column ’B’ Ans. True.
(1) Brahma (a) Local variety of cow (9) Rare and endangered plants can be grown
(2) Jersey (b) Layer chicken by tissue culture and can be protected from
(3) Devni (c) Exotic variety of cow extinction.
(4) Lehman (d) Broiler chicken Ans. True.
(10) The silk thread is formed from the secretion
Ans. (1 - d), (2 - c), (3 - a), (4 - b) of the sweat glands of silkworm.
(3) Column ’A’ Column ’B’ Ans. False. The silk thread is formed from the
secretion of the salivary glands of silkworm.
(1) Potato (a) Vistive Gold
(11) Rhode Island Red, New Hampshire,
(2) Maize (b) Amflora
Plymouth Rock, Black Rock are varieties of
(3) Soybean (c) Vaishali chicken reared for both eggs as well as meat.
(4) Tomato (d) MON 863
Ans. True.
Ans. (1 - b), (2 - d), (3 - a), (4 - c) (12) Phloem consists of thick-walled dead cells.
Introduction to Biotechnology 117

Ans. False. Phloem consists of living cells (3) Respiratory tract : Ciliated columnar epithelium
containing cytoplasm. :: Kidney tubules : ................... .
(13) Stratified squamous epithelium is present in (4) Outer layer of skin : Stratified epithelium :: Inner
inner surface of mouth, oesophagus, blood layer of skin : .................... .
vessels and alveoli. (5) Muscular tissue : Movement :: Nervous tissue :
Ans. False. Stratified squamous epithelium is ............. .
present in the outer layer of skin. (6) Tendons : Join muscles to bones :: Ligaments :
(14) Broiler chickens are raised for eggs. .............. .
Ans. False. Broiler chickens are raised for meat. Ans. (1) Columnar epithelium (2) Secretion of saliva
(15) Non-striated muscles bring about contraction (3) Cuboidal epithelium (4) Glandular epithelium
and relaxation of heart. (5) Conduction of excitation (6) Join two bones to
Ans. False. Cardiac muscles bring about contraction each other
and relaxation of heart. Q.8. Distinguish between:
Q.6. Find the odd man out: * (1) Simple Tissue in plants and Complex tissues
* (1) Epithelium, muscle fibre, nerve fibre, in plants
epidermis. Complex Tissues in
Simple Tissue in plants
Ans. Epidermis. It is a plant tissue whereas the plants
others are animal tissues. (1) They are made up of (1) They are made up of
(2) Cell body, muscle fibre, axon, dendrites. only type of cells. more than one type
Ans. Muscle fibre. It is a muscle cell whereas the of cells.
others are parts of nerve cell. (2) They are found in all (2) They are found in
(3) Tracheids, vessels, companion cells, xylem parts of the plant. the vascular regions
fibres. of the plant.
Ans. Companion cells. It is an element of phloem (3) They perform (3) They mainly
whereas the others are elements of xylem. different functions perform the function
* (4) Bone, Cartilage, Tendon, Cardiac muscle. like storage of food, of conduction of
Ans. Cardiac muscle. It is a muscular tissue support, giving water and food.
whereas the others are connective tissues. strength etc.
(5) Sieve tubes, tracheids, phloem parenchyma, (4) Examples – (4) Example – Xylem
phloem fibres. Parenchyma, and phloem.
Ans. Tracheids. It is an element of xylem whereas Collenchyma,
the others are elements of phloem. Sclerenchyma.
(6) Holstein, Brown swiss, Bombyx mori, Jersey.
(2) Xylem and Phloem
Ans. Bombyx mori. It is a variety of silkworm
whereas the others are varieties of cows. Xylem Phloem
* (7) Xylem, Phloem, Permanent tissue, Merstematic (1) Consists of mostly (1) Consists of mostly
tissue. thick-walled dead living cells containing
Ans. Meristematic tissue. It has the ability to cells. cytoplasm.
divide whereas the others have lost the ability
(2) The types of cells (2) The types of cells
to divide.
include dead cells- include living
Q.7. Complete the analogy: tracheids, vessels cells – Sieve tubes,
(1) Inner surface of mouth : Squamous epithelium :: and xylem fibres companion cells,
Inner surface of intestine : ................ and living cells – phloem parenchyma
(2) Glandular epithelium : Secretion of sweat, oil :: Xylem parenchyma. and dead cells –
Cuboidal epithelium : .................. . phloem fibres.
118 Master Key Science & Technology (Term - II) (Std. IX)

Q.9. Write short notes:

(3) Structure like (3) Tubes joined to
interconnected each other, conduct * (1) Meristematic tissue:
tubes, conduct water sugar and amino Ans.
and minerals only in acids from leaves (i) Meristematic tissue is present in specific parts of
upward direction. to various parts in a plant where growth takes place.
both upward and (ii) Cells of meristematic tissue contain thick
downward direction. cytoplasm, a conspicuous nucleus and a thin cell
(3) Striated muscles and Non-striated muscles. wall and are compactly packed together.
(iii) Vacuoles are usually absent in these cells and
Striated muscles Non-striated muscles they are highly active.
(1) Muscle cells are (1) Muscle cells are short, (iv) The main function of meristematic tissue is to
long, cylindrical, spindle-shaped, bring about plant growth.
multinucleate and uninucleate and (v) According to the location, meristematic tissues
have no branches. have no branches. are of three types: Apical meristem, intercalary
meristem and lateral meristem.
(2) There are alternate (2) Dark and light
* (2) Xylem:
dark and light bands bands are absent.
on these muscles and Not attached to Ans.
they are attached to bones. (i) Xylem is a complex permanent tissue in plants.
bones. (ii) It consists of thick-walled dead cells.
(3) They move as per (3) They are not under (iii) The type of cells in xylem are trachieds, vessels,
our will, hence they the control of our xylem fibres (dead cells) and xylem parenchyma
are called voluntary will hence they are (living cells).
muscles. called involuntary (iv) Its structure is like interconnected tubes conduct
muscles. water and minerals only in upward direction.
(4) These muscles bring (4) These muscles bring * (3) Striated Muscles:
about movements about movement Ans.
of arms and legs, of eye lids, passage (i) The cells of striated muscles are long, cylindrical,
running, speaking of food through multinucleate and have no branches.
etc. alimentary canal,
(ii) These are alternate dark and light bands on
contraction and
these muscles.
relaxation of blood
vessels etc. (iii) As they are attached to bones, they are also
called skeletal muscles.
(4) Cartilage and Bone (iv) They move as per our will, hence they are
Cartilage Bone called voluntary muscles.
(v) Striated muscles bring about movements of
(1) They are present in (1) They form the
arms and legs, running, speaking etc.
nose, ear, larynx, skeleton of the body.
trachea. * (4) Agro-complementary business:
Ans.
(2) They contain cells (2) They contain
(i) The business that are complementary to
supported by osteolytes embedded
agriculture and generate supplementary
fibrous, flexible, in solid ground
income for the farmers are called agro-
jelly – like ground substance made up of
complementary business.
substance. calcium phosphate.
(ii) These include:
(3) Lubricates the surface (3) Supports and protects (a) Animal Husbandry: It is practiced for milk
of bones, gives support different organs, helps production and for using the cattle as help in
and shape to organs. in movement. farming operations. e.g. cows and buffaloes
Introduction to Biotechnology 119

are raised for milk whereas bulls and male (viii) The silk thread is formed from the secretion of
buffaloes for pulling heavy loads. their salivary glands.
(b) Poultry farming: It is the rearing of egg and (ix) Larvae spin this thread around themselves to
meat yielding chickens. Chickens raised for form a cocoon. The cocoon may be spherical in
eggs are called layers while those raised for nature.
meat are called broilers. (x) Ten days before the pupa turns into an adult, all
(c) Sericulture: It is the rearing of silkworms the cocoons are transferred into boiling water.
(moths) for silk production. The silk fibres (xi) Due to the boiling water, the pupa dies in the
obtained are processed, reeled and then cocoon and silk fibres become loose.
woven into fabric. (xii) These fibres are unwound, processed and
* (5) Genetic engineering: reeled. Various kinds of fabric is woven from silk
Ans. threads.
(i) Genetic engineering is the deliberate (7) Animal husbandry.
modification of the characteristics of an organism Ans.
by manipulating its genetic material. (i) In India, animal husbandry is practiced for milk
(ii) An organism that is generated through genetic production and for using the cattle as help in
engineering is called a genetically modified farming operations.
organism (GMO). (ii) Example – Cows and buffaloes are raised for
(iii) Genetic engineering is applied in many fields like milk and bulls and male buffaloes for pulling the
research, agriculture, industrial biotechnology heavy loads.
and medicine. (iii) Local Indian varieties of cows like Sahiwal,
(iv) In agriculture, genetic engineering is used in Sindhi, Gir, Lal kandhari, Devni, Khillari, Dangi,
the production of cash crops, improvement etc. and exotic varieties like Jersey, Brown swiss,
in varieties of cash crops, increase in ability of Holstein, etc. are kept for their milk.
plants to withstand environmental stresses. (iv) Proper care of cattle is necessary for a clean and
(v) In medicine, genetic engineering is used for high yield of milk which includes:
vaccine production, early diagnosis of congenital (a) A balanced diet i.e. all constituents of food
disease, organ transplant, cancer research, should be given to cattle. It must include fibre-
production of artificial skin, cartilage etc. in rich coarse food, fodder, and sufficient water.
laboratories.
(b) The cattle-shed should be clean and dry with
* (6) Sericulture: proper ventilation and a roof.
Ans. (c) Cattle should be regularly vaccinated.
(i) Sericulture is the rearing of silkworms (moths) (8) Poultry farming.
for production of silk.
Ans.
(ii) Bombyx mori is the most commonly used variety
(i) Rearing of egg and meat yielding chickens is
of silkworm for this purpose.
called poultry farming.
(iii) The life cycle of silkworm consist of four stages
(ii) Chickens raised for laying eggs are called
namely egg, larva, pupa and adult.
layers . e.g. Leghorn, Minorca, Ancona, Lehman.
(iv) Thousands of eggs deposited by female
(iii) Chickens raised for meat are called broilers. e.g.
moths are incubated artificially to shorten the
Brahma, Long, Cochin, Aseel.
incubation period.
(iv) Rhode Island Red, New Hampshire, Plymouth
(v) Larvae hatching out of eggs are released on
Rock, Black Rock are varieties of chicken reared
mulberry plants.
for both eggs as well as meat. R
(vi) Larvae are nourished by feeding on mulberry
(v) The objectives behind development of new
leaves.
hybrid varieties from a cross between Indian
(vii) After feeding for 3-4 days, larvae move to varieties like Aseel and exotic varieties like
branches of mulberry plant. Leghorn are to produce good quality chickens
120 Master Key Science & Technology (Term - II) (Std. IX)

in large numbers, to develop the ability to Ans.

withstand high temperature , to use by-products (i) The term livestock refers to animals reared for
of agriculture as poultry feed etc. profit or for use.
Q.10. Answer the following: (ii) Sheep provides us with wool, skin, meat and
* (1) Explain the meaning of biotechnology and milk.
its impact on agricultural management with (iii) Therefore, rearing of sheep is a livestock.
suitable examples. (4) Blood is a complex tissue – Give reason.
Ans. The techniques of bringing about Ans.
improvements in living organisms by artificial (i) A complex tissue is made up of more than one
genetic changes and by hybridization for the type of cells.
welfare of human beings, are together called
(ii) In blood, cells of different types, colour and
biotechnology.
shapes are mixed together.
Impact of biotechnology on agricultural
(iii) Blood contains erythrocytes (RBCs), leucocytes
management:
(WBCs) and platelets in a liquid plasma.
(i) Genetically modified crops (GM crops) are
(iv) Therefore, blood is a complex tissue.
being produced by introducing changes in
DNA of natural corps. Normally, such varieties (5) Explain the different types of muscular
are not found in nature. Thus, new varieties tissues.
are produced artificially. Different useful Ans.
characters are introduced in such varieties. Striated Non-Striated Cardiac
(ii) Some naturally occurring varieties cannot muscles muscles muscles
withstand environmental stress like frequently
changing temperature, wet and dry famines,
changing climates etc. However, GM crops
can grow in any of such adverse conditions.
(iii) As GM crops are resistant to insect pests,
pathogens, chemical weedicides, etc. the use
of harmful chemicals like pesticides can be Nucleus Nucleus Striations
Nucleus
avoided. Striations
(iv) Due to use of seeds of GM crops, there is Muscle cells are Muscle cells Muscle cells
improvement in nutritive value and decease long, cylindrical, are short, are cylindrical,
in loss of crops. multinucleate spindle-shaped, uninucleate
* (2) Which two main techniques are used in and have no uninucleate and and branched.
biotechnology? Why? branches. have no branches.
Ans. Structure: Structure: Structure:
(i) The two main techniques used in biotechnology There are Dark and light Dark and
are – Genetic engineering and tissue culture. alternate dark bands are absent. light bands
(ii) These techniques are used to bring about and light Not attached are present.
improvements in living organisms by artificial bands on these to bones. Their The heart is
genetic changes and by hybridization for the muscles. As they movements made of these
welfare of human beings. are attached are not under muscles. Their
(iii) Its uses are in the production of cash crops, to bones, they the control of movements
improvement in varieties of cash crops, are also called our will, hence are not under
early diagnosis of congenital diseases, organ skeletal muscles. they are called the control
transplant, cancer research, production of They move as involuntary of our will.
artificial skin, cartilage etc. in laboratories. per our will, muscles. They They contract
hence they are are present in the and relax
* (3) Rearing of sheep is a livestock. Justify this
called voluntary alimentary canal, rhythmically.
statement.
muscles. blood vessels, etc.
Introduction to Biotechnology 121

Function: Function: Function: Ans.

These muscles Movements Contraction (i) In agritourism, plantlets of flowering,
bring about of eye lids, and relaxation medicinal, ornamental, vegetable plants and
movements passage of of the heart. fruit trees are produced on a large scale by
of arms and food through tissue culture technique.
legs, running, alimentary (ii) By growing some of the plants fully, an
speaking etc. c a n a l , agritourism centre can be developed.
contraction and (iii) If sufficient land is available, the emerging
relaxation of field of agritoursim would be a good business.
blood vessels. (iv) An agritourism centre consists of following:
(6) Explain the types of complex permanent (a) Mango, chikoo (sapota), guava, coconut,
tissues. custard apple and some other regional
Ans. fruit trees.
Name (b) Shade giving local or exotic attractive
of Xylem Phloem plants.
tissue (c) Ornamental and flowering plants.
Figure (d) Butterfly garden.
(e) Medicinal plant garden.
Tracheid Sieve tube
Vessel Companion (f) Organic vegetables and fruits.
element cell
(v) People visit places with such attraction in
Xylem Phloem
large numbers.
(vi) Selling plantlets/seedlings, fruits, vegetables
at such places can be quite profitable.
Charac- Consists of thick- Consists of cytoplasm
teristics walled dead cells containing living *(2) Define the term tissue and explain the
cells. concept of tissue culture.
Ans. A group of cells having the same origin, same
Types of Trachieds, vessels Sieve tubes, structure and same function is called tissue.
cells and xylem fibres - companion cells,
Concept of tissue culture:
dead cells. Xylem phloem parenchyma
parenchyma - living - living cells. Phloem (i) Ex vivo growth of cells or tissues in an aseptic
cells. fibres - dead cells. and nutrient-rich medium is called tissue
culture.
Function Structure like Tubes joined (ii) Nowadays, a complete organism can be
interconnected to each other, developed from a single cell or from tissue
tubes, conduct conduct sugar and with the help of the tissue culture technique.
water and minerals amino acids from
(iii) A liquid, solid or gel-like medium prepared
only in upward leaves to various
from agar, which supplies nutrients and
direction. parts in upward
energy necessary for tissue culture is used in
and downward
this technique.
direction
(iv) Tissue culture can be used to grow plants
Q.9. Answer in brief: on a large scale, which bear flowers, fruits of
* (1) Discuss agritourism in class and write a excellent quality, in shorter durations and are
project on an agritourism centre nearby. disease free.
Present it in the class in groups. (v) The various processes involved in tissue
culture are:
122 Master Key Science & Technology (Term - II) (Std. IX)

Secondary
hardening Bulb corm of
source plant

Source plant

Primary
Primary
hardening
treatment

Shooting and
rooting

Reproduction /
Multiplication
(3) Write the location, structure and function of following epithelial tissues:
(i) Squamous epithelium (ii) Stratified epithelium (iii) Glandular epithelium
(iv) Columnar epithelium (v) Ciliated epithelium (vi) Cuboidal epithelium
Ans.
Name Appearance
Location Structure Function
(diagrammaric)
Squamous Inner surface of Thin, small, flat cells Selective transport of
epithelium mouth, oesophagus, form semipermeable substances.
blood-vessels, alveoli membrane.

Startified Outer layer of skin Many layers of cells Prevention of

epithelium wearing of organs,
protection of organs.
Introduction to Biotechnology 123

Glandular Inner layer of skin, Cells contain Secretion of sweat,

epithelium etc. vesicles packed with oil (sebum), mucus
secretory material. etc.

Columnar Inner surface Column-like tall cells. Secretion of digestive

epithelium (mucosa) of intestine, Upper free surface juice, absorption of
alimentary canal. bears folds made of nutrients.
these cells at places of
absorption.

Ciliated Inner surface of Upper free surface Push mucus and air
epithelium respiratory tract. of cells bears minute forward to keep the
hair-like processes. air passage free.

Cuboidal Tubules of kidney Cells are cuboidal Reabsorption of

epithelium (nephron), salivary useful materials from
gland. urine, secretion of
saliva.

(4) Write the structure and function of following connective tissues:

(i) Blood (ii) Lymph (iii) Areolar tissue (iv) Adipose tissue
(v) Cartilage (vi) Bones (vii) Tendons and ligaments
Ans. Types of connective tissue:
Appearance
Type Location Structure Function
(diagrammatic)
Blood Closed circulatory E r y t h r o c y t e s , Transport of oxygen
system leucocytes and platelets nutrients, hormones
in a liquid plasma. and waste.

Lymph All around the cells in Fluid oozed out of Protection of body
the body. blood capillaries, from infections.
contains leucocytes
and liquid ground
substance.
Areolar Between the skin and Different types of cells Supports internal
tissue muscles, around blood loosely arranged and organs.
vessels. supported by a jelly-
like ground substance
and elastic fibres.
124 Master Key Science & Technology (Term - II) (Std. IX)

Adipose Below the skin and Cells filled with fat Insulation, supply of
tissue around internal droplets, jelly-like energy, storage of fats.
organs. ground substance.

Cartilage Nose, ear, larynx Cells supported by Lubricates the surface

trachea fibrous, flexible Jelly- of bones, gives support
like ground substance. and shape to organs

Bones Skeleton (A specific Osteocytes embedded Supports and protects

structure extending in solid ground different organs, helps
throughout the body) substance made up of in movement.
calcium phosphate

Tendons At the joints Tendons: fibrous, Tendons: join

and strong, less elastic muscles to bones.
ligaments Ligaments: strong and Ligaments: join two
highly flexible. bones to each other

(5) Describe the structure of nervous tissue with (i) Nervous tissue enables us to respond to
the help of a neat labelled diagram. stimuli like touch, sound, odour, colour, etc.
Ans. (ii) Cells of the nervous tissue are specifically
made to become excited and conduct the
Nucleus
excitation from one part of the body to another.
(iii) The main part of the nerve cell is the cell body
which contains the cytoplasm and the nucleus.
(iv) Numerous, small, branched fibres called
Nerve cell
dendrites arise from the cell body.
(v) One of the fibres, is extremely long and is
called the axon.
Dendrites (vi) The length of the nerve cell may be up to one
metre.
Cell body (vii) Many nerve cells are bound together with the
help of connective tissue to form a nerve.
(viii) Nervous tissue is present in the brain, spinal
cord and the network of nerves spread all
throughout the body.
Axon (ix) In most animals, action in response to a stimulus
occurs due to the integrated functioning of the
nervous tissue and muscular tissue.
(6) Explain the location and functions of
meristematic tissues.
Introduction to Biotechnology 125

Ans: Sub- Chlorenchy-

Figure Location Function types ma: Leaves,
Apical I n c r e a s e s performs
meristem: the length photosyn-
At the tip of the root thesis.
of the root and stem. Aerechyma:
and stem Helps aquat-
Intercalary Growth of ic plants,
meristem: branches, leaves and
At the formation of stem to float.
base of the leaves and (8) Write down the applications of biotechnology
petiole of flowers. (tissue culture) in floriculture, nurseries and
leaves and forestry.
of branches. Ans. Applications of biotechnology (tissue culture)
Lateral I n c r e a s e s in floriculture, nurseries and foresty:
meristem: girth (di- (i) Tissue culture can be used to grow those
L a t e r a l ameter) of plants on a large scale, which bear flowers,
sides of the root fruits of excellent quality.
root and and stem.
(ii) Fully grown plants can be produced in shorter
stem.
durations.
(7) Explain the types of simple permanent
(iii) Plants can be grown on a large scale even if
tissues in plants.
means of pollination or germinating seeds are
Ans. Types of simple permanent tissues. not available. For example, orchids or pitcher
Name plant do not germinate but these plants can
of Parenchyma Collenchyma Sclerechyma easily be produced by means of tissue culture.
Tissue (iv) In a bioreactor, cells can be grown in a
Figure Inter-cellular spaces Vacuole
Vacuole Simple pit pair more nutritive medium and protected
from pathogens. Bioreactors are useful for
producing plantlets on a very large scale.
Vacuole Cell wall Lumen (cavity) (v) Large number of seedlings/plantlets can be
Lignified thick
Chloroplasts
cell wall produced in a short time using minimum
resources and materials.
Struc- Living cells E l o n g a t e d Dead and
ture of with thin living cells f i b r o u s (vi) Usually, plants produced by tissue culture and
cells cell wall and with thickened cells with genetic modification techniques are disease-
intercellular cell wall at tapering free. Plantlets produced by tissue culture
spaces. corners due to ends, cell technique of the meristem are virus-free.
cellulose and wall contains (vii) Embryos produced using conventional
pectin. lignin. hybridization technique between two or more
Loca- All parts At the Stem, veins varieties may not grow fully for some reasons.
tion like roots, base of leaf of leaves, However, embryos produced by tissue culture
stem, leaves, petiole, hard coats of technique always complete their growth.
flowers and branches seeds, outer (viii) Rare and endangered plants can be grown
seeds. and stem covering of using tissue culture technique and can thus
coconut. be protected from extinction. Similarly,
Func- S u p p o r t , Support and G i v e various parts and seeds of such plants can be
tions storage of f l e x i b i l i t y strength and preserved by tissue culture and those varieties
food and to various rigidity to can be protected.
filling vacant parts. parts of the
spaces. plants.
126 Master Key Science & Technology (Term - II) (Std. IX)

Q.12. Can you recall? (4) Plants are sedentary. Animals generally
(1) Which components bring about important move from place to
processes in the living organisms? place in search of
Ans. Cells, tissues, organs, organ systems bring out food, shelter and
important processes in living organisms. partners.
(2) Which is the smallest structural and (5) Energy needs of Energy needs of
functional unit of the body of living plants are less. animals are greater.
organisms? (6) Plants can prepare Animals cannot
Ans. Cell is the smallest structural and functional their own food by prepare their own
unit of the body of living organisms. photosynthesis. food. They depend
on plants and other
(3) Which type of muscle is the diaphragm of
animals for their
the respiratory system?
food.
Ans. Diaphragm is a skeletal muscle. It is an
involuntary muscle that regulates breathing, (2) Why we cannot see our organs like the heart,
although some voluntary control can be blood vessels and intestines?
achieved. Ans. We cannot see our organs like the heart, blood
(4) What is the main difference between the vessels and intestines as they are located
growth of animals and plants? inside the body.
Ans. Q.14. Can you tell?
(i) Growth in animals is uniform whereas the (1) Suppose you want to grow a garden like the
growth in plants occurs in specific parts of the one shown in the picture, around your home
body. or school. What would you do to achieve
(ii) Growth in animals occurs for a certain period that? By which methods will you cultivate
of life whereas the growth in plants occur the seedlings?
throughout their life.
(5) Why does the growth of a plant occur only at
specific parts of the plant body?
Ans. Growth of a plant occurs only at specific parts
of the body due to the presence of meristematic
tissues which contain dividing cells.
Q.13. Think about it.
(1) Are the structure and functions of the bodies Ans.
of plants and animals the same?
(i) To grow a garden around the school or home,
Ans. No. The structure and functions of the bodies one must cultivate seedlings of different
of plants and animals are not the same. plants and those seedlings must be watered
Some differences between plants and animals: regularly and nurtured properly.
(ii) Seedlings can be cultivated by the following
Plants Animals
methods:
(1) Plants continue to Animals grow only
grow throughout for a specific period (a) Seed sowing: Seeds are sown, watered
their life. of life. and allowed to germinate.
(2) Growth in plants in Growth in animals is (b) Transplantation: Seeds are sown
not uniform. uniform. somewhere else and then the seedlings
are transplanted in the garden.
(3) Plants have dividing Animals do not have
and non-dividing different dividing (2) You must have seen flowers of same variety
tissues. and non-dividing but of 2 or 3 different colours borne by same
tissues. plant. How is this possible?
Introduction to Biotechnology 127

Ans. Ans. People choose to go to hill stations, beaches,

(i) The different coloured flowers borne by forest resorts and places where there is lot
the same plant are due to the pigments like of greenery to relax when they are tired of
anthocyanins, carotenoids etc. according to crowds and stressful life.
the genetic makeup of the plant. (7) What is the inter-relationship between the
(ii) Also, by using the latest techniques of two questions (5 and 6) above?
biotechnology and tissue culture, it is possible Ans. The inter-relationship between the above two
to manipulate the genes for flower colour and questions is that businesses like agritourism,
get the desired flower colour. ecotourism, forest resorts etc. can fetch a huge
profit as people look for these kind of places to
Q.15. Use your brain power!
relax, to be away from the hustle bustle of city
(1) What keeps the various organs and organ life and feel close to nature.
systems separate from each other? Why?
(8) Why are the cocoons transferred to boiling
Ans. The epithelial tissue keeps the various organs water before the pupa develops into an
and organ systems separate from each other adult?
by forming a layer on the organs.
Ans. Once the pupa develops into an adult, it will
(2) Why are epithelial tissues said to be simple secrete a fluid to dissolve the silk and emerge
tissues? out. Hence the cocoons are transferred to
Ans. Epithelial tissues are said to be simple tissues boiling water before the pupa develops
as they are made up of only one type of cells. in to an adult to kill the silkworms before
(3) Why do slim persons feel more cold in winter transformation is complete.
than those who are obese? Q.16. Observe.
Ans.
(1) Observe the skin of the back of your hand
(i) Below the skin there is a tissue called adipose with the help of a magnifying lens. Do
tissue. you see the closely attached squarish and
(ii) The cells of these tissue are filled with fat pentagonal shapes?
droplets. Ans. Yes, we can see the squarish and pentagonal
(iii) Due to storage of fat, it acts as an insulator and shapes. This is the stratified squamous
helps to retain heat in the body. epithelium present on the outer layer of skin.
(iv) Obese people have more fat deposited in the (2) Observe a permanent slide of blood smear
adipose tissue as compared to slim persons. under a compound microscope. What did
Therefore, slim persons feel more cold in you see?
winter than those who are obese. Ans.
(4) Why can bones not be folded? (i) A permanent slide of blood smear under a
Ans. compound microscope shows different types
(i) Bone cells called osteocytes are embedded in of cells like RBCs, WBCs and platelets.
solid ground substance made up of calcium (ii) The different types of WBCs that can be
phosphate. seen are eosinophils, basophils, neutrophils,
(ii) This makes the bone hard, rigid and non- monocytes and lymphocytes.
flexible. Therefore, bones cannot be folded. (3) Visit a modern cowshed nearby and record
(5) Which other industries can be started as an the following points – The number of
extension of the plant nursery business? cattle, their variety, total milk production,
Ans. Businesses like Agritourism, Ecotourism, cleanliness in cattle-shed, arrangements for
forest resorts and organic fruit garden, yoga health care of cattle.
and meditation centres can be started as an Ans. Students are expected to do this activity on
extension of the plant nursery business. their own.
(6) To which places do people choose to go on Q.17. Find out.
vacation in order to relax when they are tired (1) Collect information about GM varieties
of crowds and stressful life?
128 Master Key Science & Technology (Term - II) (Std. IX)

of crops in your area and make a note of alternative income for the farmers and help to
them. Also find out if there are adverse satisfy the need of food for man.
effects of GM crops on human beings and (4) Find out from the internet the average daily
environment. milk yield from local and exotic varieties of
Ans. Some of the GM crops are: cow.
(i) Maize: MON 810, MON 863 Ans.
(ii) Rice: Golden rice (i) Milk yield from local cow : 12-15 litres/day.
(iii) Brinjal: BT brinjal (ii) Milk yield from exotic cow: 15-30 litres/day.
(iv) Cotton: BT cotton Q.18. Activity based question
Effects of GM Crops on human beings: GM (1) Close your eyes and try to identify different
crops may cause toxicity and allergic reactions objects by feeling them with your hand.
in humans. Why is it possible for you to identify things
Effects of GM Crops on environment: like a note-book, text-book, bench, compass-
(i) GM crops may be toxic to pollinators and non- box, etc. only by touching them?
target species like butterflies. Ans. We can identify objects just by touching them
(ii) Many GM crops may be a threat to soil because of the memory that we retain in
ecosystem as they secrete their toxins into the our brain. The nervous tissue enables us to
soil. respond to the stimuli of touch.
(2) What is meant by white revolution? Who (2) As shown in the figure, place an onion on each
was its pioneer? What benefits did it bring? gas jar in such a way that its base (roots) will
remain dipped in water. Measure and record
Ans.
the length of the roots of both onions on the
(i) White revolution was the programme first, second and third day. On the fourth day,
launched by the National Dairy Development cut off 1 cm of the roots of the onion in flask
Board to increase the milk production in India. B. Measure the length of the roots of both
(ii) Dr. Verghese Kurien was the pioneer of white onions for the next five days and record your
revolution. observations in the following table.
(iii) It transformed India from a milk-deficient
nation to the largest producer of milk. It also
helped the dairy farmers in directing their
own development and empowering them.
It also helped to reduce the malpractices
carried out by milk traders and merchants.
(3) Collect more information about animal
husbandry.
Ans. Length
Day 1 Day 2 Day 3 Day 4 Day 5
(i) The branch of agriculture which deals with (cm)
the feeding, shelter, health and breeding of Flask A
domestic animals is called animal husbandry. Flask B
(ii) It is scientific and systematic management of Ans. (Students are expected to record their
livestock. observation in the given table).
(iii) Animal husbandry practices include: (i) Which onion has longer roots? Why?
(a) Proper food and clean drinking water. Ans. The onion in jar A has longer roots as it
(b) Proper shelter continues to grow due to the presence of
(c) Proper methods of breeding meristematic tissue at root tip which had
(d) Prevention and cure of disease. dividing cells.
(iv) Animal husbandary practices serve as an (ii) Why did the roots of the onion in jar B stop
growing?
Introduction to Biotechnology 129

Ans. The roots of onion in jar B stopped growing as (ii) A single continuous layer is formed.
the meristematic tissue present in the root tips (iii) The epidermis is covered by a waxy cuticle.
were cut off.
(4) Establish your own plant nursery near your
(3) Take a fresh and fleshy leaf of Rhoeo, lily or school or home. Prepare the seedlings of
any other plant. Pull and press it, tearing it flowering plants, fruit plants, and ornamental
obliquely in such a way that its transparent plants being grown in your area. Can you
epidermis will be visible at the cut margins. start a business in the future with the help of
Take the transparent epidermis with the this activity? Think it over.
forceps and keep it in dilute safranin
Ans. (Students are expected to do this activity on
solution for 1 minute. Spread it on a slide,
their own.)
cover it with a cover-slip and observe it
under a compound microscope. Yes, we can start a business of plant nursey
in future. If sufficient land is available, the
Ans.
emerging field of agritourism would be a
(i) The cells of the epidermis are flat and polygonal good business.
and there are no intercellular spaces between them.
vvv

ASSIGNMENT - 17
Time : 1 Hr. Marks : 30

Q.1. (A) Fill in the blanks: (2)

(1) ................. lubricates the surface of bones, gives support and shape to organs.
(2) Biotechnology includes the techniques of ................. and ................. .
(B) State whether the following statements are true or false. If false, rewrite the
correct statement: (2)
(1) Simple squamous epithelium is present in respiratory tract.
(2) Chlorenchyma helps the plant to float in water.
(C) Identify the odd man out and explain why it is odd: (2)
(1) Xylem, phloem, permanent tissue, meristematic tissue.
(2) Epithelium, muscle fibre, nerve fibre, epidermis.
Q.2. Answer the following: (10)
(1) Write short note on striated muscles.
(2) Distinguish between simple tissue and complex tissue.
(3) Write a short note on poultry farming.
(4) Explain the location, structure and function of Adipose tissue.
(5) Explain the location, structure and function of ciliated epithelium.
Q.3. Answer the following: (6)
(1) Write a note on sericulture.
(2) Explain the location and function of meristematic tissues.
(3) Write a note on Genetic engineering.
Q.4. Answer the following: (8)
(1) Explain the meaning of biotechnology and its impact on agricultural management with suitable
examples.
(2) Define the term tissue and explain the concept of tissue culture.
vvv
 18 Observing Space : Telescopes

CONCEPT MAP

Space Observation

through

Telescope Artificial Satellite

Based on such as

Visible Radio X-rays INSAT EDUSAT ASTROSAT

Radiation waves GSAT
used in
used in used in
X- ray Telecommunication Education Space
Optical Radio telescope Research
telescope telescope
e.g.
Types e.g.
Chandra
GMRT

Reflecting Refracting
Telescope Telescope
e.g.

Galilean

Newtonian Cassegrain
eg. Hubble

(3) In order to overcome the difficulties faced,

MASTER KEY QUESTION SET - 18
refracting telescopes are made using
Q.1. (A) Fill in the blanks: mirrors.
* (1) The wavelength of visible light is between (4) The images formed by do not have
to . errors of colour.
(2) Optical telescopes are also known as (5) and are the two types of
telescopes. reflecting telescopes.
(6) In cassegrain telescope the eyepiece gives a
image of the source.

(130)
Observing Space : Telescopes 131

* (7) The biggest optical telescope in India is (3) Visible radiation telescopes are also called
situated at . as .
*(8) The first scientist to use a telescope for space (a) Gamma Ray telescope
observation was . (b) Optical telescope
(9) In radio telescope is placed at focal point. (c) X-ray telescope
* (10) GMRT is used for waves. (d) Radio telescope
(11) GMRT is a collection of dishes (4) To collect the maximum amount of light
having a diameter of . coming from an object, the objective lens
(12) We cannot use the optical telescope during the should be made as as possible.
day because of . (a) Large (b) Small
(13) In 1990, the National Aeronautics and Space (c) Circular (d) Flat
Administration launched into space an optical
(5) The images formed by lenses have errors of
telescope called the telescope.
colours. This is called .
(14) In 1999, the NASA launched an x-ray telescope
(a) Chromatic disruption
named .
(b) Chromatic aberration
* (15) A certain X ray telescope is named after the
(c) Chromatic reflection
scientist .
(d) Chromatic reaction
(16) The and series of satellites
support our telecommunication network. (6) Reflecting telescopes are mainly of two types :
and .
(17) The satellite series is used for
education. (a) Newtonian and Galileoan
(18) The series of satellites are used (b) Optical and Cassegrain
for monitoring and management of natural (c) Newtonian and Cassegrain
resources. (d) Optical and Refracting
(19) In 2015, ISRO launched an artificial satellite (7) Radio telescope is made up of one or more
called . dishes of shape.
Ans. (1) 400nm, 800nm (a) Spherical (b) Hyperbolic
(2) reflecting (3) Concave (4) Mirrors (5) (c) Parabolic (d) Hexagonal
Newtonian, Cassegrain (6) Magnified (7)
(8) Giant Meterwave Radio Telescope (GMRT)
Aryabhatta Research Institute of Experimental
has been erected at near Pune.
Sciences, Nainital (8) Galileo Galilei
(9) Receiver (10) Radio (11) 30, (a) Asangaon (b) Talegaon
45 m (12) Sunlight (13) Hubble (c) Narayangaon (d) Bhategaon
(14) Chandra (15) Subramanian Chandrashekhar (9) Visible light coming from heavenly bodies
(16) INSAT, GSAT (17) EDUSAT (18) IRS have to pass through the to reach the
(19) Astrosat earth surface.
(B) Rewrite the following statements by (a) Stratosphere (b) Troposphere
selecting the correct options given below: (c) Atmosphere (d) Biosphere
(1) The first telescope was invented by . Ans. (1) Galileo (2) Electromagnetic (3) Optical
(a) Einstein (b) Galileo telescope (4) Large (5) Chromatic aberration
(c) Newton (d) Mendel (6) Newtonian and Cassegrain (7) Parabolic
(2) Light is an wave. (8) Narayangaon (9) Atmosphere
(a) Electric (b) Magnetic
(c) Electromagnetic (d) Mechanical
132 Master Key Science & Technology (Term - II) (Std. IX)

*Q.2. (A) Match the columns: through the lens. This is called refraction.
The telescopes that use such lenses are called
(1) Column ’A’ Column ’B’
refracting telescopes.
(1) X-rays (a) GMRT (5) What are the two types of reflecting
(2) Optical telescope (b) ISRO telescopes?
(3) Indian radio telescope (c) Hubble Ans. The reflecting telescopes are mainly of two
(4) Launching artificial (d) Chandra types: Newtonian and Cassegrain. Newtonian
satellite telescope uses a plane mirror and a concave
mirror. The Cassegrain telescope uses a
(5) Visible light rays (e) telecommunication convex and a concave mirror.
(6) radio waves (f) 400nm to 800nm (6) What are Radio telescopes?
(7) INSAT and GSAT (g) Longer than 20cm Ans. Many heavenly bodies emit radio waves in
addition to visible radiation. A special type of
Ans. (1 - d), (2 - c), (3 - a), (4 - b), (5 - f), (6 - g), (7 - e)
telescope is used to receive these rays which is
(B) Match the columns: known as radio telescope.
(1) Column ’A’ Column ’B’ (7) What is the purpose of launching X-Ray
telescope Chandra?
(1) Micro waves (a) 800 nm - 0.3mm
Ans. Chandra was launched to study X-rays coming
(2) Infrared waves (b) 360 pm - 400 nm from heavenly objects. Special mirrors which
(3) Visible light rays (c) 3 pm - 300 pm can reflect X-rays were used in this telescope.
(4) Ultraviolet rays (d) 400 nm - 800nm Q.4. Answer the following:
(5) X-rays (e) 0.3 mm -20cm * (1) Explain the construction of Galileo’s
telescope.
Ans. (1 - e), (2 - a), (3 - d), (4 - b), (5 - c)
Ans.
Q.3. Answer the following in one or two sentences: (i) The Galilean telescope is made up of two or
(1) What is visible radiation? more convex lenses.
Ans. Light is an electromagnetic wave. Every wave (ii) The lens facing the object is called the objective
has a characteristic wavelength. Our eyes can lens which is made as large as possible to
see only that light which has wavelengths collect the maximum amount of light coming
between 400 nm to 800 nm. Such light is called from a heavenly object.
visible radiation. (iii) The lens closer to the eye is called the eyepiece
(2) What is a Reflecting Telescope? which uses the light collected by the objective
lens and produces a large image of the source.
Ans. When light falls on the mirror, it gets reflected.
Telescopes that use concave mirrors are called (iv) Such a telescope is also called a refracting
reflecting telescope. telescope.

(3) What are optical telescopes? * (2) Explain the construction of a radio telescope.
Ans.
Ans. Our eyes are only capable of seeing visible
radiation. Thus we use the visible radiation (i) The radio telescope is made from one or more
telescopes made from regular lenses and dishes of a particular parabolic shape.
mirrors to see visible radiation coming from (ii) As in optical telescope the incident radio waves
space. These telescopes are called optical are reflected by these dishes and converge at
telescopes. the focus.
(iii) A radio receiver is placed at the focal point.
(4) What are Refracting Telescopes?
(iv) The information gathered by this receiver is
Ans. Light rays change their direction as they
passed on to a computer which analyses it and
enter a lens from the atmosphere and again
constructs an image of the source.
when they enter the atmosphere after passing
Observing Space : Telescopes 133

(5) How do refracting telescopes work?

Ans. Most refracting telescopes are made with
two or more lenses. The two lenses are
called objective lens and an eyepiece lens.
The objective lens should be large so that
maximum light can be collected from the
source. Using the light collected, the eyepiece
lens which is small in size, produces a large
image of the source.
(6) What are the difficulties in using refracting
telescopes?
Ans.
(i) We require large objective lens which is very
difficult to make. Also large lenses are heavy
and tend to get distorted.
(ii) As the objective and eyepiece lens are placed
* (3) Why can an X-ray telescope not be based on on the opposite sides of the telescope, the
the earth? length of the telescope also increases with
Ans. increase in the size of the lenses. This makes it
(i) X rays are emitted from distant heavenly difficult to manage a large telescope.
bodies. (iii) The images formed by lenses have errors of
(ii) The rays coming towards the earth will be colours. This is called chromatic aberration.
absorbed by the earth’s atmosphere and will (7) How does a radio telescope work?
go undetected. Ans.
(iii) Hence, X-ray telescopes are placed in an orbit (i) A radio telescope is made from one or more
outside the earth’s atmosphere and not on dishes of a particular parabolic shape.
earth. (ii) The incident radio waves are reflected by
* (4) What are the difficulties in using ground these dishes and converge at a focus.
based optical telescopes? How are they (iii) A radio receiver is placed at focal point.
overcome? (iv) The information gathered by this receiver is
Ans. then passed onto a computer which analyses
and constructs the image of the source.
Difficulties :
(8) Explain any two space observation telescope.
(i) The visible light coming from a heavenly body
Ans. Hubble Telescope:
has to pass through the earth’s atmosphere.
(i) In 1990, the National Aeronautics and Space
(ii) During this journey, the intensity of light
Administration launched into space an optical
decreases due to absorption.
telescope called the Hubble telescope.
(iii) Due to changes in atmosphere, light rays (ii) It has a mirror of diameter 94 inches and is
change their path. orbiting the earth at a height of 589 km from it.
(iv) Because of sunlight we cannot use optical (iii) This telescope is still working and has helped
telescopes during the day. to make important discoveries.
(v) During the night, city lights and cloudy Chandra Telescope:
weather cause difficulties. (i) In 1999, the National Aeronautics and Space
Solution: Administration launched an X-ray telescope
(i) To reduce these problems, optical telescopes named Chandra, in space, to study X-rays
are situated on top of mountains, in coming from heavenly objects.
uninhabitated places. (ii) Special mirrors which can reflect X-rays were
(ii) To get rid of all the above problems completely, used in this telescope.
the telescope is placed above the earth’s (iii) Chandra has given us very useful information
atmosphere, in space. about stars and galaxies.
134 Master Key Science & Technology (Term - II) (Std. IX)

(iv) The telescope is named after the famous Indian Ans.

scientist Subramanian Chandrashekhar. (i) A Newtonian telescope can be made using a
Q.5. Answer in detail: concave mirror, plane mirror and a lens.
* (1) Why are optical telescopes located in
uninhabited places on mountains?
Ans. Eyepiece
(i) The visible light coming from a heavenly body
has to pass through the earth’s atmosphere to Concave mirror
reach the earth’s surface.
(ii) During this journey, some of the light is Light source
absorbed by the atmosphere and the intensity
of the light reaching the earth’s surface Plane mirror
decreases.
(iii) A second problem is caused by the changes in
atmospheric pressure and temperature. Light source
(iv) These changes cause turbulence in the
atmosphere which in turn cause the light The Newtonion telescope
rays to change their path slightly and thereby
shake the position of the image. (ii) A Cassegrain telescope can be made using a
convex mirror, concave mirror and a lens.
(v) (vi) During the night too, city lights and
cloudy weather can cause difficulties in
observing the heavenly bodies. Light source
(vi) Hence, optical telescopes are located in
uninhabited places on mountains. Eyepiece

(2) Write short note : GMRT

Convex
Ans. mirror
(i) Giant Meterwave Radio Telescope (GMRT) is
a large radio telescope that was erected at
Narayangaon near Pune.
Light source
(ii) It uses radio waves having wavelengths of Concave mirror
about a metre, coming from heavenly bodies to
study those bodies. This telescope is actually a The Cassegrain telescope
collection of 30 dishes, each having a diameter (iii) A refracting telescope can be made using two
of 45 m. or more lenses.
(iii) It is called a giant telescope as the arrangement
of the 30 dishes over an area which measures
up to 25 km across, is made in such a way that
it works as a single dish having a diameter of
25 km.
(iv) This means that the GMRT gives the same Eye-piece
data that we would have got from a telescope Source Objective
having a single dish of 25 km diameter of light lens
(v) Scientists study the solar system, solar winds,
pulsars, supernova, interstellar hydrogen
clouds, etc. with the help of the GMRT.

* (3) Which type of telescopes can be made using

a concave mirror, convex mirror, plane Source Objective Eye-piece
of light lens
mirror and a lens? Draw diagrams of these
telescopes. A refracting telescope
Observing Space : Telescopes 135

(4) State some of the satellites and their uses. (i) What type of telescope is shown in the
Ans. figure?
(i) The INSAT and GSAT series of satellites (ii) Label the main parts of the telescope.
support our telecommunication network, (iii) Which type of mirror does the telescope use?
television broadcasting and meteorological (iv) What other type of telescope uses a curved
services. It is because of them that telephone, mirror?
television and internet services are available (v) Explain the working of above telescope.
everywhere in the country.
Ans.
(ii) The EDUSAT satellite is used exclusively for
education. (i) The Newtonian telescope (Reflecting telescope)
(iii) The IRS satellite series is used for the (ii)
monitoring and management of natural
resources as well as disaster management.
(iv) Astrosat: It has ultraviolet and X-ray
Eyepiece
telescopes and detectors. It is a unique system
having different kinds of telescopes on a single Concave mirror
satellite.
(5) What is the specialty of the artificial satellite Light source
Astrosat?
Ans. Plane mirror
(i) This satellite was launched by Indian Space
Research Organization (ISRO).
Light source
(ii) It has ultraviolet and X-ray telescopes and
detectors. Most of the parts used in this satelite
are made in India. (iii) Concave mirror
(iii) It is an unique system having different kinds (iv) The Cassegrain telescope
of telescopes on a single satellite. Indian
scientists are studying various aspects of the (v) Working.
Universe using the data obtained with these (a) Light rays coming from space are reflected by
telescopes. the concave mirror.

Q.6. Study the figure and answer the following (b) Before these reflected rays converge at the
questions: focus, they are deflected again by a small
plane mirror.
(c) As a result, they get focused at a point lying on
the perpendicular to the axis of the telescope’s
cylinder.
(d) They pass through the eyepiece and we get a
magnified image of the source.

Q.7. Can you tell?

* (1) What is the difference between sky and
space?
Ans. Sky: It is a layer of gas that surrounds the
earth in which sunlight is scattered making it
visible from the surface of the earth.
Space: The vast emptiness beyond the sky is
called as space.
136 Master Key Science & Technology (Term - II) (Std. IX)

* (2) What is meant by space observation? Why is (ii) Metrological services such as weather
it important? forecasting help in disaster management.
Ans. The observation of distant planets, galaxies (iii) Observation of positions of stars and other
and other astronomical objects is called as heavenly bodies has helped in the study of
space observation. solar system, solar winds, pulsars, supernova,
(i) Various space based satellites support our etc.
telecommunication networks by providing us
television broadcasting.

vvv

ASSIGNMENT - 18
Time : 1 Hr. Marks : 30

Q.1. (A) Choose the correct alternatives and rewrite the complete sententes: (4)
(1) Visible radiation has a wavelength ranging between ................. to ................. .
(a) 0.3 mm, 20cm (b) 400 nm, 800nm (c) 1m, 10m (d) 50nm, 300nm
(2) The images formed by lenses have errors of colours. This is called ................. .
(a) Chromatic disruption (b) Chromatic aberration
(c) Chromatic reflection (d) Chromatic reaction
(3) Radio telescope is made up of one or more dishes of ................. shape.
(a) Spherical (b) Hyperbolic (c) Parabolic (d) Hexagonal
(4) To collect the maximum amount of light coming from an object, the objective lens should me made
as ................. as possible.
(a) Large (b) Small (c) Circular (d) Flat
(B) Match the column: (4)

Column ‘A’ Column ‘B’

(1) X-rays (a) GMART
(2) Optical telescope (b) ISRO
(3) Indian radio telescope (c) Hubble
(4) Launching artificial satellite (d) Chandra

Q.2. (A) Answer in one sentence: (4)

(1) What is a Reflecting Telescope? (2) What are Radio Telescopes?
(3) What are Optical Telescope? (4) What are visible radiation?
(B) Answer the following: (4)
(1) How do refracting telescopes work? (2) How does a radio telescope work?
Q.3. Answer in brief: (6)
(1) Explain the construction of a radio telescope.
(2) What are the difficulties in using ground based optical telescope? How are they overcome?
Q.4. Answer in detail: (8)
(1) What short note : GMRT
(2) Why are optical telescopes located in uninhabited places on mountain?
vvv