CLASS IX CHEMISTRY

CHAPTER 1 – MATTER IN OUR SURROUNDINGS

CASE STUDY QUESTIONS

1. In an experimental activity, crushed ice was taken in a beaker. A thermometer is fitted in such a way that its bulb
was thoroughly surrounded by ice. The beaker is now slowly heated and temperature was regularly noted.
Temperature rises gradually as the heating is continued and becomes constant when ice starts changing into liquid.

Select the correct answers for the following questions:

i) What name is associated with conversion of ice into water?

a. Evaporation

b. Sublimation

c. Freezing

d. Fusion of Solid

ii) What specific name is given to the constant temperature?

a. latent heat of fusion

b. Boiling Point
c. Melting Point

d. Condensation point

iii) The heat added to the system at constant temperature is called

a. specific heat b) latent heat

c) residual heat d) none of the above

iv) Where does the heat energy go when the temperature does not rise?

a. It makes the molecular motion of the liquid faster

b. It raises the temperature of the beaker only.

c. It is utilised for bringing out the complete change of state

d. It slows down the molecular motion

2.Temperature can be expressed in three important scales. These are Celsius scale ( oC), Fahrenheit scale (oF) and
Kelvin scale (K). Kelvin scale is often used to express temperature in scientific data. Temperature in any one scale
can be easily converted into another scale by using the following equations. If x is the temperature on Celsius scale ,
then
xoC = (x+273) K and xoC = [(9/5)x + 32 ] oF

Answer the following questions using above information

i) What is the boiling point of water in Kelvin scale?

ii) If xoC = xoF, what is the value of x?

iii) Freezing point of water is

a) 0 K
b) 0oF
c) 273 K
d) 273oF

iv) If temperature of certain oil is 65oC, what is the corresponding temperature on Kelvin scale?

a) 330 K
b) 155 K
c) 298 K
d) 338 K
3. In certain investigatory project 150 ml of water is taken in each of the four beakers A , B , C and D. Beaker A and B
are maintained at temperature 25oC while C and D are maintained at temperature 65 oC. Four crystals of copper
sulphate of approximately same mass (say 2g) are taken and two of them are ground into powder form. Now,
crystals are added in beaker A and C while powdered form of the salt are added in beaker B and D respectively.

Mark the correct answer in each of the following questions:

(i) In which beaker the intermixing will be the quickest?

a) C b) D c) A d)B

(ii) Rate of intermixing will be:

a) Same in A and C
b) Same in A and B
c) Quicker in B than in A
d) Slower in C as compared to that in A

(iii) Colour of solution after intermixing is:

a) Greenish b) Bluish c) Pinkish d) Violet

(iv) Phenomenon responsible for intermixing is called

a) Diffusion of solid into liquid

b) Diffusion of liquid into solid
c) Sedimentation
d) Freezing

(v) Which of the following evidence is not provided by the experimental activity?
a) Particles of matter are in a state of motion.
b) Particle motion increases with rise in temperature
c) Particles of matter are stationary
d) There are empty spaces between the molecules.
4..When we remove the stopper from a perfume bottle, the odour or fragrance spreads rapidly throughout
the room in no time. This is because of diffusion and is caused by rapid movement of the particles of one
gas into the empty spaces of another gas. The rate of diffusion of a gas is inversely proportional to the
square root of its density. As a result, lighter gases diffuse faster as compared to heavier gases. Diffusion is
fastest in hydrogen gas which is the lightest. Air is a mixture of number of gases such as N2, O2, CO2 etc.
and these are quite uniformly mixed. This means that the diffusion of gases is not influenced by gravity.

1. Rate of diffusion of a gas is :

(a) directly proportional to its density

(b) directly proportional to its molecular mass

(c) indirectly proportional to its molecular mass

(d) inversely proportional to the square root of its density.

2. The rate of diffusion of hydrogen is:

(a) more than that of helium

(b) less than that of helium

(c) same as that of helium

(d) All statements are incorrect.

3. Which of the following will not exhibit diffusion?

(a) hydrogen, oxygen

(c) salt, sand

(b) oxygen, water

(d) sugar water.

4. Which of the following statements does not go with

the liquid state?

(a) Particles are loosely packed in the liquid state

(b) Fluidity is the maximum in the liquid state

(c) Liquid cannot be compressed

(d) Liquid takes up the shape of any container in which it is placed.

5. A bottle containing ammonia and a bottle containing hydrogen chloride are connected through a
long tube and are opened simultaneously at both ends. The white ammonium chloride solid formed as
a result of the chemical reaction, will be:

(a) at the center of the tube

 (b) near the hydrogen chloride tube

(c) near the ammonia tube

(d) throughout the length of the tube.

6.Both boiling and evaporation of a liquid appear to be similar since there is a change of state from
liquid to vapours in both the cases. However, these are actually different. Evaporation is a surface
phenomenon whereas boiling is not. Evaporation takes place of its own whereas boiling occurs only
when the liquid is heated. Cooling is always caused when the liquid evaporates since it absorbs certain
amount of energy from the surroundings. However, cooling is not observed during boiling. Actually
during evaporation, the liquid absorbs certain amount of heat energy from the surroundings. As a
result, the temperature of surrounding gets lowered. That is why, cooling is observed. But in case of
boiling, the heat energy is made available by the burner flame and not from the surroundings.
Therefore, cooling is not observed in this case.

1. If the external pressure decreases, boiling point of water

(a) decreases

(b) increases

(c) may increase or decrease

(d) does not change.

2. During evaporation, particles of a liquid change to vapours only:

(a) from the surface

(b) from the bulk

(c) from both surface and bulk

(d) neither from surface nor from bulk.

3. When a liquid boils,

(a) temperature remains constant

(b) kinetic energy increases

(c) temperature increases

(d) density of liquid increases.

4. Water kept in earthen pot becomes cool during summer due to:

(a) evaporation

(c) vaporisation

(b) diffusion

(d) large surface area.

 5. When liquid starts boiling, the further heat energy which is supplied:

(a) is lost to the surroundings as such

(b) increases the temperature of the liquid

(c) increases the kinetic energy of the particles in the liquid

(d) is absorbed as latent heat of vaporisation by the liquid.

Multiple choice question

1. Which of the following has highest intermolecular forces of attraction?

(a) liquid water

(b) liquid ethyl alcohol

(c) gaseous CO2

(d) solid CO2.

2. When water solidifies to ice, then heat is

(a) absorbed

(b) evolved absorbed

(c) heat: may be evolved or absorbed

(d) no change in heat

3. The three states of matter can be arranged in the decreasing order of interparticle forces as

(a) solid> gas liquid

(b) liquid> gas > solid

(c) solid > liquid > gas

(d) gas > liquid > solid

4. The freezing point of water is

(4) 273 K

(b) 298 K

(c) 373 K

(d) 300 K

5. 1 atm is equal to

(a) 1 Pascal

(b) 1.01 105 Pascal

(c) 1 mm Hg

(d) 100 mm Hg

6. A solid melts at 52°C. Its temperature on Kelvin scale is

(4) 52 K

(c) 352 K

(b) 325 K

(d) 425 K (NTSE 2014-15)

7. A substance is said to be in the liquid state if under normal pressure its

(a) melting point is above the room temperature

(b) boiling point is below the room temperature

(c) melting point is below the room temperature

(d) boiling point is above the room temperature.

8. Which of the following statements explains why a gas fills the container in which it is kept?

(1) The particles in a gas are larger than those in a liquid.

(i) The particles in a gas have very small attractive forces between them.

(iii) The particles in a gas are constantly moving very quickly.

(a) (i) only

(b) (ii) only

(c) (i) and (ii)

(d) (ii) and (iii)

9. When heat is supplied constantly by a gas burner with a small flame to melt ice, then the temperature
of ice during melting.

(a) increases slowly to form water

(b) remains constant

(c) first remains constant and then decreases

(d) decreases very slowly.

10. The conversion of a solid into vapours without passing through the liquid state is called

(a) sublimation
(b) vaporisation

(c) fusion

(d) liquefication

11. Latent heat of vaporisation of water is

(a) 18 kJ/kg

(b) 22.5 x 102 kJ/kg

(c) 3.34 x 105 J/kg

(d) Zero

12. Which of the following does not undergo sublimation?

(a) Sodium chloride

(b) Ammonium chloride

(c) Camphor

(d) Iodine

13. Ice melts at 0°C. This temperature is equivalent to

(a) 32°F

(b) 0°F

(c) 273°F

(d) 66°F

14. The body temperature of a normal healthy person is 98.6°F. What is the temperature on the Celsius
scale? (b) 28.6°C (c) 37°C

(a) 42°C

(b) 28.6°C

(c) 37°C

(d) 48.2°C

15. When water solidifies to ice, then heat is

(a) absorbed

(b) evolved

(c) no change

(d) may be evolved or absorbed

16. At the melting point temparature of ice,

(a) only ice is present

(b) only water is present

(c) both ice and water are present

(d) none of these is correct.

17. Dry ice is an example of ....... process.

(a) evaporation

(b) crystallisation

(c) sublimation

(d) purification

18. The boiling point of a gas is -80°C. This temperature is equivalent to

(a)-193 K

(b) 193 K

(c) 353 K

(d)-353 K.

19. The melting point of ice is

(a) 273.15 K

(b) 173.15 K

(c) 373.5 K

(d) 100 K

20. Physical state of water at 0°C is

(a) Solid

(b) Liquid

(c) Gas

(d) None of these