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CHAPTER – 1
Food: Where Does it Come From?
• Food: Nutritious substance that people or animals eat or drink, or that plants absorb. In
order to maintain life and growth.
• There is a lot of variation in the food eaten in different regions of India.
• The main sources of our food are plants and animals.
• Food sources from plants:- vegetables, pulses, spices, cereals, fruits, oils, etc.
• Food sources from animals:- milk, egg, honey, meat, fish, etc.
• Other sources of food are salt and water.
• Animals which eat only plants are called herbivores. Example: cow, goat, sheep etc.
• Animals which eat only animals are called carnivores. Example: tiger, lion, etc.
• Animals which eat both plants as well as other animals are called omnivores. Example:
bears, foxes, dogs, etc.
• Animals that live on dead and decayin food is called scavengers. Example: hyenas,
vulture, etc.

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CHAPTER – 2
COMPONENTS OF FOOD

• Nutrients: Food substances that provide nourishemt to the body.

• The major nutrients in our food are carbohydrates, proteins, fats, vitamins and minerals.
In addition, food also contains dietary fibres and water.
• Carbohydrates and fats mainly provide energy to our body.
• Carbohydrates: These are energy-giving compounds. There may be simple carbohydrates
or complex carbohydrates.
• Fats: These are very high energy-giving compounds compounds. They produce greater
amount of energy than carbohydrates.
• Minerals: These are elements required by the body in small amounts. It is essential for
growth and development of bones, teeth and red blood cells.
• Proteins: These are body-building foods. They help in the growth of the body.
• Vitamins: These are organic substances that protect the body from diseases.
• Roughage: It is the dietary fibre present in the food. It facilitates regular movement of the
bowels and prevents constipation.
• Balanced diet: It provides all the nutrients that our body needs, in right quantities, along
with adequate amount of roughage and water.
• Deficiency Diseases: These are the diseases cause due to the lack of required nutrients for
a long period in the diet.
• Some Nutrients Deficiency Diseases are:
(a) Protein: Kwashiorkar - Stunted growth, thinning of legs, protruding belly.
(b) Protein and Carbohydrates – Marasmus – Complete/partial arrest of growth, lack of
energy.
(c) Vitamin D: Rickets – Bowed legs, bent spine, deofmed bones are joints.
(d) Vitamin C: Scurvy – Bleeding and swelling of gums, weakness.
(e) Iodine: Goitre – Enlargement of thyroid gland, retarded growth.
(f) Iron – Anaemia – Fatigue, loss of appetite, pale skin.

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CHAPTER – 3
FIBRE TO FABRIC
• Fibres: There are two types of fibres:
(a) Natural Fibres: The fibres which are obtained from plants and animals. Example:
cotton, jute, silk and wool.
(b) Synthetic Fibres: Man-made fibres which are not obtrained from plant and animals
sources. Examples: rayon, nulon, polyester, etc.
• Fibres from plant sources:
(a) Cotton: cotton is grown in black soil and warm climate.
(b) Jute: jute is obtained from stem of jute plant.
• Fibres from animal sources:
(a) Wool: wool cloth is spun from yarn made from the fibres of the thick fleece of sheep.
(b) Silk: silk thread is obtained from the saliva of an insect called silkworm.
• Processing of wool: It involves four steps:
(a) Shearing: The process of removal of wool from the sheep’s skin.
(b) Grading: The process of separating fleece from damaged wool.
(c) Carding: The process after the wool has been washed and dried, it is passed through
the rollers (that have teeth).
(d) Spinning: The process by which fibrs are gathered together and drawn into a long
rope and then twisted to make yarn.
• Fabrics are made from yarns, which in turn are made from fibres.
• Making Fabric from Yarn: It is done by two processes:
(a) Weaving: The process by two sets of yarns are arranged together to form fabric. It is
done on looms.
(b) Knitting: The process by which a single yarn is used to make fabric. It is done by hand
or machines.

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CHAPTER – 4
Sorting Material into Groups
• Objects around us are made up of a large variety of materials.
• A given material could be used to make a large number of objects. It is also possible that
an object could be made of a single material or of many different types of materials.
• Different types of materials have different properties.
• Some materials are shiny in appearance while others are not. Some are rough, some
smooth. Similarly, some materials are hard, whereas some others are soft.
• Some materials are soluble in water whereas some others are insoluble.
• Some materials such as glass, are transparent and some others such as wood and metals
are opaque. Some materials are translucent.
• Materials are grouped together on the basis of similarities and differences in their
properties.
• Things are grouped together for convenience and to study their properties.
• Materials are classified based on their properties like: appearance, hardness, solubility,
float/ sink, transparency, conduction of heat, states of matter, conduction of electricity,
attraction towards magnets, combustibility.
• Advantages of classification:
(a) Helps in identification of objects.
(b) Helps in sortingof objects.
(c) Helps in locting things.
(d) Makes study of different objects easy and more meaningful rather than studying each
other separately.
(e) Helps to understanding similarities and dissimilarties among objects.

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CHAPTER – 5
SEPARATION OF SUBSTANCES

• Handpicking, winnowing, sieving, sedimentation, decantation and filtration are some of

the methods of separating substances from their mixtures.
• Methods of separation:
(i) Separation of solid from other solids:
(a) Threshing: Process by which the grains are released from the chaff.
(b) Winnowing: The process of separation of heavier and lighter components of a
mixture by wind or blowing air.
(c) Hand-picking: The process by which undesirable components are just picked
up by hand.
(d) Sieving: The process by which separate solid constituents of a mixture which
differ in their sizes.
(e) Magnetic separation: Process by which magnet is moved over such a mixture,
the magnetic material sticks to it and is removed.
(ii) Separation of water soluble solids:
(a) Evaporation: Process by which the conversion of liquid state into gaseous
state on heating.
(b) Condensation: Process by which conversion of gaseous state into liquid state
on cooling.
(iii) Separation of insoluble solids from Liquids:
(a) Sedimentation: It allows heavier matter to settle down. Example: sand, water.
(b) Decantation: The methods of separating insoluble solids from liquids.
(c) Loading: The methods by which finer particles are made to settle faster by
dissolving a small quantity of alum.
(d) Filtration: The liquid that collects in the beaker is called filtrate.
(iv) Separation of Immiscible Liquids:
(a) Funnel: The method of separting mixture of oil and water.

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(b) Centrifugation: The method in which mixture containing suspended particles

is rotated at a high speed in a centrifuge and heavier particles settle down. It is
used for separating cream from milk.
(c) Churning: The method which is used for separating lighter particles of solid
suspended in a liquid. Example: butter from curd.
• Husk and stones could be separated from grains by handpicking.
• Husk is separated from heavier seeds of grain by winnowing.
• A saturated solution is one in which no more of that substance can be dissolved.
• More of a substance can be dissolved in a solution by heating it.
• Water dissolves different amount of soluble substances in it.

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CHAPTER – 6
Changes Around Us
• Some changes can be reversed and some cannot be reversed.
• A change may occur by heating a substance or by mixing it with some other.
• Types of changes:
(a) Reversible change: A change in which the initial substance can be obtained back by
reversing the action. Example: folding of paper, dissolving sugar in water, etc.
(b) Non-irreversible change: Change in which the initial substance cannot be obtained
back by reversing the action. Example: burign of paper, grinding grains etc.
(c) Physical change: Changes in the form of substance but not in chemical identity. No
new substance formed. Changes is sometimes reversible. Example: breaking a log of
wood.
(d) Chemical changes: Changes in which substance is transformed into new substance.
Initial substance is lost. Change is always irreversible. Example: burning a log of
wood.
• Ways by which changes occur:
(a) Boiling and Condensation:
(i) Boiling: The rapid vaporization of a liquid when it is heated to its boiling point.
(ii) Condensation: The change of water vapor into liquid water on cooling.
(b) Heating of metal: Process in which a metal is heated to a certain temperature and
the cooled in a particular manner to alter its internal structure for obtaining desired
degree of physical and mechanical properties such as brittleness, hardness, and
softness.
(c) Freezing and Melting:
(i) Freezing: The process in which a liquid turns into solid when its temperature
is lowered.
(ii) Melting: The process in which a solid converts to a liquid by applying heat.

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CHAPTER – 7
GETTING TO KNOW PLANTS

• Plants are usually grouped into herbs, shrubs, trees, and climbers based on their height,
stems and branches.
• Classification of Plants on the of Growth Habit:
(a) Herbs: Have soft, green and week stems. Example: rice, wheat, maize, sunflower,
mint, etc.
(b) Shrubs: They are bushy and have hard stems that do not bend easily. These are plants
with the stem branching out near the base. Example: lemon, china rose, jasmine,
Nerium, etc.
(c) Trees: These are big plants which have a tall and strong stem (trunk). Stems have
branches in the upper part, much above the ground. Live for many years. Example:
mango, neem, banyan, coconut, etc.
(d) Climbers: Have weak stems and cannot stand erect. They take support of other trees
and climb on them. Example: pea, grape, vine, etc.
(e) Creepers: Plants which creep on the ground and spread out. Example: pumpkin and
watermelon.
• Classification of plants on the basis of their Life Cycle:
(a) Annuals: Plants whose life cycle is completed in the one season. These are generally
herbs. Example: wheat and mustard.
(b) Biennials: Plants whose life cycle requires two seasons for completion. They are
generally herbs and rarely shrubs. Example: carrot, radish and potato.
(c) Perennials: Plants whose life cycle runs for more than two seasons example: guava,
babul and palm trees.
• Parts of a Plants:
(a) Root system: It is the underground portion of the plant.
(i) Tap Root: It is the main primary root arises from lower end of the stem. A
number of tiny braches called secondary roots. Example: mustard, neem, rose,
etc.

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(ii) Fibrous Root: A bunch of roots arises from the bae of stem. Example: wheat,
maize, etc.
Functions of root system:
(i) Roots absorb water and nutrients from the soil.
(ii) Roots help the plant to stand erect.
(iii) Roots check soil erosion.
(iv) Roots store food.
(v) Prop roots offer extra support.
(b) Shoot system: The part of the plant which grows above the soil. It includes stems,
branches, leaves, flowers and fruits.
(i) Stem: Gives riese to a number of branches that bear leaves. The stem bears
leaves, flowers and fruits.
(ii) Leaf: Leaf arises from the leaf base. A leaf usually has a petiole and a lamina.
Parts of leaf:
(a) Petiole: Stalk of the leaf with which it joined to the stem.
(b) Leaf lamina: The flat green portion of the leaf.
(c) Veins: These are the network of small, narrow, tube-like structures on both
sides of the midrib present in the middle of leaf.
(iii) Flower: It is the reproductive organ of the plant.
• Function of Stem:
(i) It provides support to plant.
(ii) It bears important plant parts.
(iii) It helps in transportation of water and food.
(iv) Underground stems store food.
(v) Thick and fleshy stems make food.
(vi) Stem modified into tendrils give extra support for plants.
• Function of Leaf:
(i) Transpiration: Process of losign water by the leaves of a plant.
(ii) Preparation of food by the process of photosynthesis.
• Function of Flowers:
(i) Help in reproduction.
(ii) These become fruits that store food and seeds.

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(iii) Modified flowers like cauliflower, broccoli are rich sources of vitamins.
• Parts of Flower:
(i) Pedicel: Stalk of the flower through which the flower is joined to the branch. It has
joined to the branch.
(ii) Sepal: Small green leaf-like structures on the thalamus. They protect the flower.
(iii) Petals: Brightly colored leaf-like structures present inside the sepals. Petals
attract the insects and help in the process of reproduction.
(iv) Stamens: These are long, thin and needle-like structures. These are male organs
of the flower. It consists of two parts: Anther, Filament.
(a) Anther: The swollen tip of each stamen that encloses in it a small powdery
substance called pollen grains.
(b) Filament: Long stalk-like structure that joins the anther with thalamus.
(v) Carpel: It is a flask-shaped organ in the centre of flower. It is the female organ of
the flower. It consist three parts: Style, Stigma and Ovary.
(a) Style: Long thin tube-like structure which is swollen at the base.
(b) Stigma: Small, round and sticky part of the carpel at the top of the style the
traps the pollen grains.
(c) Ovary: Swollen part of carpel that contains ovules.
• The pattern of veins on the leaf is called venation. It can be reticulate or parallel.
• Leaves give out water vapour through the process of transpiration.
• Green leaves make their food by the process of photosynthesis using carbon dioxide and
water in the presence of sunlight.
• Roots absorb water and minerals from the soil and anchor the plant firmly in the soil.
• Roots are mainly of two types: tap root and fibrous roots.
• Plants having leaves with reticulate venation have tap roots while plants having leaves
with parallel venation have fibrous roots.
• The stem conducts water from roots to the leaves (and other parts) and food from leaves
to other parts of the plant.

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CHAPTER – 8
Body Movements
• Locomotion: Movement of organisms from place to place.
• Locomotion in human body:
(i) Human skeleton: It forms a framework that gives shape and support to the body.
It consists of 206 bones. It protects internal organs.
(a) Skull: It protect the brain. It is rigid box made up of plates of bone firmly
joined together.
(b) Rib cage: It is flexible case of ribs. Each rib curves round the side of the chest
from the backbone and is joined in front to a plate of bone called sternum. Ribs
are conneceted to one another by the muscles. Two lower most pairs of ribs
are called ‘floating ribs’.
(c) Backbone: It is also called the spine or vertebral column. It is a chain of small
bones called vertebrae. It protect the spinal cord, which carries maessages
between the brain and body. It also support the skull, ribs and limbs.
(d) Limbs: It is made up of long bones with joints that allows them to move. They
are mainly for support.
(i) Arms: fore-arms is made up of two bones and hands have several small
bones. Shoulder bones have a pair of collar bones in front and a pair of
shoulder blades.
(ii) Legs: Lower leg is made up of two bones and feet have several small
bones. Hip bones or gridles bear weight of body and are attached to
thigh bones.
(ii) Joints: The point where two bones meet. Allow movement to take place. Bones are
held together by ligaments.
(a) Movable Joints: It allows movement between bones and have cartilage
between them. Type of movable joints are:
(i) Hinge Joints: It allow movement only in one plane backwards and
forwards. Example: elbow joints, knee joints and joint between
phalanges of fingers and toes.

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(ii) Ball and Socket Joints: It permit a circular movement. Example: the
shoulder.
(iii) Gliding Joints: It allow bones to slide a little. Example: bones inside
wrists and feet.
(iv) Pivotal Joints: Joint where the neck joins the head. It allows head to
move backward and forward and turn to right and left.
(b) Immovable or Fixed Joints: The bones cannot move at these joints. Example:
bones in skull, joint between upper jaw and rest of skull.
• Locomotion in other animals:
(i) Fish: Locomotion achieved by lateral contractions of the muscular body with a
final thrust by the tail. Fish swim by forming loops alternately on two sides of the
body.
(ii) Birds: When the large flight muscles contract, they pull the wings down.
(iii) Snails: The muscular foot helps in locomotion.
(iv) Earthworms: Move by stretching out body in front and keeping the hind end fixed
to the ground.
• The bones are moved by alternate contractions and relaxations of two sets of muscles.
• The bone joints are of various kinds depending on the nature of joints and direction of
movement they allow.
• Strong muscles and light bones work together to help the birds fly. They fly by flapping
their wings.
• Snakes slither on the ground by looping sideways. A large number of bones and
associated muscles push the body forward.
• The body and legs of cockroaches have hard coverings forming an outer skeleton. The
muscles of the breast connected with three pairs of legs and two pairs of wings help the
cockroach to walk and fly.

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CHAPTER – 9
THE LIVING ORGANISMS AND THEIR SURROUNDINGS

• The surroundings where plants and animals live, is called their habitat.
• Several kinds of plants and animals may share the same habitat.
• The presence of specific features and habits, which enable a plant or an animal to live in a
particular habitat, is called adaptation.
• There are many types of habitats, however, these may be broadly grouped as terrestrial
(on the land) and aquatic (in water).
• There is a wide variety of organisms present in different habitats.
• Plants, animals and microorganisms together constitute biotic components.
• Rocks, soil, air, water, light and temperature are some of the abiotic components of our
surroundings.
• Characterisitcs of living things:
(i) They need food to grow and for the processes.
(ii) The young ones grow into adults.
(iii) They respire. Animals breathe in oxygen and breathe out carbon dioxide. Plants
take in carbon dioxide and give out oxygen.
(iv) They respond to changes in the surrounding (stimull).
(v) They all get rid of wastes produced in the body (excretion).
(vi) They reproduce their own kind.
(vii) They show movement.
• Habitat: The surroundigs whwere organisms live. It has two components biotic (living
things like plants and animals) and biotic (non-living things like rocks, soil, air and
water).
Type of Habitat:
(a) Terrestrial Habitat: Plants and animals live on land. Example: forest, grasslands,
deserts, coastal and mountain ranges.
(b) Aquatic Habitat: Plants and animals live in water. Example: ponds, swamps, lakes,
rivers and oceans.

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Adaptations: Presence of specific features or certain habits which enable an organism to

live in its surrounding.
Terrestrial:
(a) Deserts: Small animals stay in borrows deep in sand during day, and come out at
night. In plants, leaves are either absent or very smell as spines; stem has a thick waxy
coating; roots go deep into the soil.
(b) Mountains: Animals have thick skin or fur; mountain goat has strong hooves. Trees
are cone shaped having sloping branches; leaves are needle like.
(c) Grasslands: Animals are light brown in colour; Lion: Long clause in front legs that
can be withdrawn inside the toes; eyes in front of face. Deer: Srong teeth, long ears,
eyes on the sides of head.
Aquatic:
(a) Ponds:
• Plants with roots fixed in soil: Stems are long, hollow and light; leaves float on water.
• Plants with roots submerge: Leaves are narrow and thin ribbon-like.
(b) Oceans:
• Animals have streamlined body; gills to respire (dolphins and whales have
blowholes).
• Animals like squids and octopus do no have streamlined body and stay deep in
water.

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CHAPTER – 10
MOTION AND MEASUREMENT OF DISTANCES

• Different modes of transport are used to go from one place to another.

• In ancient times, people used length of a foot, the width of a finger, the distance of a step
as units of measurement. This caused confusion and a need to develop a uniform system
of measurement arose.
• Now, we use International System of Unit ( SI unit). This is accepted all over the world.
• Metre is the unit of length in SI unit.
• Motion in a straight line is called rectilinear motion.
• In circular motion an object moves such that its distance from a fixed point remains the
same.
• Motion that repeats itself after some period of time, is called periodic motion.
• Measurement: The comparison of an unkown quantity with some known quantity of the
same kind. Measurement of an object consists of :
The unit of measurement.
The number of units the object measures.
• Conventional Methods of Measurement: Conventsinal measurements have only been
approximate measurement. Differ from person to person. Lack precision.
(i) Handspan: Length between the tip of thumb and little finger.
(ii) Cubit: Length between the tip of middle finger and elbo.
(iii) Arm length: Length from shoulder to the tip of middle finger.
(iv) Footstep: It is the distance covered by a step.
• Standard units of Measurement: It is a unit to measure any quantity completely and
uniformly. Standard units for measuring, length-metre, mass-kilogram, time-second.
• Motion: When the position of a body does not change with the passage of time, the body
is said to be at rest. When the position of a body changes with the passage of time, the
body is said to be in motion.
Types of motion:
(a) Linear motion: Linear motion are further classified into two:

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(i) Rectilinear Motion: Object moves from one position to another along a
straight line. Example: group of ants moving in a line.
(ii) Curvilinear Motion: Object moving alogn a curved lines. Example: a car
moving along a curved road.
(b) Random Motion: When object moves from one position to another and changes
direction in an irregular manner. Example: butterfly, flies randomly in garden.
(c) Circular Motion: Object moves in a circular manner in relation to its own axis or
around a fixed centre. Object remains at the same distance from a fixed point which is
the centre of the path of the motion. Two types of circular motion:
(i) Revolution: Object moves as a whole around a fixed centre. Example: earth
revolving around the sun in a definite orbit.
(ii) Rotation: Object moves in a circular path in relation to its own fixed axis.
Example: blades of a moving fan, windmill, etc.
(d) Vibratory Motion: Object moves to and fro very fast. Example: strings of a guitar
when plucked.
(e) Periodic Motion: Object oscillates to and fro along the same path again and again and
with the same speed. Time taken by an object to complete one oscillation is same, no
matter how many oscillations the object takes. Example: heartbeat, pendulum of a
clock.
(f) Non-periodic Motion: Object do not repeat motion at regular intervals of time.
(g) Uniform Motion: When the body covers equal distance in equal time interval.
(h) Non-uniform Motion: Motion in which the body covers unequal distance in equal
inter of time

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CHAPTER – 11
LIGHT, SHADOWS AND REFLECTIONS

• Light: Light is the natural agent that stimulates sight and makes things visible.
• Light is classified into two:
(i) Emission of light: Classifying objects on the basis of emission of light.
(a) Luminous Objects: Objects that emit their own light. Example: sun, electric torch,
firefly, etc.
(b) Non-luminous Objects: Objects that do not emit their own light but are visible due
to light falling on them. Example: moon, chair, table, etc.
• Transparent: Objects or materials through which light can pass totally.
Example: glass, water, air, etc.
• Translucent: Objects that allow light to pass through them partially. Example:
butter paper, tissue paper, etc.
• Opaque: Objects that do not allow light to pass through them. Example: book,
brick, etc.
Shadow: Region without light that forms behing an object kept in the path of
light. Opaque object cast a dark shadow. Translucent objects produce a weak
shadow. Transparent objects do not cast a shadow at all.
Types of shadow:
Due to smaller light source: Only one dark shadow is formed and this is known
as umbra.
Due to larger light source: Two shadows are formed-a dark one in the centre
and a light one on the outside. Dark shadow is called umbra and the faint or
lighter shadow is called penumbra.
Eclipse: A shadow formed in space that makes the sun or the moon invisible for
some time.
Solar eclipse: The moon comes between the sun and the earth, so that the earth
(in the shadow) darkens during the day.

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Lunar eclipse: The moon and the sun are in a straight line such that the earth is
in the between the sun and the moon, the shadow of the earth falls on moon and
the moon cannot be seen.
(ii) Reflection of light: The process of sending back the light rays whichafall on the
surface of an object. Silver metal is one of the best reflector of light.

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CHAPTER – 12
ELECTRICITY AND CIRCUITS

• Electiricity: It is a flow of electic current.

• Electric Current: The Electic current flows around by Electric Circuit.
• Electric Circuit: In a closed electric circuit, the electric current passes from one terminal of
the electric cell to the other terminal.
• Circuit Diagram: It is a symbolic representation of the electric circuit.
• Component of Electricity:
(i) Connecting wires: Help to conduct the electric current and complete the circuit.
(ii) Bulb: Lights up when an electric current flows through it. An electric bulb has a
filament that is connected to its terminals. An electric bulb glows when electric
current passes through it.
(iii) Switch: Switch is a simple device that is used to either break the electric circuit or to
complete it. When a switch is on, a gap in the circuit is bridge by a conducting material
through which the current flows.
(iv) Electric cell: An electric cell has two terminals; one is called positive (+ ve) while the
other is negative (– ve).
• Connecting wires, bulb, switch and electric cell is used in Torch, Battery, LED (Light Emitting
Diode), etc.
• Electric current is carried by Conductor.
• Conductor: Materials that allow electic current to pass through them. All metals are good
conductors of electricity. Carbon is the only non-metal which is a good conductor of
electricity.
• Electric current is stopped by Insulators.
• Insulators: Materials which do not allow electric current to pass through them. Example:
plastic, rubber, wood, glass, polythene, PVC, etc.

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CHAPTER – 13
FUN WITH MAGNETS.
• Magnets: Materials that attract iron. Natural magnet is called Iodestone or magnetite.
• Magnetite is a natural magnet.
• Magnet attracts materials like iron, nickel, cobalt. These are called magnetic materials.
• Materials that are not attracted towards magnet are called non-magnetic.
• A freely suspended magnet always aligns in N-S direction.
• Classification of substances based on attraction to magnets:
Magnetic Substances: Materials which get attracted towards magnets. Example: copper,
iron, nickel, etc.
Non-magnetic Substances: Materials which do not get attracted towards magnets.
Example: wood, paper, plastic and most metals.
• Methods to make Magnet:
(i) Single Touch Method: A piece of iron or steel can be magnetized by strocking it
several times with a magent in one direction.
(ii) Double Touch Method: Opposite poles of two bar magnets are brought together
in the middle and then moved from the middle in the opposite directions to each
other.
(iii) Using Electric Current: The bar to be magnetized is placed inside the coils of a
conductor and current is passed through these coils of wire.
• Properties of Magnet:
(i) A magnet has two poles – north pole and south pole.
(ii) Similar poles repel each other.
(iii) Opposite poles attract each other.
(iv) Magnetic poles always exist in pairs.
• Applications of Magnet:
Compass needle: It points north-south because the earth is also a giant magnet. The
compass lines up with the earth’s magnetic field.
Used in factories for lifting heavy masses of iron like scrap iron.
Used by surgeons in hospitals to remove steel splinters from the wounds.
Used in the construction of telephones, electric bells, etc.
Used to separate iron and steel from non-magnetic materials.

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CHAPTER – 14
WATER
• Water is essential for life.
• Water which is fit for human consumption is known as Fresh water or Potable water.
• Only 2.6% of total water is fresh water.
• Only 0.01% of the total water reaches humans and animals.
• Water Cycle: The cycle of processes by which water circulates between the earth's
oceans, atmosphere, and land, involving precipitation as rain and snow, drainage in
streams and rivers, and return to the atmosphere by evaporation and transpiration.
• Water Conservation: It is the wise and judicious use of water.
• Ways of conserving water:
(i) Get all leaking taps repaired.
(ii) Use a bucket for taking bath instead of a shower.
(iii) Collect rainwater and use it for gardening and recharging ground water.
(iv) Wash your cycles, cars, etc. with a bucket of water instead of pipes.
(v) Instead of washing the floor use a mop.
• Importance of Water:
(i) Digestion of food takes place in the stomach when food is mixed with water.
(ii) Important medium for the transportation of food, oxygen and carbon dioxide in
the body.
(iii) Water is used to produce electricity.
(iv) Water is essential for the germination of seeds.
(v) Water helps in maintaining the body temperature.
• Excess of water: When it rains or snow, some of the water is retained by soil. Its caused
flood. It effects by damage property and endanger the lives of humans and animals. Rapid
run-off causes soil erosion.
• Lack of water: It is the lack of sufficient available water resources to meet water needs
within a region. It cause drought like condition. It effect by acute water crisis, crop failure,
loss of life in all forms due to starvation.

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• Rainwater Harvesting: Method of collecting rainwater and storing it for use during
scarcity. It can be used for several purposes including drinking, washing, gardening,
flushing, etc.
• Water vapour gets added to air by evaporation and transpiration.
• The water vapour in the air condenses to form tiny droplets of water, which appear as
clouds. Many tiny water droplets come together and fall down as rain, snow or hail.
• Rain, hail and snow replenish water in rivers, lakes, ponds, wells and soil.
• Excessive rains may cause floods while lack of it for long periods may cause droughts.
• The amount of usable water on earth is limited so it needs to be used carefully.

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CHAPTER – 15
Air Around Us
• Air: The invisible gaseous substance surrounding the earth, a mixture mainly of oxygen
and nitrogen.
• The blanket of air that surround the earth is called atmosphere.
• Air is found everywhere. We cannot see air, but we can feel it.
• Air in motion is called wind.
• Air occupies space.
• Air is present in water and soil.
• Air is a mixture of nitrogen, oxygen, carbon dioxide, water vapour and a few other gases.
Some dust particles may also be present in it.
• Atmosphere is essential for life on earth.
• Aquatic animals use dissolved air in water for respiration.
• Plants and animals depend on each other for exchange of oxygen and carbon dioxide from
air.
• Constituent of Air:
Nitrogen: Plants need nitrogen to grow.
Oxygen: Used by all living things to respire and help to burn things.
Carbon dioxide: Plants and animals consume oxygen and produce carbon dioxide during
respiration. It is used by green plants for photosynthesis. It is released on burning.
Water Vapour: Formed due to evaporation of water. Amount of water vapour present in
the air is called humidity. Varies from place to place and also in the same place during day
and night.
Dust and Smoke: Smoke contains a few gases and fine dust particles. It is very harmful.
Presence of dust particles in air varies from time to time and from place to place.
• Importance of Air:
(i) Air aids burning.
(ii) Air is needed for breathing.
(iii) Plants need air to make food.
(iv) Birds fly in air. Aeroplanes also go up in the air because of air pressure.
(v) Moving air is called wind. The wind makes the windmill rotate.
(vi) Air help in quick evaporation of sweat that helps in keeping us cool.

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CHAPTER – 16
GARBAGE IN, GARBAGE OUT
• Waste: A material that has no longer any value to the person who is responsible for it.
• Source of Waste:
(i) Domestic Wastes: garbage, rubbish, excreta, ashes, sullage are domestic wastes.
(ii) Industrial wastes: wastes produced by industries. The common industrial wstes are
smoke, plastic, objects, glass, fly ash, etc.
(iii) Agricultural wastes: common agricultural wastes are rice husk, dried stems and
straw, weeds and cattle waste.
(iv) Commercial wastes: wastes generated from commercial establishments such as
shops, malls, stores restarurants, hotels, motels, printing press, auto-repair shops,
medical facilities.
• Type of wastes:
(i) Biodegradable wastes: Wastes which can be broken down through the action of
microorganisms into their simple constituents. Example: plant products, organic
wastes, domestic refuse and animal wastes.
(ii) Non-biodegradable wastes: Wastes which cannot be disintegrated by action of
microorganisms and remains unaffected from decomposition. Example: plastics, glass,
metal, scraps, etc.
(iii) Plastics: Many things are made up of plastics like bags, shoes, bottles, pipes, pens, etc.
it cannot be converted into less harmful substances by composting.
• Ill effect of Plastics:
(a) Burning emits poisonous gases which cause health problems.
(b) Foods thrown in plastic bags are eaten by stray animals which can lead to death.
(c) Carelessly thrown plastic bags choke sewer system.
(d) Food stored in bad quality plastics can be harmful.
• Management of Plastics:
(a) Do not throw plastics here and there after use.
(b) Do not burn pastic bags and other plastic items.
(c) Use paper or cloth bags in place of plastic bags.
(d) Educate friends and family members about the proper disposal of plastics.
• Management and Disposal of Waste:

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(a) 3R’s – Reduce, Reuse, Recycle. It means the reduce waste production, reuse of materials
and recycle and reprocessing of waste materials for making new products
(b) Landfills or Composting: Converting plant and animal waste including that from
kitchen, into manure, is called composting. Low lying open areas to deposite
biodegradable waste.
(c) Vermi-composting: Method of preparing compost with the help of red worms. Excreta of
the worms make the compost very rich in nutrients.
• Landfill is an area where the garbage collected from a city or town is dumped. The area is
later converted into a park.
• Paper can be recycled to get useful products.
• Plastics cannot be converted into less harmful substances by the process of composting.
• We need to generate less waste and find ways of dealing with the increasing amount of
garbage in our surroundings.

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CHAPTER – 1
NUTRITION IN PLANTS

• Nutrition: It is the mode of taking food by an organism and its utilization by the body.
• Nutrients: The components of food that provide nourishement to the body.
• All organisms take food and utilise it to get energy for the growth and maintenance of their
bodies.
• Green plants synthesise their food themselves by the process of photosynthesis. They are
autotrophs.
• Photosynthesis: Green plants prepare their own food with the help of carbon dioxide and
water tekn from the environment in presence of sunlight called chlorophyll (found in
green plants) for the manufacture of food. This process is known as photosynthesis.
• Plants use simple chemical substances like carbon dioxide, water and minerals for the
synthesis of food.
• Chlorophyll and sunlight are the essential requirements for photosynthesis.
• Complex chemical substances such as carbohydrates are the products of photosynthesis.
• Solar energy is stored in the form of food in the leaves with the help of chlorophyll.
• Oxygen is produced during photosynthesis.
• Oxygen released in photosynthesis is utilised by living organisms for their survival.
• Fungi derive nutrition from dead, decaying matter. They are saprotrophs. Plants like Cuscuta
are parasites. They take food from the host plant.
• A few plants and all animals are dependent on others for their nutrition and are called
heterotrophs.
• Parasitic: Organisms that live on the body of other organisms.
• All parasitic plants feed on other plants as either:
(i) Partial Parasites: Obtain some of their nutrition from the host, e.g. painted cup.
(ii) Total Parasites: dependent completely on the host for nutrition, e.g. mistletoe.
• Saprophytic: Organisms that obtain nutrition from dead and decaying plant and animal
matter.
• Mushrooms, moulds and certain types of fungi and bacteria.

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• Insectivorous Plants: Green plants which obtain their nourishment partly from soil and
atmosphere and partly from small insects. Example: pitcher plant, bladderwort, and venus fly
trap.
• Symbiosis: Mode of nutrition in which two different individuals associate with each other to
fulfil their requirement of food.
• Lichens found on tree trunks is the association between alga and fugus. Alga obtains water
from fungus and it in turn obtains food from alga.

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Chapter – 2
Nutrition in Animals

• Classification based on Eating Habits:

(i) Herbivorous: animals that obtain their food only from plants. Example: cow, sheep,
goat, deer, elephant, kangaroo, giraffe, etc.
(ii) Carnivorous: Animals that obtain their food by killing other animals. They never eat
plants. Example: tiger, lizard, lion, etc.
(iii) Omnivorous: Animals consume plants as well as other animals as their food.
Example: bear, dog, human being, etc.
(iv) Parasites: Organisms that obtain their food from other animals either by living inside
(endoparasites) or outside (ectoparasites) their body. Example: tapeworm and
roundworm (inside body), tick and lice (outside body).
(v) Scavengers: Animals which feed on the remains of dead animals preyed by predators.
Example: vulture, crows, jackal, etc.
• Animal nutrition includes nutrient requirement, mode of intake of food and its utilisation in
the body.
• The human digestive system consists of the alimentary canal and secretory glands. It consists
of the
(i) buccal cavity,
(ii) oesophagus,
(iii) stomach,
(iv) small intestine,
(v) large intestine ending in rectum
(vi) anus.
• The main digestive glands which secrete digestive juices are
(i) the salivary glands,
(ii) the liver and
(iii) the pancreas.
• The stomach wall and the wall of the small intestine also secrete digestive juices.
• The modes of feeding vary in different organisms.
• Nutrition is a complex process involving:

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(i) ingestion,
(ii) digestion,
(iii) absorption,
(a) assimilation and
(b) egestion.
• Digestion of carbohydrates, like starch, begins in the buccal cavity. The digestion of protein
starts in the stomach. The bile secreted from the liver, the pancreatic juice from the pancreas
and the digestive juice from the intestinal wall complete the digestion of all components of
food in the small intestine. The digested food is absorbed in the blood vessels from the small
intestine.
• The absorbed substances are transported to different parts of the body. Water and some
salts are absorbed from the undigested food in the large intestine.
• The undigested and unabsorbed residues are expelled out of the body as faeces through the
anus.
• The grazing animals like cows, buffaloes and deer are known as ruminants. They quickly
ingest, swallow their leafy food and store it in the rumen. Later, the food returns to the
mouth and the animal chews it peacefully.
• Amoeba ingests its food with the help of its false feet or pseudopodia. The food is digested
in the food vacuole. It pushes out finger-like pseudopodia which engulf the prey.

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Chapter – 3
Fibre to Fabric

• Fibres: Long, fine, continuous threads or filaments are obtained from plants and animals.
Two types of fibers: (i) Animal fibres (ii) Plant fibres
• Animal fibres are obtained from two sources: Silk and Wool
• Silk comes from silkworms and wool is obtained from sheep, goat and yak. Hence silk and
wool are animal fibres.
• The hairs of camel, llama and alpaca are also processed to yield wool.
• In India, mostly sheep are reared for getting wool.
• Sheep hair is sheared off from the body, scoured, sorted, dried, dyed, spun and woven to
yield wool.
• Silkworms are caterpillars of silk moth.
• During their life cycle, the worms spin cocoons of silk fibres.
• Silk fibres are made of a protein.
• Silk fibres from cocoons are separated out and reeled into silk threads.
• Weavers weave silk threads into silk cloth.
• Wool: Sources of Wool: Wool is obtained from sheep, yak (Tibet and Ladakh), Angora goat,
goat, camels, llama and Alpaca (South America)
• Obtaining wool fibre: Shearing: Fleece of the sheep along with a thin layer of skin is
removed from its body.
• Processing of Wool Fibre:
(i) Scouring: Sheared hair is cleaned and washed in tanks to remove grease, dust and
dirt.
(ii) Soritng: Cleaned hair is sent to a factory where hair of different textures are
separated.
(iii) Hair is sent into a ‘Carding’ machine where the loose wool fibres are combed into a
sheet and then twisted into a rope or silver.
(iv) This silver is twisted and stretched into a yarn.
(v) The yarn is wound to form balls of wool.

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Chapter – 4
Heat

• Heat: It is a fomr of energy, which makes any object hot or cold.

• Temperature: Our sense of touch is not always a reliable guide to the degree of hotness of
an object.
• Temperature is a measure of the degree of hotness of an object.
• Thermometer is a device used for measuring temperatures.
• Heat is the cause of temperature.
• Clinical thermometer is used to measure our body temperature. The range of this
thermometer is from 35°C to 42°C. For other purposes, we use the laboratory thermometers.
The range of these thermometers is usually from –10°C to 110°C.
• The normal temperature of the human body is 37°C.
• In solids, generally, the heat is transferred by conduction. In liquids and gases the heat is
transferred by convection. No medium is required for transfer of heat by radiation.
• The materials which allow heat to pass through them easily are conductors of heat.
• The materials which do not allow heat to pass through them easily are called insulators.
• Clinical Thermometer: It is a thermometer used to measure the temperature of our body. It
consists of a long, narrow, uniform glass tube with a bulb containing mercury at one end.
There is a kink near the bulb. It reads a range of temperatures from 35°C to 42°C .
• Laboratory Thermometer: It is a thermometer used to measure the temperature of objects
other than our body. It consists of a column of mercury enclosed in a glass casing. The
column is continuous without any kink. It measures a range of temperature from −10°C to
110°C
• Sea Breeze: Durign the day, the land heats up faster than the sea.
Warm air above the land rises and colded air from sea takes its place.
Warm air from the land moves towards the sea to compele the cycle.
This produces a sea breeze from the sea to the land.
• Land Breeze: At night the land cools faster than sea.
• The warm air above the sea rises.
• This warm air is replaced by colder air from the land producing a land breeze.

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• Transfer of Heat: Heat flows from a hotter object to a colder object until both objects reach
the same temperature.
• The heat flows from a body at a higher temperature to a body at a lower temperature. There
are three ways in which heat can flow from one object to another. These are conduction,
convection and radiation.
• Conduction: It is the process by which heat is transferred from the hotter end to the colder
and end of an object.
• Convection: It is the flow of heat through a fluid from places of higher temperature to places
of lower temperature by movement of the fluid itself.
• Radiation: It is the mode of transfer of heat in which energy is directly transferred from one
place to another. It does not need any material medium
• Dark-coloured objects absorb radiation better than the light-coloured objects. That is the
reason we feel more comfortable in light-coloured clothes in the summer.
• Woollen clothes keep us warm during winter. It is so because wool is a poor conductor of
heat and it has air trapped in between the fibres.

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Chapter – 5
Acids, Bases and Salts

• There are three types of Substances: Acids, Bases and Indicators.

• Acids: Acids are sour in taste.
• They are corrosive in nature. A concentrated acid cuts through clothes and eats away the
wool. If it falls on the skin, it can cause burns.
• They are good conductors of electricity, as they allow the passage of electric current through
them.
• Types of Acids:
(i) Mineral Acids: These are acids prepared from minrals present in the earth’s crust.
(ii) Organic Acids: These are acids produced by plants and animals (exception,
hydrochloric acid).
(iii) Weak Acids: These do not dissociate completely in solution. Example: nitric acid,
sulphuric acid.
(iv) Strong Acids: These dissociate completely in solution. Example: tartaric acid, lactic
acid.
• Neutralization: It is the reaction between an acid and a base which results in formation of
salt and water. Acid + Base → Salt + Water . Example: HCl + NaOH → NaCl + H 2O

• Neutralisation in Everyday Life:

(i) Indigestion: Too much acid in stomach causes indigestion. It is neutralized by taking
an antacid like milk of magnesia.
(ii) Ant sting: When an ant bites, it injects formic acid into the skin. The effect is
neutralized by rubbing moist baking soda (sodium hydrogencarbonate) or calamine
(containing zinc carbonate).
(iii) Soil treatment: When the soil is too acidic, it is neutralized by treating with quicklime
(calcium oxide) or slaked lime (calcium hydroxide).
• Acid turns blue litmus red. Bases turn red litmus blue.
• Substances which are neither acidic nor basic are called neutral.
• Solutions of substances that show different colour in acidic, basic and neutral solutions are
called indicators.

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• An acid and a base neutralise each other and form a salt. A salt may be acidic, basic or neutral
in nature.
• Bases: Bases are bitter in taste and soapy to touch.
• Two types of Bases:
(i) Weak Bases: These naturally produce less hydroxide ions in solution. Example:
magnesium hydroxide, ammonium hydroxide.
(ii) Strong Bases: These produce more number of hydroxide ions on dissolving in water.
Example: caustic soda, caustic potash.
• Indicators: It is special chemical that changes its colour to indicate the presence of a
chemical substance.
• It is used to confirm the presence of an acid, a base or a neutral solution.
• Classificaiton of Indicators:
Natural Indicators:
(i) Litmus: It is extracted from lichens. It is available in the form of strips of paper or in
the form of a solution.
(ii) Turmeric: It remains yellow in neutral and acidic solutions but turns red in alkaline
solutions.
(iii) China rose: It turns acidic solutions to dark pink (magenta) and basic solution to
green.
(iv) Red cabbage: It turns acidic solutions to red and basic solutions to blue.
Other Indicators:
(i) Methyl Orange: It gives pinkish red colour with acidic solutions and yellow colour
with bases.
(ii) Phenolphthalein: It is an acid-base indicator. It is colourless in acidic solutions but
turns pink in alkali solutions.

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Chapter – 6
Physical and Chemical Changes

• Changes can be of two types, physical and chemical.

• Physical changes are changes in the physical properties of substances. No new substances
are formed in these changes. These changes may be reversible. Example: dissolution of
sugar in water, glowing of an electric bulb, tearing of paper.
• Chemical Changes are changes in which the composition and chemical properties of the
substance get changed. In chemical changes new substances are produced. This change is
permanent and irreversible. Example: burning of a candle, formation of curd from milk,
ripening of fruits.
• Chemical Reactions in Every day Life:
Rusting of Iron: Rust is a reddish-brown flaky substance that forms on the surface of iron
objects after the process of rusting.
Cooking of food: Cooking causes breakdown of complex molecules of carbohydrates, fats
and proteins into smaller molecules.
It is regarded as a decomposition reaction. Cooked food is easier to digest than uncooked
food.
Decay of Organic Substances: Microorganisms like fungi and bacteria produce enzymes
which break down complex organic compounds into smaller substances.
It is also regarded as a decomposition reaction.
Prevention of Rusting:
By Painting
By Oiling and greasing
By Chromium plating
By Galvanizing
By Alloying
• Some substances can be obtained in pure state from their solutions by crystallisation.

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Chapter – 7
Weather Climate and Adaptations to Climate

• Weather: Weather is the day-to-day condition of the atmosphere at a place influenced by

factors like humidity, temperature, wind speed, etc.
• Humidity is the amount of water vapour present in the atmosphere and is measured by a
hygrometer.
• Sun causes all weather changes.
• Climate: It is the average weather conditions at a specific place over a much longer period of
time.
• Factor affecting climate:
(i) Amount of sunshine
(ii) Whether the region is hilly or a plain
(iii) Distance from the sea
(iv) Direction of prevailing winds from the sea side brings rain to coastal areas and dry
weather to inland areas.
(v) Ocean currents.
(vi) Distance from the equator.
• Adaptations to Climate: The features and habits that help animals to live in a habitat are
called adaptations.
• Three regions are classified according to adaptation:
(i) Polar Regions: Polar regions have extreme climate. Sun does not rise at poles for 6
months and does not set for the other 6 months.
(ii) Tropical Rainforest: Have hot summers and plenty of rainfall. Days and nights are
almost equal in length throughout the year.
(iii) Desert: Have extreme climate. Receive less rainfall and large amount of sunlight.
• Migration:
(i) It is the mass movement of animals, mostly birds, from colder places to warmer
regions to escape the cold, to breed or due to shortage of food.
(ii) Birds are guided by the sun during the day and the stars at night.
(iii) Example: Siberian crane comes to India from Siberia every year.

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Chapter – 8
Winds Stroms and Cyclones

• Air: The invisible gaseous substance surrounding the earth, a mixture mainly of oxygen and
nitrogen.
• Properties of Air:
(i) Air around us exerts pressure.
(ii) Air expands on heating and contracts on cooling.
(iii) Warm air rises up, whereas comparatively cooler air tends to sink towards the earth’s
surface.
(iv) As warm air rises, air pressure at that place is reduced and the cooler air moves to
that place.
• Wind: The moving air is called wind. Air moves from region of high air pressure to region of
low air pressure.
• Types of Wind:
(i) Wind Currents: Wind currents are generated due to uneven heating on earth.
Uneven heating on the earth is the main cause of wind movements.
(ii) Thunderstorms: Storm with thunder and lighting along with rain.
• Winds carrying water vapour bring rain.
• High-speed winds and air pressure difference can cause cyclones.
• It has become easier to monitor cyclones with the help of advance technology like satellites
and radars.
• Self-help is the best help. Therefore it is better to plan in advance and be ready with defence
against any approaching cyclone.
• The following flow chart will help you to understand the phenomena that lead to the
formation of clouds and falling of rain and creation of storms and cyclones.

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Chapter – 9
Soil

• Soil is the uppermost crust that covers the earth. It is a mixture of rock particles and humus.
• Soil is important for life on the earth.
• Formation of Soil:
(i) Soil is formed by weathering or disintergration of parent rocks.
(ii) Physical weathering is degradation of rocks by physical agents like water, ice, wind,
sun, etc.
(iii) Chemical weathering is chemical decomposition of rocks.
(iv) Biological weathering is decomposition of parent rocks by bacteria and
microorganisms.
• Soil Profile: It is the vertical section of soil from the ground surface to the parent rock. Soil
profile is a section through different layers of the soil, Various layers are called horizons.
• Constituents of Soil: Soil consists of both living and non-living matter. These constituents
make the soil fertile.
• Types of Soil: Soil is of different types: clayey, loamy and sandy.
• Sandy soil: It contains soil particles with a diameter of 0.2 to 2.0 mm. It comprises of around
60% sand along with some clay. It has very low water retention capacity. It is not rich in
humus.
• Clayey soil: It contains soil particles with a diameter of less than 0.2 mm. It has an excellent
water retention capacity and air circulation is sufficient.
• Loamy soil: It contains a good mixture of sand, clay and humus. It has a good water retention
capacity and air circulation is sufficient.
• Percolation rate of water is different in different types of soil. It is highest in the sandy soil
and least in the clayey soil.
• Different types of soils are used to cultivate different types of crops. Clay and loam are
suitable for growing wheat, gram and paddy. Cotton is grown in sandy loam soil.
• Soil holds water in it, which is called soil moisture. The capacity of a soil to hold water is
important for various crops.
• Clayey soil is used to make pots, toys and statues.

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Chapter – 10
Respiration in Organisms

• Respiration is essential for survival of living organisms. It releases energy from the food.
• The oxygen we inhale is used to breakdown glucose into carbon dioxide and water. Energy is
released in the process.
• The breakdown of glucose occurs in the cells of an organism (cellular respiration).
• During heavy exercise when the supply of oxygen to our muscle cells is insufficient, food
breakdown is by anaerobic respiration.
• Types of Respiration:
(i) External Respiration: Process in which oxygen is taken inside the body and carbon
dioxide is given out. It is also called breathing.
• External Respiration:
Respiration in Plants: Leaves have pores called stomata for gaseous exchange by diffusion.
Stems have openings called lenticels for gaseous exchange by diffusion. Roots have stomatal
pores for gaseous exchange of oxygen dissolved in soil water.
Respiration in Animals: Respiration in animals are vary according to their character like:
Earthworm: through their skin
Insect: through entire body surface
Fish: respire through their gills
Frogs: through its thin, moist and smooth skin when in water and by lungs when in land
Respiration in Humans: Inhaled air passes through nostrils into nasal cavity and then into
lungs through windpipe.
• Breathing is a part of the process of respiration during which an organism takes in the
oxygen-rich air and gives out air rich in carbon dioxide. The respiratory organs for the
exchange of gases vary in different organisms.
• During inhalation, our lungs expand and then come back to the original state as the air moves
out during exhalation.
• Increased physical activity enhances the rate of breathing.
• In animals like cow, buffalo, dog and cat the respiratory organs and the process of breathing
are similar to those in humans.

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• Internal Respiration: Process in which food is broken down in body cells through various
chemical reactions.
• Internal respiration are further classified into two parts:
(i) Aerobic Respiration: Food molecules are combined with oxygen and get oxidized
inside cell into carbon dioxide and water along with energy.
(ii) Anaerobic Respiration: Food molecules are broken without using oxygen along with
release of energy.

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Chapter – 11
Transportation in Animals and Plants

• In most animals the blood that circulates in the body distributes food and oxygen to different
cells of the body. It also carries waste products to different parts of the body for excretion.
• Circulatory system consists of the heart and blood vessels.
• In humans, blood flows through arteries and veins and the heart acts as a pumping organ.
• Blood is the fluid which flows in blood vessels. It transport substance like digested food from
the small intestine too the other parts of the body.
• Blood consists of plasma, RBC, WBC and platelets. Blood is red due to the presence of a red
pigment, haemoglobin.
• The human heart beats about 70ñ80 times per minute in an adult person. This is called heart
rate.
• Arteries carry blood from the heart to all parts of the body.
• Veins carry blood from all parts of the body back to the heart.
• Removal of waste products from the body is called excretion.
• Excretory system of humans consists of two kidneys, two ureters, a urinary bladder, and
urethra.
• Salts and urea are removed along with water as sweat.
• Fish excrete waste substances such as ammonia which directly dissolve in water.
• Birds, insects and lizard excrete uric acid in semi-solid form.
• Water and mineral nutrients are absorbed by roots from the soil.
• Nutrients are transported along with water to the entire plant via the vascular tissue called
xylem.
• The vascular tissue for the transport of food to the various parts of the plant is phloem.
• A lot of water is lost by plants in the form of vapour through stomata during transpiration.
• Transpiration generates a force which pulls up water absorbed by the roots from the soil, to
reach the stem and leaves.

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Chapter – 12
Reproduction in Plants

• All organisms multiply or reproduce their own kind.

• In plants there are two modes of reproduction, asexual and sexual.
• There are several methods of asexual reproduction such as fragmentation, budding, spore
formation and vegetative propagation.
• Sexual reproduction involves the fusion of male and female gametes.
• In vegetative propagation new plants are produced from different vegetative parts such as
leaves, stems and roots.
• Flower is the reproductive part of a plant.
• A flower may be unisexual with either the male or the female reproductive parts.
• A bisexual flower has both the male and the female reproductive parts.
• The male gametes are found inside the pollen grains and female gametes are found in the
ovule.
• Pollination is the process of transfer of pollen grains from the anther of one flower to the
stigma of the same or another flower.
• Pollination is of two types, self-pollination and cross-pollination. In self-pollination, pollen
grains are transferred from the anther to the stigma of the same flower. In cross-pollination,
pollen grains are transferred from the anther of one flower to the stigma of another flower of
the same kind.
• Pollination takes place in plants with the help of wind, water and insects.
• The fusion of male and female gametes is called fertilisation.
• Fertilised egg is called zygote. Zygote develops into an embryo.
• Fruit is the mature ovary whereas ovule develops into a seed, which contains the developing
embryo.
• Seed dispersal is aided by wind, water and animals.
• Seed dispersal helps the plants to
(i) prevent overcrowding,
(ii) avoid competition for sunlight, water and minerals and
(iii) invade new habitats.

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Chapter – 13
Motion and Time

• Motion: The action or process of moving or being moved.

• The distance moved by an object in a unit time is called its speed.
• Speed of objects help us to decide which one is moving faster than the other.
• The speed of an object is the distance travelled divided by the time taken to cover that
distance. Its basic unit is metre per second (m/s).
• Periodic events are used for the measurement of time. Periodic motion of a pendulum has
been used to make clocks and watches.
• Motion of objects can be presented in pictorial form by their distance-time graphs.
• The distance-time graph for the motion of an object moving with a constant speed is a
straight line.
• Types of Motion:
(i) Uniform motion: An object moving along a straight line with a constant speed is said
to be in uniform motion. The average speed is the same as the actual speed.
(ii) Non-Uniform motion: If the speed of an object moving along a straight line keeps
changing, its motion is said to be non-uniform.
• Speed: It is the distance covered by an object in a unit time. Basic unit of speed is m/s.
Total distance covered
Speed=
Total time taken
• Distance-Time Graph: Motion of objects can be presented in pictorial form by their
distance-time graphs. The distance-time graph for the motion of an object moving with a
constant speed is a straight line.

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Chapter – 14
Electric Current and its Effects

• Electric Current: Flow of electrons through a conductor.

• It is convenient to represent electric components by symbols. Using these, an electric circuit
can be represented by a circuit diagram.
• When an electric current flows through a wire, the wire gets heated. It is the heating effect of
current. This effect has many applications.
• Wires made from some special materials melt quickly and break when large electric currents
are passed through them. These materials are used for making electric fuses which prevent
fires and damage to electric appliances.
• When an electric current flows through a wire, it behaves like a magnet.
• Electric Circuit: A complete pathway of the flow of electric current.
• Component of Electric Circuit:
(i) Cell: Provides energy for the current to flow.
(ii) Bulb: Lights ups when an electric current flows through it.
(iii) Switch: Keeps the circuit off or on.
(iv) Connecting wires: Help to conduct the electric current and complete the circuit.
• Effects of Electric Current:
Heating Effect: The wire gets hot when an electric current passes through it. This is the
heating effect of the electric current. Electric heater contains a coil of wire called element
which becomes red hot when current passes through it. The amount of heat produced in a
wire depends on its material, length and thickness.
(i) Fuse: It is a safety device which prevents damage to electric circuit. It is made by
inserting a short wire into porcelain or insulating material.
(ii) MCB: Stands for Miniature Circuit Breakers. These are switches which automatically
turn off when current in a circuit exceeds the safe limit.
Magnetic Effect: When electric current passes through a wire, it behaves like a magnet. This
is the magnetic effect of the electric current. First observed by Hans Christian Oersted.
• A current carrying coil of an insulated wire wrapped around a piece of iron is called an
electromagnet.
• Electromagnet: An electromagnet is a coil of wire wound on a soft iron core. Used to
separate magnetic material from the junk. Doctors use tiny electromagnets to take out small
pieces of magnetic material that have accidentally fallen in the eye. Many toys also have
electromagnets inside them.

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Chapter – 15
Light

• Light: It is the natural agent that stimulates sight and makes things visible.
• Light travels along straight lines.
• Any polished or a shining surface acts as a mirror.
• An image which can be obtained on a screen is called a real image. It formed by light rays
that actually pass through the screen.
• An image which cannot be obtained on a screen is called a virtual image. It is formed by light
rays that seem to pass through the screen.
• The image formed by a plane mirror is erect. It is virtual and is of the same size as the object.
• The image is at the same distance behind the mirror as the object is in front of it.
• In an image formed by a mirror, the left side of the object is seen on the right side in the
image, and right side of the object appears to be on the left side in the image.
• A concave mirror can form a real and inverted image. When the object is placed very close
to the mirror, the image formed is virtual, erect and magnified.
• A Convex mirror is the mirror that curves out; the reflecting surface is convex. Image
formed is virtual, upright and diminished. Image formed by a convex mirror is erect, virtual
and smaller in size than the object.
• A Concave lens is the lens that is thinner at the centre than at the edges. It is a diverging
lens. Image formed is virtual, erect and diminished.
• A convex lens can form real and inverted image. When the object is placed very close to the
lens, the image formed is virtual, erect and magnified. When used to see objects magnified,
the convex lens is called a magnifying glass.
• White light is composed of seven colours.
• Properties of Light:
Rectilinear Propagation of Light: It is the property of light to travel in a straight line in any
direction. The direction of path in which light make a ray.
Reflection of Light: It is the bouncing back of light after striking the surface of an object.
Shiny smooth surfaces reflect almost all the light.
Dispersion: It is the phenomenon of splitting of white light into its seven colours. White light
is mixture of: Violet, Indigo, Blue, Green, Yellow, Orange and Red (VIBGYOR) colours.

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Chapter – 16
Water: A Precious Resource

• Water is essential for all living beings. There can be no life without it.
• Water exists in three forms: solid, liquid and vapour.
• Solid: At poles of earth, snow-covered mountains and glaciers.
• Liquids: In oceans, lakes, rivers and underground.
• Gaseous: Water vapour in air.
• Surface water: Sea and oceans, Rivers, Springs, Lakes and Ponds.
• Ground water: It is the water that sweeps into the ground through soil and collects over
non-porous rocks (aquifier). Level of groundwater at any place is called water table.
Groundwater gets recharged by seepage of water into the ground (infiltration).
• Water scarcity: Depletion of water table:
(i) Increase population decreases open areas which decreases seepage of rainwater.
(ii) Increasing industries more water is drawn out from ground.
(iii) Agricultural activities irrigation systems fail due to erratic rainfall which results in
increased used of ground water.
(iv) Uneven distribution of rainfall.
(v) Scanty rainfall.
(vi) Deforestation.
• Though water is maintained by the water cycle, yet there is an acute scarcity of water in
many parts of the globe.
• There is an uneven distribution of water. Much of it has resulted from human activities.
• Rapid growth of industries, increasing population, growing irrigation requirements and
mismanagement are some of the causes for water shortage.
• We need to be worried about the wastage during the supply of water through pipes, the
leaking taps in buildings and other places.
• Unnecessary use of water and overdrawing from groundwater should be avoided. Recharge
of water to the ground should be increased.
• The need of the hour is that every individual uses water economically.
• Plants wilt and ultimately dry-up if they are not watered for a few days.

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Chapter – 17
Forests: Our Lifeline

• Forest: Large area of land thickly covered with trees, bushes, etc.
• We get various products from the forests surrounding us.
• Forest is a system comprising various plants, animals and micro-organisms.
• In a forest, trees form the uppermost layer, followed by shrubs. The herbs form the lowest
layer of vegetation.
• Different layers of vegetation provide food and shelter for animals, birds and insects.
• The various components of the forest are interdependent on one another.
• The forest keeps on growing and changing, and can regenerate.
• In the forest, there is interaction between soil, water, air and living organisms.
• Forests protect the soil from erosion.
• Soil helps forests to grow and regenerate.
• Forests are the lifeline for the forest-dwelling communities.
• Forests influence climate, water cycle and air quality.
• Importance of Forests:
(i) Provide timber.
(ii) Purify air.
(iii) Provide shelter.
(iv) Prevent soil erosion.
(v) Control floods.
(vi) Noise absorbers.
• Independence of Plants and Animals in Forest:
(i) Plnats and animals depends on each other to remain alive.
(ii) All organisms interact with each other and their physical environment to derive
energy and survive.
• Conservation of Forest:
(i) Amount of carbon dioxide in air will increase, resulting in the increase of earth’s
temperature.
(ii) Animals will not get food and shelter.

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(iii) Soil will not hold water, which will cause floods.
(iv) Endanger lives and environment.
• Conservation of Forests:
(i) Do not allow overgrazing.
(ii) Promote afforestation.
(iii) Protect wildlife.
(iv) Control forest fires.
• Food Chain: Interdependence between producers and consumers studied in form of various
linkage that appears as a chain.

• Food Web: A system of interdependent food chains used to represent various relationships
of organisms.

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Chapter – 18
Wastewater Story

• Wastewater: Rich in lather, mixed with oil, black-brown water that goes down the drains
from skins, showers, toilets, laundries is called wastewater.
• Wastewater is generated in homes, industries, agricultural fields and in other human
activities. This is called sewage.
• Sewage is a liquid waste which causes water and soil pollution.
• Wastewater is treated in a sewage treatment plant.
• Treatment plants reduce pollutants in wastewater to a level where nature can take care of it.
• Where underground sewerage systems and refuse disposal systems are not available, the
low cost on-site sanitation system can be adopted.
• By-products of wastewater treatment are sludge and biogas.
• Open drain system is a breeding place for flies, mosquitoes and organisms which cause
diseases.
• We should not defecate in the open. It is possible to have safe disposal of excreta by low cost
methods.
• Sewage Treatement:
(i) Aeration: Air is bubbled throught the wastewater while it is continuously stirred.
(ii) Filtration: Aerated water passes through a deep filter of layered sand, fine gravel and
medium gravel.
(iii) Chlorination: To the filtered water chlorine is added and mixed until water is clear.
• Wasterwater Treatemetn Plant (WWTP):
(i) Wastewater passes through screens to remove large objects.
(ii) To goes to a grit and sand removal tank at low speed.
(iii) Water is allowed to settle in large tank.
(iv) Floating solids are removed with skimmer. Settled solids (sludge) are removed with
scraper.
(v) Clear water is called clarified water.
(vi) Water is then decomposed by anaerobic bacteria in a tank and air is passed.
(vii) Microbes settled at bottom as activated sludge and water from top is removed.

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Key Notes
Chapter – 1
Crop Production and Management

• In order to provide food to our growing population, we need to adopt certain agricultural
practices.
• Same kind of plants grown and cultivated at a place constitute a crop.
• In India, crops can be broadly categorised into two types based on seasons - rabi and
Kharif crops.
• It is necessary to prepare soil by tilling and levelling. Ploughs and levellers are used for
this purpose.
• Sowing of seeds at appropriate depths and distances gives good yield. Good variety of
seeds are sown after selection of healthy seeds. Sowing is done by seed drills.
• Soil needs replenishment and enrichment through the use of organic manure and
fertilisers. Use of chemical fertilisers has increased tremendously with the introduction of
new crop varieties.
• Preparation of Soil:
(i) Few inches of the top sooil is loosened and turned ploughing/tilling.
(ii) Weeds are removed from the soil before removed from the soil before sowing the
seeds.
(iii) Ploughed field has big soil pieces (crumbs) which are broken by planks.
(iv) Field is levelled for sowing.
• Supply of water to crops at appropriate intervals is called irrigation.
• Weeding involves removal of unwanted and uncultivated plants called weeds.
• Harvesting is the cutting of the mature crop manually or by machines.
• Separation of the grains from the chaff is called threshing.
• Proper storage of grains is necessary to protect them from pests and microorganisms.
• Food is also obtained from animals for which animals are reared. This is called animal
husbandry.
• Fertiliser: The inorganic compounds containing nutrients such as nitrogen, potassium
and phosphorus. They are made in the factories. Example: Urea, ammonium sulphate,
potash, etc.

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Key Notes
• Cultivator: Used for ploughing the soil and is driven by a tractor. This helps to save time
and labour.
• Hoe: Used for loosening the soil and for removing weeds.
• Irrigation: Supplying of water to the crop plants from the wells, canals or water
reservoirs.
Method of Irrigation:
(i) Tradition methods of Irrigation: Moat, Chain pump, Dheki, Rahat.
(ii) Modern methods of Irrigation: Sprinkler system, Drip system.
• Harvesting: The cutting and collecting of the matured crops from the fields. Harvesting
in our country is either done manually by sickle or by a machine called harvester.
• Storage: Harvested food grains normally contain more moisture than required for
storage. Large scale of storage of grains is done in silos and granaries to protect them
from pest like rats and insects. Farmers store grains in jute bags or metallic bins.
• Manure: A natural substance prepared from decomposition of plant and animal wastes
(cow dung, animal bones, dead leaves, dead insects and vegetable wastes) by the action of
microbes.

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Key Notes
Chapter – 2
Microorganisms: Friend and Foe

• Microorganisms: Microorganisms are too small and are not visible to the unaided eye.
• They can live in all kinds of environment, ranging from ice cold climate to hot springs and
deserts to marshy lands.
• Microorganisms are found in air, water and in the bodies of plants and animals.
• They may be unicellular or multicellular.
• Microorganisms include bacteria, fungi, protozoa and some algae. Viruses, though
different from the above mentioned living organisms, are considered microbes.
• Viruses are quite different from other microorganisms. They reproduce only inside the
host organism; bacterium, plant or animal cell.
• Some microorganisms are useful for commercial production of medicines and alcohol.
• Some microorganisms decompose the organic waste and dead plants and animals into
simple substances and clean up the environment.
• Protozoans cause serious diseases like dysentery and malaria.
• Some of the microorganisms grow on our food and cause food poisoning.
• Some microorganisms reside in the root nodules of leguminous plants. They can fix
nitrogen from air into soil and increase the soil fertility.
• Some bacteria and blue green algae present in the soil fix nitrogen from the atmosphere
and convert into nitrogenous compounds.
• Certain bacteria convert compounds of nitrogen present in the soil into nitrogen gas
which is released to the atmosphere.
• Pathogens: Some of the microorganisms cause diseases in human beings, plants and
animals. Such disease causing microorganisms are called pathogens.
• Cleaning of Environment: The microorganisms decompose dead organic waste of plants
and animals converting them into simple substances. These substances are again used by
other plants and animals. Microorganisms can be used to degrade the harmful and smelly
substances and thereby clean up the environment.

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Key Notes
Chapter – 3
Synthetic Fibres and Plastics

• Synthetic fibres and plastics, like natural fibres, are made of very large units called
polymers. Polymers are made up of many smaller units. Polymers are made up of many
smaller units.
• While natural fibres are obtained from plants and animals, synthetic fibres are obtained
by chemical processing of petrochemicals. Like natural fibres, these fibres can also be
woven into fabrics.
• Synthetic fibres find uses ranging from many household articles like ropes, buckets,
furniture, containers, etc. to highly specialized uses in aircrafts, ships, spacecrafts,
healthcare, etc.
• Depending upon the types of chemicals used for manufacturing synthetic fibres, they are
named as Rayon, Nylon, Polyester and Acrylic.
• The different types of fibres differ from one another in their strength, water absorbing
capacity, nature of burning, cost, durability, etc.
• Today, life without plastics cannot be imagined. Be it home, or outside, plastic is every
where.
• The waste created by plastics is not environment friendly. On burning plastics release
poisonous gases. On dumping in the ground they may take years to degenerate. This is
because of their non-biodegradable nature.
• We need to use synthetic fibres and plastics in such a manner that we can enjoy their
good qualities and at the same time minimise the environmental hazards for the living
communities.
• Types of Synthetic Fibers:
(i) Rayon: It is made from cellulose obtained from wood pulp. It is used to make
containers, car upholstery, etc.
(ii) Nylon: A polyamide made from petroleum. It is lightweight, strong and durable.
The fabric allows easy evaporation and dries quickly. It is used in parachutes, flak
vest, combat uniforms, tires, etc.

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Key Notes
(iii) Polyester: A versatile and important man-made fabric. It has an outstanding
characteristic of resisting wrinkle and springing back into its crisp, smooth shape.
It is strong and soft. It is used in dresses, suits, rainwear, etc.
(iv) Acrylic: A fibre similar to that of wool and is used to make sweater, blankets,
shawls, etc. It is lightweight, soft and warm. Also it is cheaper than natural wool. It
is resistant to chemicals, moths and sunlight. Therefore, they are widely in use
nowadays.
• Plastics: Like synthetic fibres, plastic is also a polymer. Some plastics have a linear
arrangement of the units and some have a cross-linked arrangement of the units.
Examples: Polythene.
• Characteristics of Plastics:
(i) Non-reactive: Not affected by air, water, soil, etc.
(ii) Light, strong and durable: Light, strong and durable and can be moulded into
different shapes and sizes.
(iii) Poor Conductors: Do not allow heat and electricity to flow through them.
• Effect of Plastics on Environment: Natural materials like wood and paper are
biodegradable (bio = living; degeradable = able to broken down). In contrast, most
plastics do not decay, therefore, they are non-biodegradable. The lightweight nature of
plastics can also be a problem. Burning of plastics also release poisonous fumes into the
atmosphere. This way plastics pollute the environment.

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Key Notes
Chapter – 4
Materials: Metals and Non-Metals

• Metals are lustrous whereas non-metals have no lustre.

• Generally, metals are malleable and ductile. Non-metals do not have these properties.
• Generally, metals are good conductors of heat and electricity but non-metals are poor
conductors
• On burning, metals react with oxygen to produce metal oxides which are basic in nature.
Non-metals react with oxygen to produce non- metallic oxides which are acidic in nature.
• Some metals react with water to produce metal hydroxides and hydrogen gas. Generally,
non- metals do not react with water.
• Metals react with acids and produce metal salts and hydrogen gas. Generally, non-metals do
not react with acids.
• Some metals react with bases to produce hydrogen gas.
• More reactive metals displace less reactive metals from their compounds in aqueous
solutions.
• Metals and non-metals are used widely in every day life.

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Key Notes
Chapter – 5

Coal and Petroleum

• Natural Resources: Resources include everything provide by the nature. They form the

wealth of a country.

• Types of Natural Resources:

(i) Inexhaustible: There are some resources that are present unlimited in nature and

will not be exhausted even if used continuously. Example: Sunlight, Air.

(ii) Exhaustible: These resources are limited and can soon get exhausted because of

their excessive use. Example: Forests, wildlife, minerals, coal, petroleum, etc.

• Coal, petroleum and natural gas are fossil fuels.

• Fossil fuels were formed from the dead remains of living organisms millions of years ago.

• Fossil fuels are exhaustible resources.

• Coke, coal tar and coal gas are the products of coal.

• Petroleum gas, petrol, diesel, kerosene, paraffin wax, lubricating oil are obtained by

refining petroleum.

• Coal and petroleum resources are limited. We should use them judiciously.

• Refining: Petroleum is mixture of various constituents such as petroleum gas, petrol,

diesel, lubricating oil, paraffin wax, etc. Refining is the process of refracting the various

constituents / fractions of petroleum. It carried out in a petroleum refinery.

• Natural Gas: A very important fuel as it easy to transport through pipes and can be

compressed and stored under high pressure as Compressed Natural Gas. It causes no

pollution and has high calorific value.

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Key Notes
Chapter – 6
Combustion and Flame

• Combustion: The process of burning a substance in the presence of air (oxygen) and
undergoes a chemical reaction to produce heat and light.
• The substances which burn in air are called combustible.
• Oxygen (in air) is essential for combustion.
• During the process of combustion, heat and light are given out.
• Ignition temperature is the lowest temperature at which a combustible substance catches
fire.
• Flame: It is a zone or burning vapour. The substances which vapourise during burning give
flames. Example: Kerosene oil and molten wax.
• Inflammable substances have very low ignition temperature.
• Fire can be controlled by removing one or more requirements essential for producing fire.
• Water is commonly used to control fires.
• Water cannot be used to control fires involving electrical equipments or oils.
• There are various types of combustions such as rapid combustion, spontaneous combustion,
explosion, etc.
• There are three different zones of a flame - dark zone, luminous zone and non-luminous
zone.
• An ideal fuel is cheap, readily available, readily combustible and easy to transport. It has high
calorific value. It does not produce gases or residues that pollute the environment.
• Fuels differ in their efficiency and cost.
• Fuel efficiency is expressed in terms of its calorific value which is expressed in units of
kilojoule per kg.
• Types of Fuels:
(i) Solid Fuels: Combustile substances which are solid at room temperature. Example:
coal, coke, wood, charcoal, etc.
(ii) Liquid fuels: Volatile liquids which produce combustible vapour. Example: Petrol,
kerosene, alcohol, diesel, etc.

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Key Notes
(iii) Gasous fuels: Combustible gases or mixture of combustile gases. Example: Natural
gas, LPG, biogas, coal gas, etc.
• Effects of Burning of Fuels:
(i) Carbon fuels like wood, coal petroleum release unburnt carbon particles. These are
dangerous pollutants causing respiratory diseases, such as asthma.
(ii) Incomplete combustion of carbon fuels gives carbon monoxide which is a poisonous
gas.
(iii) Increased concentration of carbon dioxide in the air is believed to cause global
warming.
(iv) Oxides of Sulphur and nitrogen dissolve in rain water and form acids. Such rain is
called acid rain. It is very harmful for crops, buildings and soil.
• Unburnt carbon particles in air are dangerous pollutants causing respiratory problems.
• Incomplete combustion of a fuel gives poisonous carbon monoxide gas.
• Increased percentage of carbon dioxide in air has been linked to global warming.
• Oxides of sulphur and nitrogen produced by the burning of coal, diesel and petrol cause
acid rain which is harmful for crops, buildings and soil.

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Key Notes
Chapter – 7
Conservation of Plants and Animals

• Biodiversity: Occurrence of innumerable number of different types of organisms and the

whole range of their varieties (biotypes) adapted to different climates, environments and
areas.
• Wildlife sanctuary, national park and bio-sphere reserve are names given to the areas
meant for conservation and preservation of forest and wild animals.
• Biodiversity refers to the variety of living organisms in a specific area.
• Plants and animals of a particular area are known as the flora and fauna of that area.
• Endemic species are found only in a particular area.
• Endangered species are those which are facing the danger of extinction.
• Red Data Book contains a record of endangered species.
• Migration is the phenomenon of movement of a species from its own habitat to some
other habitat for a particular time period every year for a specific purpose like breeding.
• We should save, reuse and recycle paper to save trees, energy and water.
• Reforestation is the restocking of destroyed forests by planting new trees.
• Flora: Different types of plants belonging to an area. Example: Silver ferns, sal, teak,
mango, etc.
• Fauna: All animals found in an area. Example: dog, frog, insects, bull, jackal, etc.
• Endemic Species: Species of plants and animals found exclusively in a particular area.
These are not naturally found anywhere else.
• Extinct Species: Species of plants and animals which have already been lost. Example:
Dodo, Indian cheetah, Pink-headed duck, etc.
• Threatened Species: Species that is liable to become extinct if it is not allowed to realise
its full biotic potential by removed the caused of threat.
• Type of Threatened Species:
(i) Endangered Species: A species of animal or plant that is seriously at risk of
extinction. Example: Indian rhinoceros, Asiatic lion, Asiatic wild ass, etc.

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Key Notes
(ii) Vulnerable Species: A vulnerable species is a species of animals or plants which
are likely to become endangered unless something changes. Example: Chinkara
deer and black buck, golden langur, etc.
(iii) Rare Species: Species whose population are originally small and scattered in the
world.
• National Parks: Protective areas reserved exclusively for the betterment of the wildlife.
These are established at the approval of legislature. Example: Hazaribagh National Park
in Jharkhan, Desert National Park in Rajathan, etc.
• Sanctuaries: Hunting prohibited areas set up by government are known as sanctuaries.
These are only for the protection of wild animals. Example: Jaldapara in Madarihat (West
Bengal), Keoladeo Ghana in Bharatpur (Rajasthan)
• Migration: The regular, periodic, two way movements of birds and some animals from
their place of residence to some other place along well defined routes. It is linked to
seasonal factors, breeding, shortage of foods, etc. The Bharatpur bird sanctuary is known
for the migratory birds.

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Key Notes
Chapter – 8
Cell — Structure and Functions

• Cell: The smallest structural and functional unit of an organism, which is typically
microscopic and consists of cytoplasm and a nucleus enclosed in a membrane.
• All organisms are made of smaller parts called organs.
• Organs are made of still smaller parts. The smallest living part of an organism is a ‘cell’.
• Cells were first observed in cork by Robert Hooke in 1665.
• Cells exhibit variety of shapes and sizes.
• Number of cells also varies from organism to organism.
• Some cells are big enough to be seen with the unaided eye. Hen’s egg is an example.
• Some organisms are single-celled, while others contain large number of cells.
• The single cell of unicellular organisms performs all the basic functions performed by a
variety of cells in multicellular organisms.
• The cell has three main parts, (i) the cell membrane, (ii) cytoplasm which contains
smaller components called organelles, and (iii) the nucleus.
• Cell membrane: The basic component of a cell. The cytoplasm and nucleus are enclosed
within cell membrane. There is an outer thick layer in cells of plants called cell wall.
• Cytoplasm: The jelly-like substance present between the cell membrane and the nucleus.
Various organelles present in the cytoplasm are:
(i) Mitochondria
(ii) Plastids (present only in plant cell)
(iii) Endoplasmic reticulum (ER)
(iv) Ribosome
(v) Lysosome
(vi) Vacuole
(vii) Golgi body
(viii) Centrosome (present only in animal cell).
• Nucleus: Nucleus is separated from cytoplasm by a nuclear membrane. It is generally
spherical in the centre of the cell.

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Key Notes
• Nuclear membrane: Nucleus is separated from the cytoplasm by a membrane called the
nuclear membrance.
• Nucleolus: Nucleus contains a still smaller round body known as nucleoulus.
• Chromosomes: Nucleus contains thread-like structures called chromosomes. These
carry genes and help in inheritance or transfer of character from the parents to the
offsprings
• Cells without well organised nucleus, i.e. lacking nuclear membrane, are called
prokaryotic cells.
• Plant cells differ from animal cells in having an additional layer around the cell
membrane termed cell wall.
• Coloured bodies called plastids are found in the plant cells only. Green plastids containing
chlorophyll are called chloroplasts.
• Plant cell has a big central vacuole unlike a number of small vacuoles in animal cells.
• Size of cells: The size may be as small as a millionths of a metre or may be as large as a
few centimetres. Size of the cells has no relation with the size of the body of the animal or
plant. It is related to its function.

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Key Notes
Chapter – 9
Reproduction in Animals

• There are two modes by which animals reproduce. These are: (i) Sexual reproduction, and
(ii) Asexual reproduction
• Reproduction resulting from the fusion of male and female gametes is called sexual
reproduction.
• The reproductive organs in the female include ovaries, oviducts and uterus.
• The reproductive organs in male include testes, sperm ducts and penis.
• The ovary produces female gametes called ova and the testes produce male gametes called
sperms.
• The fusion of ovum and sperm is called fertilization. The fertilized egg is called a zygote.
• Fertilization that takes place inside the female body is called internal fertilization. This is
observed in human beings and other animals such as hens, cows and dogs.
• Fertilization that takes place outside the female body is called external fertilization. This is
observed in frogs, fish, starfish, etc.
• The zygote divides repeatedly to give rise to an embryo.
• The embryo gets embedded in the wall of the uterus for further development.
• The stage of the embryo in which all the body parts are identifiable is called foetus.
• Animals such as human beings, cows and dogs which give birth to young ones are called
viviparous animals.
• Oviparous Animals: Animals that lay eggs are called oviparous animals, e.g., frogs, lizards,
butterflies, etc.
• Animals such as hen, frog, lizard and butterfly which lay eggs are called oviparous animals.
• The transformation of the larva into adult through drastic changes is called metamorphosis.
• The type of reproduction in which only a single parent is involved is called asexual
reproduction.
• In hydra, new individuals develop from buds. This method of asexual reproduction is called
budding.
• Amoeba reproduces by dividing itself into two. This type of asexual reproduction is called
binary fission.

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Key Notes
Chapter – 10
Reaching the age of Adolescence

• Humans become capable of reproduction after puberty sets in. Between the ages of 11
years and 19 years children are called ado- lescents.
• The onset of puberty brings about growth of the reproductive organs. Hair grow at
various places on the body. Breasts develop in girls and facial hair (moustache and beard)
appear in boys. Voice of boys becomes hoarse as voice box enlarges during adolescence.
• Children gain height during adolescence.
• Puberty: It is the time when sex organs begin to work. It brings about growth in
reproductive organs and changes in the body.
• Changes during Puberty:
(i) Increase in Height: The bones of the legs and arms elongate and the individual
becomes tall and lanky.
(ii) Changes in Body Shape: In boys, the body becomes more muscular, the shoulder
becomes wider. In girls, the body shows curves in certain parts and the region
below the waist become wider and broader.
(iii) Change in Voice: In boys, the voice becomes hoarse and heavy due to the extra
growth of larynx (voice box). In girls, the voice becomes high pitched and shriller.
(iv) Sweat and sebaceous glands: It become more active and secrete more sweat and
oil.
(v) Emotional aspects develop.
(vi) Mental and intellectual development is at its peak.
• The onset of puberty and maturity of reproductive parts are controlled by hormones.
• Hormones are secretions of endocrine glands which pour them directly into the blood
stream.
• Pituitary gland secretes hormones which in- clude growth hormone and hormones that
make other glands such as the testes, ovaries, thyroids and adrenals, secrete hormones.
Pancreas secretes insulin, thyroid produces thyroxine and adrenals produce adrenalin.
• Testosterone is the male hormone and estrogen, the female hormone. The uterine wall in
females prepares itself to receive the developing fertilised egg. In case there is no
fertilisation, the thickened lining of the uterine wall breaks down and goes out of the
body along with blood. This is called menstruation.
• Sex of the unborn child depends on whether the zygote has XX or XY chromosomes.
• It is important to eat balanced food and maintain personal hygiene during adolescence.

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Key Notes
Chapter – 11
Force and Pressure

• Force: A push or a pull, that changes or tends to change the state of rest or uniform
motion of an object or changes its direction or shape.
• A force arises due to the interaction between two objects.
• Force has magnitude as well as direction.
• A change in the speed of an object or the direction of its motion or both implies a change
in its state of motion.
• Force acting on an object may cause a change in its state of motion or a change in its
shape.
• A force can act on an object with or without being in contact with it.
• Types of Forces:
• Contact Forces: The forces act on a body when the source of force is in actual contact
with the body.
(i) Muscular Force: The force exerted by the muscles of the body.
(ii) Mechanical Force: The force produced by a machine.
(iii) Frictional Force: The force that opposes the motion of an object.
• Non-Contact Forces: Forces which do not involve physical contact between two bodies
on which they act.
(i) Magnetic Force: A magnet exerts a non-contact force on objects made of iron,
steel, cobalt or nickel.
(ii) Electrostatic Force: The force which result due to repulsion of similar charges or
attraction of opposite charges.
(iii) Gravitational Forces: The force that exists between any two masses because of
their mass.
• Force per unit area is called pressure.
• Liquids and gases exert pressure on the walls of their containers.
• The pressure exerted by air around us is known as atmospheric pressure.

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Key Notes
Chapter – 12
Friction

• Friction: A force that opposes motion between two objects that are in contact with each
other. Smoother surfaces exhibit less friction, rougher surfaces exhibit more friction.
• Friction opposes the relative motion between two surfaces in contact. It acts on both the
surfaces.
• Friction depends on the nature of surfaces in contact.
• Types of Friction:
(i) Static Friction: When a body is at rest, the force of friction is called the static
friction and is always equal and opposite to the applied force. The force of friction
which acts when the body is just at the verge of sliding on the surface is called
limiting friction.
(ii) Sliding friction: The friction force which opposes the actual relative sliding
motion between two contact surfaces. Sliding friction is smaller than static
friction.
(iii) Rolling Friction: The frictional force that exists between two surfaces when a
body rolls over the other. Rolling friction is smaller than sliding friction.
• Increasing Friction: By pressing the surfaces together more strongly. When brakes are
applied on a bicycle or car, the brake pads press against a moving part of the wheel and
the force of friction increases.
• Reducing Friction: Polishing, Lubricating, using ball bearings, separation of surfaces by
air, streamlined shape.
• Causes of friction: Friction is caused by the irregularities on the two surfaces in contact.
Even those surfaces which appear very smooth have a large number of minute
irregularities on them.
• For a given pair of surfaces friction depends upon the state of smoothness of those
surfaces.
• Friction depends on how hard the two surfaces press together.
• Static friction comes into play when we try to move an object at rest.
• Sliding friction comes with play when an object is sliding over another.

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Key Notes
• Sliding friction is smaller than static friction.
• Friction is important for many of our activities.
• Friction can be increased by making a surface rough.
• The sole of the shoes and the tyres of the vehicle are treaded to increase friction.
• The friction is sometimes undesirable.
• Friction can be reduced by using lubricants.
• When one body rolls over another body, rolling friction comes into play. Rolling friction is
smaller than the sliding friction.
• In many machines, friction is reduced by using ball bearings.
• Fluid friction can be minimised by giving suitable shapes to bodies moving in fluids.

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Key Notes
Chapter – 13
Sound

• Sound: A kind of sensation received by our ears and perceived by our brain. Sound is
produced by vibrating objects.
• Musical Sound: The sound which produce a pleasing effect on the ear.
• Noise: The sounds which produce a jarring or unpleasant effect.
• Types of Sound:
(i) Audible Sound: Vibrations whose frequency lies between 20 Hz to 20,000 Hz (20
kHz)
(ii) Inaudible Sound: The sounds having frequencies above 20,000 Hz and below 20
Hz cannot be heard by the normal human ear.
• In human beings, the vibration of the vocal cords produces sound.
• Sound travels through a medium (gas, liquid or solid). It cannot travel in vacuum.
• The eardrum senses the vibrations of sound, It sends the signals to the brain. This process
is called hearing.
• The number of oscillations or vibrations per second is called the frequency of oscillation.
• The frequency is expressed in hertz (Hz)
• Larger the amplitude of vibration, louder is the sound.
• Higher the frequency of vibration, the higher is the pitch, and shriller is the sound.
• Unpleasant sounds are called noise.
• Excessive or unwanted sounds lead to noise pollution. Noise pollution may pose health
problems for human beings.
• Attempts should be made to minimise noise pollution.
• Plantation on the roadside and elsewhere can reduce noise pollution.
• Amplitude: The maximum distance of a vibrating or swinging object from its position of
rest.
• Time Perios: One complete to and fro movement of the pendulum around its mean
position is called one oscillation. The time taken by the vibrating particle to complete one
oscillation is called time period.

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Key Notes
• Frequency: The number of vibrations or oscillations made by a vibrating body in a
second. The unit of frequency is hertz (Hz).
• Characteristics of Sounds:
(i) Loudness: The sensation produced in the ear which enables us to distinguish
between a loud and a faint sound. Larger the amplitude of vibration, the louder is
the sound produced.
(ii) Pitch: The characterisitics of sound which distinguishes between a shrill sound
and a soft sound. Higher the frequency of vibration, higher is the pitch.
(iii) Quality: Characteristic which enables us to distinguish between musical notes
emitted by different musical instruments or voices even though they have the
same pitch and loudness.

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Key Notes
Chapter – 14
Chemical Effects of Electric Current

• On passage of electric current through a solution following chemical effects may be seen:
(i) Bubbles of a gas on electrodes
(ii) Deposits of metal on electrodes
(iii) Change of colour of solution
• Conduction of Electricity by Liquids:
(i) Liquids containing salts, acids or bases conduct electricity.
(ii) Distilled water does not conduct electricity because it does not have free ions.
(iii) The liquid which conducts electricity and undergoes decomposition is called the
electrolyte.
(iv) The electrode connected to the positive terminal of battery is called anode while
the connected to the negative terminal is called cathode.
• Electrolysis: The chemical decomposition of constituents solution on passage of electric
current.
• Electroplating: It is the process of depositing a thin layer of a metal on any conducting
substance by the process of electrolysis.
The object to be electroplated is made the cathode (negative electrode) by connecting it
to the negative terminal of the battery. The metal which has to be deposited is made the
anode (positive electrode) by connecting it to the positive terminal of the battery. The
electrolyte is usually a salt solution of the metal to be coated.
• Application of Electroplating:
(i) Metals that rust are often coated with other metals to prevent rusting.
(ii) Chromium plating is found on bath taps, car bumpers, etc. to give a bright
attractive appearance and resist scratches and wear.
(iii) Silver plating is done on cutlery and jewellery items.
• Some liquids are good conductors of electricity and some are poor conductors.
• Most liquids that conduct electricity are solutions of acids, bases and salts.
• The passage of an electric current through a conducting liquid causes chemical reactions.
• The resulting effects are called chemical effects of currents.
• The process of depositing a layer of any desired metal on another material, by means of
electricity, is called electroplating.

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Key Notes
Chapter – 15
Some Natural Phenomena

• Some objects can be charged by rubbing with other objects.

• There are two kinds of charges — positive charge and negative charge
• Like charges repel and unlike charges attract each other.
• The electrical charges produced by rubbing are called static charges.
• When charges move, they constitute an electric current.
• An electroscope may be used to detect whether a body is charged or not.
• The process of transfer of charge from a charged object to the earth is called earthing.
• The process of electric discharge between clouds and the earth or between different clouds
causes lightning.
• Lightning strike could destroy life and property.
• Lightning conductors can protect buildings from the effects of lightning.
• An earthquake is a sudden shaking or trembling of the earth.
• Earthquake is caused by a disturbance deep inside the earth’s crust.
• It is not possible to predict the occurrence of an earthquake.
• Earthquakes tend to occur at the boundaries of earth’s plates. These boundaries are know as
fault zones.
• Destructive energy of an earthquake is measured on the Richter scale. The earthquake
measuring 7 or more on Richter scale can cause severe damage to life and property.
• We should take necessary precautions to protect ourselves from earthquakes.
• Richter Scale: A logarithmic scale, ranging from 1 to 10 for indicating the intensity of an
earthquake.
• Seismic Waves: The energy released at the focus of an earthquake, propagates outwardly.
• Seismograph: An instrument by which seismic waves of an earthquake are monitored.
• Epicentre: A point on the earth above the seismic force.
• Fault Zones: Earthquake prone areas in the earth’s crust.

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Key Notes
Chapter – 16
Light

• Light: The natural agent that stimulates sight and makes things visible. Light is reflected
from all surfaces.
• Regular reflection takes place when light is incident on smooth, polished and regular
surfaces.
• Diffused/irregular reflection takes place from rough surfaces.
• Reflection of Light: Bouncing back of light after striking the surface, in the same
medium, is called reflection.
• Types of Reflection:
(i) Regular Reflection: When a narrow beam of light strikes a mirror, the light will
not reach your eye unless your eye is positioned at just the right place where the
law of reflection is satisfied.
(ii) Diffused or Irregular Reflection: When light is incident upon a rough surface, it
is reflected in many directions.
• Two laws of reflection are
• The angle of incidence is equal to the angle of reflection.
• Incident ray, reflected ray and the normal drawn at the point of incidence to the reflecting
surface, lie in the same plane.
• Image formed in a plane mirror undergoes lateral inversion.
• Two mirrors inclined to each other give multiple images.
• Beautiful patterns are formed in a kaleidoscope because of multiple reflections.
• Sunlight, called white light, consists of seven colours.
• Splitting of light into its constituent colours is known as dispersion.
• Important parts of the eye are cornea, iris, pupil, lens, retina and optic nerve.
• A normal eye can see nearby and distant objects clearly.
• Visually challenged persons can read and write using Braille system.
• Visually challenged persons develop their other senses more sharply to improve their
interaction with their environment.
• Parts of Human Eye:

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Key Notes
(i) Cornea: Transparent bulge on the front surface of the eyeball which protects the
eye and helps in refraction of light.
(ii) Iris: Coloured diaphragm behind the cornea which controls the amount of light
entering the eye.
(iii) Pupil: Dark hole in the middle of iris through which light enters the eye.
(iv) Eye lens: Transparent, crystalline structure behind pupil and iris.
(v) Ciliary muscles: Hole the eye lens in position and control the focal length of the
eye lens.
(vi) Retina: Surface of the rear part of the eyeball where the light entering the eye is
focused.
(vii) Rods and Cones: Rod cells respond to the brightness of light while cone cells
respond to colours.
(viii) Blind spot: It is the least sensitive point where no rodsd and cones are present.
(ix) The space between the cornea and the eye lens is filled with aqueous humour.
(x) The space between the eye lens and the retina is filled with vitreous humour.

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Key Notes
Chapter – 17
Stars and the Solar System

• The phases of the moon occur because we can see only that part of the moon which reflects
the light of the Sun towards us.
• Stars are celestial bodies that emit light of their own. Our sun is also a star.
• It is convenient to express distances of stars in light years.
• Stars appear to move from east to west.
• The pole star appears to be stationary from the Earth, because it is situated close to the
direction of the axis of rotation of the Earth.
• Constellations are groups of stars that appear to form recognisable shapes.
• The solar system consists of eight planets and host of asteroids, comets and meteors.
• A body revolving around another body is called a satellite.
• Moon is the natural satellite of the Earth. Some planets also have natural satellites.
• Venus is the brightest planet in the night sky.
• Jupiter is the largest planet of the solar system.
• The artificial satellites revolve around the Earth. They are much closer than the moon.
• Artificial satellites are used for weather forecasting, long distance communication and
remote sensing.
• Sun: It is the source of almost all energy on Earth. It continuously emits huge amounts of
heat and light.
• Planets: A planet has a definite path in which it revolves around the sun called orbit. Time
taken by a planet to complete one revolution increases as the distance from the sun
increases.
• There are eight planets in our solar system: Mercury, Venus, Earth, Mars, Jupitar, Saturn,
Uranus, Neptune.
• Other members in our solar system are:
(i) Asteroids: These are rocky planetary bits orbiting around sun. asteroid belt lies
between Mars and Jupiter.
(ii) Comets: These are heavenly bodies that revolve around the sun. It appears generally
as a bright head with a long tail.

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Key Notes
(iii) Meteors and Meteorites: Meteor is a brief streak of light in the night sky caused by a
meteoroid. Smalle meteors melt and burn up creating streaks of light. Few meteoroids
which survive as they pass through the Earth’s atmosphere and reach the Earth
surface are called meteorites.
(iv) Artificial Satellites: Man-made objects sent into space to orbit the earth. Example:
IRS, EDUSAT, INSAR.
• Constellations: A group of stars forming some kind of recongnisable figures or patterns are
known as constellations.
• Constellations appear to move from east to west as Earth rotates from west to east.
• Orion- the Hunter, Ursa Major- the Great Bear or Saptarishi, Cassiopeia are some
constellations.

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Key Notes
Chapter – 18
Pollution of Air and Water

• Pollution: An undesirable change in the physical, chemical or biological characteristics of air,

water and land that may be harmful to human life and other animals, living conditions,
industrial processes and cultural assets.
• Pollutants: The agents that pollute our environment are called pollutants. Pollutants are the
substances which contaminate air and water.
• Air pollution is the contamination of air by impurities which may have a harmful impact on
the living organisms and the non-living components.
• Source of Air Pollution:
Natural Sources: Smoke and dust arising from forest fires or volcanic eruptions. Methane
gas arising from decaying organic matter.
Man-made Sources: Exhaust gases from factories, power plants and automobiles.
• Carbon monoxide, nitrogen oxides, carbon dioxide, methane and sulphur dioxide are the
major pollutants of air.
• Increasing levels of greenhouse gases like CO2 are leading to global warming.

• Water pollution is the contamination of water by substances harmful to life.

• Sewage, agricultural chemicals and industrial waste are some of the major contaminants of
water.
• Water which is purified and fit for drinking is known as potable water.
• Water is a precious natural resource. We must learn to conserve it.
• Greenhouse Effect:
Earth absorbs a part of Sun’s radiation and reflects back the other.
Reflected radiation traps in atmosphere.
This warms the Earth.
Process enhanced by the increased amount of CO2 in atmosphere.

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 CHAPTER – 1 “Matter in our Surroundings”

CONCEPT DETAILS

KEY CONCEPTS : [ *rating as per the significance of concept]

1. Particle nature of Matter ***

2. States of Matter ****
3. Interchange in states of Matter *****
4. Evaporation & Boiling ****
5. Kelvin , Celsius scale ***

Pre requisites
 Definition of matter.
 Elementary idea of three physical states of matter .

SURVEY ANALYSIS

Conceptual levels of comprehension on the basis of feedback taken from the students

8
1. Particle Nature of Matter

[ refer NCERT text book activities 1.1 to 1.8 ]

 Anything that occupies space and has mass and is felt by senses is called matter.
 Matter is the form of five basic elements the Panch tatva – air , earth ,fire , sky and
water.
 Characteristics of particles of matter
 Made of tiny particles.
 Vacant spaces exist in particles.
 Particles are in continuous motion.
 Particles are held together by forces of attraction.
Q.1 Define matter.
Q.2 What happens if you put copper sulphate crystals in water?

2. States of Matter

[ refer NCERT text book activities 1.9 to 1.11 ]

Basis of Classification of Types

 Based upon particle arrangement
 Based upon energy of particles
 Based upon distance between particles
 Five states of matter

Gas

Liquid Plasma

Bose-
Solid Matter Einstein
condensate

9
 (i) SOLID (ii) LIQUID (iii) GAS

 Fixed shape and  Not fixed shape but fixed  Neither fixed shape
definite volume . volume. nor fixed volume.

 Inter particle distances  Inter particle distances  Inter particle distances

are smallest. are larger. are largest.

 Incompressible.  Almost incompressible.  Highly compressible.

 High density and do  Density is lower than  Density is least and

not diffuse. solids and diffuse. diffuse.

 Inter particle forces of  Inter particle forces of  Inter particle forces of

attraction are attraction are weaker attraction are weakest.
strongest. than solids .

 Constituent particles  Constituent particles are  Constituent particles

are very closely less closely packed. are free to move
packed. about.

(iv) Plasma (non –evaluative)

 A plasma is an ionized gas.
 A plasma is a very good conductor of electricity and is affected by
magnetic fields.
 Plasma, like gases have an indefinite shape and an indefinite
volume. Ex. Ionized gas

(v) Bose-Einstein condensate (non –evaluative)

 A BEC is a state of matter that can arise at very low
temperatures.

 The scientists who worked with the Bose-Einstein

condensate received a Nobel Prize for their work in 1995.
 The BEC is all about molecules that are really close to each
other (even closer than atoms in a solid).

10
 Microscopic Explanation for Properties of Solids
Solids have a definite shape and a Solids do not flow easily because Solids are not easily compressible
definite volume because the the particles cannot move/slide because there is little free space
particles are locked into place past one another between particles

Microscopic Explanation for Properties of Liquids

Liquids are not easily compressible
Liquids have an indefinite shape Liquids flow easily because the
and have a definite volume because
because the particles can lide particles can move/slide past
there is little free space between
past one another. one another.
particles.

Microscopic Explanation for Properties of Gases

Gases have an indefinite shape
Gases are easily compressible Gases flow very easily because
and an indefinite volume because
because there is a great deal of the particles randomly move past
the particles can move past one
free space between particles one another.
another.

(non –evaluative)↓

Microscopic Explanation for Properties of Plasmas

Plasmas have an indefinite shape Plasmas are good conductors of
Plasmas are easily compressible
and an indefinite volume because electricity &are affected by
because there is a great deal of
the particles can move past one magnetic fields because they are
free space between particles.
another. composed of ions

Microscopic Explanation for Properties of BEC

Particles are less energetic than Particles are literally BEC shows superfluidity because
solids because Exist at very low indistinguishable because they Particles can flow without
temperature . are locked into same space . friction.

Q.1 A substance has a definite volume but no definite shape ? State whether this
substance is a solid , a liquid or a gas.
Q.2 Arrange the following substances in increasing order of force of attraction between the
particles. (a) Milk (b) Salt (c) Oxygen.
Q.3 A substance has neither a fixed shape nor a fixed volume . State whether it is a solid ,
a liquid or a gas.
Q.4 The melting point of a substance is below the room temperature . Predict its physical
state.

11
3.Interchange in states of matter
[ refer NCERT text book activities 1.12 to 1.14 ]
Matter Can Change its State
Water can exist in three states of matter –
• Solid, as ice ,
• Liquid, as the familiar water, and
• Gas, as water vapour.
Sublimation : The changing of solid directly into vapours on heating & vapours into solid on
cooling. Ex. Ammonium chloride , camphor & iodine.
a) Effect of change in temperature
The temperature effect on heating a solid varies depending on the nature of the solid
& the conditions required in bringing the change .
 On increasing the temperature of solids, the kinetic energy of the particles increases
which overcomes the forces of attraction between the particles thereby solid melts
and is converted to a liquid.
 The temperature at which a solid melts to become a liquid at the atmospheric
pressure is called its melting point.
 The melting point of ice is 273.16 K.
 The process of melting, that is, change of solid state into liquid state is also known as
fusion.
b) Effect of Change of Pressure
 Increasing or decreasing the pressure can change the state of matter. Applying
pressure and reducing temperature can liquefy gases.

 Solid carbon dioxide (CO2) is stored under high pressure. Solid CO2 gets converted
directly to gaseous state on decrease of pressure to 1 atmosphere without coming
into liquid state. This is the reason that solid carbon dioxide is also known as dry ice.
Latent Heat :
The hidden heat which breaks the force of attraction between the molecules during
change of state.

12
 Fusion Vaporisation
Heat energy required to change Heat energy required to change 1kg of
1kg of solid into liquid. liquid to gas at atmospheric pressure at
its boiling point.

Thus, we can say that pressure and temperature determine the state of a substance ,
whether it will be solid, liquid or gas.
[ refer fig. 1.9 NCERT Text Book , page-8 ]
Q.1 What is vapour ?
Q.2 Name the temperature at which the solid and liquid states of substance can exist
together .
Q.3 What is the effect of pressure on boiling point?
Q.4 Name any two substances which sublime.
Q.5 Define Condensation.
Q.6 For any substance, why does the temperature remain constant during the
change of state?

4. Evaporation & Boiling

 Particles of matter are always moving and are never at rest.

 At a given temperature in any gas, liquid or solid, there are particles with different
amounts of kinetic energy.
 In the case of liquids, a small fraction of particles at the surface, having higher
kinetic energy, is able to break away from the forces of attraction of other
particles and gets converted into vapour .
 This phenomenon of change of a liquid into vapours at any temperature below its
boiling point is called evaporation.
 Factors Affecting Evaporation
 The rate of evaporation increases with an increase of surface area.
 With the increase of temperature, more number of particles get enough kinetic energy
to go into the vapour state.
 Humidity is the amount of water vapour present in air. The air around us cannot hold
more than a definite amount of water vapour at a given temperature. If the amount
of water in air is already high, the rate of evaporation decreases.
 Wind speed : the higher the wind speed , the more evaporation.

13
 Evaporation cause cooling.
The particles of liquid absorb energy from the surrounding to regain the energy lost
during evaporation,

Evaporation Vs Boiling
 Boiling is a bulk phenomenon. Particles from the bulk (whole) of the liquid change
into vapour state.
 Evaporation is a surface phenomenon. Particles from the surface gain enough
energy to overcome the forces of attraction present in the liquid and change into the
vapour state.

Q.1 Which is the slow process , Evaporation or Boiling ?

Q.2 State the effect of surface area on rate of evaporation.
Q.3 Why are we able to sip hot tea faster from saucer rather than from a cup?

5. Kelvin & Celsius Scale

 Kelvin is the SI unit of temperature, 00 C =273.16 K. we take 00 C = 273 K.

 SI unit of temperature is Kelvin. T (K)= T (oC) +273
 Kelvin scale of temperature has always positive sign , hence regarded as better scale
than Celsius.
 Atmosphere (atm) is a unit of measuring pressure exerted by a gas. The SI unit of
pressure is Pascal (Pa):
 1 atmosphere = 1.01 × (10 to the power 5) Pa. The pressure of air in atmosphere is called
atmospheric pressure. The atmospheric pressure at sea level is 1 atmosphere, and is
taken as the normal atmospheric pressure.

Q.1 What is the SI unit of temperature?

Q.2 Kelvin scale of temperature is regarded as better scale than Celsius. Why?
Q.3 Convert 10oC into Kelvin scale.

14
 QUESTION BANK [ *HOTS ]

1 Mark Questions:
1. Pressure on the surface of a gas is increased. What will happen to the inter particle
forces?
2. Name the three states of matter.
3. What happens when a liquid is heated ?

4. A gas can exert pressure on the walls of the container. Assign reason.
5. Convert the following temperature to Kelvin Scale (a) 100°C (b) 37°C
6. What is meant by density?
7. Give the characteristics of the particles of matter.
8. Water droplets seen on the outer surface of a glass containing ice-cold water is due
to _____________ .
9. Change of gaseous state directly to solid state without going through liquid sate is
called _____________________ .
10. __________________ is a surface phenomenon.

2 Marks Questions:
1. Define Latent heat of vaporisation.
2. Explain why temperature remain constant during the change of state of any
substance?
3. Define Sublimation with examples.
4. *Do we sweat more on a dry day or humid day ? Justify your reason.
5. Why do we see water droplets on the outer surface of a glass containing ice cold
water?
6. Convert the following temperature to the Kelvin scale (a) 25°C (b) 373°C
7. List two properties that liquids have in common with solids.
8. List two properties that liquids have in common with gases.
9. *What will happen to the melting point temperature of ice if some common salt is
added to it? Justify your answer.
10. *How will you show that air has maximum compressibility?

15
3 Marks Questions:
1. Define the term (a) Latent heat of fusion (b) Latent heat of vaporization
2. *State the effect of (i) surface area (ii) nature of the liquid on the rate of evaporation.
3. *Liquids generally have lower density as compared to solids. But you must have
observed that ice floats on water. Why?
4. What is the physical state of water at 250°C, 100°C, 0°C?
5. Give reasons :
i) A sponge can be pressed easily; still it is called a solid.
ii) Water vapours have more energy than water at same temperature.
6 . What are intermolecular forces ? How are these related to the three states of matter ?
7. Is it possible to liquify atmospheric gases? If yes, suggest a method.

5 marks Questions:
1. a) What is meant by evaporation? What are the factors on which the rate of
evaporation depend upon?
b) How does evaporation causes cooling?
2. State the properties of all the five states of matter.
3. Define : Melting point , Freezing point & Boiling point

You are expected to know………

 Particle nature of matter.

 All five states of matter & their behaviour
 Inter conversion of states of matter
 Latent heat
 Conversion between Kelvin scale & Celsius scale

******************

16
 CHAPTER – 2 “Is Matter Around Us Pure”

CONCEPT DETAILS

KEY CONCEPTS : [ *rating as per the significance of concept ]

1. Pure Substance & Mixture ***

2. Types of Mixtures ****
3. Methods of Separation of Mixtures ******
4. Concentration & Types of Solutions *****
5. Physical & Chemical Changes ***
6. Alloys **

Pre requisites

 Basic knowledge of particle nature of matter

 Different states of matter
SURVEY ANALYSIS

Conceptual levels of comprehension on the basis of feedback taken from the students

120%
100%
80%
60%
40% Very Difficult
20%
Difficult
0%
Easy

17
1. Pure Substance & mixture

PURE SUBSTANCE MIXTURE

 Pure substance consists of a single  Mixture consists of two or

type of substance . more pure substances.

 Pure substance cannot be  Mixture can be separated into

separated into other substances by its components by physical
physical methods. methods.
 Pure substance has its own  Mixture shows the
definite properties. properties of its components.

Elements are made up of one kind of atoms only. Compounds are made up of one kind of
molecules only.

Difference between Compound &Mixture

[ refer NCERT text Book Tab.2.2, page 26]

Q.1 Is air around us a compound or mixture?

Q.2 Water is a compound. Justify.
Q.3 Classify the following as element , compound and mixture: Iron , sea water , Milk
Q.4 Are the naturally occurring material in nature chemically pure substances?

18
2. Types of Mixtures
Mixtures can also be grouped
i) on the basis of their physical states:

SOLID LIQUID GAS

SOLID  Salt and sugar  Salt and water  Dust in air

LIQUID  Mercury and copper  Alcohol and water  Clouds

GAS  Hydrogen and palladium  Oxygen and water  Air

ii) on the basis of miscibility:

Homogeneous Mixture Heterogeneous Mixture

 It consists of single phase.  It consists of two or more phase.

 Uniform composition.  Does not have uniform composition.
 Example: Sugar dissolved in water  Example: Air, sand and common salt.

Q.1 Give one example for each of the following mixtures: i) Solid/solid (homogeneous)
ii) Solid/solid (heterogeneous) iii) Liquid/liquid (homogeneous) iv) Liquid/liquid
(heterogeneous) v) Gas/liquid (homogeneous)..
Q.2 Classify the following as homogeneous & heterogeneous mixture:
i) sodium chloride & water ii) glucose & water iii) sand & water iv) air

4. Separating the components of a mixture

The components of a heterogeneous mixture can be separated by

 simple methods like -
hand picking , sieving , & Winnowing
 special techniques like -
i) Evaporation : a mixture of salt and water or sugar and water.
ii) Centrifugation : Butter from curd, Fine mud particles suspended in water.
iii) Decantation (Using separating funnel) : Oil from water.
iv) Sublimation : Camphor from salt,
v) Chromatography : Different pigments from an extract of flower petals.
vi) Distillation and fractional distillation : Separating components of Petroleum
viii) Magnetic separation: Iron pins from sand.

19
Q.1 Name the process you would use to :
i) recover sugar from an aqueous sugar solution.
ii) separate mixture of salt solution and sand.
Q.2 How will you separate a mixture of sand , water and mustard oil ?

5. Concentration of Solution

The amount of solute present in a given amount (mass or volume) of solution.

Amount of solute Amount of solute
Concentration of a solution = _________________ OR ____________________
Amount of solvent Amount of solution

The concentration of a solution can be expressed as mass by mass percentage or as mass by

volume percentage.
Mass of solute
Mass by mass percentage of a solution = ------------------ x 100
Mass of solution
Mass of solute
Mass by volume percentage of a solution = ------------------ x 100
Volume of solution

Types of Solutions

a) on the basis of size of solute particles:

True solution Sol [ Colloid] Suspension

 Homogeneous  Heterogeneous  Heterogeneous

 Size of solute  Size of solute particles  Size of solute particles
particles is less than is between 1 nm to is more than 1000 nm.
1 n m or 10-9 m . 1000 nm.

 Particles cannot pass  Particles can pass  Particles cannot pass

through filter paper. through filter paper. thorough filter paper.

 Stable  Stable and settle only  Unstable and settle

on centrifugation. down on its own.

 Solution of sodium  Milk , Fog  muddy water, chalk &

water,
chloride in water,
 smoke in the air.
sugar & water.

20
 [ types of colloids : refer NCERT Text Book table 2.1 , page 18 ]

Colloidal solution is a heterogeneous mixture. It consists of two phases:-

(i) Dispersed phase : component present in small proportion
(ii) Dispersion medium : component present in large proportion
The particles of colloid are large enough to scatter a beam of light passing through it and
make its path visible. Thus, they show Tyndall effect.
The colloidal particles are moving at random in a zigzag motion in all directions.
This type of zig-zag motion of colloidal particles is called Brownian movement.

b) on the basis of amount of solute:

Unsaturated solution Saturated Solution Supersaturated solution
A solution which has lesser A solution which has A solution which can dissolve
amount of solute that it can maximum amount of solute amount of solute by increasing
dissolve at a given temperature that it can dissolve at a given temperature saturated solution
is known as unsaturated temperature is known as is known as supersaturated
solution. saturated solution. solution.

c) on the basis of nature of solvent

Aqueous solution Non-Aqueous solution
The solution in which the solvent is water is The solution in which the solvent is other
known as aqueous solution. than water (ether, alcohol or aceton) known
as non-aqueous solution.

Q.1 Classify the following substances into true solutions and colloidal solutions.
Milk , ink , starch dissolved in water.
Q.2 A solution has been prepared by dissolving 5g of urea in 95 g of water. What is the mass
percent of urea in the solution?
Q.3 Give an example of an aqueous solution in which gas is dissolved.

6.Physical & Chemical Changes

Physical changes - Changes that do not result in the production of a new substance.
 If you melt a block of ice, you still have H2O at the end of the change.
 If you break a bottle, you still have glass.
21
 Examples : melting, freezing, condensing, breaking, crushing, cutting, and bending.

Chemical changes - Changes that result in the production of another substance.

 As in the case of autumn leaves, a change in color is a clue to indicate a chemical
change.
 a half eaten apple that turns brown.

Q.1 Which of the following is an example of physical change?

a. Mixing baking soda and vinegar together, and this causes bubbles and foam.
b. A glass cup falls from the counter and shatters on the ground.
c. Lighting a piece of paper on fire and the paper burns up and leaves ashes.
d. Baking a birthday cake for your mother.
Q.2. Which of the following is an example of chemical change?
a. Filling up a balloon with hot air.
b. Taking a glass of water and freezing it by placing it in the freezer.
c. A plant collecting sunlight and turning it into food.
d. Your dog ripping up your homework.
3. Which change can be easily be reversed?
a. Chemical Change
b. Physical Change
c. Both a physical and chemical change
d. Neither a physical or chemical change

7.Alloys

A material that has metallic properties and is composed of two or more chemical
elements of which at least one is a metal .
 These cannot be separated into their components by physical methods.
 However, these are considered as mixture because these show the properties of its
constituents and can have variable composition.
The benefit of alloys is that you can combine metals that have varying characteristics to
create an end product that is stronger, more flexible, or otherwise desirable to
manufacturers.

 Aluminium alloys are extensively used in the production of automotive engine

parts.
 Copper alloys have excellent electrical and thermal performance, good corrosion
resistance, high ductility and relatively low cost.

22
  Stainless steel alloys are used for many commercial applications such as watch
straps, cutlery etc.
 Titanium alloys have high strength, toughness and stiffness & are used in
aerospace structures .

Q,1 Why should we use alloys instead of pure metals?

Q.2 State uses of Aluminium & Stainless steel alloys.

QUESTION BANK [ *HOTS ]

1 Mark Questions:
1. What is meant by pure substance?
2. What is meant by mass percentage of solution?
3. Name the process of separation of miscible liquids.
4. Arrange the following in decreasing order of size of the particles.
True Solution , Suspension , Colloid.
5. *Give an example of an aqueous solution in which gas is dissolved.
6. Name the dispersion medium and dispersed phase in the white material inside an egg.
7. What happens when hot saturated solution is cooled?
8. How would you separate a mixture of chalk and water?
9. *How much water should be added to 15 grams of salt to obtain 15 % salt solution?
10. What type of mixtures are separated by technique of crystallization ?

2 Marks Questions:
1. Which of the following materials fall in the category of a pure substance?
a) Ice b) Milk c) Iron d) Hydrochloric acid
e) Calcium oxide f) Mercury g) Brick h) Wood.
2. What do you understand by saturated solution and unsaturated solution?
3. *What do you observe when sunlight passes through a dense forest?
4. List two points of differences between homogeneous and heterogeneous mixtures.
5. State the difference between aqueous & non aqueous solution .
6. Which of the following will show “Tyndal Effect” & Why ?
a) Salt Solution b) Milk c) Copper Sulphate Solution d) Starch Solution

23
7. *How can we obtain pure copper sulphate from an impure sample?
8. Give two differences between compounds and mixtures.
9. Why is hydrogen considered as element ? Give two reasons.
10. Why water is a compound and not a mixture?

3 Marks Questions:
1. Classify the following into elements, compounds and mixtures:
a) Sodium b) Soil c) Sugar solution d) Silver e) Calcium carbonate f) Tin
g) Silicon h) Coal i) Air j) Soap k) Methane l) Carbon dioxide m) Blood.
2. Give any two applications of centrifugation.
3. Which of the following is chemical change?
a) Growth of a plant b) Rusting of iron c) Mixing of iron fillings and sand
d) Cooking of food e) Digestion of food f) Freezing of water g) Burning of a candle.
4. *State the difference between simple distillation & fractional distillation.
5. * A solution contains 40 ml of ethanol mixed with 100 ml of water. Calculate the
concentration in terms of volume by volume percentage of the solution.

5 Marks Questions:
1. *What is meant by Tyndall effect? What is its cause? Illustrate with example.
2. How would you separate the mixture containing sulphur and sand ?
3. What is crystallization? Give its two applications.
4. How are sol, solution and suspension different from each other?
5. How do we obtain coloured components, i.e. dye from Blue/Black ink ?

You are expected to know………

 Types of mixtures.
 Method of Separation of mixtures.
 Types of solutions.
 Concentration terms of solution.
 Physical and Chemical Change.
 Significance of alloys.
**********
24
 CHAPTER - 3 “Atoms and Molecules”

CONCEPT DETAILS
KEY CONCEPTS : [ *rating as per the significance of concept]

1. Laws of Chemical Combination ***

2. John Daltons Atomic Theory **
3. Atoms, ions & Chemical Formula ****
4. Mole Concept *****
5. Molar Mass & Avogadro constant ****

Pre requisites
Basic knowledge all states of matter.
Difference in the different states of matter .

SURVEY ANALYSIS

Conceptual levels of comprehension on the basis of feedback taken from the students

120%
100%
80%
60%
40%
20% Very Difficult
0% Difficult
Easy

25
1.Laws of Chemical Combination

Law of Conservation of mass: Law of definite proportion:

proposed by the French chemist proposed by Louis Proust
Antoine Lavoisier (1774) (1799)

Mass can neither be 'A chemical compound

created nor destroyed in a always consists of the
chemical reaction. same elements combined
OR together in the same ratio,
For any chemical process in
a closed system, the mass irrespective of the method
of the reactants must be of preparation or the
equal the mass of the source from where it is
products. taken'.

C + O2 = CO2 One molecule of a compound

water always contains same ratio
12g +32g = 44g of Hydrogen and Oxygen by mass
i.e.
H2O = 2 : 16 = 1 : 8

Verification of “Law of Conservation of mass”

A solution of sodium chloride and silver nitrate are taken separately in the two limbs
of an 'H' shaped tube. The tube is sealed and weighed precisely. The two reactants
are made to react by inverting the tube. The following reaction takes place.
AgNO3(aq) + NaCl (aq)  AgCl (s) + NaNO3 (aq)
The whole tube is kept undisturbed for sometime so that the reaction is complete.
When the tube is weighed again it is observed that:
Weight before the reaction = Weight after the reaction
Limitation of “Law of definite proportion”
This law does not hold good when the compound is obtained by using different
isotopes of the combining elements .

Q.1 Why chemical reactions are in accordance with the Law of conservation of mass?
Q.2 Calculate the ratio of atoms present in 5 g of magnesium and 5 g of iron.
[Atomic mass of Mg=24 u, Fe=56 u]

26
2. John Daltons Atomic Theory

[ for postulates ,refer NCERT text book article 3.1.2 -page no.32 ]
Using his theory, Dalton rationalized the various laws of chemical combination which were in
existence at that time. However, he assumed that the simplest compound of two elements
must be binary.
Q.1 In what respect does Dalton’s Atomic theory hold good even today?
Q.2 Which of the following is not the postulate of Dalton’s Atomic theory of matter ?
a) Each element is made up of extremely small particles called atoms.
b) Atoms of a given element are identical in chemical properties but have different
physical properties.
c) Atoms cannot be created nor destroyed.
d) Compounds are formed by the chemical union of atoms of two or more elements in
fixed proportion .

3. Atoms ,Molecules, Ions & Chemical Formula

Atom Molecule
An atom is the smallest particle of
The smallest particle of matter
an element which can take part in a
(element or compound) which can
chemical reaction. It may or may
exist in a free state.
not exist freely.

Each atom of an element shows all The properties of a substance are

the properties of the element. the properties of its molecules.

 MOLECULES OF ELEMENT : The molecules of an element are constituted by the same

type of atoms.
 MOLECULES OF COMPOUND: Atoms of different elements join together in definite
proportions to form molecules of compounds.(hetero atomic molecules)

 ATOMICITY : The number of atoms contained in a molecule of a substance (element or

compound) is called its atomicity.

Element Formula Atomicity

Ozone O3 3
Phosphorus P4 4
Sulphur S8 8
Oxygen O2 2
27
 Based upon atomicity molecules can be classified as follows.
Monoatomic molecules: Noble gases helium, neon and argon exist as He Ne and Ar
respectively.
Diatomic molecules: H2 , O2, N2,Cl2, CO , HCl .
Triatomic molecules: O3 ,CO2 , NO2.
 SYMBOLS
 The abbreviation used to represent an element is generally the first letter in
capital of the English name of element.
Oxygen  O Nitrogen  N
 When the names of two or more elements begin with the same initial letter,
the initial letter followed by the letter appearing later in the name is used to
symbolize the element
Barium  Ba Bismuth  Bi
Symbols of some elements are derived from their Latin names

ELEMENT LATIN NAME SYMBOL

Sodium Natrium Na
Copper Cuprum Cu
Potassium Kalium K
Iron Ferrum Fe
Mercury Hydragyrum Hg
Tungsten Wolfram W

Q.1 Give one example each of molecule of element & molecule of compound.
Q.2 How does an atom differ from molecule ?
Q.3 Name a triatomic gas.
Q.4 Name the element represented by Hg , Pb, Au.
Q.5 What is the difference between an atom of hydrogen and a molecule of hydrogen?

28
 Cation Anion
ION + Formed by __ Formed by
An ion is a charged particle
formed by loss or gain loss or loss of gain of
gain of electrons. electron electron

Polyatomic Ion : A group of atoms carrying a charge is as polyatomic ion.

eg: NH4+ - Ammonium Ion ; CO32- - Carbonate ion

Valency : The number of electrons which an atom can lose , gain or share to form a bond.
OR
It is the combining capacity of an atom of the element.
[ for valency of various cations & anions ,refer NCERT text book table 3.6 , page no. 37 ]

 Chemical Formula: A chemical formula is a short method of representing chemical

elements and compounds.

Writing a Chemical Formula -CRISS-CROSS rule

RULE 1 [a] write the correct symbols of two elements.
Ex : Aluminium & Oxygen Al O

[ b] above each symbol, write the correct valence

Al3+ O2-

[c] Criss-cross the valence and drop the algebraic sign.

Al2O3

RULE 2 > When the subscript is number 1, subscript is not written.

Ex. Sodium Chloride - Na1+ Cl1- --- NaCl

RULE 3> When the valence of both elements are numerically equal , the subscripts are
also not written.
Ex. Calcium Oxide- - Ca2+ O2- --- CaO

29
 RULE 4 > When there are multiple numbers of an individual polyatomic ion ,
parentheses must be used to separate the polyatomic ion from the subscirpt.
Ex. Ammonium Sulphate- - NH41+ SO42 -....... (NH4)2 SO4

RULE 5 > All subscripts must be reduced to lowest term (except for molecular or
covalent copound).
Ex. Tin (IV) Chloride ~ Sn4+O2- ------ SnO2

EXAMPLES

CATION ANION FORMULA NAME

Al 3+ SO42─ Al2(SO4)3 Aluminium sulphate
Ca HCO3─ Ca(HCO3)2 Calcium bicarbonate
NH4 + Cl─ NH4Cl Ammonium chloride
Na + CO32─ Na2CO3 Sodium carbonate
Mg2+ OH─ Mg(OH)2 Magnesium hydroxide
Na+ PO43─ Na3PO4 Sodium phosphate

Q.1 What is the difference between an anion & cation ?

Q.2 Write down chemical formula of
i) Hydrogen peroxide ii) Tin chloride
iii) Barium sulphate iv) Silver chloride
Q.3 Write chemical names of
i) Ni(NO3)2 ii) CdCO3 iii) NaOH iv) NH4NO2

4. Mole Concept

The mole (mol) is the amount of a substance that contains as many elementary entities as
there are atoms in exactly 12.00 grams of 12C

The Avogadro constant is named after the early nineteenth century Italian scientist
Amedeo Avogadro.

30
 I MOLE ≡ 6.O22 x 10 23 particles

Substance > Element ║ Compound

Particles > Atom ║ Molecule

Ex. > ELEMENT - SODIUM - Na

I MOLE > 23 u / 23g / 6.O22 x 10 23 atoms of sodium

Ex. > COMPOUND- WATER - H2O

I MOLE > 18 u / 18 g / 6.O22 x 10 23 molecules of water

S.No. Symbol / Atomic / 1mole Avogadro no. Molar mass

formula of atom molecular mass ( in g) ( g mol -1)
/ molecule ( u)
1. O 16 u 16 g 6.022 x 1023 atoms 16 g mol -1
2. N2 28 u 28 g 6.022 x 1023 molecules 28 g mol -1
3. HCl 36.5 u 36.5 g 6.022 x 1023 molecules 36.5 g mol -1

GRAM MOLECULAR MASS

Gram molecular mass is the mass in grams of one mole of a molecular substance.
Ex: The molecular mass of N2 is 28, so the gram molecular mass of N2 is 28 g.

ATOMIC MASS UNIT

An atomic mass unit or amu is one twelfth of the mass of an unbound atom of carbon-12. It
is a unit of mass used to express atomic masses and molecular masses.
Also Known As: Unified Atomic Mass Unit (u).

31
 MOLECULAR MASS : A number equal to the sum of the atomic masses of the atoms in a
molecule. The molecular mass gives the mass of a molecule relative to that of the 12C atom,
which is taken to have a mass of 12.

Examples: The molecular mass of C2H6 is approximately 30 or [(2 x 12) + (6 x 1)] . Therefore
the molecule is about 2.5 times as heavy as the 12C atom or about the same mass as the NO
atom with a molecular mass of 30 or (14+16) .

Q.1 What term is used to represent the mass of 1 mole molecules of a substance?
Q.2 What is the gram atomic mass of i) Hydrogen ii) oxygen ?
Q.3 Calculate molar mass of C2H2 .

5.Molar Mass & Avogadro Constant

Ex: i) Convert 35 g of Al into mol.

MASS
A: Molar mass of Al= 27 g
27 g = 1mol
1mol
= 35 g x -------
Molarmass / 1mol 27 g
= 1.3 mol of Al

1mol / Molar mass ii) How many grams of SiO2 are

present in 0.8 mol ?

A: Molar mass of SiO2 = 60.1 g

1 mol = 60.1 g
60.1g of SiO2
MOLE = 0.8 mol of SiO2 x ----------
1mol of SiO2

= 48.1 g SiO2

32
 MOLE Ex . How many mol of CO2 are
present in 55.5 L ?

A: 22.4 L = 1mol
1mol / 22.4 L
1mol
= 55.5 L x -----
22.4 L / 1mol 22.4 L
= 2.48 mol of CO2.

VOLUME AT STP

MOLE Ex Calculate number of molecules

in 200 g of N2O.
Molar mass of N2O = 44 g

i ) to find number of moles:-

1mol / 6.02 X 10 23 44 g = 1 mol
particles
1mol
6.02 X 10 23 particles /
= 200 g x -------
1mol
44.0 g
= 4.55 mol of N2O

ii) to find number of molecules

Number of 1 mol =6.02 x 1023 molecules
representative paticles
6.02 x 1023 molecules N2O
= ----------------------
1/ 4.55

= 2.74 x 1024 molecules N2O

33
Ex. Calculate the number of aluminium ions present in 0.051 g of aluminium oxide.

Ans : Molar mass of Al2O3 = 102 g

Al2O3 ↔ 2 Al3+ + 3 O2-

102 g of Al2O3 contains = 2 x 6.02 x 1023 Al3+ ions

2 x 6.02 x 1023 Al3+ ions

0.051 g of Al2O3 contains = ----------------- x 0.051
102
= 2 x 6.02 x 1020 Al3+ ions

Q.1 Calculate the mass of one atom of sodium?

Q.2 The atomic mass of calcium is 40 u. What will be the number of calcium
atoms in 0.4 u of calcium?
Q.3 How many atoms of oxygen are present in 120 g of nitric acid ?

QUESTION BANK [ *HOTS ]

1 Mark Questions:

1. Who gave law of conservation of mass ?

2. What term is used to represent the mass of 1 mole molecules of a substance?

3. What name is given to the number 6.023 x 10 23 ?

4. What is molecular mass?

5. Give Latin names for sodium & mercury.

6. *How many atoms are there in exactly 12 g of carbon ?

7. Define mole.

8. Calculate formula unit mass of CaCl2. [ At. Mass : Ca = 40 u , Cl = 35.5 u ]

9. Name a diatomic gas.

10. How many atoms are present in H2SO4.

34
2 Marks Questions:
1. Give the chemical symbols for the following elements: Gold, Copper , Potassium & Iron.
2. *What do the following symbols represent - i) 1 H & i) H2

3. Neon gas consists if single atoms , what mass of neon contain 6.022 x 10 23 atoms.
4. What elements do the following compounds contain ?
i) Water ii) Lead nitrate
5. State the differences between an atom or a molecule.
6. Molar Mass of water is 18 g mol-1 , what is the mass of 1 mole of water? .
7. *The number of atoms in 1 mole of hydrogen is twice the number of atoms in one mole
of helium. Why?
8. Write the chemical formulas for the following:
i) Silver oxide ii) Iron (III) sulphate
9. Calculate molar mass of H2O2 & HNO3.
10. What is the mass of 0.2 moles of oxygen molecules?

3 Marks Questions:
1. State the main postulates of John Dalton’s atomic theory.
2. What are polyatomic ions ? Give two examples.
3. State the following
i) Law of conservation of mass. ii) Law of constant proportion
4. What is the mass of :
i) 1 mol of N atoms. ii) 4 mol of Al atoms.
5. What is meant by the term atomicity ? State the atomicity of i) Phosphorous
ii) Sulphur

5 Marks Questions:
1. i) What is molecular formula ? State with example what information can be derived from a
molecular formula .
ii) Write the names of the compounds represented by the following formulas:
a) Mg(NO3)2 b) K2SO4 c )Ca3N2

35
2.* i) What is gram molecular mass?
ii) Write the formulas & names of the compounds formed between :
a) Ferrous and sulphide ions b) Aluminium and sulphate ions
c) Potassium and chlorate ions d) Barium and chloride ions
3. i) Calculate the number of moles for the following:
a) 52 g of He b) 17 g of H2O
ii) How many molecules are present in 34 g of ammonia ?
iii) Calculate the mass of 0.5 mole of sugar (C12H22O11).

You are expected to know…………

 Laws of Chemical combination.

 John Dalton’s imagination about atom & the limitation of his theory.

 Difference between an atom & molecule.

 Types of ions

 Writing chemical formula of compounds.

 Relationship between Mole , Molar Mass & Avogadro Constant

**********

36
 CHAPTER -4 “STRUCTURE OF ATOM”

CONCEPT DETAILS

KEY CONCEPTS : [ *rating as per the significance of concept]

1. Dalton’s Atomic theory **

2. J J Thomson Experiments ***
3. Rutherford’s Scattering Experiments ********
4. Sub atomic particles ******
5. Atomic number & Mass number *****
6. Neil Bohr’s Atomic Model ***
7. Electronic Configuration & Valency *******
8. Isotopes & Isobars ****

 Pre requisites:
 Difference between an atom & molecule.
 Gram atomic mass & Molar mass.
 Dalton’s Atomic theory.

SURVEY ANALYSIS

Conceptual levels of comprehension on the basis of feedback taken from the students

37
Contribution to the Atomic theory Timeline

SCIENTIST PROPOSED MODEL OF ATOM

Democritus

Greek philosopher
(400 B.C)

 More than 2400 years ago, he named the smallest piece of matter “ATOMOS ,”
meaning “not to be cut.”
To Democritus,
 Atoms were small, hard particles that were all made of the same material but were
different shapes and sizes.
 Atoms were infinite in number, always moving and capable of joining together

1. Dalton’s Atomic theory:

SCIENTIST PROPOSED ATOMIC MODEL

John Dalton

He proposed the Atomic theory of

English Chemist matter based on his experimental
[proposed atomic theory in 1803] observations.

38
  First recorded evidence that atoms existed.
 Using his theory, Dalton rationalized the various laws of chemical combination

Dalton's theory was based on the premise that the atoms of different elements could be
distinguished by differences in their weights.
 Limitations
o The indivisibility of an atom was proved wrong , for, an atom can be further
subdivided into protons, neutrons and electrons.
o The atoms of same element are similar in all respects , but isotopes of same
element have different mass.
o Dalton's theory was based on the premise that the atoms of different
elements could be distinguished by differences in their weights.

2. J J Thomson Experiments:

SCIENTIST PROPOSED ATOMIC MODEL

Joseph John Thomson

British Physicist and Nobel laureate PLUM –PUDDING MODEL

 Discovered electrons in 1897.

 Showed us that the atom can be split into even smaller parts.
His discovery was the first step towards a detailed model of the atom .
 An atom is a uniform sphere of positive charges (due to presence of protons) as well
as negative charges (due to presence of electrons).
 Atom as a whole is electrically neutral because the negative and positive charges are
equal in magnitude.

39
  An electron is a negatively charged component of an atom which exists outside the
nucleus. Each electron carries one unit of negative charge and has a very small
mass as compared with that of a neutron or proton.

JJ Thomson used cathode ray tubes to demonstrate that the cathode ray responds to both
magnetic and electric fields.
Since the ray was attracted to a positive electric plate placed over the cathode ray tube
(beam deflected toward the positive plate) he determined that the ray must be composed of
negatively charged particles.
He called these negative particles "electrons."
Limitation: Model failed to explain how protons and electrons were arranged in atom so
close to each other.

Eugene Goldstein:

SCIENTIST PROPOSED ATOMIC MODEL

Eugene Goldstein
a German physicist

40
  E. Goldstein in 1886 discovered the presence of new radiations in a gas discharge and
called them canal rays. These rays were positively charged radiations which ultimately
led to the discovery of another sub-atomic particle.
 Used a Cathode Ray Tube to study "canal rays" which had electrical and magnetic
properties opposite of an electron
 Canal Rays: The positively charged radiation produced in the discharge tube at low
pressure and high voltage are called canal rays.
Protons:
The canal rays have positively charged sub-atomic, particles known as protons (p).

Q.1 What was the model of an atom proposed by Thomson?

Q.2 What is the nature of charge on electrons?
Q.3 What are canal rays ?
Q.4 State the nature of the constituents of canal rays.

3. Rutherford’s Scattering Experiments:

SCIENTIST PROPOSED ATOMIC MODEL

Sir Earnest Rutherford

Nobel prize 1908

41
Experiment: Rutherford took a thin gold foil and made alpha particles , [ He 2+ ] positively
charged Helium fall on it.

S.No OBSERVATION INFERENCE

1. Most of the a-particles passed through Most of the space inside the atom is
the gold foil without getting deflected. empty.
2. Very few particles were deflected. Positive charge of the atom occupies
very little space.
3. A very few alpha particles, 1 in 100000 Nucleus of an atom is very small as
completely rebound on hitting the gold compared to the total size.
foil.

Alpha particle

 Limitation: In Rutherford’s atomic model , Nucleus & electrons are held together by
electrostatic force of attraction which would lead to the fusion between them. This
does not happen in the atom.
Atomic radius ~ 100 pm = 1 x 10-10 m
Nuclear radius ~ 5 x 10-3 pm = 5 x 10-15 m

42
 SCIENTIST PROPOSED ATOMIC MODEL

James Chadwick

English Physicist & Nobel

laureate

 In 1932, James Chadwick proved that the atomic nucleus contained a neutral particle
which had been proposed more than a decade earlier by Ernest Rutherford officially
discovered the neutron in 1932,
 Chadwick received the Nobel Prize in 1935.

A neutron is a subatomic particle contained in the atomic nucleus. It has no net electric
charge, unlike the proton's positive electric charge.

Q.1 Who discovered the nucleus of the atom?

Q.2 What is the charge on alpha particles ?
Q.3 Which observation of Rutherford’s scattering experiment established the presence
large empty space in atom?
Q.4 What is the nature of charge on nucleus of atom?
Q.5 Who discovered neutron ?

43
4. Sub Atomic Particles:

Name Symbol Location in the atom Charge Relative Mass Actual Mass (g)
Electron E Around the nucleus 1- 1/1840 9.11 x 10 -28
Proton P In the nucleus 1+ 1 1.67 x 10 -24
Neutron n In the nucleus 0 1 1.67 x 10 -24

Protons & Neutrons collectively are known as NUCLEONS.

Q.1 Why is the relative mass of an electron is taken as negligible ?

Q.2 Give the actual masses of electron & proton in kg?
Q.3 What are nucleons?

5.Atomic Number & Mass Number:

“Atomic number of an element is defined as the number of unit positive charges on the
nucleus (nuclear charge) of the atom of that element or as the number of protons present
in the nucleus.”

Atomic number, Z = Number of unit positive charge on the nucleus

= Total number of unit positive charges carried by all protons present in the nucleus.
= Number of protons in the nucleus (p)
= Number of electrons revolving in the orbits (e)
Eg :- Hydrogen – Atomic number = 1 (1 proton)
Helium - Atomic number = 2 (2 protons)

Mass number[ A] : It is defined as the sum of the number of protons & neutrons present in
the nucleus of an atom.
Mass Number = Mass of protons + Mass of neutrons
Eg :- Carbon – Mass number = 12 (6 protons + 6 neutrons) Mass = 12u
Aluminium – Mass number = 27 (13 protons + 14 neutrons) Mass = 27u

44
 mass number
atomic number Symbol
Q.1 The mass number of an element is 18. It contains 7 electrons .What is the number of
protons and neutrons in it ?
Q.2 An atom contains 3 protons , 3 electrons and 4 neutrons .
i) What is its atomic number ? ii) What is its mass number?
31
Q.3 An element is represented by 15 P . Give the number of electrons and neutrons in it.

6. Niel Bohr Atomic Model:

SCIENTIST PROPOSED ATOMIC MODEL

Danish physicist

Main Postulates of the Bohr Model [refer NCERT Text Book article 4.3 ,page number-49]

Q.1 What happens when an electron jumps from lower to higher energy level?
Q.2 Which energy shell is nearest to the nucleus of an atom?
Q.3 Which energy shell has higher energy L or N ?

7. Electronic configuration & Valency:

Bohr and Bury Scheme - Important Rules
2n2
S.No Electron Shell Maximum Capacity
where n = shell number

1 K Shell 2 x (1) 2 2 electrons

2
2 L Shell 2 x (2) 8 electrons
2
3 M shell 2 x (3) 18 electrons
2
4 N shell 2 x (4) 32 electrons

45
 The outermost shell of an atom cannot accommodate more than 8 electrons, even if it
has a capacity to accommodate more electrons. This is a very important rule and is also
called the OCTET RULE. The presence of 8 electrons in the outermost shell makes the
atom very stable.
Q.1 An atoms has atomic number 13. What would be its configuration.
Q.2 What is octet rule?
Q.3 How many electrons M shell can accommodate?
Q.4 If an atom has complete K and L shell, what would be its atomic number?

8. Isotopes & Isobars:

ISOTOPES ISOBARS
Chemically same , physically different Chemically different , physically same
Number of electrons is same Number of electrons is different .
Cannot be separated by chemical means Can be separated by chemical means
[ for application of isotopes refer NCERT Text Book article 4.6 ,page number-53]
Q.1 Why atoms of isotopes are chemically same?
Q.2 Give the representation of three isotopes of carbon which are C-12 , C-13 and C-14.

QUESTION BANK [ *HOTS ]

1 Mark Questions:
1. Write the names of three elementary particles which constitute an atom.
2. Name the scientist & his experiment to prove that nucleus of an atom is positively
charged.
3. Which is heavier , neutron or proton ?
4. *How many times a proton is heavier than an electron?
5. What was the model of an atom proposed by Thomson ?
6. How many electrons at the maximum can be present in the first shell ?
7. What type of charge is present on the nucleus of an atom?

8. Give the number of protons in 35Cl17

9. *What are iso bars ?
10. Name the particles which determine the mass of an atom.
2 Marks Questions:
1. Define the following terms: a) Atomic number b) Mass number
2. Write the charges on sub atomic particles.
46
 33
3. Identify the isotopes out of A , B , C & D ? A17 , 40B20 , 37C17 , 38D19
4.* Give one Achievement and one limitation of J.J Thomson’s model of atom?
5. What are valence electrons? Give example.
6. *Which kind of elements have tendency to lose electron ? Give example.
7. How many electrons are present in the valence shell of nitrogen & argon?
8. State the maximum capacity of various shells to accommodate electrons.
9. Give the symbol , relative charge & mass of the three sub atomic particles.
10. From the symbol 32 S16 state :
i) Atomic number of sulphur, ii) Mass number of sulphur
iii) Electronic configuration of sulphur.
3. Marks Questions:
1. Why do Helium has Zero valency?
2. An atom contains 3 protons , 3 electrons and 4 neutrons .What is its atomic number , mass
number & valency?
3. *How are the isotopes of hydrogen represented ?
4. Write the complete symbol for the atom with the given atomic number [Z] & mass
number[A].
i) Z= 17 , A = 15 ; ii) Z=4 , A = 9; iii) Z= 92 ; A=233
5. *What would be the electronic configuration of Na+ , Al3+ , O2- , Cl -.
5 Marks Questions:
1.* a) Give the observations as well as inferences of Rutherford’s Scattering experiment for
determining the structure of an atom.
b) On the basis of above experiment write the main features of atomic model.
2. Write the main postulates of Bohr’s Model of Atom.

You are expected to know…………

 The scientists who discovered subatomic particles.

 Rutherford established the existence of nucleus.
 Difference between Atomic number and Mass number
 Electronic configuration & its relation with Valency.
 Difference between Isotope and Isobar.

**********
47
 Chapter 5: “The Fundamental Unit of Life”
KEY CONCEPTS : [ *rating as per the significance of concept]
CONCEPTS RATING
Study of historical perceptive related to cell *****
discovery
Study of Microscope **
Study of Hypotonic/Isotonic/ ****
Hypertonic solutions relation to osmosis.
Cell wall ***
Nucleus *****
Cytoplasm ***
Cell organelles *****

1. All the living organisms are made up of fundamental unit of life called” cell”.
2. The cell is a Latin word for “a little room”.
3. The scientist Robert Hooke saw a little room in the cork (the bark of a tree)
resembled the structure of a honeycomb. The use of the word “Cell” to describe
these units is used till this day in Biology as” Cell Biology”.
4. The Compound Microscope consist eye piece,objective lens and condenser to
observe a cell after putting a drop of Safranin (for plant cell) and methylene blue (for
animal cell). ( Please refer to Fig. 5.1: Compound Microscope NCERT Book Page-57)
5. The scientist Leeuwenhoek saw free living cells in the pond water for the first time. (
father of microbiology)
6. The scientist Robert Brown discovered the nucleus in the cell.
7. The cell theory states that all the plants and animals are composed of cells, it was
proposed by Schleiden and Schwann.
8. The cell theory was further expanded by Virchow by suggesting that “all cells arise
from the pre-existing cells”.
9. The cells differ in size, shape, structure (Please refer to Fig. 5.2/5.3: Onion
peel/Various cells in Human body, NCERT Book Page-57/58):Types of cells: Onion
cells, Smooth muscle cell, Blood cells, Bone cell, Fat cell, Nerve cell, Ovum, Sperm
etc. Each kind of cell performs specific function.

58
 10. A single cell may constitute a whole organism as in Amoeba, Chlamydomonas,
Paramecium and Bacteria; these are called as unicellular organisms. Whereas in
multi-cellular organisms (Human beings) division of labor is seen.
11. The feature in almost every cell is same: Plasma membrane, nucleus and
cytoplasm.
12. Plasma membrane: It is the outermost covering of the cell.
- It is called as selective permeable membrane (because it prevents
movement of some materials).
- It helps in diffusion and osmosis
- Diffusion: movement of substance from high concentration to low
concentration.
Eg; exchange of carbon dioxide or oxygen with external environment.

osmosis: it is the passage of water from the region of high water concentration to a region
of low water concentration through a selective permeable membrane.

a) The cell gains water, if the medium surrounding the cell has a higher water
concentration (Hypotonic solution) than the cell.

b) The cell maintains the same water concentration as the cell (Isotonic solution),
water crosses the cell membrane in both directions.

59
 c)The cell loses water, if the medium has lower water concentration (Hypertonic
solution) than the cell.

Note - The cell drinking is endosmosis;

- omission of water is called ex-osmosis.

13. The cell engulfs food is called endocytosis and ejects solid is called exocytosis.
Amoeba acquires food through endocytosis and excretion of solid is called
exocytosis.
14. The cell wall is a rigid outer covering composed of cellulose. It provides structural
strength to plant cells. When a living cell loses water, there is shrinkage of contents
of a cell away from the cell wall. This phenomenon is called as plasmolysis. The cell
walls permit the cells of plants, fungi and bacteria to withstand very dilute
(Hypotonic) external media without bursting.
15. The Nucleus: It is a dark colored, spherical or oval, dot-like structure near the center
of a cell called Nucleus. The nucleus plays a central role in cellular activities/
reproduction. The chromatin material gets organized into chromosomes. The
chromosomes contain information for inheritance of features from parents to next
generations in the form of DNA( Deoxyribo Nucleic Acid ) and protein molecules. The
functional segments of DNA are called genes.
16. In some organisms like Bacteria nucleus is not covered by nuclear membrane. Hence
it is called as prokaryote. (Pro= primitive; karyote = karyon = nucleus.) The organisms
with cells having a nuclear membrane are called eukaryotes.
17. Differences between prokaryotes and eukaryotes( Please refer to Fig. 5.4:
Prokaryotic cell NCERT Book Page-62)

Prokaryotes Eukaryotes

Size: generally small (1-10 µm) Size: generally large. (5-500 µm)

60
 Nuclear region: Not well defined Nuclear region: Well defined and
and not surrounded by a nuclear surrounded by a nuclear membrane
membrane & known as nucleoids.

Chromosome: Single Chromosome: More than one

chromosome

Membrane-bound cell organelles Membrane-bound cell organelles

absent present

Eg- bacteria, blue green algae Eg fungi, plant cell and animal cell.

18. Cell organelles: Every cell has fluid matrix (other than nucleus) is called cytoplasm.
The nucleus and cytoplasm is together called as protoplasm. The protoplasm term
was coined by Purkinje. It has important cell organelles: Endoplasmic Reticulum (ER),
Golgi apparatus, Lysosomes, Mitochondria, Plastids, and vacuoles.
19. Endoplasmic Reticulum (ER): It is a large network of membrane –bound tubules and
vesicles.

- There are two types of Endoplasmic Reticulum

- Rough Endoplasmic Reticulum (RER) (It looks rough because Ribosomes are
attached to its surface. They are the sites of protein synthesis).
- Smooth Endoplasmic Reticulum (SER) (It looks smooth because Ribosomes
are not attached to its surface. They are the sites of fat molecules synthesis).

1. SER ; help in the functioning of enzymes and hormones to carryout

biochemical activities.
2. SER detoxifies many poisons and drugs from the cell.
2. ER serves as channel for the transport of material between various regions of
the cytoplasm and the nucleus.
3. Proteins and fat molecules produced by ER helps in membrane biogenesis.
20. Golgi apparatus: It was first described by a scientist Camillo Golgi. It is a system of
membrane bound vesicles called cisterns. It functions include the storage,

61
 modification and package of cell products. The complex sugars are made from simple
sugars in the Golgi apparatus. It is also involved in the formation of lysosomes.
21. Lysosomes: They contain membrane-bound sacs with powerful digestive enzymes
(enzymes are made by RER) to digest the worn-out cell organelles. When the cell
gets damaged, lysosomes may burst and the enzymes digest their own cell, hence
called as “Suicidal bags of a cell”. It is a waste disposal system of the cell.
22. Mitochondria: It is covered by a double membrane. Outer membrane is very porous
and the inner membrane is deeply folded. These folds create a large surface area for
ATP (Adenosine Triphosphate) molecule synthesis. ATP is the energy currency of a
cell; hence the Mitochondria are called as Power House of a Cell. Mitochondria have
their own DNA and Ribosomes; therefore they can make their own proteins.
23. Plastids: They are present only in plant cells. They are two types.
1. Chromoplasts (Colored Plastids: Chloroplasts – Green pigmented and
useful in Photosynthesis and also contains various other pigments like
yellow or orange)
2. Leucoplasts (White or colorless plastids; stores materials such as oils,
proteins, fats etc. ) Plastids are also covered by a double membrane.
The matrix is called Stroma, seat for enzymatic actions. Plastids have
their own DNA and Ribosomes; therefore they can make their own
proteins.
24. Vacuoles: Storage sacs for solid or liquid contents. They are small in size in animals
while plants have large, may occupy 50-90 % of the cell volume. Helps to provide
turgidity and rigidity to the cell. Many substances like amino acids, sugars, organic
acids and proteins are stored in vacuoles. In Amoeba food vacuole is specialized to
play an important role.
25. Cell: It is the fundamental structural unit of living organisms, helps in respiration,
obtaining nutrition and clearing waste material or forming a new protein.
Differences between Plant cell and Animal Cell
(Please refer to Fig. 5.5 Animal cell & 5.6: Plant cell NCERT Book Page-63&64)

62
 ANIMAL CELL PLANT CELL

Cell wall absent Cell wall present

Plasma membrane is the Cell wall is the outer layer which

outer layer which provides gives rigidity and turgidity to the
turgidity to the cell cell

Vacuoles are small in size Vacuoles are big in size

Plastids are absent Plastids are present

Nucleus lies in the centre. Nucleus lies on one side

Question Bank

1. All the living organisms are composed of fundamental unit called as…………. ( Cell)
2. Who discovered the nucleus in the cell……………………….( Robert Brown)
3. Who saw the free living cells for the first time……………..( Leeuwenhoek)
4. Name two unicellular organisms …………….. ………………..( Amoeba, Chlamydomonas,)
5. Write two differences between prokaryotes and eukaryotes……………..( Nuclear
region/ Chromosome)
6. What are the two types of ERs ……. ( RER/ SER)
7. What are the functions of Golgi Bodies? (It includes the storage, modification and
package of cell products. The complex sugars are made from simple sugars in the
Golgi apparatus).
8. What are the types of plastids (Chromoplasts& Leucoplasts)
9. Which are the substances stored in vacuoles? (Substances like amino acids, sugars,
organic acids and proteins are stored in vacuoles)
10. Draw and label Animal cell & Plant cell( Ref NCERT Book Page-63&64)

63
 QUESTION PAPER:FORMATIVE ASSESSMENT – I (For Practice)
Marks- 40 Time: 90 minutes
* General Instructions
1. Questions 1-5 ( 1 Mark each) 2. Questions 6-10 ( 2 Mark each)
3. Questions 11-15 ( 3Mark each) 4. . Questions 16-17 ( 5Mark each)
Q.1 What is ATP, expand the term ……………………………………..
Q.2 Cellulose is a Fat (Mention,True/False)……………………………
Q.3 Which cell organelle is synthesizing the enzymes for the Golgi Apparatus……………
Q.4 The flexibility of the cell membrane to engulf food and other material is called
Endocytosis (Mention, True / False) ………………………………………
Q.5 What is the main function of Leucoplasts?
Q.6 Draw the structure of Ovum.
Q.7 Why the Plasma membrane is called as Selective Permeable Membrane?
Q.8 Describe what is an isotonic solution
Q.9 What is Plasmolysis?
Q.10 Write any two parts of a Compound microscope.
Q.11 Distinguish between Prokaryotic and Eukaryotic Cell.
Q.12 Write about the three properties of Cytoplasm.
Q.13 What is the significance of Vacuoles
Q.14 Write a short notes on Mitochondria.
Q.15 Explain the concept of diffusion.
Q.16 Draw the structure of a plant Cell and label it.
Q.17 Write the differences between a plant and animal cell.

----------------X---------------

64
 Chapter 6: “Tissues”

KEY CONCEPTS : [ *rating as per the significance of concept]

CONCEPTS RATING
Meristems in plants **
Permanent tissues in plants ****
Animal tissues *****

1. Tissue is a group of cells having similar origin, structure& function. Study of tissues is
called Histology
2. In unicellular organism (Amoeba) single cell performs all basic functions, whereas in
multi-cellular organisms (Plants and Animals) shows division of labor as Plant tissue
& Animal tissues.
3. Plant tissues are two types: Meristems & Permanent tissues.
4. Meristems: The Meristems are the tissues having the power of cell division. It is
found on those region of the plant which grows.
5. Types of Meristems;

1. The Apical meristems – It is present at the growing tip of the stem

and roots and increases the length.
2. The lateral meristems - present at the lateral side of stem anf root
(cambium) and increases the girth.
3. The intercalary meristems - present at internodes or base of the
leaves and increases the length between the nodes.

( Please refer to Fig. 6.2: location of meristems in plant body , NCERT Book Page- 69).

26. Permanent tissues: Two types such as Simple permanent tissues & Complex
permanent tissues.

a) Simple permanent tissues: subdivided as

(i): Parenchyma: Tissues provide the support to plants.They are loosly packed and has
large intracellular space.

65
 - Parenchyma with chlorophyll which performs photosynthesis is
called as chlorenchyma.
- The parenchyma with large air spaces to give buoyancy is
called as aerenchyma .Parenchyma also stores food and water.
(ii) Collenchyma: Tissue provides mechanical support, thickened at the corners, have
very little intercellular space. It allows easy bending of various parts of a plants without
breaking
(iii) Sclerenchyma: Tissue makes the plant hard and stiff, thickened due to lignin and
no intercellular space. Cells of this tissue are dead and commonly seen in the husk of
coconut.
(iv) Guard cells& Epidermal tissue: the tissue aids in protection and exchange of
gases. Guard cells kidney shaped in dicots, dumb bell shaped in monocots to guard the
stomata. The epidermal tissues of roots aid in absorption of water and minerals. The
epidermal tissues in desert plants have a thick waxy coating of Cutin with waterproof
quality. The epidermal tissues form the several layer thick Cork or the Bark of the tree.
(Please refer to Fig. 6.3- 6.6, NCERT Book Page-70-73).

b) Complex permanent tissues: The complex tissues are made of more than one type
of cells. All these cells coordinate to perform a common function.
They are subdivided as;
Xylem: It consists of tracheids, vessels, xylem parenchyma and xylem fibers. The cells have
thick walls,
Function - aids in conduction of water and minerals.
Phloem: It consists of sieve tubes, companion cells, phloem parenchyma, and phloem fibers.
Function - Phloem transports food material to other parts of the plants.
(Please refer to Fig. 6.7, NCERT Book Page-73).

6. Animal tissues: Sub divided as epithelial tissue, connective tissue, muscular tissue
and nervous tissue.

i. Epithelial tissue: It is a protective covering forming a continuous sheet. Simple

epithelium is the one which is extremely thin in one layer, whereas stratified
epithelium are arranged in pattern of layers.

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 Depending on shape and function they are classified as:

a) Squamous epithelium in the lining of mouth and esophagus.

b) Cuboidal epithelium in the lining of kidney tubules and salivary glands.
c) Columnar epithelium in the intestine &Columnar epithelium with cilia in the
lining of respiratory tract.
d) Glandular epithelium in the Glands aids in a special function as gland cells,
which can secrete at the epithelial surface.
(Please refer to Fig. 6.9, NCERT Book Page-75).
ii) Connective Tissue: Five Types, such as;
a) Blood: The Blood is a fluid connective tissue. Blood plasma has RBCs (Red Blood
Cells) WBCs (White Blood Cells) and platelets. Blood plasma contains proteins, salts and
hormones. Blood flows and transports gases, digested food, hormones and waste materials.
b) Bone: The bone is a connective tissue with hard matrix, composed of calcium
and phosphorus. A bone is connected by another bone with another connective tissue called
ligaments. A bone is connected by muscle with another connective tissue called tendon.
c) Cartilage: The cartilage is a connective tissue with solid matrix composed of
proteins and sugars. It is commonly seen in nose, ear, trachea, and larynx.
d) Areolar Connective Tissue: It is found between the skin and muscles, around
the blood vessels. It supports internal organs and aids in repair of tissues.
e)Adipose Connective Tissue: It is filled with fat globules for the storage of fat.
It acts as insulator. (Please refer to Fig. 6.10, NCERT Book Page-76).
Muscular tissues: They have special contractile proteins responsible for movements. Three
types, such as;
Striated muscles/skeletal muscles/voluntary muscles :
They are cylindrical, un-branched and multinucleated.They have dark bands and light bands.
Unstriated muscles/smooth muscles/involuntary muscles:
They are commonly called as Smooth muscles, having no striations (dark bands/ light bands
are absent). Commonly found alimentary canal, uterus, Iris of an Eye. They are spindle
shaped. Involuntary in nature
Cardiac Muscles: They are commonly called as Heart muscles, cylindrical,

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branched and uni-nucleate. Involuntary in nature.(Please refer to Fig. 6.11, NCERT Book
Page-77).
Nervous Tissue: The tissue responds to stimuli. The brain, spinal cord and nerves are
composed of nervous tissue or neurons. A neuron consists of Cell Body, cytoplasm, Nucleus,
Dendrite, Axon, nerve ending. The neuron impulse allow us to move our muscles when we
want to respond to stimuli. (Please refer to Fig. 6.12, NCERT Book Page-78).

Question Bank

1. Define the term tissue……………. ( A group of cells forms tissue)

2. What is Histology? ( Study of different tissues)
3. How many types of meristems are present in plants? (3 : Apical meristems, Lateral
meristem, Intercalary meristem )
4. Name the Parenchyma with chlorophyll which performs photosynthesis…………………
(chlorenchyma)
5. Which plant tissue makes the plant hard and stiff and thickened due to lignin with no
intercellular spaces …………………….( Sclerenchyma)
6. Give the details of epidermal tissue in Plants. (For protection and exchange of gases.
Guard cells kidney shaped in dicots, dumb bell shaped in monocots to guard the
stomata. The epidermal tissues of roots aid in absorption of water and minerals.)
7. Which elements constitute the Phloem? (Sieve tubes, companion cells, phloem
parenchyma, and phloem fibers.)
8. Distinguish between ligament and tendon (A bone to bone connective tissue called
ligament. A bone to muscle connective tissue called tendon.)
9. Name the three muscular tissues in the animals……..(Striated muscles ,Un- Striated
muscles, Cardiac Muscles)
10. Draw the neuron and label it (Please refer to Fig. 6.12, NCERT Book Page-78).

68
 QUESTION PAPER: FORMATIVE ASSESSMENT – I (For Practice)
Marks- 40 Time: 90 minutes
* General Instructions
1. Questions 1-5 (1 Mark each) 2. Questions 6-10 ( 2 Mark each)
3. Questions 11-15 (3Mark each) 4. . Questions 16-17 (5Mark each)
Q.1 What is a group of cells that are similar in structure and work called?
Q.2 Which is the hardest connective tissue?
Q.3 What is the name of Blood matrix?
Q.4 By what process permanent tissues are formed?
Q.5 Two bones are connected with ligaments. Mention True/ False…………….
Q.6 What are the two main types of tissues found in plants?
Q.7 Draw the structure of Stomata and label it.
Q.8 Write the main functions of parenchyma
Q.9 What are the fluid connective tissues?
Q.10 What is the difference between voluntary and involuntary muscles?
Q.11 Write a short notes on Cardiac muscles.
Q.12 Draw a labeled diagram of areolar tissue.
Q.13 Mention the three elements of Xylem tissue.
Q.14. Write a short notes on Glandular Epithelium.
Q.15. Write three significant points about Sclerenchyma
Q.16 With the help of suitable diagram, describe the Phloem.
Q.17 Draw and label the Nerve Cell.Explain in brief.

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69
 Chapter 7: “Diversity in Living Organisms”

KEY CONCEPTS : [ *rating as per the significance of concept]

CONCEPTS RATING
Basis of classification ***
Hierarchy of classification ****
Kingdom Plantae *****
Kingdom Animalia *****

1. Each organism is different from all other organisms.

2. In this activity, we decide which characteristics (we can run, but the Banyan tree
can’t run is a characteristic) are important in forming the desired category.
3. Greek thinker Aristotle classified animals according to whether they lived on land,
in water or in air. This classification is a landmark in ideology, but has limitations. For
example, animals that live in the sea include Corals, Whales, Octopus, Starfish, and
Shark. In fact they are different from each other.
4. Classification and Evolution: organisms are classified based on body design,
hierarchy in developing, relation to evolution. Charles Darwin first described the
idea of evolution in 1859 in his book “ The Origin of Species”
5. The Biologists, such as Haeckel, Whittaker & Carl Woese tried to classify all living
organisms into broad Kingdoms. The Whittaker proposed five kingdoms: Monera,
Protista, Fungi, Plantae and Animalia. Carl Woese introduced by dividing Monera
into Archaebacteria and Eubacteria.

70
6. Hierarchy of Classification :

7. Monera: They have unicellular, Prokaryotic organisms (do not have defined nucleus
or organelles). The cell wall may or may not present. The mode of nutrition is
autotrophic (synthesizing food on their own) (or)heterotrophic (getting food from
environment). Ex. Bacteria, Anabaena. ( (Please refer to Fig. 7.1 Monera NCERT Book
Page-83)
8. Protista: They have unicellular eukaryotic organisms (do have well defined nucleus
or organelles). The body is covered by cilia, flagella for locomotion. The mode of
nutrition is autotrophicorheterotrophic. Ex. Diatoms, protozoans.(Please refer to
Fig. 7.2 NCERT Book Page-84)

71
 9. Fungi: These are multi-cellular eukaryotic organisms with cell wall, made up of
Chitin. They do not perform Photosynthesis (heterotrophic), Saprophytic (derive
nutrition from decaying material). Ex. Aspergillus, Penicillium, Mushroom, Rhizopus.
The fungi living with algae forms Lichen (Symbiotic Association) .(Please refer to Fig.
7.3 NCERT Book Page-84).
10. Plantae: These are multi-cellular eukaryotic organisms with cell wall, made up of
Cellulose. Able to perform photosynthesis (autotrophic). Ex. Rice, wheat.
11. Animalia: These are multi-cellular eukaryotic organisms without cell wall. They are
not able to perform photosynthesis (heterotrophic). Ex Human beings, Peacock.

(Please refer to Fig. 7.4 NCERT Book Page-85).

DETAILS OF KINGDOM PLANTAE

1. The kingdom Plantae is further classified as Thallophyta, Bryophyta, Pteridophyta,

Gymnosperms, Angiosperms .

2.Thallophyta: The plants do not have well defined body design, commonly called as”
Algae”, mostly aquatic. Ex. Spirogyra, Ulothrix. (Please refer to Fig. 7.5 NCERT Book Page-
86).

3. Bryophyta: These are commonly called as the “Amphibians of Kingdom”. The plant body
is differentiated into roots like, stem like and leaf like structures. No specialized tissues for
the conduction of water and food.Ex. Marchantia, Funaria. (Please refer to Fig. 7.6 NCERT
Book Page-86).

4.Pteridophyta: These are commonly called as the “First vascular land plants ”. The plant
body is differentiated into root, stem and leaf. Specialized tissues for the conduction of
water and food are developed in these plants. The reproductive organs are inconspicuous.
Ex. Marsilea, Fern. (Please refer to Fig. 7.7 NCERT Book Page-87).

Special Note: The reproductive organs are inconspicuous in Thallophyta, Bryophyta,

Pteridophyta are can’t develop seeds. They are together called as” Cryptogamae (Non-
Flowering Plants)”. The plants with well differentiated reproductive organs and that

72
ultimately make seeds are called” Phanerogams (Flowering Plants)”. This group is further
classified Gymnosperms (Bear naked Seeds) &Angiosperms (Bears seeds inside Fruit).

5. Gymnosperms: These are commonly called as “Naked seed bearing plants”. They
areusually perennial, evergreen and woody. Ex. Pinus, Cycas (Please refer to Fig. 7.8 NCERT
Book Page-87).

6. Angiosperms: These are commonly called as “Enclosed seed bearing plants”. Plants with
seeds having a single cotyledon are called as” Monocotyledons or Monocots”. Plants with
seeds having two cotyledons are called as “Dicots”. Ex. Ipomoea, Paphiopedium.
(Please refer to Fig 7.9 &. 7.10 NCERT Book Page-87 ;Fig. 7.11 Page-88).

DETAILS OF KINGDOM ANIMALIA

These are Eukaryote, multicultural and hetero-tropic.

They are further classified as Non- Chordates( Porifera, Coelenterata, Platyhelminthes ,

Nematoda, Annelida, Arthropoda, Mollusca, Echinodermata) and Chordates {
Protochordata, Vertebrata ( Pisces, Amphibians, Reptilia, Aves, Mammalia)} .

I.Non- Chordates

1. Porifera: The word Porifera” means organisms with holes”. The canal system helps in
circulating water, food, oxygen. They are non-motile with cellular level of organization and
mainly marine organisms with hard outer coat called as Skeleton. They are commonly called
as Sponges. Ex. Spongilla, Sycon( Please refer Fig. 7.12, NCERT Text Book Page- 89)

2. Coelenterata: The wordCoelenterata” means organisms with body cavity

calledCoelenteron” . They are radially symmetrical, Diploblastic ( two layers of cells),
commonly called as Cnidarians ( Stinging cells for protection are present in the body). Ex.
Hydra, Sea Anemone (Please refer Fig. 7.13, NCERT Text Book Page- 89).

3. Platyhelminthes: The word Platyhelminthes means organisms with flatworms (

dorsocentrally flattened)”.They are bilaterally symmetrical Triploblastic ( three layers of

73
cells ), either free-living or parasitic. No true Coelom is present - Acoelomates. Ex. Planaria(
Free living) , Tape worm( Parasitic)( Please refer Fig. 7.14, NCERT Text Book Page- 90).

4. Nematoda: The word Nematoda “means organisms with roundworms”. They are
bilaterally symmetrical Triploblastic ( three layers of cells ), familiar with parasitic worms.
The false Coelom is called as Pseudocoelome. Ex. Ascaris, Wuchereria (Filarial worm
causes elephantiasis).)( Please refer Fig. 7.15, NCERT Text Book Page- 90).

5.Annelida: The word Annelida “ means organisms with metameric-segmented”. They are
bilaterally symmetrical Triploblastic(three layers of cells) with closed circulatory system,
familiar with earth worms. The Coelom is called as true Coelom. Ex. Neris, Earth worm,
Leech (Please refer Fig. 7.16, NCERT Text Book Page- 90).

6. Arthropoda: The word Arthropoda “means organisms with jointed legs” They are
bilaterally symmetrical Triploblastic(three layers of cells ), familiar with cockroaches. The
Coelom is blood filled called as Haemo Coelom. Ex. Prawn, Scorpion, Housefly (Please
refer Fig. 7.17, NCERT Text Book Page- 91).

7. Mollusca: The word Mollusca “means organisms with soft body” They are bilaterally
symmetrical, Triploblastic(three layers of cells), familiar with Octopus, Pila. Foot is for
moving, kidney like organ for excretion, with open circulatory system. Ex. Unio, chiton(
Please refer Fig. 7.18, NCERT Text Book Page- 91).

8. Echinodermata: The word Echinodermata “means organisms with spiny skinned”.

Exoskeleton is with calcium carbonate. They are radially symmetrical Triploblastic ( three
layers of cells ) with coelomic cavity, familiar with Star fish. They are exclusively free-living
marine animals. Ex. Sea Cucumber, Feather Star (Please refer Fig. 7.19, NCERT Text Book
Page- 91).

II.Chordates: They are further classified as two major groups such as Protochordata&
Vertebrata

(A).Protochordata: Notochord present in at least larval forms, but very rudimentary. It is a

rod like supporting structure, runs along with nervous tissue from the gut of animal. They

74
are bilaterally symmetrical, triploblastc(three layers of cells) with a Coelom, familiar with
Amphioxus. Ex. Balanoglossus(Please refer Fig. 7.20, NCERT Text Book Page- 92).

(B).Vertebrata: Notochord is replaced by vertebral column and internal skeleton. They are
bilaterally symmetrical, triploblastic, coelomic and segmented having paired gill pouches.
Vertebrates are grouped into five classes.

1. Pisces: These are commonly called as “fishes”, exclusively aquatic. Body is streamlined
and a tail for locomotion. Gills for respiration, heart is two chambered, cold blooded, skin
is covered with scales, plates. They are cold-blooded animals. Skeleton of bone ( Rohu) /
cartilage( Shark). They lay eggs. Ex. Lion Fish, Dog Fish (Please refer Fig. 7.21, NCERT Text
Book Page- 92).

2. Amphibians: These are commonly called as “Amphibians” because they can live on land
and in water”. Body is streamlined and a webbed foot/ foot for locomotion. Gills or lungs
or skin for respiration, heart is three chambered, cold blooded, skin is lack of scales,
plates. They are cold-blooded animals. They lay eggs. Ex. Rana, Hyla (Please refer Fig. 7.22,
NCERT Text Book Page- 93).

3. Reptilia: These are commonly called as “Reptilians”. A lung for respiration, heart is three
chambered (Crocodile heart is four chambered), skin have scales. They are cold-blooded
animals. They lay eggs. Ex. Snakes, Turtles (Please refer Fig. 7.23, NCERT Text Book Page-
93).

4. Aves :These are commonly called as “Birds”. A lung for respiration, heart is four
chambered, fore limbs are modified for flight, skin has feathers. They are warm-blooded
animals. They lay eggs. Ex. Ostrich (Flightless Bird), Pigeon, Sparrow (Please refer Fig. 7.24,
NCERT Text Book Page- 94).

5. Mammalia: These are commonly called as “animals with mammary glands for producing
milk to nourish their young ones”. A lung for respiration, heart is four chambered, skin has
hairs, sweat or oil glands. They are warm-blooded animals. They lay eggs (Platypus,
Echidna), give birth to young ones poorly developed (Kangaroo) & give birth to developed

75
young ones (Human beings). Ex. Lion, Whale, Bat (Please refer Fig. 7.25, NCERT Text Book
Page- 94& Fig.7.26, classification of Animals, Page- 95).

DETAILS OF NOMENCLATURE

NOMENCLATURE: The system of scientific naming or nomenclature was introduced by

Carolus Linnaeus. It is unique to identify in the world. We limit ourselves to writing the
names of the Genus and Species of that particular organism. The world over, it has been
agreed that both these names will be used in Latin forms.When printed is given in italics
and when written by hand, the Genus and Species name have to be underlined separately.
Ex. Ostrich (Common name): Struthiocamelus(scientific name with two parts namely the
Genus and Species).

QUESTION BANK

1. What is the book written by Charles Darwin?...................... (The Origin of Species)

2. Who proposed the five kingdoms such as, Monera, Protista, Fungi, Plantae and Animalia?
(Whittaker)

3.Monera members areunicellular, Prokaryotic organisms, mention TRUE/ FALSE ….. (TRUE)

4. The Diatoms belongs to the kingdom................. ( Protista)

5. TheAnabaena belongs to the kingdom …………………(Monera)

6……………………. are commonly called as the“Amphibians of Plant Kingdom”.( Bryophyta)

7. The warm-blooded animals with fore limbs modified for flight, skin has feathers are called
as………………….. (Aves/Birds)

8. Write the four salient features of Reptiles.

9.Compare the Pisces and Amphibians.

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10..Write the five salient features of Mammalia, give two examples.

QUESTION PAPER:FORMATIVE ASSESSMENT – I (For Practice)

Marks- 40 Time: 90 minutes
* General Instructions
1. Questions 1-5 (1 Mark each) 2. Questions 6-10 ( 2 Mark each)
3. Questions 11-15 (3Mark each) 4. . Questions 16-17 (5Mark each)
Q.1 Anabaena is member of the Phylum…………………………………
Q.2 Aspergillum is a member of the Phylum……………………………..
Q.3 Define the term Autotrophic mode of nutrition………………….
Q.4 The fungus living with algae is called as ……………………………..
Q.5 Name the scientist who has divided the Monera into two sub-groups…………………..
Q.6 Draw and label Paramecium.
Q.7 Distinguish the meaning of terms Gymnosperms and Angiosperms.
Q.8 What is Pseudocoelome? Give one example of it.
Q.9 What is Haemocoelome? Give one example of it.
Q.10 Write two salient features of mammalian group.
Q.11 What is the basis of nomenclature of organisms, give the scientific name of Ostrich.
Q.12 Give three salient features of Amphibia.
Q.13 Mention three features of Chordates.
Q.14. Draw and label Balanoglossus.
Q.15 Give two salient features of Aves and mention one example of a flightless bird.
Q.16 Write about the Hierarchy of Classification- Groups and mention basic unit of
classification.
Q.17 Give the salient features of Bryophytes and draw the diagram of Funaria.

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77
 Chapter 8 : “Motion”
KEY CONCEPTS [ *rating as per the significance of concept ]
1 Motion ****
2 Graphical Representation of Motion ***
& Graphs
3 Equation of motion ****
4 Uniform Circular Motion **

1 Motion (Uniform Motion And Non Uniform Motion, Acceleration and Velocity)
 A particle is a point-like object, has mass but infinitesimal size
 The object’s position is its location with respect to a chosen reference point, In
the diagram, the road sign the reference point
 Motion occurs when an object changes its position.
Both Distance and Time are important in describing motion.
 Sometimes you know motion has occurred even if you didn’t see it happen.
(mail truck)
 Relative motion: when two objects are moving in a plane (either in same
direction or opposite) each have relative motion with respect to second. e.g. a
person sitting in a train and watching a tree, in this case tree is stable but is
assumed to be moving but with respect to train.
Distance vs. Displacement
• Distance: How far an object has moved. It has only magnitude without
direction. (total)
• Displacement: How far and in what direction an object has moved from its
start position. i.e. the direct distance between two points.
Speed
 Speed = the distance an object travels in a given amount of time

 Speed =

 sI unit of speed is m/s

96
Types of Speed
 Constant speed: speed doesn’t change (set your car on cruise control)
 Changing speed: Riding a bike for 5 km. Take off and increase speed, slow
down up hill, speed up down hill, stop for stop sign. The trip took you 15 min
(.25 h)

 Average speed:

 Instantaneous speed: speed at any given time.

Velocity
 Velocity: includes speed and DIRECTION
 Storm is moving at 20km/hr.
 Should you be seeking shelter?
 Suppose two trains are going with the same speed in opposite direction so
they are having different velocities.
 Race car going around an oval track might have constant speed, but
different velocities at each point.
Acceleration
 Any change in velocity over a period of time is called acceleration.
 The sign (+ or -) of indicates its direction. + sign shows the acceleration and –
sign shows de-acceleration.
 Uniform (constant) acceleration equation
 a = v/t

97
  Images of car are equally spaced.
 The car is moving with constant positive velocity (shown by red arrows
maintaining the same size) .
 The acceleration equals to zero

 Images of car become farther apart as time increases

 Velocity and acceleration are in the same direction
 Acceleration is uniform (Arrows below the car maintain the same length)
 Velocity is increasing (Arrows above the car are getting longer)
 This shows positive acceleration and positive velocity

The instant speed at points of equal elevations is the same.

The velocities are different because they are in opposite
Free Fall & Air Resistance

98
 Galileo Galilei Italian physicist and astronomer

Formulated laws of motion for objects in free fall

 A freely falling object is any object moving freely under the influence of gravity
alone.
 It does not depend upon the initial motion of the object
 Dropped – released from rest
 Thrown downward
 Thrown upward
 The acceleration of an object in free fall is directed downward, regardless of the
initial motion
 The magnitude of free fall acceleration (gravitational acceleration) is g = 9.80
m/s2
 g decreases with increasing altitude
 g varies with latitude, height and depth from earth surface.
 9.80 m/s2 is the average at the Earth’s surface
 The italicized g will be used for the acceleration due to gravity
 Not to be confused with g for grams

 With negligible air resistance, falling objects can be considered freely falling.
objects of different shapes accelerate differently (stone vs feather)
 Speed both upward and downward

99
  The path is symmetrical.
 Acceleration is constant.
 The magnitude of the velocities is the same at equal heights.
 Images become closer together as time increases
 Acceleration and velocity are in opposite directions when ball goes upward.
 Acceleration is uniform (violet arrows maintain the same length)
 Velocity is decreasing in upward motion (red arrows are getting shorter)
 Positive velocity and negative acceleration
 Velocity becomes zero at maximum height.
 Time duration flight in going upward and coming back is always same.
Test Yourself :
1. What is SI Unit of displacement?
2. Name the quantity which represents rate of change of velocity.
3. A particle describes a semicircle of radius l 14m. What are its distance and
displacement covered?
2 Graphical Representation Of Motion & Graphs (Refer to article 8.4 of NCERT text
book.)
Test Yourself :
1. What does slope of Position – Time graph represent?
2. If velocity –time graph is parallel to time axis, what type of motion does it represent?

100
3 Equation of motion
(1) When object is moving in straight line-
 v = vo + at
 x = xo + vot + ½ at2
 v2 = vo2 + 2a(∆x)
 Average acceleration describes how fast the velocity is changing with respect to
time.  x 
 
v t
aave    
t t

 where:
aave = average acceleration
v = change in velocity
x = displacement
t = elapsed time
(2) when object is coming vertically downward-
 v = vo + gt
 h = vot + ½ gt2
 v2 = vo2 + 2ah
(3) when object is coming vertically upward-
v = vo - gt
h = vot - ½ gt2
v2 = vo2 - 2gh
 The SI unit of velocity is the m/s.
Average accleration is + or – depending on direction.
 Instantaneous Acceleration

 v 
a  lim  
t 0
 t 
 Instantaneous acceleration is the limit of v/t as t approaches zero.
 Instantaneous acceleration is zero where slope is constant
 Instantaneous acceleration is positive where curve is concave up
 Instantaneous acceleration is negative where curve is concave down

101
 Test Yourself :
1. Give the equation for uniform motion.
2. When a car stops after applying brakes, what is the final velocity?
4 Uniform Circular Motion
In this kind of motion the object moves on circle with fix speed but the direction is
changed by the time so the velocity of the change so its called acceleration motion. This
acceleration is called centrifugal acceleration. It is directed toward the centre.
Test Yourself:
1. What remains constant in uniform circular motion?
2. What changes continuously in uniform circular motion?

QUESTION BANK

One Mark questions

1. Can displacement be zero even when distance is not zero?
2. Can the distance travelled by an object be smaller than magnitude of its displacement?
3. A particle is moving with uniform velocity. What is its acceleration?
4. How can you get speed of an object from its distance – time graph?
5. How can you get distance of an object from its speed – time graph?
6. A brick & an elephant are in free fall. What is common in their motion?
7. When an object is thrown vertically upwards. What is its velocity at the highest point?
8. Can velocity & acceleration point in opposite directions?
9. Define acceleration.
10. What is non uniform motion?

Two Marks questions

1. Differentiate scalars & vectors?
2. What is retardation? How does it affect the speed?
3. Can speed of a body vary with its velocity constant? Explain.
4. Why is circular motion with constant speed called accelerated motion?
5. State the difference between distance & displacement.

102
6. What is the difference between speed & velocity?
7. What does a speedometer & odometer indicate?

Three Marks questions

1. If an object is thrown vertically upwards with speed 49 ms-1. How long does it take to
complete upward journey? What maximum height does it achieve?
2. An object starting from rest covers 20 metres in first 2 seconds & 160 metres in next 4
seconds. What is its velocity after 7 seconds from the start?

Five Marks questions

1. Derive all the three equations of motion for uniform acceleration using graphical method.
2. A car a moving at rate of 72km/h and applies brakes which provide a retardation of 5ms-2.
(i) How much time does the car takes to stop.
(ii) How much distance does the car cover before coming to rest?
(iii) What would be the stopping distance needed if speed of the car is doubled?

*******

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 CHAPTER -9 “Force & Laws Of Motion”
KEY CONCEPTS [ *rating as per the significance of concept]
1 Balanced and Unbalanced Forces ***

2 Laws of Motion *****

3 Inertia and Mass *****

4 Conservation of Momentum ****

1 Balanced and Unbalanced Forces

Balanced Forces The net force is when two or more forces are applied on
the same object and at the same time. The applied forces combined are
called the net force. = 0 25 N 25 N
Balanced Forces The force I apply in one direction plus the force you apply
in the opposite direction are added together. 25 N -25 N = 0 Because the
forces are equal and balanced…just like a balanced scale…this is an
example of balanced forces. Unbalanced Forces What does it mean to
have something unbalanced? Unequal, not the same, different How could
we have unbalanced forces?

Unbalanced Forces A force is applied in one direction and either another

smaller or larger force is applied in the opposite direction or no force is
applied at all in the opposite direction.
Unbalanced Forces If I have a chair and I push on one side of it with a force

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 of 50 N and you push on the other side, with a force of 25 N, will the chair
move? Which way will it move? The direction in which the most force is
applied. What is the net force? 50 N 25 N.
Unbalanced Forces 50N -25N = 25N These forces are unequal so the forces
are considered unbalanced forces. 50 N 25 N = 25 N
Unbalanced Forces If I push the chair in one direction with 25 N force and
you push the chair in same direction with 25 N force, will the chair move?
Why? Because the applied net force is UNBALANCED!
Unbalanced Forces 25 N 25 N = 50 N The result would be the chair moving
in the direction it was pushed with a combined force of 50 N.
Test Yourself
1. An object of 5 kg is acted upon by two forces, 70 N each in opposite
directions. What is its acceleration?
2. Why does an object accelerate during free fall?
2 Laws of Motion
Newton's First Law
1st Law – An object at rest will stay at rest, and an object in motion will
stay in motion at constant velocity, unless acted upon by an unbalanced
force.
An object at rest will stay at rest, and an object in motion will stay in
motion at constant velocity, unless acted upon by an unbalanced force.
Newton's Second Law
"If the net force on an object is not zero, the object will accelerate. The
direction of the acceleration is the same as the direction of the net force.
The magnitude of the acceleration is directly proportional to the net force
applied, and inversely proportional to the mass of the object."
Mathematical symbols provide a convenient shorthand for all of this:

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The Effect of Mass
A force applied to an automobile will not have the same effect as the same
force applied to a pencil. An automobile resists accelerating much more
than a pencil does, because it has more inertia, or mass.
The acceleration of an object depends not only on how hard you push on
it, but also on how much the object resists being pushed.
What is the effect of mass on acceleration? This, too, turns out to be quite
simple (I wonder why...). For the same force, an object with twice the mass
will have half the acceleration. If it had three times the mass, the same
force will produce one-third the acceleration. Four times the mass gives
one-fourth of the acceleration, and so on.
This type of relationship between quantities (double one, get half the
other) is called an inverse proportion or inverse variation. In other words,
then:
Newton’s Second Law of Motion The acceleration of an object is
dependent upon both force and mass. Thus, if the colliding objects have
unequal mass, they will have unequal accelerations as a result of the
contact force which results during the collision.
Newton's Third Law
Newton's Third Law is stated as:
For every action there is an equal and opposite reaction.
"action...reaction" means that forces always occur in pairs. (Forces are
interactions between objects, like conversations are interactions between
people.)

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 Single, isolated forces never happen. The two forces involved are called
the "action force" and the "reaction force."
These names are unfortunate for a couple of reasons :
Either force in an interaction can be the "action" force or the "reaction"
force
The action and reaction forces exist at the same time.
"equal" means
Both forces are exactly the same size. They are equal in magnitude.
Both forces exist at exactly the same time. They both start at exactly the
same instant, and they both stop at exactly the same instant. They
are equal in time.
"opposite" means that the two forces always act in opposite directions -
exactly 180o apart.
Newton's third law of motion In every interaction, there is a pair of forces
acting on the two interacting objects. The size of the force on the first
object equals the size of the force on the second object. The direction of
the force on the first object is opposite to the direction of the force on the
second object. Forces always come in pairs - equal and opposite action-
reaction force pairs.
Newton's third law of motion applied to collisions between two objects. In
a collision between two objects, both objects experience forces which are
equal in magnitude and opposite in direction. Such forces cause one object
to speed up (gain momentum) and the other object to slow down (lose
momentum). According to Newton's third law, the forces on the two
objects are equal in magnitude.
Test Yourself
1. Can action reaction balance each other?
2. What does a force do?
3 Inertia and Mass
Inertia is the tendency of an object to resist any change in its motion. An
object will continue to move at the same speed in the same direction

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 unless acted upon by an unbalanced force. Inertia & Mass
Inertia & Mass of a bowling ball rolled down the road would eventually
come to a stop. Friction is an unbalanced force that causes the ball to stop
or slow down. Without friction, the ball would keep going.
Inertia & Mass of a bowling ball and a tennis ball have the same inertia.
Inertia & Mass If you had a tennis racket and I threw tennis ball at you,
what would happen? If you had a tennis racket and I threw a bowling ball
at you, what would happen? Why could you change the motion of the
tennis ball but not the motion of the bowling ball?
Mass is the amount of matter in an object. A bowling ball has more mass
than a tennis ball. The greater the mass of an object the greater its inertia.
Mass is the measurement of inertia.
Test Yourself
1. Why do we fall forward if we alight from a moving bus?
2. Why does an athlete run for some distance before long jump?
4 Conservation of Momentum
Law of Conservation of Momentum
In a closed system, the vector sum of the momenta before and after an
impact must be equal.
Before After
m1v1 +m2v2 = m1v1’ + m2v2’
Internal and External Forces

QUESTION BANK
One Mark questions
1. Define momentum.
2. State first law of motion.
3. What is inertia?
4. Can action and reaction balance each other?
5. How does one climb up a rope?
6. Why cannot we walk in space?

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7. What does rate of change of momentum represent?
8. Why do we continuously paddle to keep the cycle moving?
9. Why does a scooter tend to skid while executing a sharp turn?
10. Which one would have more inertia : 10 kg mass & 5 kg mass?

Two Marks questions

1. Explain the functioning of shockers in cars.
2. How much force is needed to pull an object of mass 40 kg in vertically upward direction
with acceleration of 2.2 m / s2.
3. Why does a fan keep moving for sometime when switched off?
4. What do you mean by conservation of momentum?
5. Inflated balloon lying on the surface of a floor moves forward when pricked with a pin.
Why?

Three Marks questions

1. An iron sphere of mass 10 kg is dropped from a height of 80 cm, if ‘g’ = 10 m / s2.
Calculate the momentum transferred to the ground by the body.
2. What would be the force required to stop a car of mass 1000 kg and a loaded truck of
mass 10,000 kg in 2 seconds each moving with velocity 5 m / s.
3. Deduce law of conservation of momentum using third law of motion.

Five Mark questions

1. Name and define three different types of inertia & give an example of each.

********

109
 CHAPTER 10- “GRAVITATION”
KEY CONCEPTS [ *rating as per the significance of concept]
1 Gravitation ***

2 Universal Law Of Gravitation ****

3 Free Fall **

4 To Calculate The Value Of G ****

5 Mass & Weight ***

6 Weight Of The Object On Moon ***

7 Thrust & Pressure ***

8 Pressure In Fluids ***

9 Buoyancy ****

10 Why Objects Float Or Sink When ***

Placed On The Surface Of Water?
11 Archimedes’s Principle *****

12 Relative Density ***

Gravity is one of the most basic forces in the universe. It plays a fundamental role not
only in the structure of our solar system but also in the way objects behave on Earth. In
this section, we will talk about gravity on a small scale. We will discuss topics such as
weight, free fall, and ballistics. We will learn the physics of phenomena we experience
daily and take for granted
1.Gravitation
Gravitation is the force of attraction between two objects in the universe.
Gravitation may be the attraction of objects by the earth.
This force is proportional to the product of masses of the objects and inversely proportional
to the square of the distance between them. It is independent of medium.

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 Gravitational force =

Eg :- If a body is dropped from a certain height, it falls downwards due to earth’s

gravity.
If a body is thrown upwards, it reaches a certain height and then falls downwards
due to the earth’s gravity.
 Gravitation may be the attraction between objects in outer space.
Eg :- Attraction between the earth and moon.
Attraction between the sun and planets.
GRAVITY
 A natural force that pulls all objects toward the center of the earth
 keeps the moon orbiting
 It holds stars together . . .
 And binds galaxies together for billions of years ….Prevents Planets from losing their
atmospheres.

Test yourself:
1. When we move from the poles to the equator. Hence, the value of g
decreases. Why?
2. What is the difference between gravity and gravitation?

2.Universal law of gravitation: - “Inverse square law”- All bits of matter attract all
other bits of matter………..
 The universal law of gravitation states that, ‘Every object in the universe attracts
every other object with a force which is directly proportional to product of the
masses and inversely proportional to the square of the distance between them.’

 The SI unit of G is N m2 kg -2 and its value is 6.673 x 10-11 N m2 kg -2

 The strength of the gravitational attraction between two objects depends on two
factors:

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  How big the objects are (how much mass they have) and
 How far apart they are.

Test Yourself
1. What is the difference between gravity and gravitation?
2. What does it mean to say that the Force of gravity is proportional to the masses
of the bodies, and inversely proportional to the distance between them?

3. Free Fall
 With negligible air resistance, falling objects can be considered freely falling.
objects of different shapes accelerate differently (stone vs feather)

Test Yourself
1. A coin and a feather are dropped from the roof of a building. Which one will fall to
the ground first

4 .To calculate the value of” g “(acceleration due to gravity)

 The acceleration due to gravity is denoted by g.
 The unit of g is same as the unit of acceleration ms -2
 From the second law of motion, force is the product of mass and acceleration.

F = ma
 For free fall, force is the product of mass and acceleration due to gravity.

F = mg or mg = =

or g =

where M is the mass of the

Earth and d is the distance between the object and the earth.
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  For objects near or on the surface of the earth d is equal to the radius of the earth R

 F = mg or mg = =

 or g =

Test Yourself
1. Calculate the value of g on the surface of earth.
2. What is the difference between "weight" and "mass”?

5. Mass and Weight:

 Mass is a fundamental, universal property. You have the same amount of mass no
matter where you are in the Universe.
 Weight is not fundamental its value depends on circumstances in the Universe. Weight
is a force. It is the resultant gravitational force exerted on a body with mass m by all the
other bodies on the Universe.

Weight = Fg = G m Me / R2 = mg
where Me is the mass of the Earth and R is the radius of the Earth.
Test Yourself
1. An astronaut has 80 kg mass on earth (a)what is his weight on earth? (b) What
will be his mass and weight on mars where g=3.7 m/s2 .

2. When you put an object on a spring balance, do you get the mass of an object or
its weight?

6.Weight Of The Object On Moon

 The mass of the moon is less than the mass of the earth. So the moon exerts lesser
force on the objects than the earth.

 The weight of an object on the moon is one sixth (1/6 th) of its weight on the earth.
 The weight of an object on the earth is the force with which the earth attracts the
object and the weight of an object on the moon is the force with which the moon
attracts the object.

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 Celestial body Mass (kg) Radius (m)

Earth 5.98 x 1024 6.37 x 106

Moon 7.36 x 1022 1.74 x 106

Test Yourself
1. What will be the weight of the body on the moon whose mass is12 kg?

7.Thrust & Pressure

 Thrust is the force acting on an object perpendicular to the surface.

 Pressure is the force acting on unit area of a surface

Thrust
Pressure = ----------
Area
 The SI unit of thrust is N/m2 or N m-2 . It is called Pascal (Pa).

8. Pressure In Fluids
 . Fluids exert pressure in all directions
 Pressure exerted on fluids is transmitted equally in all directions.
9. Buoyancy
When an object is immersed in a fluid it experiences an upward force called buoyant
force. This property is called buoyancy or upthrust.

10. Why objects float or sink when placed on the surface of water?
 Take some water in a beaker. Take a piece of cork and an iron nail of the same mass.
Place them on the water. The cork floats and the nail sinks.
 If the density of an object is less than the density of a liquid, it will float on the liquid
and if the density of an object is more than the density of a liquid, it will sink in the
liquid.
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11. Archeimedes Principle
 Archimedes’ principle states that, When a body is partially or fully immersed
in a fluid it experiences an upward force that is equal to the weight of the
fluid displaced by it.’

12 .Relative density
 The relative density of a substance is the ratio of the density of a substance
to the density of water. It is a ratio of similar quantities and has no unit.

QUESTION BANK
One Mark questions
1. Explain what Centrifugal force is.
2. What do you mean by the weight of the body on moon.
3. Give the value of G with proper units.
4. Give the value of g with proper units.
5. What is measured by physical balance?

Two Marks questions

1. At what height above the earth’s surface would the value of acceleration due to gravity
be half of what it is on the surface? Take radius of earth to be R.
2 . A body of 90 kg f on the surface of earth. How much will it weigh on the surface of
moon whose mass is 1/9 and radius is ½ of that of earth?
3. A piece of paper takes much longer to fall than a stone through the same distance.
Explain the reason.
4. Consider a heavenly body which has a mass twice that of the earth and radius thrice
that of the earth .What will be the weight of the book on this heavenly body, if its

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 weight on earth is 900 N?
Three Marks questions
1. Why gravitational force is usually unnoticeable?
2. Prove that acceleration due to gravity is independent of mass of the body.
3. How can the average density of the earth can be determined?
4. What is buoyancy and buoyant force? Upon what factors do they depend
Five Marks questions
1. Find the percentage change in the weight of a body when it is taken from equator to
poles. The polar radius is 6,357 Km and equatorial radius is 6,378 Km.
2. The density of ice is 918kgm-3 and that of sea water is 1,030kgm-3.An iceberg floats
with a portion 224 liters outside water. Find the volume of iceberg.
3. What are the laws of flotation? Give some illustrations.

********

116
 CHAPTER 11 “Work & Energy”
KEY CONCEPTS [ *rating as per the significance of concept]
1 Work Done By A Constant Force ***

2 Energy And Its Forms(Kinetic Energy & *****

Potential Energy)
Are Various Energy Forms Inter convertible?
3 Potential Energy Of An Object At A Height *****

4 Law Of Conservation Of Energy ****

5 Rate Of Doing Work & Commercial Unit Of ****

Energy

1.Work Done By A Constant Force

 Work is a scalar quantity equal to the product of the displacement x and the
component of the force Fx in the direction of the displacement..
 Work is defined as a force acting upon an object to cause a displacement
 Mathematically, work can be expressed by the following equation.
 W= F x d cos q ( cos 00 = 1)
 where F = force, d = displacement, and the angle (theta) is defined as the angle
between the force and the displacement vector
 Three things are necessary for the performance of work:
 There must be an applied force F.
 There must be a displacement x.
 The force must have a component along the displacement


Negative Work

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 The friction force f opposes the displacement
Positive Work

Force F contributes to displacement x.

Test Yourself:
1.Calculate Work when F= 40 N and x = 4 m.
2.Calculate Work when F = -10 N and x = 4 m.
3. A lawn mower is pushed a horizontal distance of 20 m by a force of 200 N directed at an
angle of 300 with the ground. What is the work of this force?
4. A student lifts a 50 pound (lb) ball 4 feet (ft) in 5 seconds (s). How many joules of work has
the student completed?
2.Energy And Its Forms

James Joule
The metric system unit of energy is the joule (J), after James Joule.
• Mechanical energy is the energy which is possessed by an object due to its motion or
its stored energy of position

Forms of Energy
• Kinetic energy : is the energy of motion

Energy which a body possesses because of its motion, which occurs anywhere
from an atomic level to that of a whole organism

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 Examples of Kinetic Energy: This is not an all-inclusive list.
 Electrical – The movement of atoms
 Electromagnetic or Radiant – The movement of waves
 Thermal or Heat – The movement of molecules
 Motion – The movement of objects
 Sound – The movement through waves

Engineers generally refer to thermal/heat energy as “internal energy” and use

“kinetic energy” strictly in reference to motion.
Potential Energy (Stored energy or gravitational energy)
 The capacity to do work by virtue of position or configuration
 an object can store energy as the result of its position or elastic source
 Potential Energy is maximum at the maximum HEIGHT

Energy transformation involves the conversion of one form of energy into another form.
Examples of energy transformation include:

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 • Chemical – Food is consumed and converted into motion for playing sports or taking
a test.

• Radiant – Sunlight is consumed by plants and converted into energy for growth.

• Electrical – Energy transferred to an oven is converted to thermal energy for heating

our food.

Now you know the basic forms of energy. The next question is “What are the energy
sources?”
There are renewable and nonrenewable sources of energy. A renewable energy source
is a form of energy that is constantly and rapidly replenished by natural processes.
Examples of renewable energy sources include:
• Biomass – The use of a living or once living organism as fuel

• Hydropower – The energy produced from the movement of water

• Geothermal – The use of heat from within the Earth or from the atmosphere
near oceans to warm houses or other buildings

• Wind – The use of wind to generate electricity

Solar – The use of the sun as a source of heat; for instance, to heat a room within a
house, etc.
Energy Conversion
Examples
Fossil fuels Chemical → Heat → Mechanical → Electrical
Solar cells Sunlight → Electrical
Wind turbines Kinetic → Mechanical → Electrical
Hydroelectric Gravitational potential → Mechanical → Electrical
Nuclear Nuclear → Heat → Mechanical → Electrical
Vehicle System Conversion

Mechanical Heat

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 Test Yourself
1. How much potential energy is lost by a 5Kg object to kinetic energy due a decrease in
height of 4.5 m.
3. Potential energy of an object at a height
An object increases its energy when raised through a height.
The potential energy of an object at a height depends on the ground level or the zero level

4. Law Of Conservation Of Energy

The principle of Conservation of Mechanical Energy
The total mechanical energy (E=KE+PE) of an object remains constant as the object moves,
provided that the net work done by external non-conservative forces is zero, Wnc=0J
Total mechanical energy: the sum of kinetic energy and gravitational potential energy
E = KE + PE
Wnc = (KEf - KE0) + (PEf - PE0)
Wnc = (KEf + PEf) - (KE0 + PE0)
Wnc = Ef - E0
Ef = KEf + PEf) E0 = KE0 + PE0

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5. Rate of Doing Work & Commercial Unit Of Energy
POWER
Rate at which work is performed or energy is expended

W
P=
t
Watt is the base unit of Power
One watt is equal to 1 joule of work per second
Types of Power
 Electrical Power
Uses electrical energy to do work
 Mechanical Power
Uses mechanical energy to do work (linear, rotary)
 Fluid Power
Uses energy transferred by liquids (hydraulic) and gases (pneumatic)
• Power is the rate that we use energy.
• Power = Work or Energy / Time
• P = W/t = F x d/t = F v
• The unit joule is too small .The bigger unit of energy called kilowatt hour (kW h)
1 kW h is the energy used in one hour
at the rate of 1000 J s–1 (or 1 kW).
1 kW h = 1 kW *1 h
= 1000 W*3600 s
= 3600000 J
1 kW h = 3.6 x 106 J.

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 Test Yourself
1. A 5 Kg Cart is pushed by a 30 N force against friction for a distance of 10m in 5
seconds. Determine the Power needed to move the cart.
2. A student lifts a 50.0 pound (lb) ball 4.00 feet (ft) in 5 .00seconds (s). How many
watts of power are used to lift the ball?

Important Points for Work Problems:

• Always draw a free-body diagram, choosing the positive x-axis in the same
direction as the displacement.
• Work is negative if a component of the force is opposite displacement
direction
• Work done by any force that is at right angles with displacement will be zero
(0).
• For resultant work, you can add the works of each force, or multiply the
resultant force times the net displacement.
• Energy is the ability to move
• Potential is stored energy (Statics)
• Dependant on height
• Kinetic is moving energy (Dynamics)
• Dependant on velocity
• Springs store energy dependant on distance and constant

QUESTION BANK
One mark questions
1. Does work have a direction?
2. Does the kinetic energy of an object depend on its direction of motion?
3. Cam matter be converted into energy?
4. Give an example of conversion of chemical energy into heat energy.
Two marks questions

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 1. Two persons do the same amount of work. The first person does it in 10 s and
the second, in 20 s.Find the ratio of the power used by the person to that by the
second person.
2. A body of mass 25 g has a momentum of 0.40 kgm/s.Find its kinetic energy.
3. Define work and write its units.
4. By what factor does the kinetic energy of an object depend on its direction of
motion?
Three marks questions
1. How much time will it take to perform 440 j of work at a rate of 11 W.
2. A body of mass 3.0kg and a body B of mass 10 kg are dropped simultaneously
from a height of 14.9m.Calculate their Momenta, their Potential energies and
kinetic energies when they are 10m above the ground.
3. lA man does 200j ofl work in 10 seconds and a boy does 100j of work in 4
seconds. Who is delivering more power? Find the Ratio of power delivered by the
man to that by the boy.
Five marks questions
1. Show that the work done by a force is given by the product of the force
and the projection of the displacement along the force.
2. Find the expression for gravitational potential energy of a body of mass m
at height h.
3. Why does a person standing for a long time get tired when he does not
appear to do any work?
4. How can you justify that a body kept at a greater height has larger
energy?

******

124
 CHAPTER 12 – “Sound”
KEY CONCEPTS [ *rating as per the significance of concept]
1 Production of Sound ****

2 Propagation of Sound *****

3 Reflection of Sound *****

4 Echo ****

5 Uses Of Multiple Reflection ***

Of Sound
6 Range of Hearing ***

7 Applications of Ultrasound **

8 SONAR **

9 Structure of Human Ear ****

1. Production of Sound
Sound is produced due to the vibration of objects. Vibration is the rapid to and fro motion of an
object.
Vibrating objects are the source of all sounds Irregular, chaotic vibrations produce noise Regular,
controlled vibration can produce music All sound is a combination of pure frequencies
A stretched rubber band when plucked vibrates and produces sound.

2. Propagation of Sound
When an object vibrates, the particles around the medium vibrate. The particle in contact with the
vibrating object is first displaced from its equilibrium position
The disturbance produced by the vibrating body travels through the medium but the particles do not
move forward themselves.
A wave is a disturbance which moves through a medium by the vibration of the particles of the
medium. So sound is considered as a wave.Sound waves Require medium for transmission.Sound
waves are called mechanical waves. When a vibrating object moves forward, it pushes and
compresses the air in front of it forming a region of high pressure called compression (C). When the
vibrating object moves backward, it forms a region of low pressure called rarefaction (R).

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A vibrating object producing a series of compressions (C) and rarefaction (R)
In these waves the particles move back and forth parallel to the direction of propagation of the
disturbance. Such waves are called longitudinal waves.
There is another kind of waves called transverse waves. In these waves the particles oscillate up
and down perpendicular to the propagation of the direction of disturbance.
Sound propagates in a medium as a series of compressions (C) and rarefactions (R).
Compressions are the regions of high pressure and density where the particles are crowded and
are represented by the upper portion of the curve called crest.
Rarefactions are the regions of low pressure and density where the particles are spread out and
are represented by the lower portion of the curve called trough
Characteristics of a sound wave

Frequency of sound wave

The number of oscillations per unit time is called the frequency of the sound wave.
It is represented by the symbol ٧ (Greek letter nu). Its SI unit is hertz (Hz)

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Time period of sound wave
Frequency and time are represented as follows:-
٧ for one oscillation
1 1
T = ---- or ٧ = ----
٧ T
Amplitude of sound wave
The amplitude of sound wave is the height of the crest or tough.
It is represented by the letter A.
The SI unit is the same as that of density or pressure.

Wavelength and Amplitude

The wavelength is the distance between the "crests" of two waves that are next to each other.
The amplitude is how high the crests are.
Pitch and loudness of sound
The pitch of sound (shrillness or flatness) depends on the frequency of vibration.
If the frequency is high, the sound has high pitch and if the frequency is low, the sound
has low pitch
Speed of sound
The speed of sound is more in solids, less in liquids and least in gases.
The speed of sound also depends on the temperature of the medium. If the temperature
of the medium is more, the speed of sound is more
3. Reflection of Sound
Sound gets reflected at the surface of a solid or liquid and follows the laws of reflection.
i) The angle of incidence is equal to the angle of reflection.

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 ii) The incident ray, the reflected ray and normal at the point of incidence all lie in the
same plane.

4. Echo
If we shout or clap near a reflecting surface like tall building or a mountain, we hear the
same sound again. This sound which we hear is called echo. It is caused due to the reflection
of sound.
To hear an echo clearly, the time interval between the original sound and the echo
must be at least 0.1 s.
Since the speed of sound in air is 344 m/s, the distance travelled by sound in 0.I s = 344
m/s x 0.1 s = 34.4 m
So to hear an echo clearly, the minimum distance of the reflecting surface should be
half this distance that is 17.2 m.
Reverberation
Echoes may be heard more than once due to repeated or multiple reflections of sound
from several reflecting surfaces. This causes persistence of sound called reverberation.
In big halls or auditoriums to reduce reverberation, the roofs and walls are covered by
sound absorbing materials like compressed fibre boards, rough plaster or draperies.
5. Uses Of Multiple Reflection Of Sound
Megaphones, horns, musical instruments like trumpets, etc. are deigned to send sound by
multiple reflection in a particular direction without spreading in all directions.
ii) Doctors listen to sounds from the human body through a stethoscope. The sound of
heartbeat reaches the doctor’s ears by multiple reflection.
iii) Generally the ceilings of cinema halls and auditoriums are curved so that sound after
multiple reflection reaches all parts of the hall.

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 Sometimes a curved sound board is placed behind the stage so that sound after multiple
reflection spreads evenly across the hall.
6. Range of Hearing
Human beings can hear sound frequencies between 20 Hz and 2000 Hz.
Sound whose frequency is less than 20 Hz is called infrasonic sound
Sound whose frequency is more than 2000 Hz is called ultrasonic sound
7. Uses of ultrasonic sound
Ultrasonic sound is used to clean objects like electronic Components, used to detect cracks
in metal blocks, used in ultra sound scanners for getting images of internal organs of the
human body used to break small stones formed in the kidneys into fine grains.
8 Sonar
It is a device which uses ultrasonic waves to measure distance, direction and speed of
underwater objects. The distance of the object can be calculated by knowing the speed of
sound in water and the time taken between the transmission and reception of ultrasound

9.Structure of the human ear

The sound waves passes through the ear canal to a thin membrane called eardrum. The
eardrum vibrates. The vibrations are amplified by the three bones of the middle ear called

129
hammer, anvil and stirrup. Middle ear then transmits the sound waves to the inner ear. The
brain then interprets the signals as sound.
QUESTION BANK
One mark questions
1. What do you understand by sound waves?
2. Give an example to show that sound travels at a finite speed.
3. Is sound wave longitudinal or transfer.
4. Name two quantities that vary periodically at a place in air as a sound wave
travels through it .
5. An airplane produces a sound wave with frequency of 5 KHz and wavelength
30 m. In how much time would the sound wave cover the distance of 4 Km?

6. With the help of a diagram show how longitudinal waves like sound waves
travel in air.
7. With the help of a diagram show how longitudinal waves like sound waves
travel in air.

8. Can we hear the ringing of a mobile phone placed in a vacuum chamber?

9. Can two astronauts talk on moon a they does on the surface of the earth?

Two marks questions

1. Explain how echoes are used by bats to judge the distance of an obstacle?
2. State the special properties of ultrasound that make it useful to us .In
general, how these properties are utilized.
3. Why is soft furnishing avoided in concert halls?
4. Draw a diagram depicting low pitched sound and high pitched sound and
write main difference between the two?
5. Distinguish between longitudinal and transverse waves. Give one example
each.
6. An explosion takes place at the moon. After what time would it be heard at
the earth?

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Three marks questions
1. Two sources A and B vibrate with the same amplitude. They produce sounds
of frequencies 1 kHz and 30 kHz respectively. Which of the two waves will
have greater power?
2. Find the time period of the source of a sound wave whose frequency is
400Hz.
3. A sound wave travels at a speed of 340m/s. If its wavelength is 2 cm, what is
the frequency of the wave? Will it be in the audible range?
4. The grandparents and parents of a two year girl are playing with her in a
room. A sound source produces a 28—kHzsound.who in the room is most
likely to hear the sound?

Five marks questions

1. Sound cannot travel in vacuum. Describe an experiment to demonstrate this.
2. With the help of a diagram describe how compression and rarefaction pulses
are produced in air near a source of sound.
3. Explain briefly how a flaw in a mental component can be detected using
ultrasound?
4. Explain the working and application of SONAR.
5. A monkey drops a coconut from the top of a tree. He hears the sound of the
coconut hitting the ground 2.057 seconds after dropping it .If the monkey
was 19.6 metres above the ground, what is the speed of sound in air?(take g
= 9.8m/s2).
6. Draw a neat diagram of human ear. Explain the function of various parts.

What have you learnt

Longitudinal waves: Those in which the direction of vibration is the same as their direction
of propagation. So the movement of the particles of the medium is either in the same or in
the opposite direction to the motion of the wave. Exemple: sound waves, what changes in
this case is the pressure of the medium (air, water or whatever it be).

131
Transverse waves: The oscillations occur perpendicularly to the direction of energy transfer.
Exemple: a wave in a tense string. Here the varying magnitude is the distance from the
equilibrium horizontal position
A general property of waves is that their speed relative to medium depends on the
properties of medium but is independent of the motion of the source of waves. If the
observer is in motion with respect to the medium, the velocity of wave propagation relative
to the observer wil be different. A remarkable exception is encountered in the case of light
PROPERTIES
Frequency
- Wavelength
- Period
- Amplitude
- Intensity
- Speed
- Direction
Perception of Sound
For humans, hearing is limited to frequencies between about 20 Hz and 20000 Hz, with the
upper limit generally decreasing with age.

KEY LEARNING:

Vibration - repetitive back and forth motion

Periodic motion - a motion that repeats itself
Mechanical waves require medium for propagation
Waves move through medium but medium remains in place
Longitudinal waves-Vibration direction parallel to wave propagation direction Particles in
medium move closer together/farther apart .Example: sound waves
Gases and liquids - support only longitudinal waves
Transverse waves-
Vibration direction perpendicular to wave propagation direction .Example: plucked string
Solids - support both longitudinal and transverse waves Sound waves Require medium for
transmission
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1. Sound is a wave motion, produced by a vibrating source.
2. A medium is necessary for the propagation of sound waves.
3. Sound is a longitudinal wave in which the particles of medium move along the direction of
motion of wave.
4. The part or region of a longitudinal wave in which the density of the particles of the
medium is higher than the normal density is known as compression.
5. The part or region of a longitudinal wave in which the density of the particles of the
medium is lesser than the normal density is called a rarefaction.
6. The point of maximum positive displacement on a transverse wave is known as crest.
7. The point of maximum negative displacement on a transverse wave is known as through.
8. A wave or short duration which is confined to a small portion of a medium at any given
time is known as a pulse.
9. The maximum displacement of particles of the medium from their mean positions during
the propagation of a wave is known as amplitude of the wave.
10. The distance traveled by a wave in one second is called wave velocity. It depends upon
the nature of the medium through which it passes.
11. The speed of sound depends primarily on the nature and the temperature of the
transmitting medium.
12. Sound travels faster in solids than in air. The speed of sound in solids is much more than
the speed of sound in liquids or gases.
13. The distance between two consecutive compressions or two consecutive rarefactions is
called the wavelength.
14. Frequency is defined as the number of oscillations per second.
15. The time taken by the wave for one complete oscillation of the density or pressure of
the medium is called the time period, T.
16. How the brain interprets the frequency of an emitted sound is called the pitch of sound.
17. Loudness is the degree of sensation of sound produced.
18. Sound properties such as pitch, loudness and quality are determined by the
corresponding wave properties.
19. Sound gets reflected and follows the same law as the reflection of light.
20. The persistence of sound due to repeated reflection and its gradual fading away is called
reverberation of sound.
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21. Echo is a repetition of sound due to the reflection of original sound by a large and hard
obstacle.
22. The audible range of hearing for average human beings is in the frequency range of 20
Hz – 20 kHz.
23. The amount of sound energy passing each second through unit area is called the
intensity of sound.
24. Sound of frequency less than 20 Hz is known as infrasound and greater than 20 kHz is
known as ultrasound.
25. Ultrasound has many medical and industrial applications.
26. SONAR stands for Sound Navigation and Ranging and it works on the principle of
reflection of sound waves.
27. The SONAR technique is used to determine the depth of the sea and to locate under
water hills, valleys, submarines, icebergs sunken ships etc.

*******

134
 Chapter 14: “Natural resources”
KEY CONCEPTS : [ *rating as per the significance of concept]
CONCEPTS RATING
Breath of air **
A wonder liquid ***
Biogeochemical cycles *****

1. The” Biosphere” is the life supporting zone of the earthwith three sub-zones called as
lithosphere (rock part), atmosphere (air part)and hydrosphere (water part).

Breath of air
2. Composition of Air

3.The interactions between different components of the Biosphere to maintain the balance
between the biotic and a biotic component makes “Biogeochemical cycle”. Ex. Water
Cycle, Nitrogen Cycle, Carbon cycle, Oxygen Cycle,

4. Role of atmosphere in climate control : atmosphere act as protective blanket for the
earth. Since atmosphere is a bad conductor of heat, it keeps the average temperature of the
earth constant. At night, it slows down the escape of heat into outer space.

5. The movement of air : the atmosphere gets heated from the radiation that is reflected
back by the land or water bodies. As a result of heating, convection currents are set up in
the air. Since land gets heated faster than water, the air over land gets heated faster than
air above water bodies.

82
6. In coastal regions, during the day, the air above the land gets heated faster and starts
rising. So a region of low pressure is created and air over sea moves into this area of low
pressure. The movement of air from one region to the other region causes Wind.

7. During the day, the direction of wind would be from the sea to the land and at night, both
land and sea starts to cool. Since water cools down slower than the land, the air above
water would be warmer than air above land, thus the direction of wind would be from the
land to the sea.

8. Air pollution : it is an undesirable change in the physical, chemical or biological

characteristics. It is caused due to an increase in the content of harmful substances
(pollutant) such as oxides of nitrogen and sulphur, etc.

9. Harmful effect of air pollution :

 It affects the respiratory system causing breathing difficulties eg; bronchitis, asthma,
lung cancer, tuberculosis, etc.
 Burning of fossil fuels like coal and petroleum releases oxides of nitrogen and
sulphur. Inhalation of these gases is dangerous.
 Combustion of fossil fuel also increases the amount of suspended particles in air. The
presence of high levels of all these pollutants, reduce visibility in cold weather where
water also condenses out of air forming smog.
 Acid rain formed from the gases like sulphur dioxide and nitrogen oxides present in
polluted air. It causes damage to living and non- living thing.

3. The Water Cycle:

a) The process in which water evaporates and falls on the land as rain and later flows back
into the sea via rivers is known as the “Water Cycle”. Water flows through rocks containing
soluble minerals, some of them get dissolved in the water. Thus the rivers carry many
nutrients from the land to sea and these are used by the marine organisms.

b) When the water vapors condense as water droplets and grow big and heavy, they fall
down in the form of “rain”. It ranges from 5 cm to 200 cm of rain fall in a year in our

83
country. In large parts of India, rains are mostly brought by the south-west or north-east
monsoons. Depressions in the Bay of Bengal may also cause rains in some areas.

c) Water is a wonder liquid because all cellular processes take place in a water medium;
substances are transported in a dissolved form; terrestrial forms require fresh water to
maintain the equilibrium of salts; major resource to determine the life on the earth.

d) The dissolved fertilizers (NPK fertilizers), pesticides (DDT), sewage (Disease causing
Organisms), waste from factories (Mercury) and water released from the dams can affect
the life forms on the earth. The dissolved Oxygen is being used by the animals and plants
that live in water, would adversely affect the aquatic organisms. The change in temperature
would be dangerous for the eggs and larvae of the various animals particularly susceptible
to temperature changes. It leads to “water pollution”.

(Please refer Fig. 14.5, NCERT Text Book Page- 197).

4. Nitrogen Cycle:

a) The nitrogen gas makes up 78% of our atmosphere. It is essential for the synthesis of
proteins, DNA, RNA, urea, alkaloids and Vitamins.

b) The simple molecular nitrogen from the atmosphere is converted into more complex
molecules in the living beings and back again to atmosphere is called “Nitrogen Cycle”.

i) Nitrogen fixation by Lightening: During lightning, the molecular nitrogen is converted into
oxides of nitrogen and dissolves in water to give nitric and nitrous acids and fall on lands
along with rains. These are then utilized by various life forms.

ii) Nitrogen fixation by Bacteria: The molecular nitrogen is converted into nitrates and
nitrites, by free living bacteria or the bacteria present in the root nodules of legumes.

iii) The conversion of molecular nitrogen into nitrates and nitrites is called as” Nitrification”.
Plants generally covert them into amino acids. The conversion of nitrates and nitrates into
Ammonia is called as” Ammonification”. The conversion of Ammonia into molecular
Nitrogen is called as” Denitrification”. Thereby nitrates and nitrites are converted into

84
molecular or elemental nitrogen in the nature. (Please refer Fig. 14.6, NCERT Text Book
Page- 198).

5. The Carbon cycle:

i) The Carbon dioxide gas makes up 0.039 % of our atmosphere. Carbon occurs in the
elemental form as diamonds and graphite in earth. Carbon is essential for the synthesis of
proteins, carbohydrates, fats, nucleic acids and Vitamins in living organisms.

ii) The Carbon dioxide Fixation: Green plants convert Carbon dioxide into glucose in the
presence of sunlight through Photosynthesis. The glucose molecules are converted into
other biologically important molecules. And many marine animals use carbonates dissolved
in sea water to make shells, exoskeletons.

iii) The combustion: The Carbon dioxide in the atmosphere is added by the process of
combustion, where fuels are burnt to provide energy for various needs like heating, cooking,
transportation, and industrial process.

iv) The Greenhouse Effect: The percentage of Carbon dioxide in the atmosphere is said to
have doubled since the industrial revolution when human beings stated burning fossil fuels
on a very large scale. The Carbon dioxide is a greenhouse gas. The increase in the Carbon
dioxide content would cause more heat to be retained by the atmosphere and lead to
Global Warming. It is called” Greenhouse Effect”

v) The carbon cycle is repeated through different physical and biological activities. (Please
refer Fig. 14.7, NCERT Text Book Page- 199).

6 .Oxygen Cycle:

i) The Oxygen gas makes up 21 % of our atmosphere. Oxygen is essential component of

proteins, carbohydrates, fats, nucleic acids in living organisms.

ii) Oxygen from our atmosphere is used up in three processes, namely combustion,
respiration and in the formation of oxides of nitrogen. Oxygen is returned to the
atmosphere in only one major process, that is, Photosynthesis, it is called as Oxygen Cycle.

85
iii) The air is heated faster than water; the air over land would also be heated faster than
the air over water bodies. The movement of air from one region to the other creates winds,
during the day the direction of the wind would be from the sea to land. At night, both land
and sea start to cool.

iv) The oxides of nitrogen and sulphur gases dissolve in rain to gives rise to “Acid rains”. The
smog is a visible indication of Air Pollution. The pollutants bring respiratory, cardiac
problems and allergies. The organisms called Lichens are found on the bark of trees, they
are indicators of pollution free environment. Three atoms of Oxygen ( O3) is called as Ozone.
The Ozone is poisonous but absorbs harmful radiations from the Sun. The Ozone layer
around the earth, if, dwindles further may cause Health hazards including Cancers . Recently
discovered the Ozone hole; in the region of Antarctica. (Please refer Fig. 14.8 & 14.9,
NCERT Text Book Page- 200).

QUESTION BANK

1. What are the three sub-zones in the Biosphere? {Lithosphere (rock part),
atmosphere (air part)and hydrosphere (water part)}.
2. The process in which water evaporates and falls on the land as rain and later flows
back into the sea via rivers is known ……………..(Water Cycle).
3. In large parts of India, rains are mostly brought by………………… monsoons.( the south-
west or north-east monsoons).
4. Why water is a wonder liquid? Justify ( A major resource to determine life on the
earth)
5. What are the four major water Pollutants?{ (NPK fertilizers, pesticides (DDT), sewage
(Disease causing Organisms), waste from factories (Mercury)}
6. Write a short notes on Nitrogen fixation by Bacteria.{The molecular nitrogen is
converted into nitrates and nitrites, by free living bacteria or the bacteria present in
the root nodules of legumes}.
7. What is Greenhouse Effect? {The Carbon dioxide is a greenhouse gas. The increase in
the Carbon dioxide content would cause more heat to be retained by the
atmosphere and lead to Global Warming. It is called” Greenhouse Effect”}
8. What is the percentage of Oxygen gas in our atmosphere? {21 %}

86
 9. Which organisms are found on the bark of trees as indicators of pollution free
environment? { Lichens}
10. Write about the Ozone hole in the Antarctica. {The Ozone layer around the earth is
dwindling further to damage and cause Health hazards including Cancers. Recently
discovered Ozone hole in the Antarctica.}
QUESTION PAPER:FORMATIVE ASSESSMENT – I (For Practice)
Marks- 40 Time: 90 minutes
* General Instructions
1. Questions 1-5 (1 Mark each) 2. Questions 6-10 ( 2 Mark each)
3. Questions 11-15 (3Mark each) 4. . Questions 16-17 (5Mark each)
Q.1 What is called Lithosphere, define it.
Q.2 Water covers 75% of the Earth’s surface. Mention True/ false…………….
Q.3 What is the percentage of Carbon dioxide on Venus……………………….
Q.4 What is the range of temperature on the Moon……………………………..
Q.5 Define the term Pollutant……………………………………………………………….
Q.6 What are the two ways to fix Carbon dioxide on earth.
Q.7 Mention any two important features of Water.
Q.8 How the Depressions effect our environment?
Q.9 Define the term Soil Pollution. Give one reason for it.
Q.10 How changes of temperature effect living organisms in water?
Q.11 What is Humus? Mention its importance in two points.
Q12 What is deforestation? Give two reasons for it.
Q.13. Define Global Warming, mention two causes for it.
Q.14 What is Ozone Depletion? Give two reasons for it.
Q.15 Draw the schematic diagram of Water Cycle in the nature.
Q.16. Write any five salient features of Nitrogen Cycle with a suitable diagram.
Q.17 Write about Industrial Pollution and mention five effects in the environment.

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87
 Chapter 13: “Why do we fall ill?”
KEY CONCEPTS : [ *rating as per the significance of concept]
CONCEPTS RATING
Significance of Health **
Disease and Its causes ***
Infectious diseases *****
Principles of prevention of diseases ****

1.”Health” is a state of being well enough to function well physically, mentally, and socially.

2.”Disease”( disturbed ease) means being uncomfortable. One or more systems of the body
will change, give rise to “Symptoms” ( Cough, loose motions, pus formation, headache,
fever, breathlessness, vomiting, fits, unconsciousness, inflammation , swelling and general
effects - a Doctor look for the basis of symptoms). Diseases are basically two types- Acute
Disease & Chronic Disease

3. Acute Disease: The disease which lasts for only a short period of time is called Acute
Disease Ex. Common Cold.

4.Chronic Disease: The disease which lasts for long period of time is called Chronic Disease
Ex. Tuberculosis.
Acute Disease Chronic Disease
They are short duration disease They are long lasting disease
Patient recovers completely after the cure Patient does not recover completely
There is no loss of weight or feeling of tiredness There is often loss of weight of feeling of
afterward tiredness
There is short duration loss of work and There is a prolonged loss of work and efficiency
efficiency

5. Causes of Diseases : Most of the diseases have many causes, rather than one single
cause, like unclean water, nourishment, genetic differences, genetic abnormalities e.g.
Based on the causes diseases are of two types: Non-Infectious Diseases and Infectious
Diseases.

78
6. Non-Infectious Diseases: Not caused by infectious agents, mostly internal and non-
infectious cause. Ex. Cancer

7. Infectious Diseases: Caused by infectious agents.

SN Type Of Disease Example

1 Bacterial diseases - Typhoid, Cholera, Tuberculosis, Acne, Anthrax,

2 Viral diseases - Common Cold, Influenza, Dengue fever, AIDS, Japanese

encephalitis or brain fever

3 Fungal diseases Skin diseases

4 Protozoan diseases -Malaria ( Plasmodium), Kalaazar (Leishmania), Sleeping

sickness( Trypanosomes)

5 Worm diseases - Ascariosis ( Round worm), Elephantiasis(Wuchereria )

(Please refer Fig. 13.1 (a-e), NCERT Text Book Page- 181).

a)The infectious diseases spread by agents are called as Communicable Diseases.

SN Type of Disease Example

1 Air born Diseases - Pneumonia, common cold, Tuberculosis;

2 Water born diseases - Cholera, hepatitis

3 Sexual Diseases - HIV, Syphilis.

4 Animal born Disease - Rabbis.

*(Vector- the animal carrying infectious agent from a sick
person to another potential host without getting affected Ex.
Mosquito carrying Malaria Parasite).
(Please refer Fig. 13.2 & 13.3, NCERT Text Book Page- 183).

9. Principles of Treatment:

1. Antibiotics- many bacteria make a cell wall to protect themselves, the antibiotic
(Penicillin) blocks the bacterial process that builds cell wall and blocks the
biochemical pathways. Antibiotics do not work against viral infections. Antiviral
medicine is harder than making Antibacterial medicine because Virus has only few
biochemical mechanisms of their own. Other medicines bring down fever, reduce
pain or loose motions. We can take bed rest to conserve energy.

79
10 Principles of Prevention : Following three limitation are normally confronted while
treating an infectious disease:
 Once someone has disease, their body functions are damaged and may never
recover completely.
 Treatment will take time, which means that someone suffering from a disease is
likely to be bedridden for some time even if we can give proper treatment.
 The person suffering from an infectious disease can serve as the source from where
the infection may spread to other people.

General ways of preventing infectious disease :

 Air-borne – We can prevent exposure by providing living condition that are not
overcrowded.
 Water-borne – prevent by providing safe drinking water. This is done by treating the
water to kill any microbial contamination.
 Vector-borne – We can provide clean environment, which would not allow mosquito
breeding.

11. Immunity: Even in cells there is repair mechanism called” Immunity”. Immune cells
manage to kill off the infectious agents. Smallpox disease is eliminated by developing
memory cells for particular infection by mimics the microbes, called” Vaccine”. The basis of
Immunization- if you had smallpox once, there was no chance of suffering from it again.
Proper nutrition is essential to maintain body immunity. There are vaccines against tetanus,
diphtheria, whooping cough, measles, polio and many other diseases.

12. Prevention of disease is better than cure. Hygiene is the basic key to maintain good
health.

QUESTION BANK:
1. Define Health……. (It is astate of being well enough to function well physically, mentally,
and socially)
2. Name any two Symptoms of diseases………………………. (Cough& loose motions)
3. The disease which last for only a short period of time is called……………….( Acute Disease)
4. State whether Tuberculosis is aChronic Disease or Acute Disease…… (Chronic Disease)
5. Mention the causal organism for Sleeping sickness ………… (Trypanosoma)
6.Cholera is a waterborne disease, mention TRUE/ FALSE ……….. (TRUE)
7. Antibiotics do not work against viral infections, mention TRUE/ FALSE ……….. (TRUE)
8. Write short notes on Immunity

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(Even in cells there is repair mechanism called” Immunity”. Immune cells manage to kill off
the infectious agents.)
9. Explain with an example the term Vaccine. ( Smallpox disease is eliminated by developing
memory cells for particular infection by mimics the microbes, called” Vaccine”).
10. State reasons to support “Prevention of disease is better than cure”.

QUESTION PAPER:FORMATIVE ASSESSMENT – I (For Practice)

Marks- 40 Time: 90 minutes
* General Instructions
1. Questions 1-5 (1 Mark each) 2. Questions 6-10 ( 2 Mark each)
3. Questions 11-15 (3Mark each) 4. . Questions 16-17 (5Mark each)
Q.1 Define Health
Q.2 Mention any two symptoms of diseases.
Q.3 Typhoid is a bacterial disease. Mention True/ False…………….
Q.4 Sleeping sickness is caused by……………………………………………
Q.5 Elephantiasis is caused by…………………………………………………….
Q.6. Mention two Air born diseases1…………………………..2………………….
Q.7 Mention two Sexually Transmitted Diseaes1………………..2……………….
Q.8 Mention two Viral Diseaes1………………..2……………….
Q.9 What is called vector. Give one example.
Q.10 Give two examples of Chronic diseases.
Q.11 Distinguish between Infectious and Non-infectious diseases.
Q.12 Write a short notes on Small Pox.
Q.13 What is immunity? Write short notes on it.
Q.14 What is Vaccination? Give the details, how it works in human body.
Q.15 Write three reasons for Cancers.
Q.16 What are the basic five principles of treatment for diseases.
Q.17 How Hygiene could help you to maintain good health and mention five situations to
take care about health.

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 Chapter 15: “Improvement in food resources”
KEY CONCEPTS : [ *rating as per the significance of concept]
CONCEPTS RATING
Improvement in crop yield ***
Crop variety improvement ****
Crop production management *****
Crop protection management ***
Animal Husbandry ****

1. Food Resources: Cereals (Wheat, rice, maize, millets and sorghum) provide us
carbohydrates; Pulses (Grams, pea and lentil) provide us proteins; Oil seeds (Soya bean,
ground nut, sesame, and castor) provide us fats; Vegetables, spices and fruits provide us a
range of minerals, nucleic acids and vitamins. In addition to these food crops, fodder crops
like berseem, oats or sudan grass are raised as food for the livestock are called as fodder
crops.

2. The Kharif crops: The crops grown in rainy season are called as Kharif crops (Paddy, Soya
bean, pigeon pea and maize). They are grown from June to October.

3. The Rabi crops: The crops grown in winter season are called Rabi crops (Wheat, gram,
peas, and mustard). They are grown November to April.

Compare Kharif crops and Rabi crops:

SN Crop Season Example

1 Kharif crops June to October ( Rainy Season) Paddy, Soya bean, and maize

2 Rabi crops November to April ( winter Wheat, gram, peas, and

season) mustard

4. The Green Revolution: Food supplies are generally as proteins, carbohydrates, fats,
minerals, nucleic acids and vitamins in all living organisms. Indian population is growing
enormously. Green Revolution is the need of the hour to increase food-grain production.

88
5. Sustainable Practices: For sustained livelihood, one should undertake mixed farming,
intercropping, and integrated farming practices, for example, combining agriculture with
livestock/ poultry/ fisheries/bee-keeping. The major group of activities for improving crop
yield can be classified as: Crop varietal improvement, Crop production improvement, Crop
protection improvement

6. The Crop varietal improvement:

a) Hybridization: It refers to crossing between genetically dissimilar plants;It is all to get

higher yield, improved quality, biotic and abiotic resistance, change in maturity duration,
wider adaptability and desirable agronomic characteristics.

SN Type Context

1 Intervarietal Hybridization between different varieties

2 Interspecific Hybridization between different species

3 Intergeneric Hybridization between different genera

4 Genetically Modified Crops (GMC). Another way of improving the crop is by

introducing a gene that would provide the
desired characteristic.

7. The Crop production improvement: They include” no cost production”,” low cost
production” or “high cost production” practices.

a) Nutrients( Sixteen elements are required for growth are called as essential elements
Carbon, oxygen, hydrogen+ Macronutrients & Micronutrients. They increase the yield):

SN Macronutrient Micronutrient

1 Six elements are required in larger Other seven elements are required
quantity in small quantity

2 Ex.Nitrogen, phosphorus, Ex. Iron, manganese, boron, zink,

calsium,Postasium, magnisium, sulphur copper, molybdinum, chlorine

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b)Manure & Fertilizers:

SN Manure Fertilizers

1 Manure is prepared by the Fertilizers are commercially produced

decomposition of animal excreta and plant nutrients.
plant waste is called as Humus. It
decides the texture of the soil. Excess fertilizers destroy the soil fertility.
Compost: Farm waste, cow dung etc. Organic farming: No use of chemicals
Vermi compost: Compost prepared fertilizers, herbicides, pesticides etc.(
by using earthworms. Culturing blue green algae, neem leaves,
healthy cropping systems.

2 It is cheap and prepared in rural It is costly and is prepared in factories

homes and fields

3 It is voluminous and bulky It is compact and concentrated

4 It is inconvenient to store, transport, It is easy to store, transport, handle.

handle.

5. It is not nutrient specific. It is nuteient specific and can provide

specifically nitrogen, phosphorus etc.

Add great humus to the soil Does not add humus to the soil.

3. Irrigation: India has variety of water resources: Wells, canals, river lift system, tanks,
rainwater harvesting, water shedding management to increase in ground water
levels and to check the water flowing away to the sea. Planning to reduce soil
erosion.
4. Cropping patterns:

SN Mixed cropping Inter-cropping Crop rotation

1 Two or more crops Two or more crops grown Growing different

grown simultaneously simultaneously on the same piece crops on a piece of
on the same piece of of land in a definite pattern land in a pre-
land planned succession

2 Ex. Wheat+ Gram; Soyabean + maize/bajra+Cowpea Two or three crops

Wheat+ Mustard; ((Please refer Fig. 15.2, NCERT Text can be grown in a
Wheat+ gram; Book Page- 208). year depending
Groundnut+ upon the duration.
sunflower.

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 3 A type of insurance A few rows of one crop alternate The availability of
against failure of one with a few rows of a second crop. moisture and
of the crops. Crops are selected such that their irrigation facilities
nutrient requirements are decides the choice
different. This ensures the of the crop to be
maximum utilization of the cultivated.
nutrients supplied and prevents
pests and diseases spreading in the
crop field.

8. Crop protection improvement/ management: Field crops are infested by large number
of weeds, insects pests, diseases & storage of grains

SN Weeds Insect pests Diseases Storage of grains

1 Weeds are Insect pest is Disease is caused Different factors are

unwanted plants in nuisance in the crop by pathogens in responsible.
the crop field field the field

2 Weeds take up Insect pest affect Diseases alter the Different factors
nutrients and the health of crop physiology of reduce the quality of
reduce the growth and reduce the crops and reduce stored grains
yield. the yield

3 Ex. Xanthium, Ex. Caterpillars, Ex. Bacteria, Virus Biotic factors:

Parthenium dragonfly insects, rodents,
fungi
Abiotic factors:
moisture &
temperature

4 Removal of weeds Spread of chemicals Spread of Systematic

at an early stage is such as pesticides chemicals to kill management of
recommended. pathogens ware house.
Spray weedicides

9. Animal Husbandry: It is a scientific management of animal livestock, includes feeding,

breeding and diseases control. Animal-based farming includes cattle farming, Poultry
farming, fish farming, and bee Keeping.

SN Content Cattle Poultry Fish farming Bee Keeping.

farming farming

1 Purpose Milk (milch Meat, Cheep source of Honey, wax,

animals) and chicken, egg animal protein. medicinal

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 draught labor production Fish production is preparations.
(draught aquaculture. Additional
animals) in Growing of income to the
agriculture. marine fishes is farmer.
called
mariculture.

2 Cross Exotic- Exotic & Both Exotic & Exotic- high

breeding: To quality of Indigenous Indigenous fishes honey collection
get desired lactation breeds are used capacity
qualities Indigenous &stingless.
breeds- Indigenous bees-
quality of are used
disease
resistance

3 Desirable Good Good Fish farming/ Value or quality

maintenance ventilation in ventilation in locating large depends upon
sheds sheds schools of fish/ the pasturage or
Roughage/ Roughage/ use of satellites the flowers
concentrates concentrates and echo-sounds available for the
Protection Protection In Composite fish taste of honey.
from from culture seed is
parasites & parasites & wild, mixed with
skin diseases skin diseases other species.
Vaccination Vaccination Hormonal
stimulation to
bring desired
quality in fish
production.

4 Example Exotic or Exotic- Fresh water ( Apisceranaindica

foreign Leghorn Macrobrachium) dorsata
breeds ( Indigenous & Marine( A.florae
Jercy, brown breeds- Aseel Peneaus) prawns
Swiss) Fresh water
Local breeds fishes
(Red sindhi, Marine fishes(
Sahiwal) Bombay duck,
sardines)
Common

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 QUESTION BANK

1. Give two examples of Cereals (Wheat, rice)

2. Define the Kharif crop and give two examples (The crops grown in rainy season are
called as Kharif crops Ex. Paddy, Soya bean).
3. Write about the importance of Green Revolution (Indian population is growing
enormously. Green Revolution is the need of the hour to increase food-grain
production.
4. Define the term Hybridization(Crossing between genetically dissimilar plants)
5. What is the importance of Genetically Modified Crops? (It is another way of
improving the crop is by introducing a gene that would provide the desired
characteristic.)
6. Define the term mixed cropping and give two examples. (Two or more crops grown
simultaneously on the same piece of landEx. Wheat+ Gram; Wheat+ Mustard)
7. Distinguish between weeds, insects pests(Weeds are unwanted plants in the crop
field Insect pest is nuisance in the crop field)
8. What is Animal Husbandry? It is a scientific management of animal livestock,
includes feeding, breeding and diseases control. Animal-based farming includes
cattle farming, Poultry farming, fish farming, and bee keeping.
9. Distinguish between aquaculture and mariculture. (Fish production is aquaculture.
Growing of marine fishes is called mariculture.)
10. What is the importance of Bee Culture? (It is useful for honey, wax, medicinal
preparations. And also for additional income to the farmer.)

QUESTION PAPER:FORMATIVE ASSESSMENT – I (For Practice)

Marks- 40 Time: 90 minutes

* General Instructions

1. Questions 1-5 (1 Mark each) 2. Questions 6-10 (2 Mark each)

3. Questions 11-15 (3Mark each) 4. . Questions 16-17 (5Mark each)

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Q.1 Maize and Millets are Pulses. Mention True/False……………………………………

Q.2 What is the Scientific name of Honey Bee………………………………………………….

Q.2 What led us to improve food grain production?

Q.3 Which revolution led to the availability of milk for efficient use?

Q.4 What is the process of injecting semen of desired bull into the vagina of cows is called?

Q.5 Name any one exotic breed usually used for variety of improvement programmes.

Q.6 What is the significance of GMC

Q.7 Mention the significance of Irrigation in developing agriculture.

Q.8. What is Pest and give one example.

Q.9 What is Weed and give one example.

Q.10 Give two examples for Inter-cropping.

Q.11 Distinguish between Kharif and Rabi Crops

Q.12 What is called Sustainable Practice in improvement in food resources.

Q.13. Mention three techniques of Hybridization used to achieve desirable agronomic

characteristics.

Q.14.Distinguish between Macro Nutrients and Micro Nutrients

Q.15 Distinguish between Compost and Vermi Compost.

Q.16 Distinguish between Cattle farming and Poultry farming.

Q.17 Distinguish between Fish farming and Bee keeping.

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 CHAPTER – 1
Chemical Reactionsand Equations
q Chemical Reaction : – Whenever a chemical change occurs we can say that
a chemical reaction has taken place

eg – Food gets digested in our body

– Rusting of iron.

q Chemical Equation :– A chemical reaction can be expressed symbolically

by using chemical equation

eg magnesium is burnt into air to form magnesium oxide can be represented

as

Mg + O2 →  MgO
– We can observe or recognise a chemical reaction by observing change
in state, colour, by evolution of gas or by change in temperature.

q Physical state of the reactant and products are mentioned to make chemical
reaction more informative. eg we use (g) for gas, (l) for liquid, (s) for solid
and (aq) for aqueous.

q Balancing Equation :– We balance the chemical equation so that no. of

atoms of each element involved in the reaction remain same at the reactant
and product side.

eg Fe + H2O → Fe2O3 + H2 can be written as

3 Fe(s) + 4H2O(g) → Fe2O3(s) +4H2(g)
q Combination Reaction :– The reaction in which two or more substances
combine to form a new single substance

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 eg CaO(s) + H2O(l) 
→ Ca(OH)2 (aq)
Calcium Water Calcium hydroxide
oxide (slaked lime)

Quick lime

– Ca(OH)2 slaked lime is used for white washing walls. It reacts will CO2 to
form CaCO3 and gives a shiny finish to the walls.

Ca(OH)2 CO2 
→ CaCO3 H2O (l)
(aq)+ (g) (s)+

Calcium Calcium

hydroxide Carbonate

– Burning of Coal

C(s) + O2(g) → CO2(g) + heat + light

– Formation of water

2H2(g) + O2(g) → 2H2O(l)

q Exothermic Reactions :– Reaction in which heat is released along with the

formation of products.

eg. CH4(g) + 2O2(g) → CO2(g) + 2H2O(g)

– Respiration is also exothermic reaction.

– De composition of vegetable matter into compost.

q De compositon Reactions :– The reaction in which a single substance

decomposes to give two or more substances. De composition reactions can
be of three types

Thermal Decompositon :– When a decompositon reaction is carried out by

heating

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– Silver bromide behaves similarly
Sunlight 2Ag(s) + Br (g)
2Ag Br  
→ 2

– The above two reactions are used in black and white photography.

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– Endothermic Reactions – The reactions which require energy in the form
of heat, light or electricty are called Endothermic Reactions.

2Ba(OH)2 + NH4Cl → 2BaCl2 + NH4OH

– Displacement Reaction : The chemical Reaction in which an element

displaces another element from its solution

Fe(s) + CuSO4(aq) → FeSO4 + Cu(s)

Copper (aq)
Sulphate Iron Sulphate

– The nail becomes brownish in colour and the blue colour of Copper Sulphate
solution fade.

– Other examples Zn(s) + CuSO4 → ZnSO4 + Cu(s)

(aq) (aq)

Copper Zinc
Sulphate Sulphate

Pb(s) + CuCl2 → PbCl2 + Cu(s)

(aq) (aq)

Copper Lead
Chloride Chloride

– Zinc and lead are more reactive elements than copper. They displace copper
from its compounds.

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– Double Displacement Reaction : The reaction in which two different atoms
or group of atoms are mutually exchanged

eg. Na2 SO4 + BaCl2 

→ BaSO4(s) + 2NaCl
(aq) (aq) (aq)

Sodium Barium Barium Sodium

Sulphate Chloride Sulphate Chloride
A white substance is formed due to above reaction. The insoluble substance
is called precipitate.

Precipitation Reaction – Any reaction that produces a precipitate is called a

precipitation reaction.
eg. Pb(NO3)2 + 2KI → PbI2  +2KNO3
(aq) (aq) (aq)

Lead Nitrate Potassium Lead Potassium

Iodide Iodide Nitrate
– Oxidation : Oxidation is the gain of oxygen or loss of hydrogen
eg. 2Cu + O2  Heat → 2CuO

When Copper is heated a black colour appears. If this CuO is reacted with
hydrogen gas then again Cu becomes brown as reverse reaction takes place
CuO + H2  Heat → Cu + H2O

– Reduction : Reduction is the loss of oxygen or gain of hydrogen.

– Redox Reaction : The reaction in which one reactant gets oxidised while
other gets reduced

eg. ZnO + C → Zn + CO

MnO2 + 4HCl → MnCl2 + 2H2O + Cl2

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– Corrosion : When a metal is attacked by substances around it such as
moisture, acids etc.

eg. Reddish brown coating on iron.

(ii) Black coating on Silver.

– Rancidity : When fats and oils are oxidised they become rancid and their
smell and taste change.

– Antioxidants are added to foods containing fats and oil.

EXERCISE
(Question Bank)
(1 Mark)

Answer the following questions very breifly

1. What happens when the milk is left at room temperature during summer?
2. Write a chemical equation when magnesium is burnt in air to give magnesium
oxide.
3. A substance under goes chemical reactions to produce simpler products,
what type of reaction is this?
4. Why do copper vessels lose their shine when exposed to air?
5. Which gas is produced by the action of dilute hydrochloric acid on zinc
granules?
6. Fe2O3 + 2Al → Al2O3 + 2Fe
The above reaction is an example of which type of reaction.
7. Name the type of reaction in which energy is absorbed.
8. Why does the colour of copper sulphate solution change when an iron nail is
dipped into it?
9. Give an example of decomposition reaction which proceeds by absorbing
electric energy.

10. Why do we balance the chemical equation?

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Answer the following questions briefly (2 mark)
1. Write down the observations which indicate the occurence of a chemical
reaction.
2. Why is respiration considered as an exothermic reaction? Explain.
3. Transfer the following statements into Chemical equations and then balance
them.
a) Hydrogen gas combines with nitrogen to form ammonia.
b) Potassium metal reacts with water to give potassium hydroxide and
hydrogen gas.
4. Identify the substances that are oxidised and the substances that are reduced
to the folllowing reactions.
1. Na + O2 
→ Na2O
(s) (g) (s)

CuO + H2 
→ Cu + H O
2 (l)
(s) (g) (s)

5. What happens when silver chloride is exposed to sunlight? Give one practical
application of this reaction. Write the equation also.
6. Why is the bag used for potato chips flushed with nitrogen gas?
Answer the following questions in detail (3 marks)
1. Write down the balanced chemical equations for the following reactions.
a) Zinc Carbonate(s) → Zinc Oxide + Carbon Dioxide(g)
b) Aluminium(s) + Chlorine(g) → Aluminium Chloride(s)
c) Magnesium(s)+ Water(l) Heat →
 Magnesium Hydroxide(l)+ Hydrogen(g)

2. Choose combination, displacement and double displacement reactions out of

the given reactions.

i) MnO2 + 4HCl(l) → MnCl2 + Cl2 + 2H2O

(s) (s) (g) (l)

ii) CaO + CO2 

→ CaCO3
(s) (g) (s)

iii) 2AgCl(s) → 2Ag(s) + Cl2

(g)

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3. What happens when CO2 is passed through slaked lime? Write the balanced
(g)
chemical equation. Write the type of reaction that has occured.

Explain the following questions detail (5 marks)

1. Balance the following chemical equation and identify the type of reaction they
represent

KClO3 → KCl + O2

NH3 + O2 → NO + H2O

Na2O + H2O → NaOH

Na + H2O → NaOH + H2

FeCl3 + NaOH → Fe (OH)3 + NaCl.

2. Define various types of chemical reactions. Write one chemical equation for
each type.

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 CHAPTER – 2

ACIDS, BASES AND SALTS

q
Acids Bases
– Sour in taste – Bitter in taste
– Change the blue litmus to red – Change red litmus to blue
– eg. HydrochloricAcid HCl eg. Sodium hydroxide NaOH
– SulphuricAcid H2SO4 Potassium hydroxide KOH
– Nitric Acid HNO3 Calcium hydroxide Ca(OH)2
– Acetic Acid CH3 COOH – Ammonium hydroxide NH4OH

q Some Naturally occuring acids

Vinegar – Acetic Acid
Orange – Citric Acid
Lemon – Citric Acid
Tamarind – Tartaric Acid
Tomato – Oxalic Acid
Sour milk (Curd) – Lactic Acid
Ant and Nettle sting – Methanoic Acid
q Acid – Base Indicators – Indicate the presence of an acid or base in a
solution.
q Litmus solution – It is a natural indicator. It is a purple day extracted from
Lichens. Other examples are Red Cabbage and coloured petals of Petunia
and turmeric.
q Olfactory indicators – Show odour changes in acidic or basic media. eg.
onion and clove.

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q Acid – Base Indicators

S. No. Name of the Colour Change Colour Change

Indicator with Acid with Base
A. Blue litmus solution To red No change
B. Red litmus solution No change To blue
C. Turmeric No change To red
D. Methyl orange To red To yellow
E. Phenolphthalein (colourless) No change To pink
q Dilute Acid : Contains only a small amounts of acid and a large amount of
water.
q Concentrated Acid : A concentrated acid contains a large amount of acid and
a small amount of water.
q Chemical Properties of Acids and Bases
Acid + Metal → Salt + Hydrogen
(Refer activity 2.3 on page No. 19 of NCERT Book)
2HCl + Zn → ZnCl2 + H2

2HNO3 + Zn → Zn (NO3)2 + H2

H2SO4 + Zn → ZnSO4 + H2

2CH3COOH + Zn → (CH3COO)2 Zn + H2

q Pop test : When a buring candle is brought near a test tube containing
hydrogen gas it burns with a ‘Pop’ sound. This test is conducted for examining
the presence of hydrogen gas.
q Base + Metal → Salt + Hydrogen
NaOH + Zn → Na2ZnO2 + H2
Sodium Zincate
Note – Such reactions are not possible with all the metals.

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q Action of Acids with metal Carbonates and metal bicarbonates
Metal Carbonate + Acid → Salt + Carbondioxide + Water
Na2CO3 + 2HCl(aq) → 2NaCl(aq) + H2O(l) + CO2(g)
(s)
Metal bicarbonate + Acid → Salt + Carbondioxide + Water
NaHCO3 + HCl → NaCl + CO2 + H2O
q Lime water Test : On passing the CO2 gas evolved through lime water,
Ca(OH)2 (aq) + CO2(g) → CaCO3(s) + H2O(l)
Lime water White precipitate
On passing excess CO2 the following reaction takes place
CaCO3(s) + H2O(l) + CO2(g) → Ca(HCO3)2 aq
Soluble in water
q Neutralisation Reactions
Base + Acid → Salt + Water

NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)

Neutralisation reacton takes place when the effect of a base is nullified by
an acid and vice versa to give salt and water.
q Reactions of metal oxides with acids
Metal Oxide + Acid → Salt + Water
CuO + HCl → CuCl2 + H2O
Copperoxide Hydrochloric Copper + Water
acid chloride

Note : Appearance of blue green colour of the solution because of formation

of CuCl2.
Metallic oxides are said to be basic oxides because they give salt and water
on reacting with acids.
q Reaction of Non Metallic Oxide with Base
Non metallic oxide + Base → Salt + Water
Ca(OH)2 + CO2 → CaCO3 + H2O
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 Note : Non Metallic oxides are said to be acidic in nature because on reacting
with a base they produce Salt and Water.
q All acidic solutions conduct electricity
Refer activity 2.3 on page 22 of NCERT Book
– Glowing of bulb indicates that there is a flow of electric current through the
solution.
q Acids or bases in a Water Solution
Acids produce H+ions in the presence of water
HCl + H2O → H3O+ + Cl–
H3O+ – Hydronium ion.
– H+ion cannot exist alone. It exists as H+(aq) or (H3O+) hydronium ion.
H+ + H2O → H3O+
– Bases provide (OH–) ions in the presence of water
H2O
NaOH(s)  + –
→ Na (aq) + OH (aq)
H2O
KOH(s)  + –
→ K (aq) + OH (aq)
H2O
Mg(OH)2(s)  2+ –
→ Mg (aq) + 2OH (aq)
q Alkalis
All bases donot dissolve in water. An alkali is a base that dissolves in water.
Common alkalis are
NaOH Sodium hydroxide
KOH Potassium hydroxide
Ca(OH)2 Calcium hydroxide
NH4OH : Ammonium hydroxide
Note : All alkalis are bases but all bases are not alkalis.
q Precaution must be taken while mixing acid or base with water. The acid must
always be added to water with constant stirring as it is highly exothermic
reaction.

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 When an acid or a base is mixed with water they become dilute. This results
in the decrease in the concentration of H3O+ or OH– per unit volume in acids
and bases respectively.
q Strength of an Acid or Base
Strength of acids and bases depends on the no. of H+ions and OH–ions
produced respectively.
With the help of a universal indicator we can find the strength of an acid or
base. This indicator is called PH scale.
pH = Potenz in German means power.
This scale measures from 0 (very acidic) to 14 (very alkaline) 7 Neutral
(water in Neutral).
pH paper : Is a paper which is used for measuring PH.
Variation of PH

S. PH Colour of the Nature of H+ion O H –i o n

No. Value pH Paper Solution Conc. Conc.
1. 0 Dark red Highly acidic very high very low
2. 4 Orange or yellow Acidic high low
3. 7: Green Neutral Equal Equal
4. 10 Bluish green or blue Alkaline low high
5. 14 Dark blue or voilet highly basic very low very high
– strong Acids give rise to more H+ions.
eg. HCl, H2SO4 and HNO3.
– Weak Acids give rise to less H+ ions
eg. CH3 COOH, H2 CO3 (Carbonic acid)
– Strong Bases – Strong bases give rise to more OH– ions.
eg. NaOH, KOH, Ca(OH)2
– Weak Bases : give rise to less OH– ions.
eg. NH4OH

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q More about Salts
Salts and their derivation

S. No. Name of Salt Formula Derived from Derived from

1. Potassium Sulphate K2 SO4 KOH H2SO4
2. Sodium Sulphate Na2SO4 NaOH H2SO4
3. Sodium Chloride NaCl NaOH HCl
4. Ammonium Chloride NH4Cl NH4OH HCl
Note : NaCl and Na2 SO4 belong to the family of sodium salts as they have
the same radicals. Similarly NaCl and KCl belong to the family of chloride
salts.
Importance of pH in our daily life
q Importance of pH in our digestive system – pH level of our body regulates
our digestive system. In case of indigestion our stomach produces acid in a
very large quantity because of which we feel pain and irritation in our stomach.
To get relief from this pain antacids are used. These antacids neutralises the
excess acid and we get relief.
q pH of Acid Rain : When pH of rain water is less than 5.6 it is called Acid
Rain.When this acidic rain flows into rivers these also get acidic, which causes
a threat to the survival of aquatic life.
q pH of Soil : Plants require a specific range of pH for their healthy growth. If
pH of soil of any particular place is less or more than normal than the farmers
add suitable fertilizers to it.
q Our body functions between the range of 7.0 to 7.8 living organisms can
survive only in the narrow range of pH change.
q Tooth decay and pH : Bacteria present in the mouth produce acids by
degredation of sugar and food particles remaining in the mouth. Using toothpaste
which is generally basic can neutralise the excess acid and prevent tooth
decay.
q Bee sting or Nettle sting contains methanoic acid which causes pain and
irritation. When we use a weak base like baking soda on it we get relief.

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 Neutral Salts : Strong Acid + Strong base
pH value is 7
eg. NaCl, CaSO4
Acidic Salts : Strong Acid + weak base
pH value is less than 7
eq. NH4Cl, NH4 NO3
Basic Salts : Strong base + weak acid
pH value is more than 7
eg. CaCO3, CH3 COONa
q Chemicals from Common Salt
– Sodium chloride is called as common salt used in our food. It is derived
from seawater.
– Rock Salt is the brown coloured large crystals. This s mined like coal.
– Common Salt is an important raw material for many materials of daily use
such as.
Sodium hydroxide
Washing Soda
Bleaching Power.
q Sodium Hydroxide
Preparation : Prepared by the method called chlor-alkali
Called chlor-alkali because we get chlorine and a base in this.
2NaCl(aq) + 2H2O(l) → 2NaOH(aq) + Cl2(g) + H2(g)

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q Bleaching Power
Preparation → Ca(OH)2 + Cl2 → CaOCl2 + H2O
calcium hydroxide chlorine bleaching water
power

uses in textile, factories and laundry, used as disinfectant

q Baking Soda
– Common name – Sodium Hydrogen Carbonate

Preparation NaCl + H2O + CO2 + NH3 → NH4Cl + NaHCO3

Sodium Water Carbon Ammonia Sodium hydrogen
chloride dioxide carbonate

On heating NaHCO3 produces :

NaHCO3 Heat →
 Na2CO3 + H2O + CO2
CO2 produced causes dough to rise and make cakes, pastries spongy.
Uses : In household, ingredients of antacid
In making baking power
On heating baking powder produces
NaHCO3 + H+ → CO2 + H2O + Sodium Salt of acid
q Washing Soda
Preparation : Recrystallisation of sodium carbonate
Na2CO3 + 10H2O Heat →
 Na2CO3. 10H2O
Uses
– Used in glass, soap and paper industry
– Cleaning agent for domestic purposes.
– Removal of hardness of water.
– Manufacturere of borax.
q Water of crystallisation : Fixed no. of water molecules present in one formula
unit of a salt.
– On heating copper sulphate crystals water droplets appear, formula of
hydrated copper sulphate – CuSO4. 5H2O.

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 – gypsum also contains water of crystallisation.
– Formula of gypsum – CaSO4.2H2O
– On heating gypsum at 373k it becomes CaSO4.½H2O is plaster of
paris.
– Plaster of Paris is used as plaster for fractured bones.
– When plaster of Paris is mixed with water it changes to gypsum.
CaSO4.½ H2O + 1½ H2O → CaSO4.2H2O
Uses of plaster of Paris : Making toys, decorative material and smooth surfaces.

EXERCISE
(Question Bank)
Very Short answer type questions (1 mark)
1. Two solution have pH number 4 and 9 respectively which solution has more
H+ ion concentration?
2. Why should cured and sour substances not be kept in brass and copper
vessel?
3. What is the chemical name of bleaching powder?
4. Write down the molecular formula for one strong and one weak acid.
5. Explain why plaster of Paris should be stored in a moisture proof container?
6. Name the gas evolved when dil. sulphuric acid acts on sodium carbonate.
7. What is the use of common salt in soap industry?
8. What do you observe when a buring candle is brought near the testube
containing hydrogen gas?
9. Name the indicator used to measure pH values over the whole range.
10. Write the formula of washing powder.
Short Answer Type Questions (2 marks)
1. Write two physical properties of an acid
2. Complete the reaction CaCO3 + H2O → name the products formed.
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3. A testtube contains solution of NaOH and Phenolphthalein. Why the colour
of the solution changes when HCl in added to it.
4. Why metallic oxides are called as basic oxides and non-metallic oxides are
calles acidic oxides?
5. In a beakey a solution of HCl is poured and an electric circuit containing bulb
is placed systemtically. What happens to the bulb and why?
What will happen if HCl is repplaced by NaOH?
6, Identify the type of reaction
H X + M OH → MX + HOH
7. Why all bases are not alkalies but all alkalis are bases?
Answer the following questions in detail (3 marks)
1. What is acid rain? What is its pH? How does it affect the aquatic life?
2. What happens when a metal react with dilute hydrochloric acid? Write the
reaction
© NaOH + Zn → _________ + _________.
3. What happens when an acid or a base is added to the water? Why does the
beaker appear warm? Why should we always add acid or base to the water
and not water to the acid or base.
Answer the following question in detail (5 marks)
1. (a) Write down five products formed with the help of common salt on
industrial level.
(b) Write down the chemical name of these compounds and one use of
each of them.
2. Fill in the blanks
a) Acid + ______ → Salt + Water..
b) _____ + Metal → Salt + _____
c) Metal carbonate / metal hydrogen carbonate + acid
 → _______ + _______ + _______.

d) NaOH 
H2 O
→ _______ + _______
e) Na2CO3 + 10H2O → _______.

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 CHAPTER – 3

METALS AND NON-METALS

q About 118 elements are known today. There are more than 90 metals, 22
non metals and a few metalloids.
q Sodium (Na), potassium (K), magnesium(Mg), aluminium(Al), calcium(Ca),
Iron(Fe), Barium(Ba) are some metals.
q Oxygen(O), hydrogen(H), nitrogen(N), sulphur(S), phosphorus(P), fluorine(F),
chlorine(Cl), bromine(Br), iodine(l) are some non-metals
*Physical properties of metals:
q Solid at room temperature except mercury
q Ductile (drawn into wires)
q Malleable (beaten into thin sheets)
q Sonorous(produce sound)
q Lustrous(natural shine)
q Have high melting point. Cesium and gallium have very low melting point.
q Generally good conductor of heat and electricity, except lead and mercury
which are comparatively poor conductors. Silver and copper are best
conductors.
q Have high density. Sodium and potassium can be cut with knife, they have
low density.
Physical properties of non-metals:
q Occur as solid or gas. Bromine is liquid.
q Generally bad conductors of heat and electricity. Graphite a natural form of
carbon is a good conductor.
q Non-sonorous.

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q Non-lustrous, only iodine has lustre.
q Metals form basic oxides like Magnesium oxide(MgO), while non-metals
form acidic oxides (as in acid rain).
*Chemical properties of metals:
1. Reaction with air
Metals can burn in air, react or don't react with air.
Metal + oxygen → Metal Oxide
q Some metals like Na and K are kept immersed in kerosene oil as they react
vigorously with air and catch fire.
q Some metals like Mg, Al, Zn, Pb react slowly with air and form a protective
layer.
q Mg can also burn in air with a white dazzling light to form its oxide
q Fe and Cu don't burn in air but combine with oxygen to form oxide. When
heated iron filings burn when sprinkled over flame.
q Metals like silver, platinum and gold don't burn or react with air.
2Na + O2 
→ Na2O
2Mg + O2 
→ 2MgO
2Cu + O2 
→ 2CuO

4Al + 302 
→ 2Al2O3

Amphoteric Oxides : metal oxides which react with both acids as well as
bases to form salt and water e.g. Al2O3, ZnO.
Al2O3 + HCl 
→ AlCl3 + H2 O
Al2O3 + NaOH 
→ NaAlO2 + H2 O
2. Reaction with water :

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 Na + H2 O 
→ NaOH + H2
K + H2 O 
→ KOH + H2
Ca + H2 O 
→ Ca(OH)2 + H2
Mg + H2 O 
→ Mg(OH)2 + H2
In case of Ca and Mg, the metal starts floating due to dubbles of hydrogen
gas sticking to its surface.
Al + H2 O 
→ Al2O3 + H2
Fe + H2 O 
→ Fe3O4 + H2
Try Balancing these Chemical equations yourself
3. Reaction with dilute acids:
Metal + dilute acid → Salt + Hydrogen gas
Metals react with dilute hydrochloric acid and dilute sulphuric acid to form
salt and hydrogen gas.
Fe + 2HCl 
→ FeCl2 + H2
Mg + 2HCl 
→ MgCl2 + H2
Zn + 2HCl 
→ ZnCl2 + H2
2Al + 6HCl 
→ 2AlCl3 + 3H2
Copper, mercury and silver don’t react with dilute acids.
Hydrogen gas produced is oxidised to water when metals react with nitric
acid. But Mg and Mn, react with very dilute nitric acid to evolve hydrogen
gas.
Mg + 2HNO3 
→ Mg(NO3)2 + H2
4. Reaction of metals with other metal salts :
Salt Salt
Metal A + solution 
→ solution + Metal B
of B of A
All metals are not equally reactive. Reactive metals can displace less reactive
metals from their compounds in solution. This forms the basis of reactivity
series of metals.

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 Reactivity series is a list of metals arranged in order of their decreasing
activities.

Fe + CuSO4 
→ FeSO4 + Cu

Zn + CuSO4 
→ ZnSO4 + Cu
Reaction between Metals and Non-Metals :
– Reactivity of elements can be understood as a tendency to attain a completely
filled valence shell.
– Atom of metals can lose electrons from valence shells to form cations (+ve
ions).
– Atom of non-metals gain electrons in valence shell to form anions (–ve ions).
– Oppositely charged ions attract each other and are held by strong electrostatic
forces of attraction forming ionic compounds.
Formation of MgCl2
Mg 
→ Mg2+ + 2e–
2,8,2 2,8 (Magnesium ion)
Cl2 + 2e– 
→ 2Cl–
2,8,7 2,8,8 (Chloride ion)

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Properties of Ionic Compounds :
– Are solid and mostly brittle.
– Have high melting and boiling points. More energy is required to break the
strong inter-ionic attraction.
– Generally soluble in water and insoluble in kerosene, petrol.
– Conduct electricity in solution and in molten state. In both cases, free ions are
formed and conduct electricity.
Occurance of Metals
Minerals : elements of compounds occuring naturally are minerals.
ORES : mineral from which metal can be profitably extracted is an ore. For example,
sulphide ore, oxide ore, carbonate ore.
– Metals at the bottom of activity series like gold, platinum, silver, copper
generally occur in free state. But copper and silver also occur in sulphide and
oxide ores.
– Metals of medium reactivity (Zn, Fe, Pb etc.) occur mainly as oxides, sulphides
or carbonates.
– Metals of high reactivity (K, Na, Ca, Mg and Al) are very reactive and thus
found in combined state.
GANGUE : ores are naturally found mixed impurities like soil, sand, etc. called
gangue. The gangue is removed from the ore.
METALLURGY : step-wise process of obtaining metal from its ore.
*Enrichment of ore
*Obtaining metal from enriched ore.
*Refining of impure metal to obtain pure metal.
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Extracting Metals Low in the Activity Series :
By heating the ores in air at high temperature.
*Mercury from cinnabar
Heat → 2HgO + 2SO2
2HgS + 3O2 
Heat → 2Hg + O2
2HgO 
* Copper from copper sulphide
Heat → 2Cu2O _ 2SO2
Cu2S + 3O2 
Heat → 6Cu + SO2
2Cu2O + Cu2S 
Extracting Metals in the Middle of Activity Series :
*Metals are easier to obtain from oxide ores, thus, sulphide and carbonate ores are
converted into oxides.
*Metal ore heated strongly in excess of air (Roasting)
Heat → 2ZnO + 2SO2
2ZnS + 3O2 
Metal ore heated strongly in limited or no supply of air (Calcination)
Heat → ZnO + CO2
ZnCO3 
Reduction of Metal Oxide :
1. USING COKE: Coke as a reducing agent.
Heat → Zn + CO
ZnO + C 

2. USING DISPLACEMENT REACTION : highly reactive metal like Na, Ca

and Al are used to displace metals of lower reactivity from their compounds.
Heat → 3Mn + 2Al2O3 + heat
MnO2 + 4Al 
Heat → 2Fe + Al2O3 + heat
Fe2O3 + 2Al 

– In the above reaction molten iron is formed and is used to join railway tracks.
This is called thermit reaction.

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Extracting Metals at the Top of Activity Series :
These metals
– have more affinity for oxygen than carbon.
– are obtained by electrolytic reduction. Sodium is obtained by electrolysis of
its molten chloride NaCl → Na+ + Cl–
As electricity is passed through the solution metal gets deposited at cathode
and non-metal at anode.
– At cathode :
Na+ + e– → Na
– At anode :
2Cl– → Cl2 + 2e–
Refining of Metals :
– Impurities present in the obtained metal can be removed by electrolytic refining.
Copper is obtained using this method. Following are present inside the
electrolytic tank.
– Anode – slab of impure copper
– Cathode – slab of pure copper
– Solution – aqueous solution of copper sulphate with some dilute sulphuric
acid
– From anode copper ions are released in the solution and equivalent amount
of copper from solution is deposited at cathode.
– Impurities containing silver and gold gets deposited at the bottom of anode
as anode mud.

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Corrosion :
– Metals are attacked by substances in surroundings like moisture and acids.
– Silver - it reacts with sulphur in air to form silver sulphide and articles become
black.
– Copper - reacts with moist carbon dioxide in air and gains a green coat of
copper carbonate.
– Iron-acquires a coating of a brown flaky substance called rust. Both air and
moisture are necessary for rusting of iron.
Prevention of corrosion:
– Rusting of iron is prevented by painting, oiling, greasing, galvanizing, chrome
plating, anodising and making alloys.
– In galvanization, iron or steel is coated with a layer of zinc because zinc is
preferably oxidized than iron.
Alloys : These are mixture of metals with metals or non-metals
– Adding small amount of carbon makes iron hard and strong.
– Stainless steel is obtained by mixing iron with nickel and chromium. It is hard
and doesn’t rust.
– Mercury is added to other metals to make amalgam.
Brass : alloy of copper and zinc.
Bronze : alloy of copper and tin.
– In brass and bronze, melting point and electrical conductivity is lower than
that of pure metal.
Solder : alloy of lead and tin has low melting point and is used for welding
electrical wires.
Question Bank
1 MARK
1 Name a metal which is the best conductor of electricity and one which is poor
conductor of electricity.
2 Why food cans are coated with tin and not with zinc?
3. Name any two alloys whose electrical conductivity is less than that of pure
metals.
4. Name the non-metal with lustre.
5. Define amphoteric oxide.
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6. An aqueous solution of Al2O3 is electrolysed. Name the element collected at
anode.
7. An oxide of an element was dissolved in water. The final solution turned red
litmus blue. Is the element metal, non-metal or a metalloid?
8. What happens when cinnabar is heated?
9. Ionic compounds have high melting point. Why?
10. Name two metals which are found in nature in free state.
2 MARKS
1. Why Magnesium and calcium float when they react with water?
2. Write the chemical equations of heating of Cu and Fe.
3. Write two chemical equations to show that Al2O3 is an amphoteric oxide.
4. What is galvanization? Why it is done?
5. Hydrogen gas is not evolved generally when metals react with nitric acid.
Explain.
6. Explain the thermit process. Write the chemical equation involved.
7. Distinguish between roasting and calcination.
8. Every ore is a mineral but not every mineral is an ore. Explain.
9. Why highly reactive metals can't be obtained from their oxides using coke as
a reducing agent?
3 MARKS
1. Diagrammatically show the formation of MgO.
2. Ionic compounds are good conductors of electricity under specific conditions.
Name the two conditions and give reasons.
5 MARKS
1. i) What is reactivity series of metals? Arrange the metals zinc, magnesium,
aluminium, copper and iron in a decreasing order of reactivity.
ii) What is observed when you put
a) Some zinc pieces into blue copper sulphate solution.
b) Some copper pieces into green ferrous sulphate solution.
iii) Name a metal which combines with hydrogen gas. Name the compound
formed.

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2. Give reasons:
i) Platinum, gold and silver are used to make jewellery.
ii) Sodium and potassium are stored under oil.
iii) Aluminium is a highly reactive metal, still it is used to make utensils for
cooking.
iv) Carbonate and sulphide ores are usually converted into oxides during
the process of extraction.
METALS AND NON-METALS
IN BRIEF
– Metals are generally solid, sonorous, lustrous, good conductor of heat and
electricity, malleable, ductile, high melting point, high densities, form basic
oxides, form +vely charged ion.
– Non-metals are generally solid or gas, non-lustrous, non-sonorous, bad
conductor of heat and electricity, have low melting point, form acidic oxides
and form -vely charged ions.
– Metals like Na, K and Ca are highly reactive, while others like Magnesium,
Aluminium, Zinc and Lead are less reactive and some others are least reactive
like silver, gold and platinum.
– Metals generally displace hydrogen from acids.
– Reactivity series is based on displacement capability of metals and is a series
of metals in the order of their decreasing reactivity.
– Metals and non-metals react to form ionic compounds which are soluble in
water, have high melting point and are good conductor of electricity in their
aqueous solution or molten state.
– Ores are minerals from which a metal can be profitably extracted.
– Metals are extracted from their ores according to their reactivity.
– Sulphide and chloride ores are roasted while carbonate ores are roasted.
– Pure metals can be obtained using electrolytic refining process.
– Metals are generally attacked by air and corrode. To alter the properties of
metals alloys are made.
– Steel, stainless steel, amalgams, brass, bronze and solder are some alloys.

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 CHAPTER – 4

CARBON AND ITS COMPOUNDS

q Carbon is a versatile element.
q In earth’s crust, carbon is 0.02% and found in form of minerals.
q Atmosphere has 0.03% of Carbon dioxide.
q All living structures are carbon based.
Covalent Bond in Carbon
– The atomic number of carbon is 6 and its electronic configuration is 2, 4. To
attain a noble gas configuration it can
1. Gain 4 electrons. But it would be difficult for nucleus to hold 4 extra electrons.
2. Lose 4 electrons. But it would require a large amount of energy to remove
4 electrons.
– It is difficult thus for an atom of carbon to either gain or lose electrons.
– Carbon attains the noble gas configuration by sharing its valence electrons
with other atoms. Atoms of other elements like hydrogen, oxygen, nitrogen,
chlorine also show sharing of valence electrons.
– Formation of H2, O2 and N2 is shown as below :

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– It is evident that the number of shared pair of electrons can be one, two or
three. Try making the structures of H2O and CH4.
– Bond formed by the sharing of an electron pair between two atoms is called
covalent bond.
– Covalently bonded molecules have low melting and boiling points because of
comparatively weaker intermolecular forces, unlike ionic compounds.
– These molecules are generally poor conductor of electricity since no charged
particles are formed.
Versatile Nature of Carbon Atoms:
Two important properties of carbon atom enable carbon to form enormously large
number of compounds.

CATENATION : property of carbon atom to form bond with other atoms of

carbon is called catenation. Like carbon, silicon forms compounds with hydrogen
upto seven or eight atoms of silicon.

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TETRAVALENCY : Having a valency of 4, carbon atom is capable of bonding
with atoms of oxygen, hydrogen, nitrogen, sulphur, chlorine and other elements.
The smaller size of carbon atom enables nucles nucleus to hold the shared pair of
electrons strongly, thus carbon compounds are very stable in general.
Saturated and Unsaturated Carbon Compounds

– ALKANE : CnH2n+2
– ALKENE : CnH2n
– ALKYNE : CnH2n–2
– Electron dot structure of a saturated carbon compound, ethane is as follows:

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– Electron dot structure of an unsaturated cabon compound, ethene is as follows:

TRY DRAWING THE ELECTRON DOT STRUCTURE OF ETHYNE

Formulae and Structures of Saturated Compounds of Carbon and Hydrogen

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On the basis of structures the hydrocarbons can be:

Structural isomers : these are the compounds having identical molecular formula
but different structures. For example, isomers of butane.

Heteroatom and Functional Group :

*In hydrocarbon chain, one or more hydrogen atoms can be replaced by other
atoms in accordance with their valencies. The element that replaces hydrogen is
called a heteroatom.
*These heteroatoms and the group containing them impart chemical properties to
the compound and hence are called functional groups.

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Homologous Series:
– It is a series of compounds in which the same functional group substitutes for
hydrogen in a Carbon chain.
– For instance, the ALCOHOLSs: CH3 OH, C2H5 OH, C3H7 OH, C4H9 OH.
– The successive member differs by –CH2-; unit and 14 units of mass.
– The chemical properties are imparted by the functional group thus all members
have similar chemical properties. But the members have different physical
properties.
– The physical properties vary among the members of homologous series due
to difference in their molecular mass.
– Melting point and boiling point increases with increasing molecular mass.
Nomenclature of Carbon Compounds:
1. Identify the number of carbon atoms in the compound.
2. Functional group is indicated either by prefix or suffix.
Functional Group Suffix Prefix
Alkene ene
Alkyne yne
Alcohol ol
Aldehyde al
Ketone one
Carboxylic acid oic acid
chlorine chloro

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3. If a suffix is added, then final ‘e’ is removed from the name eg. methanol
(methane-e = methan + ol).
Chemical properties of Carbon compounds :
1. COMBUSTION :
*Carbon compounds generally burn (oxidize) in air to produce carbon dioxide and
water, and release heat and light energy.
CH4 + O2 → CO2 + H2O + heat and light
*Saturated hydrocarbon burns generally with a blue flame in good supply or air and
with a yellow sooty flame in limited supply of air.
*Sooty flame is seen when unsaturated hydrocarbons are burnt.
*Burning of coal and petroleum emits oxides of sulphur and nitrogen which are
responsible for acid rain.
2. OXIDATION :
*Alcohols can be converted to carboxylic acids by oxidizing them using alkaline
potassium permanganate or acidified poatassium dichromate (they add oxygen to
the reactant, thus are called oxidizing agents).

Alkaline KMnO 4 + heat

CH 3 - CH 2 OH CH 3 COOH
Acidified K 2 Cr2 O7 + heat

3. ADDITION REACTION:
Hydrogen is added to unsaturated hydrocarbon in presence of palladium or nickel
as catalyst.
Vegetable oils are converted into vegetable ghee using this process.

Saturated fatty acids are harmful for health and oils with unsaturated fatty acids
should be used for cooking.

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4. SUBSTITUTION REACTION :
In saturated hydrocarbons, the hydrogen attached to carbon can be replaced by
another atom or group of atoms in presence of sunlight.
CH4 + Cl2 → CH3Cl + HCl (sunlight required)
IMPORTANT CARBON COMPOUNDS : Ethanol and Ethanoic Acid
Ethanol :

*Consumption of dilute ethanol causes serious health issues and intake of pure
alcohol is lethal.

CHEMICAL PROPERTIES OF ETHANOL

C2H5OH Reacts with Sodium When C 2 H 5 OH is Heated with
to from Sodium Ethoxide and Concentrated Sulphuric Acid at 443
Hydrogen k, It is Dehydrated to Ethene

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Ethanoic Acid (CH3COOH) / Acetic Acid :

*5-8% solution of acetic acid in water is called vinegar.

*Pure acetic acid is called glacial acetic acid.

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Esterification :
Carboxylic acids react with alcohols in presence of few drops of concentrated
sulphuric acid as catalyst and form sweet smelling compounds called ester.
Hydrolysis :
On heating with an acid or a base the ester forms back the original alcohol and
carboxylic acid.
CH3COO CH2CH3 + NaOH → CH3COONa + CH3-CH2OH

CH3COO CH2CH3 

Dil.H 2 SO 4
HEAT
→ CH3COOH + CH3-CH2OH

*Alkaline hydrolysis of ester is also called saponification.

Soaps and Detergents
– Soap is sodium and potassium salt of carboxylic acids with long chain.
– Soaps are effective with soft water only and ineffective with hard water.
– Detergents are ammonium or sulphonate salts of carboxylic acids with long
chain. They are effective with both soft as well as hard water.
An ionic part (hydrophilic) and a long hydrocarbon chain (hydrophobic) part
constitutes the soap molecule.

Structure of a Soap Molecule

Cleansing Action of Soaps :
– Most dirt is oily in nature and the hydrophobic end attaches itself with dirt,
while the ionic end is surrounded with molecules of water. This result in
formation of a radial structure called micelles.

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– An emulsion is thus formed by soap molecule. The cloth needs to be
mechanically agitated to remove the dirt particles from the cloth.
– Scum : The magnesium and calcium salts present in hard water reacts with
soap molecule to form insoluble products called scum, thus obstructing the
cleansing action. Use of detergents overcome this problem as the detergent
molecule prevents the formation of insoluble product and thus clothes get
cleaned.

EXERCISE
(Question Bank)
1MARK
1. How an atom of carbon attain noble gas configuration?
2. Draw the electron dot structure of a molecule of water.
3. Define catenation.
4. The kerosene/gas stove used at home has inlets for air. Give reason.
5. Write only the chemical equation for dehydration of ethanol by hot conc.
Sulphuric acid.
6. Write the number of covalent bonds present in propane.
7. Define the term: oxidising agent.
8. Write the formula for first member of ketone.

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9. Would you be able to check if water is soft by using a soap?
10. Write the molecular formula of an alkyne containing 10 atoms of hydrogen.
2 MARKS
1. Define saponification. Write a chemical equation for it.
2. Covalent compounds generally don't conduct electricity. Why?
3. Specify the condition in which ethanol undergo oxidation to form ethanoic
acid. Write the chemical equation.
4. Define isomerism. Draw the structures of the two isomers of butane.
5. Identify the functional group present in the following compounds: HCOOH,
HCHO, CH3Br and C10H21OH
3 MARKS
1. What is a homologous series? Write any two characteristic features of any
homologous series using one example.
2. Write any three differences between soaps and detergents.
5 MARKS
1. Differentiate between ethanol and ethanoic acid on the basis of any three
physical properties and two chemical properties.
2. An organic compound 'A' is used as a preservative in pickles and has molecular
formula C2H4O2. This compound reacts with ethanol to form a sweet smelling
compound 'B'.
i) Determine the compound 'A'.
ii) Write the chemical equation for its reaction with ethanol to form
compound 'B'.
iii) Write any two uses of compound 'B'.
iv) Which gas is produced when compound 'A' reacts with washing soda?
Write the chemical equation
v) How can vinegar be obtained from compound 'A'?

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CARBON AND ITS COMPOUNDS IN BRIEF
– Carbon is a versatile non-metal.
– Carbon atom like atoms of other non-metals like oxygen, nitrogen, hydrogen
and chlorine shares electrons.
– Carbon forms large number of compounds due to catenation and tetravalency.
– Carbon can form single, double and triple covalent bonds.
– The compounds of hydrogen and carbon are called hydrocarbons, which can
be saturated or unsaturated.
– Structurally hydrocarbons can have straight chain, branches or cyclic structure.
– Difference in Structural arrangement of same molecule gives rise to isomerism.
– In a hydrocarbon, a heteroatom can replace the hydrogen atom and imparts
it chemical properties.
– Homologous series is a series of compounds with same general formula and
same chemical properties but different physical properties.
– Carbon based compounds are excellent fuels.
– Ethanol is an important industrial compound. It reacts with reactive metals and
is also dehydrated to ethene.
– Ethanoic acid is another important compound. It combines with ethanol to
form sweet smelling esters.
– Soaps and detergents are used as cleansing agents. Detergents efficiently
cleanses with soft and hard water.

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 CHAPTER – 5

PERIODIC CLASSIFICATION OF
ELEMENTS
q Elements : Substances containing atoms of only one type. eg. Na, Au, Mg etc.
– There are around 118 elements known to us.
q Elements are classified to make the study easy.
q Dobereiner’s Traids : When the elements were written in order of increasing
atomic masses the atomic mass of the middle was the average of the atomic
mass of the other two elements.
eg. Elements Atomic Mass
Ca 40.1
Sr 87.6
Ba 136.3
Limitations : Only three triads were recognised from the elements known at
that time.
q Atomic mass of an element is the relative mass of its atom as compared widh
the mass of a Carbon-12 atom taken as 12 units
q Newland’s law of octaves :
– Based on increasing atomic mass of elements.
– When elements are arranged it was found that every eighth element had
properties similar to that of the first. eg properties of sodium and Lithium are
the same.
Limitations :
– Applicable only upto Calcium
– Properties of new elements couldn’t fit in it.

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– It some cases properties of the elements were not same as defined by octave.
– Worked well only with lighter elements.
Mendeleev's periodic law :– The properties of elements are the periodic function
of their atomic mass.
Mendeleev's periodic table based on the chemical properties of elements.
Contain eight vertical columns called groups and seven horizontal rows called periods
form Mendeleev’s peridic table.
Achievements of Mendeleev’s Periodic table
– Elements with similar properties could be grouped together
– Some gaps were left for the undiscovered elements.
– Noble gases could be placed without disturbing the existing order.
Limitations:
– No fixed position for hydrogen
– No place for isotopes
– No regular trend in atomic mass.
Modern Periodic Table
Modern Periodic Law : Properties of elements are a periodic function of their
atomic number.
– Atomic Number – denoted by Z and equals to the no. of protons in the
nucleus of an atom.
– Modern periodic table contains 18 vertical columns known as groups and 7
horizontal rows known as periods.
– Elements in a group have valence electrons
– No. of the shells increases as we go down the group.
– Elements in a period have same number of shells.
– Each period marks a new electronic shell getting filled.
– No. of elements placed in a particular period depends upon the fact that how
electrons are filled into various shells.

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– Maximum no. of electrons that can be accomodated in a shell depend on the
formula 2n2 where n is the no. of the given shell.
eg. k shell – 2 x (1)2 = 2 elements in the first period L shell – 2 x (2)2 = 8
elements in the second period.
– Position of the element in the periodic table tells about its reactivity.
Trends in the Modern Periodic Table
– Valency : No. of valence electrons present in the outermost shells.
– Atomic Size : Atomic size refers to radius of an atom.
– Atomic size or radius decreases in moving from left to right along a period
due to increase in nuclear charge
– Atomic size increases down the group because new shells are being added
as we go down the group.
Metallic Character : Metallic character means the tendency of an atom to lose
electrons.
– Metallic character decreases across a period because the effective nuclear
charge increases that means the tendency to lose electrons decreases.
– Metals are electropositive as they tend to lose electrons while forming bonds.
– Metallic character increases as we go down a group as the effective nuclear
charge is decreasing. Non metals are electronegative. They tend to form
bonds by gaining electrons.
– Metals are found on the left side of the period table while non-metals are
towards the right hand side of the periodic table.
– In the middle we have semi-metals or metalloid because they exhibit some
properties of both metals and non metals.
– Oxides of metals are basic in nature while oxides of non-metals are acidic in
nature.
(Refer the table given on side page)

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Gradation in Periodic Properties
S. Property Variation Reason Variation Reason
No. across period along group

1. Atomic size Decreases Due to increase Increases due to addition

in nuclear charge of new shells.

due to increase in
distance between
outer most electron
and nucleus.

2. Metallic Decreases due to increase Increases due to decrease in

Character in effective effective nuclear
nuclear charge charge tendency to
tendency to lose lose valence electrons
valence electrons increases.
decreases.

3. Non-Metallic Increases due to increase Decreases due to decrease in

Character in effective effective nuclear
nuclear charge charge tendency to
tendency to gain gain electron
electrons increases decreases

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 EXERCISE
(Question Bank)
Very Short Answer type Questions. (1 mark)

1. Write down three elements which represent Dobereiner’s triad.

2. Write down two drawbacks of Newland’s law of octaves.

3. Which important property did Mendeleev used to classify the elements in his
periodic table.

4. Explain why the number of elements in the third period is 8?

5. Name the most metallic and most non-metallic element in the periodic table.

6. Define Isotopes.

7. What was the need for classification of elements?

8. Name two elements that have two electrons in their outermost shell.

9. How many vertical columns and horizontal rows are there in modern periodic
table. What is the special name assigned to them?

10. Name the element having electronic configuration 2, 8, 2.

Short Answer type Questions (2 Marks)

1. Why He, Ne and Ar are called inert gases?

2. Which one has greater atomic size – Cl or Br?

3. What were the drawbacks of Mendeleev’s periodic table? Write any two.

4. How does the tendency to lose electrons will change in a group and why?

5. Justify the statement – Atomic size of an element decreases along a period

whereas increasing down the group.

6. Why metallic oxides are basic in nature whereas Non-metallic oxides are
acidic in nature.

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Long Answer Type (3 Marks)

1. How do we calculate the valency of an element from its electronic configuration?

– How does the valency vary in a period?

– How does the valency vary in going down a group?

2. Study the variation in the atomic radii of elements given below and arrange
them in an increasing order

Na Li Rb Cs K

186 152 246 262 231

ii) Name the element which has the smallest and the largest atoms.

iii) How does the atomic size vary as we go down a group.

3. Four elements ABCD along with their electronic configurations are given
below

Elements – A B C D

Electronic Configuration – 2, 1 2, 8 2, 8, 1 2, 8, 8

4. Now answer the following questions

a) Which two elements belong to the same period,

b) Which two elements belong to the same group

c) Which element out of A and C is more reactive and why?

Long Answer Type Question (5 Marks)

1. Write down five major differences between Mendeleev periodic table and
modern periodic table.

2. Examine elements of the third period and classify them as metals and non
metals.

ii) On which side of the table do you find metals and why.

iii) On which side of the table do you find the non-metals and why?
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 CHAPTER – 6

LIFE PROCESSES
All living things perform certain life processes like growth, excretion, respiration,
circulation etc.
All the processes like respiration, digestion, which together keep the living organisms
alive and perform the job of body maintenance are called life processes.
Examples :

Kinds of nutrition in which in organic Kinds of nutrition in which in organisms do

materials like CO2, water etc are utilized to not possess the ability to synthesize their
prepare organic food by the process of own food. They depend on autotrophs for
photosyntheses their food supply directly or indirectly.
Eg. Green Plants eg. Animals, Fungi

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Autotrophic Nutrition :
The organisms which carry out autotrophic nutrition are called autotrophs (green
plants)

Autotrophic nutrition is fulfilled by the process by which autotrophs take in CO2 and
H2O and convert these into carlohydrates in the presence of chlorophyll, sunlight is
called PHOTOSYNTHESIS
Equation :

Raw Materials for Photosynthesis :

q Sunlight
q Chlorophyl  Sunlight absorbed by chlorophyll
q CO2  enters through Stomata, and Oxygen (O2) is released as by product
through stomata on leaf.
q Water  water + dissolved minerals like Nitrogen phosphorous etc are taken
up by the roots from the soil.
Site of Photosynthesis :
Chloroplast in the leaf. Chloroplast contain chlorophyll. (green pigment)
Main Events of Photosynthesis :
q Absorption of light energy by chlorophyll
q Conversion of light energy into chemical energy + splitting (breaking) of water
into hydrogen and oxygen.
q Reduction of CO2 to carbohydrates.
STOMATA : Tiny pores present on the surface of the leaves
FUNCTIONS :
(i) Exchange of gases O2/CO2
(ii) Loses large amount of water [water vapour] during transpiration.

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How do organisms obtain their food
Unicellular / single celled organism : food is taken up through entire surface.
Example : (i) Amoeba. (ii) Paramaecium

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 NUTRITION IN HUMAN BEINGS
The human digestive system comprises of alimentary canal and associated disgestive
glands.
Mouth  Intake of whole food

Teeth  Chewing/grinding of food.

Tongue  Rolling of food
 +
Tasting of food
+
Swallowing / pushing down of the food
Salivary Glands  Secrete Saliva + Mucus.
Salivary

→
 Starch amylase Sugar
[Saliva]
Oesophagus  Taking food from mouth to stomach by
 Peristaltic movements
[contraction and expansion of muscles of the oesophagus]
Stomach  Gastric glands secrete Gastric juice

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Small Intestinal 

Small Intestine  Villi → helps in absorption of food into the blood.
[finger like projections]

small intestine  Receives

secretion from

Emulsification : The process of breakdown of large fat

globules into smaller fat globules by bile juice.

Large intestine  Absorb excess of water.

 The rest of the material is removed from the body via the
anus. (Egestion)

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 Respiration
Respiration involves
(i) Gaseous exchange : Intake of oxygen from the atmosphere and release of
CO2 → Breathing
(ii) Breakdown of simple food in order to release energy inside the cell → Cellular
Respiration
Breakdown of Glucose by various pathways

* Takes place in the presence of * Takes place in the absence of

oxygen oxygen
* Occurs in mitochondria * Occurs in cytoplasm
* End products are CO2 and H2O * End products are alcohol or lactic
* More amount of energy is released acid.
* Less amount of energy is released.
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 Human Respiratory System
Passage of air through the respiratory system.
Nostril

Nasal Passage

Nasal Cavity

Pharynx

Larynx

Trachea

Bronchi

Lungs

Bronchioles

Alveolar → Blood capillaries

* During inhalation the thoracic * Thoracic cavity contracts

cavity (chest cavity) expands * Ribs move downwards
* Ribs lift up Diaphragm becomes dome shaped
* Diaphragm become flat in shape * Volume of lungs decreases and air
* Volume of lungs increases and air exits from the lungs.
enters the lungs

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Exchange of Gases between alveolus, blood and tissues.

Terrestial Organism – use atmospheric oxygen for respiration

Aquatic Organisms – used dissolved oxygen for respiration
Respiration in Plants :
Respiration in plants is simpler than the respiration in animals. Gaseous exchange
occur through
1. Stomata in leaves
2. Lenticels in stems
3. General surface of the roots.

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 Life Process (II)
Transporation and Excretion
– Human beings like other multicellular organism need regular supply of food,
oxygen etc., This function is performed by circulatory system or Transport
system.
– The circulatory system in human beings consists of :
The circulatory system in human beings consists of :

A Pumping Organ Blood vessels A circulatory medium

Heart - Arteries & Veins Blood & Lymph

Deoxygenate Vena Right Right Right

Blood Cava Atrium Atrium Ventricle
(from body) (Relaxed) (contracts) (relaxed)

Body Parts Right

Blood Circulation ventricle
in Human Heart contracts
via AoRTA
Lungs
Left Left Left Left Oxygenated
Ventricle Ventricle Atrium Atrium blood
(contracts) (relaxed) (contracts) (relaxed)
AORTA

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 Blood
(A fluid Connective Tissue)

Solid Component Liquid Component

Blood Corpuscles PLASMA

R.B.C.s Blood W.B.C.

A yellow colour fluid
Platelets
Provide Body contain 90% water &
- carries respect helps in defence by 10% Organic substances
gas (O2, CO2) Blood engulfing the like
- contain Hb Clotting germ cells & - Plasma Proteins viz.
impart red colour producing albumin, globulin
to me blood antibodies inorganic-mineral ions

- Lymph - a yellowish fluids escapes from the blood capillaries into the
intercellular spaces contain less proteins than blood. Lymph flows from the
tissues to the heart assisting in transportation and destroying germs.
Blood Vessels

Arteries Veins
1. Carry Oxygenated blood from 1. Carry deoxygenated blood
heart to body part except from body parts to heart
pulmonary Artery except pulmonary vein.
2. Also called distributing Vessel 2. Also called collecting Vessel.
3. Thick and elastic 3. Thin and Less elastic.

Transportation in Plants
- There are two main conducting Pathways in a Plant

Xylem Phloem
1. Carries water & minerals 1. Carries product of
from the roots to other part photosynthesis from leaves
of the plant to the other part of the plant.
2. No energy is used. 2. Energy is used from ATP

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– Transpiration is the process of loss of water as vapour from aerial parts of the
plant.
Function :
1. Absorption and upward movement of water and minerals by creating
PULL.
2. helps in temperature regulation in Plant.
– Transport of food from leaves (food factory) to different part of the plant is
called Translocation.
EXCRETION
– The process of the removal of the harmful metabolic wastes from the body.
– Excretory system of human beings includes :
1) A pair of kidneys
ii) A Urinary Bladder
iii) A pair of Ureter
iv) A Urethera

– Urine produced in the kidneys passes through the ureters into the urinary
bladder where it is stored until it is released through the urethera.
– The purpose of making urine is to filter out waste product from the blood ie,
urea which is produced in the liver.
– Each kidney has large numbers of filtration units called nephrons.
– The Urine formation involves three steps
1. Glomerular Filtration : Nitrogenous wastes, glucose water, amino acid
filter from the blood into Bowman Capsule of the nephron.
2. Tubular reabsorption : Now, useful substances from the filtrate are
reabsorbed back by capillaries surrounding the nephron.
3. Secretion Extra, water, salts are secreted into the tubule which open up
into the collecting duct & then into the ureter.

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– Haemodialysis : The process of purifying blood by an artificial kidney. it is
meant for Kidney failure patient.
Excretion in Plants

Through stomata
– Oxygen, CO2 & H2O (Transpiration)

– Other wastes may be stored in leaves, bark etc. which fall off from the plant.
– Plants excrete some waste into the soil around them.
– Gums, Resin fi
In old Xylem
– Some metabolic wastes in the form of crystals of Calcium oxalates in the
leaves of colocasia and stem of Zamikand.

Life Processes
EXERCISE
(Question Bank)
Very Short Answers (1 Mark)
1. State one difference between autotrophic and heterotrophic mode of
nutrition.
2. What will happen to a plant if the xylem is removed.
3. What is the role of saliva in the digestion of food?
4. Name the tissue that transports water and minerals in plants.
5. What is the role of acid in our stomach?
6. What is emulsification
7. Name the organelle in which photosynthesis occur.
8. Name the largest artery in the human body.
9. Define transpiration
10. What are structural and functional unit of kidneys called.
Short Answers (2 Marks or 3 Marks)
1. How is small intestine designed to absorb digested food?
2. What are stomata? Draw a labelled diagram of stomata.

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3. Write the equation for the process of breakdown of glucose in a cell
i) in the presence of oxygen
ii) in the absence of oxygen.
4. Write the difference between inhalation and exhalation.
5. List the three events which occur during photo synthesis.
6. How does transpiration helps in upward transport of substances.
7. Describe the process of double circulation in human beings.
8. Write the functions of the components of blood.
Long Answers (5 Marks)
1. Explain the process of digestion of food in mouth stomach and small
intestine in human body. Draw a well labelled diagram.
2. Draw a diagram showing Human Respiratory system. Label the following
parts
i) Larynx ii) Trachea
iii) Bronchus iv) Lungs

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 CHAPTER – 7
Control and Coordination
Living organisms respond and react to various stimuli like heat, light, cold, touch,
pressure etc. Plants and animals both respond to stimuli but in different manner.
Example : withdrawl of hand on touching a hot object.
Control and Coordination in Animals
It is brought about in all animals with the help of two main systems
a) Nervous System b) Endocrine System
Nervous System :
Functions
i) To receive the information from environment
ii) To receive the information from various
body parts. (Stimuli fi
Response)
iii) To act accordingly through muscles and glands.
Stimulus : Any change in environment or within that bring about the reaction eg:
touching a hot plate.
Response : The reaction of our body to these changes. eg. withdrawal of our hand
How do we detect that we are touching a hot object?
Receptors : Are specialised tips of some nerve cells that detect the information
from the environment.
Receptors
are
Sense Organs

Inner Photo receptors Skin Olfactory Gustatory

Ear Eyes Receptor Receptor
(Nose) (Tongue)
Hearing/ Visual Pain Smell Taste
Balance of Stimulus Touch Detection Detection
the body Heat

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 Neuron : Structural and functional unit of nervous system.
Neuron (3 main parts)

I II III
Dendrite Cell body Synapse
and Axon

Information is Information Part where

acquired travels as an electrical signal
electrical impulse is converted into
chemical message
for onward transmission
to next neuron
by release of neurotransmitters

Nucleus
Nerve
Dendrite ending
Axon

Cellpody
Structure of neuron
Fig. 7.1 (a) P 115
Synapse : The point of contact between the terminal branches of axon of one
neuron with the dendrite of another neuron is called synapse.
Reflex Action
A quick, sudden, immediate response of the body to the certain stimuli that
involves Spinal cord. eg. (not brain) withdrawal of hand, knee jerk etc.
Reflex arc : The pathway through which impulses pass is called reflex arc.

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 Stimulus RECEPTOR Sensory Nerves
› ORGAN
eg. Heat (SKIN)
Spinal Cord

Response EFFECTOR
› ORGAN Motor Nerves
eg. Withdrawal (MUSCLE)
of
Hand
Refer to diagram Fig 7.2 Reflex arc

Response
Responses are of three main types
Voluntary : Controlled by fore brain
eg. Talking, Writing
Involuntary : Controlled by mid and hind brain
eg. Heart beat, vomiting, regulation of heartbeat
Reflex action : controlled by spinal cord
eg. Withdrawl of hand on touching a hot object.
Human Nervous System

Central Nervous Peripheral Autonomic

System Nervous Nervous
System System
(CNS (PNS) (ANS)

Brain Spinal Cranial Spinal Sympathetic Para

Cord. Nerves Nerves Nervous Sympathetic
System Nervous
Fore Brain Arise from Arise from System
Mid Brain the brain Spinal Card

Hind Brain

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 Human Brain
Human brain has three major parts or regions
a) Forebrain b) Mid Brain c) Hind Brain
FOREBRAIN
Most complex/specialized part of the brain is CEREBRUM

FUNCTIONS :
1. Thinking part of the brain
2. Control the voluntary actions.
3. Store information (Memory)
4. Centre associated with HUNGER
5. Receives sensory impulses from various body parts and integrates it
Mid Brain :
HYPOTHALAMUS : Chemical co-ordination
PITUITARY GLAND : Secretes hormones
Hind Brain :
CEREBELLUM i) Controls posture and balance
ii) Control precision of voluntary actions
MEDULLA Controls involuntary actions
eg. blood pressure, salivation, vomiting
PONS Involuntary action, regulation of respiration

Fig 7.3 Human Brain

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 PROTECTION OF BRAIN AND SPINAL CORD
Brain : Brain is protected by a fluid filled balloon which acts as shock
absorber and enclosed in cranium (Brain Box)
Spinal Cord : Spinal Cord is enclosed in Vertebral column.

Coordination between Nervous and Muscular Tissue

Information Central Information
[collected by Nervous Processed
Nervous tissue] System by
(Sensory Nerve) [CNS] [CNS]

Action Decesion
made
[by CNS]
Muscle shorten (Motor Nerves)
Message
Contraction Muscles Passed to
[Muscle cell] [Change in shape muscles
and arrangement
of proteins]
Coordination in Plants
Movement in Plants

Movement dependent Movement independent

on growth of growth
[immediate response
to stimulus]
Tropic movements eg. dropping of leaves
[directional movements of Touch-me-not
in response to stimulus] plant on touching it

Phototropism Geotropism Chemotropism Hydrotropism

Movement Movement Movement Movement

towards light towards gravity towards Chemicals/ towards /
growth of pollen water
tube towards avule

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Plant hormones :
Are chemical compounds which help to coordinate growth, development and
responses to the environment.
Plant hormones : Main plant hormones are :
a) Auxin : [Synthesized at shoot tip]
Function : – Helps in growth
Phototropism : more growth of cells towards light.
b) Gibberellin : Helps in the growth of the stem
c) Cytokinins : Promotes cell division
d) Abscisic acid : Inhibits growth, cause witting of leaves.
(Stress hormone)
Hormones in Animals
Hormones : These are the chemical messengers secreted in very small amounts by
specialised tissues called ductless glands. They act on target tissues/organs usually
away from their source.
Endocrine System helps in control and coordination through chemical compounds
called HORMONES

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 S. Hormone Endocrine Location Functions
No. Gland

1. Thyroxine Thyroid Neck/ Regulation of metabolism

Throat of carbohydrates, fats
region and proteins.

2. Growth Pituitary Mid Regulates growth and

hormone development.

3. Adrenaline Adrenal Above Regulation (increasing)

both of blood pressure, heart
kidneys heat, carbohydrate
metabolism (during
emergency)
G

{
4. Testosterone Testes O
Genital/ Changes associated
SEX in Males N lower with puberty
Hormone A abdomen (Sexual maturity)
D
estrogen Ovaries S area

5. Insulin Pancreas Below Reduces and regulates

stomach blood sugar level

IODISED SALT IS NECESSARY BECAUSE :

Iodine mineral is essential part of thyronine hormone so it is important that we
must consume iodised salt as in turn it is essential for thyroid gland as it controls
carbohydrate, proteins and fat metabolism for best balance of growth deficiency of
iodine might cause disease called goitre
Diabetes :
Cause : It is due to deficiency of Insulin hormone secreted by Pancreas that is
responsible to lower/control the blood sugar levels.
Treatment : Patients have to internally administer injections of insulin hormone
fiwhich helps in regulating blood-sugar level.
Feedback Mechanism
fi makes sure that hormones should be secreted in precise quantities and at right
time, which is regulated by feedback mechanism.

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 Sugar level in the blood rises
SWITCH OFF
Feedback sent
Detected by cells of Pancreas

Synthesis insulin

Blood sugar level falls

(like a float in watertank)
Stop secreting more
insulin

EXERCISE
(Question Bank)
Very Short Answers (1 Mark)
1. Where is auxin synthesized in plants?
2. Which gland is known as Master gland?
3. Name the hormone that regulates blood sugar level.
4. What is synapse.
5. What are tropic movements? Give one examples
6. Define hormones
7. Which hormone has inhibiting effect on growth of plants
8. What is phototropism?
9. What are the components of central Nervous System.
10. What happens at synapse between two neurons.
Short Answers (2 Marks)
1. Draw diagram of neuron and label cell body, dendrites and axon.
2. What is reflex arc? Explain with the help of a flow-chart.
3. Mention one function of each of the following
i) Cerebellum
ii) Pons.
4. What is the cause of diabetes? How it can be controlled.
5. Why it is advisable to use iodised salt.

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6. What are the different receptors present in our body? What are their
functions.
7. What are plant hormones? Name a plant hormone that promotes growth in
plants.
8. What are sensory and motor neurons? Write their functions.
Long Answers (5 Marks)
1. What are hormones (in animals) List four characteristics of hormones. Name
the hormone required for the following.
i) Development of moustache and beard in human male
ii) Lowering of blood glucose.
2. Mention the functions of
a) Fore brain
b) Mid brain
c) Hind brain

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 CHAPTER – 8
How do Organisms Reproduce
– Reproduction is the process by which living organisms produce new
individuals similar to themselves.
– Reproduction ensured continuity of life on earth.
– Reproduction - A bridge to hereditary transmission.
– It involves continuation of characters from the parents to daughter cells by
Copying of DNA (Deoxyribose Nucleic Acid) molecules present in the
chromosomes of the cell.
– Copying of DNAs is also not a foolproof exercise, even minute changes bring
about Variation in the blue print of the offsprings.
– The useful variations are retained while the harmful one does not go beyond.
– Actually variations help the species to withstand drastic environmental
changes, thus save the species from becoming extinct and promotes its
survival for a longer time.
– This inbuilt tendency of variation is the "fuel" for Evolution.
REPRODUCTION

Asexual Reproduction Sexual Reproduction

1. A single parent is involved 1. Both Parents involved
2. Gametes not formed 2. Gametes are formed
3. Progeny is Identical to parent 3. Progeny is only genetically
eg. Fission in Amoeba similar to the parent.

– Asexual Reproduction is extremely useful as a mean of rapid multiplication.

It is common in lower plants and animals.
– Different form of Asexual Reproduction.
1. FISSION : the parent cell divides/splits into two daughter cell-Binary
Fission; splits into many cells-multiple Fission

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2. BUDDING : A new organism is produced as an outgrowth of the parent
body part.

3. Spore Formation : Spores are

small, bulb like structure develops
at the top of the erect hyphae of the
fungus plant, released into the air
and germinate, into new
individuals after landing into food
or soil.

4. FRAGMENTATION : It is the accidental process when the broken pieces

of an organism (fragments) grows into a complete organism.

eg. fragmentation in
spirogyra

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 5. REGENERATION : When the simple animals like Hydra Planaria
develop a new individual from their broken older part it is known as
regeneration. It is carried out by specialised cells which grow large numbers
of cells.

VEGETATIVE PROPAGATION :
A mode of reproduction in which part like the stem, root, leaves develop into new
plant under favourable conditions.
Benefits
1. Plants can bear flowers, fruits earlier than those produced from seeds.
2. Growing Banana, orange, rose, jasmine that have lost the capacity to produce
seeds.
3. Genetical similarity is maintained in the plants.
eg. Sugarcane, rose, grapes by layering or grafting.
SEXUAL REPRODUCTION
When reproduction takes place as a result of fusion between two gamets, one from
each parent, it is called sexual reproduction.
– This process of fusion between two gamets is called fertilization.
– The formation of gamets involves exchange of chromosomal (genetic)
fragments between homologous chromosomes causing genetic
recombination which leads to variation.
SEXUAL REPRODUCTION IN PLANTS
It occurs mostly in flowering plants. In fact flowers are the reproductive organ of
plants.

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 FLOWERS

Bisexual Flowers Unisexual Flowers

Both male and female Either male or female
reproductive part i.e., stamen & reproductive part is present.
carpel present. Eg. Papaya, Watermelon
Eg. Hibiscus, mustard

A typical flower consists of four main whorls namely calyx (sepals), Corolla
(Petals), Androecium (Stamens) and Gynoecium (Carpels).

Reproductive Part of Flower

STAMEN CARPEL
(male part (female part)
(2n) Style Stigma
Filament Anther Ovary
(2n)
MEIOSIS Egg cell (ovule) [n]
(n) Pollen grain
(male gamet)
– Pollen grains of a flower transfer to stigma of the carpel of the same flower
(Self-Pollination) or to the carpel of the another flower (Cross-Pollination).
– This transfer of pollens is achieved by agent like wind, water or animals.
– After Pollination, the pollen grains reach to the egg cell in the form of a pollen
tube.

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– Fertilization : The fusion between the pollen grain and female egg cell. It
occurs inside the ovary. Zygote is produced in this process.

– Zygote divides several times to form an embryo within the ovule. The ovule
develops a tough coat and is converted into a seed.
– Ovary grows rapidly and ripens to forms a fruit, while the seed contains the
future plant or embryo which develops into a seedling under suitable
condition. This process is known as Germination.
REPRODUCTION IN HUMAN BEINGS
– Humans use a Sexual Mode of reproduction.
– It needs sexual maturation which includes creation of the germ cells ie, egg
(ova) in the female and sperm in the male partener & this period of sexual
maturation is called Puberty.
– Human beings have a well developed male and female reproductive system.
– The formation of male germ cell (sperms) takes place in the testes (male
reproducture organ)
– Actually a pair of testes are located inside scrotum situated outside the
abdominal cavity. It is meant to keep relatively a low temperature needed for
the production of sperms by testes.
– Moreover testes release a male sex hormone called testosterone whose
function is to:
1. Regulate the production of sperm
2. Brings about changes in appearance seen in boys at the time of puberty.

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– The sperms along with the secretion of prostate gland and seminal vesicle,
together constitute semen, which is released and made to enter into the female
genital tract during Copulation.

FEMALE REPRODUCTIVE SYSTEM

?
The female germ cells or eggs are made in the ovaries, a pair of which is
located in both side of abdomen.
?
When a girl is born, the ovaries already contain thousands of immature eggs.
?
At the puberty, some of these Eggs start maturing. One egg is produced every
month by one of the ovaries.
?
The Egg is carried from the ovary to the womb through a fallopian tube. These
two fallopian tube unite into an elastic bag like structure known as Uterus.
?
The Uterus opens into the vagina through the cervix.
?
Fertilization occurs in the fallopian tube of female genital tract.
The fertilized egg also called zygote (2n) gets implanted in the lining of the
?
Uterus, and start dividing. Actually uterus is richly supplied with blood to
nourish the growing embryo. If zygote is not formed, the inner wall of uterus
breaks which causes bleeding through vagina. This process is called
MENSTRUATION. It occurs at a regular interval of 28 days.
The Embroyo gets nutrition fromthe mother's blood with the help of a special
?
tissue called PLACENTA. It provides a large surface area for glucose and
oxygen to pass from the mother to the embryo. Similarly the wastes from
developing embryo are removed to mother's blood through placenta.
The child is born as a result of rhythmic contractions of the muscles in the
?
uterus. after Nine months (36 weeks) of development inside mother's womb.
It is also called Gestation Period.

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 The sexual cycle in a woman continues upto the age of 45 to 50 years. After
that the ovary do not release egg. This stage is called Menopause. It a also
marks the end of menstruation in the woman.
REPRODUCTIVE HEALTH
Reproductive Health means a total well-being in all aspects of reproductive,
?
ie., physical emotional, social and behavioural.
Contraception : It is the avoidance of pregnancy. It can be achieved by
?
Methods of contraception

PHYSICAL SURGICAL CHEMICAL

BARRIER METHOD METHOD

To prevent union of Also called sterilization Oral contraceptive

sperm & egg. in Vasectomy, the vas (OCs) - changes the
Use of condoms, deferens of male is hormonal balance to
Diaphragm & cervical blocked to prevent check the egg release in
caps. sperm transfer. females. OCs cause side
In Tubectomy, the effect.
fallopian tube of female
is blocked to prevent
egg to reach uterus.
Copper-T or loop is
placed in uterus to
prevent pregancy.

Healthy society needs a balanced sex ratio that can be achieved by educating
?
the people to avoid malpractices like female foeticide & pre-natal sex
determination.
Sexually Transmitted Disease (STDs)

VIRAL STDs Bacterial STDs

Eg. H.I.V. - AIDS Eg. Syphilis &
Warts Gonorrhoea
STDs are communicated during unsafe sexual contact.

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 EXERCISE
(Question Bank)
1. Where is the DNA present in the cell?
2. What is bisexual/hermaphrodite?
3. Write suitable condition necessary for seed germmration.
4. Write the function of the secretion of seminal vesicle and prostate gland.
5. Name the part of female body in which the egg is fertilized.
6. Name the chemical method to prevent the pregnancy.
2 Marks
7. What is importance of DNA copying in reproduction.
8. Why is variation beneficial to the species but not necessarily for the
individual?
9. Why is vegetative propagation practised for growing some types of plants?
10. Name any two STDs. What measures can you suggest to prevent them.
11. Distinguish between male & female gamete.
12. Write two important function of testosterone.
13. What is placenta. Also write its two functions?
14. Draw a well labelled diagram of human female reproductive system.
Explain the menstrual cycle of female.
15. Draw a labelled diagram to explain the fertilization in the higher plant.

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 CHAPTER – 9
Heredity and Evolution
Genetics : Branch of science that deals with Heredity and variation.
Heredity : It means the transmission of features/ characters/ traits from one
generation to the next generation.
Variation : The differences among the individuals of a species/ population are
called variations.
MENDEL AND HIS WORK ON INHERITANCE
Gregor Johann Mendel (1822&1884) : Started his experiments on plant
breeding and hybridisation
Mendel fi
was known as Father of Genetics
Plant selected by Mendel : Pisum sativum (garden pea). Mendel used a number
of contrasting characters for garden pea.

TABLE OF CONTRASTING CHARACTERS. (SEVEN PARTS)

CHARACTER DOMINANT RECESSIVE
TRAIT TRAIT
Flower colour Purple White
Flower position Axial Terminal
Seed colour Yellow Green
Seed shape Round Wrinkled
Pod shape Inflated Constricted
Pod colour Green Yellow
Height of plant Tall Dwarf

Seven pairs of contrasting characters in Garden

Pea
Mendels Experiments : Mendel conducted a series of experiments in which he
crossed the pollinated plants to study one character (at a time)
Monohybrid Cross :
Cross between two pea plants with one pair (monohybrid cross) contrasting
characters
Example : Tall / Short Plants.

80 X-Science
PARENT Tall plant ·Dwarf plant
GENERATION
TT ·tt
GAMETES T T

Tt All tall plants

F1 GENERATION
(first filal generation)

Tt · Tt
SELF POLLINATION
(F1) Tt (F1)

GAMETES
T t T E

TT Tt Tt tt
F2 GENERATION
(Second Final TALL TALL TALL SHORT
Gneration
Phenotypic ratio 3:1
Phenotypic ratio 1:2:1

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82 X-Science
TT Both dominant gene Pure or homozygous
tt Both recessive gene conditon

Tt One dominant, one Hetrozygous

recessive gene condition.
[Hybrid]
Phenotypic ratio : 3:1

Genotypic ratio : 1:2:1

Phenotype fi
Physical appearance [Tall or Short]
Genotype fi
Genetic make up [TT, Tt or tt]

Observations : 1. All F1 progeny were tall

(no medium height plant (half way characteristic)
2. F2 progeny ¼ were short
3. Phenotypic ratio F2 – 3:1
Genotypic ratio F2 – 1:2:1
Conclusions : 1. TT and Tt both are tall plants while tt is a short plant.
2. A single copy of T is enough to make the plant tall, while
both copies have to be 't' for the plant to be short.
3. Characters/Traits like 'T' are called dominant trait (because
it express itself) 't' are recessive trait (because it remains
supressed)
Dihybrid Cross : A cross macle between two plants having two pairs of
contrasting characters is called dihybrid cross.
PARENT ROUND ·WRINKLED
GENERATION GREEN SEEDS YELLOW SEEDS

RRYY rryy
GAMETES fl fl
RY ry
F1

RrYy
[round, yellow]

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 F1 · F1
Selfing F1fi RY RY G
A
Rr Yy Ry ·Rr Yy Ry H
E
rY rY T
E
ry ry S

fl
F2 RY Ry rY ry
RY RRYY RRYy RrYy RrYy
flRy RRYy RRyy RrYy Rryy
rY RrYY RrYy rrYY rrYy
ry RrYy Rryy rrYy rryy
PHENOTYPIC RATIO : Round, yellow :9
Round, green :3
Wrinkled, yellow :3
Wrinkled, green :1
GENOTYPIC RATIO : RRYY ; 1
RRYy : 2
RrYY : 2
RRyy : 1
RrYy : 4
Rryy : 2
rrYY : 1
rrYy : 2
rryy : 1
RATIO : 1 : 2 : 2 : 1 : 4 : 2 : 1 : 2 : 1
Observations : 1. When RRYY was crossed with rryy in F1 generation all
were Rr Yy round and yellow seeds.
2. Self pollination of F1 plants gave parental phenotype + two
mixtures (recombinants) Round wrinkled, green yellow :
seeds plants appeared in the ratio of 9:3:3:1
Conclussions : 1. Round and yellow seeds are DOMINANT characters
2. Occurence of new phenotypic combinations show that
genes for round and yellow seeds are inherited
independently of each other.

84 X-Science
 Sex Determination
Phenomenon of decision or determination of sex of an offspring
FACTORS
Responsible for Sex Determination

Environmental Genetic
In some animals the temperature In some animals like humans gender or
at which the fertilised eggs are individual is determined by a pair of
kept decides the gender. chromosome called sex chromosome
eg. in Turtle XX – Female
XY – Male
Sex Chromosomes : In human beings there are 23 pairs of chromosome. Out of
these 22 chromosomes pairs are called autosomes and the last pair of
chromosomes that help in deciding gender of that individual are called sex
chromosome.
XX – female
XY – male
Sex determination in Human beings
PARENTS : FATHER MOTHER
XY XX

GAMETES X Y X X
(Reproductive cells)

Zygote XX XX XY XY
formed FEMALE FEMALE MALE MALE
after fusion
of gametes 50% probability 50% probability
of a female child of a male child

This shows that half the children will be boys and half will be girls. All children
will in herit an X chromosome from their mother regardless whether they are boys
or girls. Thus sex of children will be determined by what they inherit from their
father, and not from their mother.

85 X-Science
 Evolution
SITUATION-I
Group of red beetles

Colour variation arises during reproduction

All beetles red except One beetle Green

one that is green Reproduction
Crows feed on red beetle Progeny beetles green

No. of beetles reduces Crow could not feed on

green beetles as they
got camouflaged
in green bushes

Number of green
beetles increases
Situation 1 : Green beetles got the survival advantage or they were naturally
selected as they were not visible in green bushes. This natural selection is exerted
by crows resulting in adaptations in the beetles to fit better in their environment
SITUATION-II
Group of red beetles
Reproduction
All beetles are red except one
that is blue One blue beetle
Reproduces Reproduces
Number of red beetle No. of blue
increases beetle increases

Crows can see both blue and red beetles and can eat them

Number reduces but still red beetles are more and blue ones are few

Suddenly elephant comes and stamps on the bushes

But now beetles left are mostly blue.

86 X-Science
Situation 2 : Blue beetles did not get survivals advantage. Elephant suddenly
caused major havoc in beetle population otherwise there number would have been
considerably large.
From this we can conclude that accidents can change the frequency of some genes
even if they do not get survival advantage: This is called genetic drift and it leads to
variation.
Mechanism of Heredity
Characters or traits of an organism are controlled by the genes
A Section of DNA (cellular)

Gene

Provides information

For synthesis of Proteins

Proteins controls a character

Example :
Gene T responsible for More Results
synthesis of efficient production in
enzyme (Protein) of growth Tall
hormone Plants
Gene t responsible for Less Results
synthesis of less production in
efficient enzyme of growth short
hormone Plants

87 X-Science
 Genetic drift. It leads to diversity without any adaptation
SITUATION-III
Group of red beetles

Habitat of beetles (bushes)

Suffer from plant disease

Average weight of beetles

decreases due to poor nourishment

No of beetles kept on reducing

Later plant disease gets eliminated

Number and average weight of the beetles

increases again
Situation 3 : No genetic change has occured in the population of beetle. The
population gets affected for a short duration only due to environmental changes

Acquired and Inherited Traits

Acquired Traits Inherited Traits
1. These are the traits which are 1. These are the traits which are
developed in an individual due passed from one generation to
to special conditions the next.
2. They cannot be transferred to 2. They get transferred to the
the progeny progeny.
3. They cannot direct evolution 3. They are helpful in evolution.
eg. Low weight of starving eg. Colour of eyes and hair
beetles.

88 X-Science
 Speciation
Micro evolution : It is the evolution which is on a small scale. eg. change in body
colour of beetles.
Speciation : it is the process of formation of new species.
Species : A group of similar individuals that along to a population that can
interbreed and produce ferrite off spring.
Geneflow : It is exchange of genetic material by interbreeding between
populations of same species or individuals
WAYS BY WHICH SPECIATION TAKES PLACE

Speciation takes place when variation is combined with geographical isolation.

Gene flow : occurs between population that are partly but not completely
seperated
Interbreeding
Sub Population Gene Variation
X1 (local) flow in
[Reproduction] Local
population
Sub Population
X1 (migrant)

Genetic Drift
It is the random change in the frequency of alleles (gene pair) in a population over
successive generations.
*Natural Selection : The process by which nature selects and consolidate those
organisms which are more suitably adapted and posesses favorable variations
POPULATION Z

Sub Population GEOGRAPHICAL Sub Population

Z1 BARRIER Z2
ISOLATION
(River, Mountain)

Over many-many generations

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 Results in Accumulation of different variations in
Sub population Z1 and Z2

Genetic drift

Natural selection

Sub population Z1 and Z2 incapable

of interbreeding
Reproductive
Barrier
Formation of Formation of
new Species 1 new Species 2

Genetic drift takes place due to

a) Severe changes in the DNA
b) Change in number of chromosomes

Evolution and classification

Both evolution and classification
are interlinked.
1. Classification of species is
reflection of their
evolutionary relationship.
2. The more characteristic two
species have in common the
more closely they are
related.
3. The more closely they are
related, the more recently
they have a common
ancestor.
4. S i m i l a r i t i e s a m o n g
organisms allow us to group
them together and to study
their characteristic

90 X-Science
 Tracing Evolutionary Relationships
(Evidences of Evolution)

I. Homologous Organs : (Morphological and anatomical evidences. These are

the organs that have same basic structural plan and origin but different
functions.
Example :
Forelimb of Horse (Running) Same basic
Winds of bat (flying) plan,
Paw of a cat (walk/scratch/attack) different
functions
II. Analogous Organs : These are the organs that have different origin and
structural plan but same function example :
Design different
Wings of bat fi elongated fingers with skin folds same function
ie. flight
Wings of bird fi Feathery covering along the arm
III. Fossils : (Palaeontological evidences)
The remains and relics of dead organisms of the past.
Example :
i) Fossil of wooly mammoth
ii) Archeopteryx (fossil bird)
iii) Dead insect caught in hot mud.
FOSSILS ARE PRESERVED TRACES OF LIVING ORGANISMS
Eg. AMMONITE - Fossil invertebrate
TRILOBITE - Fossil in vertebrate
KNIGHTIA - Fossil fish
RAJASAURUS - Fossil dinosaur skull

91 X-Science
 AGE OF THE FOSSILS
1. ...........................
i. Deeper the fossil, older it is. 2. ...........................
Recent
II. Detecting the ratios of different of 3. ...........................
the same element in the fossil 4. ...........................
material ie Radio-carbon dating.
5. ..........................
[C-(14) dating) Older
6. ..........................
Evolution by stages
Evolution takes place in stages ie bit by bit over generations.
I. Fitness advantage
Evolution of Eyes
Evolution of complex organs is not sudden it occurs due to minor changes
in DNA, however takes place bit by bit over generations.
enough to
Flat worm has rudimentary eyes give fitness
advantage
Insects have compound eyes
Humans have binocular eyes
II. Functional Advantage
Evolutions of feathers
Feathers fi
provide insulation in cold weather
but later they might become useful for flight.
Example :
Dinosaurs had feathers, but could not fly using feathers. Birds seem to have
later adapted the feathers to flight.
Artificial Selection :
Humans have been a powerful agent in modifying wild species to suit their own
requirement through out ages by using artificial selection. eg (i) Wild cabbage the
dissimilar looking structures have evolved from a common ancestral design. (ii)
Wheat (many varieties obtained due to artificial selection)

92 X-Science
 WILD KALE
CABBAGE
CABBAGE

with larger
leaves
with short distance
between the leaves
BROCCOLI KOHL RABI
CAULIFLOWER

Has sterile With Swollen

Arrested flower flowers parts
development

Molecular Phylogeny :
It is based on the idea that changes in DNA during reproduction are the basic
?
events in evolution
Organisms which are more distantly related will accumulate greater
?
differences in their DNA

93 X-Science
 Human Evolution
Tools to Study Human Evolutionary Relationship

Excavating Time dating Fossils Determining

DNA
Sequences
Although there is great diversity of human forms all over the world get all humans
are a single species
GENETIC FOOTPRINTS OF HUMANS
Hundreds/thousand of years ago
Earliest members arose in Africa
East Asia
South Africa

Africa Island West Central Australia

Philippines of Asia Asia Eurasia
Indonesia

They did'nt go in a single line

?
They went forward and backward
?
Moved in and out of Africa
?
Sometimes came back to mix with each other.
?

94 X-Science
 EXERCISE
(Question Bank)
Very Short Answers (1 Mark)
1. Define variation
2. What is monohybird cross?
3. What is dominant trait.
4. What are genes?
5. Define Homologous organs
6. If an individual has XX chromosome [22+XX] will that individual be male
or female.
7. Which plant Mendel had choosen for his experiments.
8. How do Mendel's experiment show that traits may be dominant or recessive?
9. Define analogous organs? Give example.
Short Answers (2 Marks)
1. Differentiate between acquired and Inherited traits? Give example of each.
2. Explain what are fossils? How the age of fossils be determined
3. What is speciation? What factors lead to formation of a new species.
4. Explain the mechanism of sex determination in humans.
5. Differentiate between homologous and analogous organs. by giving
examples.
6. Define inheritance. What are the units of inheritance
7. What is genetic drift? How it contributes to the formation of new species
8. Explain monohydrid cross by taking tall and dwarf plants. Mention the
phenotypic and genotypic ratio of F1 and F2 off springs.
Long Answer (5 Marks each)
1. Explain the process of artificial selection by taking the example of wild
cabbage plant.
2. Explain about the human evolution.

95 X-Science
 CHAPTER – 10
LIGHT-REFLECTION
& REFRACTION
Light is a form of energy, which enable us to see the object.
In this chapter we will study the phenomena of reflection and refraction using the
property of light i.e. straight line propagation (Light wave travel from one point to
another, along a straight line).
Reflection of Light
When the light is allowed to fall on highly polished surface, such as mirror, most of
the light gets reflected. normal
Laws of Reflection
1. The angle of incidence is always equal to
Reflected
angle of reflection. ray
Incident
— i=— r ray
i r
2. The incident ray, reflected ray and the
normal to the reflecting surface at the
point of incidence lie in the same plane.
Points of incidences
Image formed by Plane Mirror (Plane reflecting surface)
Plane Mirror

A A1

Object Image

—
i
B —r B1

1) Virtual (imaginary) & Erect (Virtual The image that do not form on
screen.)
2) Laterally inverted (The left side of object appear on right side of image)
3) The size of image is equal to that of object
96 X-Science
4. The image formed is as for behind the mirror as the object is in front of it.
Reflection of light by spherical Mirrors
Mirrors, whose reflecting surface are curved inward or outward spherically are
called spherical mirror.
For example - Spoon } fi
The curved surface of shinning spoon can be considered
as curved mirror.
If it is curved inward fi
Act as concave mirror
If it is curved outward fi
Act as a convex mirror.

Reflecting Reflecting
side side

Concave Convex
Mirror mirror
OR CONVERGING OR DIVERGING
MIRROR MIRROR

Few Basic terms related to Spherical Mirror

Radius of curvature
Principal R Concave
P
Axis C F f Mirror
focal length

Radius of curvature
Principal R
Axis P f F C
focal length
Convex
Mirror

97 X-Science
1. Principal axis : Line joining the pole and centre of curvature of the spherical
mirror.
2. Pole : The geometrical central point of the reflecting spherical surface.
(aperture), denoted by (P).
3. Aperture : The width of reflecting spherical surface.
4. Centre of curvature : The reflecting surface of a spherical mirror form a part
of sphere. It has a centre, which is known as centre of curvature, denoted by
(C)
5. Radius of curvature : The separation between the pole and the centre of
curvature. ie. PC = R
6. Focus point : The point on the principal axis, where all parallel rays meet
after reflection, denoted by (F)
7. Focal length : The length between the pole and focus point i.e. PF = f
8. Relationship between focal length and Radius of curvature.
F= R
2
Image formation by spherical Mirror
Before we learn the formation of image or ray diagram, let us go through few tips
a) Remember, A say of light which is parallel to principle axis always pass
through focus (meet at focus) or vice-versa

P P
Principal C F Principal C F
Axis Axis CONCAVE
CONCAVE MIRROR
MIRROR

Principal P F C
Axis
CONVEX MIRROR
Appear as if coming
from focus pt in case of convex mirror

98 X-Science
 Principal P F C
Axis

b) A ray of light which passes through centre of curvature (it is also known as
normal at the point of incidence on spherical mirror) will retrace their path
after reflection

Pole (P)
Principal C F CONCAVE
Axis MIRROR

P
Principal F C CONVEX
Axis MIRROR

c) A ray of light falling on pole get reflected at the same angle on the other side of
principal axis.

i P —
i=—
r
r
C
F

—
i=—
r
— i
—
r F C

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Note : A ray of light passes through centre of cus-valerie reflecting spherical
surface is always act as normal at the point of incidence. If we know the normal we
can draw angle of incidence and angle of reflection

i
r
P
al
norm dence C F
ng t of inci
(passi c) at p
r oug h
th

—
r
—
i

P F C

Note : The image will only form when two or more rays meets at apoint. Image
formation by a concave mirror for different position of the object

1. Object Position of Nature

At infinity Image Real and
P At focus Inverted
C F
Size of
Image
Highly diminished
(point size)

2. Object A Position of Nature

Beyond C Image Real and
object
B1 — i P Between F&C Inverted
B C image F —
r

Size of
A1 Image
Small

3. Object Position of Nature

A Image
At C Real and
At C Inverted
B1 B P
F Size of
Image
A
Same Size
of object

100 X-Science
4. Object A — i=— r
Between C&F Object Position of Nature
B1 B —
i P Image Real and
—
r
C F Beyond C Inverted
Image
Size of Image
A 1 Enlarged

5. Object — i=— r
At F A Position of Nature
Image Real and
B —
i P At (infinity) Inverted
F —
r
C
Size of Image
Highly enlarged
A1

6. Object
Between F&P A
(Special Case)
—
i P
B —
r B1
C F
Position of Image Nature
Behind the mirror Virtual
and
Size of Image
Erect
Enlarged

Image formation by Convex Mirror

1. Object
At infinity P
F C

Position of Image Size of Image Nature

At focus Highly diminished Virtual & erect

101 X-Science
1. Object
Anywhere between
infinity and pole A
of the mirror A1
P
B B1 F

Position of Image Size of Image Nature

Between P & F Very small Virtual & erect

Uses of Concave Mirror

1. Used in torches, search light and headlight of vehicle.
2. Used to see large image of face as shaving mirror
3. Used by dentist to see large images of the teeth
4. Large concave mirror used to focus sunlight (heat) in solar furnaces.
Uses of Convex Mirror
1. Used as rear-view mirror in vehicles because it gives erect image. It also helps
the driver to view large area.
Sign Convention for Reflection by Spherical Mirror
1. The object is always placed to the left side of mirror.
2. All distance should be measured from pole (P); parallel to principal axis.
3. Take 'P' as origin. Distances measured
Right of the origin (+ x - Axis) are taken positive
Left of the origin (– x-Axis) are taken negative
Perpendicular to and above principal axis (+y-Axis) are taken positive
Perpendicular to and below principal axis (–y-Axis) are taken negative
+y

o (Cartesian system)
–x +x

–y

102 X-Science
MIRROR FORMULA
f fi
distance between F and Pole
1 1 1
v fi
distance of image from Pole
F = v + u
u fi
distance of object from Pole
R R fi
distance between centre of curvature and pole.
where f = 2

MAGNIFICATION
It is expressed as the ratio of the height of the image to height of the object
height of image h1
m= = 1
height of object h
It is also related to 'u' and 'v'
–v
m= u 2

\
from 1 and 2 equation
1
– v where h fi
image height from principle axis
1
h
m= h = u 1
h fi
Object height from principle axis.

It magnitude m > 1 _____ Image is magnified

m = 1 _____ Image is of same size
m < 1 _____ Image is dimirushed

Few tips to remember sign convention for Spherical mirror

Object height h fi
always positive | Image height h
1
} Real - negative
Virtual - positive
Object distance from pole u fi
is always negative

Image distance from pole v fi

}
Real - Image always negative
Virtual - Image always positive
Focal length f fi }
Concave mirror – always negative
Convex mirror – always positive
REFRACTION OF LIGHT
Refraction of Light : Happens in Transparent medium when a light travels from
one medium to another, refraction takes place.
A ray of light bends as it moves from one medium to another

103 X-Science
Refraction is due to change in the speed of light as it enters from one transparent
medium to another.
Speed of light decreases as the beam of light travel from rarer medium to the denser
medium.

normal normal

Incident Denser medium

Raver medium
Ray

Denser medium Rarer medium

Refracted Ray
When ray travel from Rarer to Denser it bends When ray travel from denser to
towards normal after refraction rarer medium it bends away
from normal

Some Commonly observed phenomenon due to Refraction

1. The stone at the bottom of water tub appear to be raised.
2. A fish kept in aquarium appear to be bigger than its actual size.
3. A pencil partially immersed in water appears to be displaced at the interface of
air and water.
Refraction through a Rectangular Glass Slab
A
N
Incident ray Air (Rarer Medium)
i1
K L
O

r1

1
Glass
i2 N (Denser
Medium)
1
N O M
e Air (Rarer Medium)
Here light ray changes is
1
direction at O and O , the
point at the interface of (Refracted Ray)
transparent medium. C
B

104 X-Science
When a incident ray of light AO passes from a rarer medium (air) to a denser
medium (glass) at point. O on interface AB, it will bends towards the normal. At pt
1
O , on interface DC the light ray entered from denser medium (glass) to rarer
medium (air) here the light ray will bend away from normal OO1is a refracted ray
OB is an emergent ray. If the incident ray is extended to C, we will observe that
emergent ray O1B is parallel to incident ray. The ray will slightly displaced laterally
after refraction.
Note : When a ray of light is incident normally to the interface of two media it will
go straight, without any deviation.
Laws of refraction of light-
1. The incident ray, the refracted ray and the normal to the interface of two
transparent media at the point of incidence, all lie in the same plane.
2. The ratio of sine of angle of incidence to the sine of angle of refraction is a
constant ie.
Sin i constant
Sin r = (r)

for given colour and pair of media, this law is also known as Snells Law
Constant n is the refractive index for a given pair of medium. It is the refractive
index of the second medium with respect to first medium.
Sin i n2 Where 2 is for second
Sin r = n1 = n21 medium and 1 is for first
medium

Refractive Index
The refractive index of glass with respect is air is given by ratio of speed of light in
air to the speed of light in glass.
ng Speed of light in air c
nga = n = = v
a Speed of light in glass
C fi Speed of light in vacuum = 3· 108 m/s
speed of light in air is marginally less, compared to that in vacuum.
Refractive index of air with respect to glass is given by
na
( a fi
g fi
air
glass )
nag = n =
g
Speed of light in glass
Speed of light in air
v
= c

105 X-Science
The absolute refractive index of a medium is simply called refractive index
Speed of light in air c
nm = = v
Speed of light in the medium
Refractive index of water (nw) = 1.33
Refractive index of glass (ng) = 1.52

Spherical Lens
A transparent material bound by two surface, of which one or both surfaces are
spherical, forms a lens.
CONVEX LENS
A lens may have two spherical surfaces, bulging outwards, is
called double convex lens (or simply convex lens.
It is also known as converging lens because it converges the light.
CONCAVE LENS
A lens bounded by two spherical surfaces, curved inwards is
known as double concave lens (or simply concave lens)
It is also known as diverging lens because it diverges the light.
Few Basic Terms related to spherical lens.

R
Principal f Convex
Axis C1 F1 O F2 C2 Lens
or (2F1) or (2F2)
Optical
centre (O)

R
Optical centre (O)
Principal Concave
Axis C1 F1 O F2 C2 Lens

C1 O C2

106 X-Science
1. Centre of curvature - A lens, either a convex lens or a concave lens has two
spherical surfaces. Each of these surfaces form a part of sphere. The centre of
these two spheres are called centre of curvature represented by C1 and C2.
2. Principal axis - Imaginary straight line passing through the two centres of
curvature
3. Optical Centre - The central point of lens is its optical centre (O). A ray of
light, when passes through 'O' it remains undeviated i.e. it goes straight.
4. Aperture - The effective diameter of the circular outline of a spherical lens.
5. Focus of lens - Beam of light parallel is principal axis, after refraction from
1) Convex lens, converge to the point on principal axis, denoted by F,
known as Principal focus

Principal Axis
F1 O F2

2) Concave lens, appear to diverge from a point on the principal axis, known
as principal focus.

Principal
F1 O F2 Axis

The distance OF2 and OF1 is called as focal length

Tips for drawing Ray diagram
a) After refraction, a ray parallel to principal axis will pass through F.

Principal
Axis
F1 O F2 F1 O F2

(Converge) (Diverge)

107 X-Science
b) A ray passes through F, after refraction will emerge parallel to principal axis.

F2
Principal F1 F2 Principal
F1 Axis Axis
O O

c) A ray passes through optical centre 'O', paeses without any deviation.

Principal
F1 F2 F1 O F2 Axis
O

Image formation by a convex lens for various position of object

1. Object Position of Image Nature
At infinity At focus Real &
F2 inverted
Size of Image
2F1 F1 F2 2F2 Highly
diminished
(point size)
2. Object
Beyond 2F1
Position of Image Nature
A
Between F2 & 2F2 Real &
inverted
B1 Size of Image
B 2F1 F1 O 2F2 Small
F2
A1
3. Object
At 2F1
A
Position of Image Nature
B1
At 2F2 Real &
B
2F1 F1 F2 2F2 inverted
O Size of Image
Same size of
A1 object

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4. Object Position of Image Nature
Between F1 & 2F1 Beyond 2F2 Real &
A inverted
Size of Image
Enlarged
B
2F2 B1
2F1 F1 O F2

A1
Object
5. Position of Image Nature
At focus F1
at infinity Real &
A
inverted
Size of Image
B Highly Enlarged
2F1 F1 O F2 2F2

6. (Special Case) Size of Image Nature

A1 Enlarged
Object Virtual &
Between F1 and A Erect
optical centre 'O'
B1
Position of Image 2F1 F1 B O F2 2F2
On the same
side of the
object

Image formation by concave lens

1. Object Position of Image Nature
Alt infinity At F1 Virtual &
Size of Image Erect
Highly Diminished
2F1 F1 O F2 2F2

109 X-Science
2. Object Position of Image Nature
Between infinity Between F1 & O Virtual
and optical centre & Erect
Size of Image
(at any point)
Very small
A
A
B
2F1 F1 B O F2 2F2

Sign Convention for Refraction by spherical lens

Similar to that of spherical mirror, only the difference is that all the measurement
are made from optical centre 'O'
+ y-axis

o
– x-axis + x-axis

– y-axis

LENS FORMULA
'O' fioptical centre
1 1 – 1
= f - distance between F and 'O'
f v u
u - distance of object from 'O'
R v - distance of image from 'O'
f= r - distance between centre
2
of curvature & 'O'
MAGNIFICATION
It is defined as the ratio of the height of image to the height of object.
1
h – image height
m=
height of image
height of object
=
h
h
1

= 1
} from principal axis
h – object height
from principal axis
It is also related to 'u' & 'v'
v
m= 2
u

110 X-Science
 From equation 1 & 2
h1 v
m= =
h u

If magnitude of m > | fi
Image is magnified
m = 1 fi
Image is of same size
m < | fi
Image is deminished
Few tips to remember sign convention for spherical lens
Object height h fi
is always positive

Image height h1 Real fi is always negative

Virtual fi is always positive
Object distance from optical centre u fi
is always negative

Image distance from optical centre v fi }

Real fi positive
virtual fi
negative

Focal length v fi }
Convex lens fi
is always positive
Concave lens fi
is always negative
Power of Lens
The degree of convergence or divergence of light ray achieved by a lens is known
as power of a lens.
It is difined as the reciprocal of its focal length Represented by P
It f is given in meter, then
1
1 P=
f= f
f It f is given in cm, then
100
P=
f

SI unit of power of a lens is "dioptre" denoted by 'D'

I dioptre or ID fi
It is the power of lens whose focal length is 1m
1
ID = OR ID = 1m–1
1m

111 X-Science
Power convex lens or converging lens is always positive

f is +ve
O F2

Power of concave lens or diverging lens is always negative

f is –ve
F1 O

If any optical instrument have many lens, then net power will be
P = P1 + P2 + P3....

EXERCISE
(Question Bank)
Very Short Answers Type Questions (1 Mark)
1. If the angle of incidence is O°, what is the angle of reflection?
2. What is the nature of image formed by concave mirror if the magnification
produced by the mirror is +3?
3. Give two uses of concave mirror?
4. Find the focal length of a convex mirror, whose radius of curvature is 30 cm?
5. What do you understand by magnification of a spherical mirror?
6. An object is held at the principal focus of a concave lens of focal length f.
Where the image will form?
7. Show the angle of incidence and angle of refection.

8. Complete the ray diagram.

2F1 F1 O F2 2F2

112 X-Science
9. Define the SI unit of power of lens.
10. When light undergoes refraction at the surface of seperation of two media,
what happens to speed of light.
Short Answer Type Questions (2-3 Marks)
1. What do you understand by refraction of light. Draw the labelled ray
diagram, when ray passes through glass slab.
8
2. The refractive index of glass is 1.54 and the speed of light in air is 3x10 m/s.
Calculate the speed of light in water?
3. A convex mirror used on an automobile has a focal length of 6m. If vehicle
behind is at a distance of 12m. Find the nature and location of image.
(4m, virtual erect small)
4. A concave lens of focal length 15cm, forms an image 10 cm from the lens.
How far is the object placed from the lens? Draw the ray diagram?
5. Two thin lens of power +3.5D and - 2.5D are placed in contact. Find the
power and focal length, if the lens are in combination. (p = + 10, f = 1m)
6. What are the law of refraction. Define refractive index of a medium.
Very Long Answer Type Questions (5 Marks)
1. Draw the ray diagram, showing the image formed by concave mirror, when
object is placed at
a) at infinity b) between F22F
c) At 2F d) At F
e) between F&P
2. Draw the ray diagram, showing the image formed by convex lens, when
object is placed at.
a) At infinity b) between F1 & 2F1
c) At 2F1 d) Beyond 2F1
e) between F1 & optical centre 'O'

113 X-Science
 CHAPTER – 11
The Hyman Eye and the Colourful World
In this chapter we will study Human eye that uses the light and enable us to see the
objects.
We will also use the idea of refraction of light in some optical phenomena in nature
i.e. Rainbow formation, twinkling of star, blue and red colour of sky etc.
Human Eye : A Sensitive sense organ
It acts like a camera, enable us to capture the colourful picture of the surroundings.
It forms an inverted, real image on light sensitive surface Retina

The Various parts of eye and their functions

1. Cornea : It is a thin membrane through which light enters. It forms the
transparent bulge on the front of eyeball. Most of the refraction occurs at the
outer surface of the cornea.
2. Eyeball : it is approximately spherical in shape, with a diameter of about
2.3cm.
3. Iris : It is a dark muscular diaphragm that controls the size of pupil. It is
behind the cornea.
4. Pupil : It regulates and control the amount of light entering the eye. It is the
black opening between aqueous humour & lens.
5. Crystalline eye lens : Provide the focussed real & inverted image of the
object on the retina. It is composed of a fibrous, jelly like material. This is
convex lens that converges light at retina.

114 X-Science
6. Ciliary muscles : It helps to change the curvature of eyelens and hence
changes its focal length so that we can see the object clearly placed at different
positon.
7. Retina : Thin membrane with large no. of sensitive cells.
8. When image formed at retina, light sensitive cells gets activated and generate
electrical signal. These signals are sent to brain via optic nerue. Brain analyse
these signals after which we perceive object as they are.
How pupil works ?
Example : You would have observed that when you come out of the cinema hall
after watching movie in the bright sun light, your eyes get closed . And when you
entered the hall from the bright light, you won't be able to see and after some time
you would be able to see.
Here the pupil of an eye provide a variable aperture, whose size is controlled by iris
a) When the light is bright : Iris contracts the pupil, so that less light enters the
eye.
b) When the light is din : Iris expand the pupil, so that more light enters the eye.
Pupil open completely, when iris is relaxed.
Persistence of Vision : It is the time for which the sensation of an object continue
th
in the eye. It is about 1/16 of a second.
Power of Accommodation :
The ability of eye lens to adjust it focal length is called accommodation with the
help of ciliary muscles.

Ciliary Muslces

Relaxed Contract
1. Eye lens become thin 1. Eye lens become thick
2. Increases the focal length 2. Decreases the focal length
3. Enable us to see distant object clearly 3. Enable us to see nearby object clearly

Near point of the Eye For point of the Eye

It is 25cm for normal eye. The It is infinity for normal eye. It is the
minimum distance at which object can farthest point upto which the eye can
be seen most distinctly without strain. see object clearly.

115 X-Science
DEFECTS OF VISION AND THEIR CORRECTION
1. CATARACT : The image can not be seen distinctly because eye lens become
milky and cloudy. This condition is known as cataract, it can cause complete
or partial loss of vision.
This can be corrected by surgical removal of extra growth (cataract surgery)
2. Myopia : (Near Sightedness)
A person can see nearby object clearly, but cannot see distant object distinctly.
Image formed in front of the retina.

Normal O Image
Eye Object formed
at Retina

Myopic
O1 O Eye

The Reason of defect

1. Excessive curvature of eye lens (thick, decrease focal length)
2. Elongation of the eye ball.
CORRECTION
Corrected by using a Concave Lens of appropriate power.

O1 O

Correction of Myopita

116 X-Science
(3) Hypermetropia (Far - Sightedness) –
A person cannot see nearby object clearly, but can see distant object distinctly.
Image formed at a point behind the retina

NORMAL Image formed

EYE N at Retina

Hypermetropic
NORMAL eye
EYE N N1

The Reason of defect

1. Increase in focal length of the eye lens (Thin eye lens)
2. Eye ball has become too small.
CORRECTION
Corrected by using a Convex Lens of appropriate power.

N
N1

Correction of Hypermetropic eye

117 X-Science
4. Presbyopia
As we become old, the power of accommodation of the eye usually decreases,
the near point gradually recedes away.
This defect is called Presbyopia. Person may suffer from both myopia and
hypermetropia.
Reason of defect- Gradual weakening of ciliary muscles and decreasing the
flexibility of the eye lens.
Correction- Using of Bifocal lens with appropriate power.
Bifocal lenses consist of both concave and convex lens, upper position consist
of concave lens and lower portion consist of convex lens.
Refraction of light through a Prism
Prism- It has two triangular bases and three rectangular lateral surfaces.
These surfaces are inclines to each other. The angle between its two lateral
faces is called Angle of Prism.
A Angle of Prism

D (Angle of deviation)
Ð
Ð
i- incident angle
Ð
i
Ð
r Ð
e
t (emergent angle)
ligh
Sun
Em
B C erg
ent
ray

Angle of Deviation (D) ®

The angle between the incident ray and emergent ray.
Dispersion fo white light by a Glass Prism

Ð
D for red colour
ÐD for violet colour
ht
h ite lig
W
R
beam While light
Spectrum
V
Ð
D for violet colour > Ð
D for red colour

118 X-Science
Inclined refracting surfaces of glass prism show exciting phenomenon.
Splitting of White light into band of colours
The band of the coloured components of light beam as called Spectrum i.e.
VIBGYOR
The splitting of light into its component colours is called Dispersion.
The different component colour of light bends at different angle with respect to
incident angle the red light bends the least while the violet bends most.
ISSAC NEWTON ® He was the first, who obtained spectrum of sunlight by
using glass prism.
He tried to split the spectrum of white light more by using another similar prism,
but he could not get any more colours.
He repeated the experiment using second prism in on inverted position with
respect to the first prism.
Allowed all the colours of spectrum to pass through second prism. He found white
light emerges on the other side of second prism.
en
Scre

te
ght R R whi
h ite li ligh t
w
V V
rce
Sou

He concluded that sun is made up of seven visible colour ‘VIBGYOR’

RAINBOW ® It is the spectrum of sunlight in nature It is formed due to the
dispersion of sunlight by the tiny water droplet, present in atmosphere.
Water droplet act like prism.
It refract and disperse the incident sunlight, then reflect it internally (internal
reflection) and finally refract it again, when it emerges out of the water droplet.
A rainbow is always form in a direction opposite to that of sun.
Due dispersion and internal reflection of light different colour reaches to
observer’s eye.
Red colour appear on top & violet at the bottom of rainbow

119 X-Science
 Sunlight Rain drop
A

At ‘A’®
Refraction & dispersion takes place B
At ‘B’®
Internal refraction takes place
C
At ‘C’®
Refraction & dispersion takes place
R
V

Atmospheric Refraction –
1. Apparent Star Position– It is due to atmospheric refraction of star light.
The temperature and density of different layer of atmosphere keeps varying.
Hence we have different medium.
Distant star act as point source of light. When the starlight enter the earth’s
atmosphere it undergoes refraction continuously, due to changing refractive
index i.e. from Rarer to denser. It bends towards the normal.
Due to this the apparent position of the star is different from actual position.
The star appear higher than its actual position.

Apparent position of star

Actual
position
of Star In atmosphere layer
.............................................
.............................................
Refractive index
.............................................
.............................................
decreases
.............................................
.............................................
.............................................
.............................................
Atmosphere
.............................................
.............................................
EARTH

2. Twinkling of Star– It is also due to atmospheric refraction

Distant star act like a point source of light. As the beam of starlight keeps
deviating from its path, the apparent position of star keeps on changing
because physical condition of earth’s atmosphere is not stationary
Hence the amount of light enters our eyes fluctuate some time bright and some
time faint.
This is the “Twinkling effect of star”

120 X-Science
Q. Why Planet do not twinkle?
Ans. Planets are closer to earth and are seen as extended source of light i.e. the
collection of large no: of point sized sources of light. Therefore the total
amount of light entering our eyes from all individual point source will nullify
the twinkling effect.
(3) Advance Sunrise and delayed sunset
This is also due to atmospheric refraction.
Because of this sun is visible about 2 minutes earlier than actual sunrise and
about 2 minutes after the actual sun set. Apparent
position
Atmosphere of sun
n
rth o

Horizon
Ea rver
se
Ob

EARTH Actual
Sun

Apparent flattering of the sun’s disc at sun set and sun rise is due to atmospheric
refraction.
Scattering of Light
Tyndall Effect– When a beam of light strikes the minute particle of earth’s
atmosphere suspended particles of dust and molecule of air the path of beam
become visible. The phenomenon of scattering of light by the colloidal particle
gives rise to Tyndall Effect.
It can be observed when sunlight passes through a canopy of a dense forest.
The colour of the scattered light depends on the size of the scattering particles

Very fine particle Large size particle Very large enough

(scatter mainly (Scatter light of (The sky appear
blue colour short longer wave length white)
wave length) i.e. red)
(1) Why cloud Appear white– The size of water droplet (scattering particle) is
very large, hence scattered all wavelength of light almost equally.
(2) Why colour of sky is blue– The molecules of air and other fine particles in
the atmosphere have size smaller than the wavelength of visible light. Since
the blue has shorter wavelength than red, hence it will scattered the most.

121 X-Science
 According to Rayleigh scattering
1
Scattering of light a l 4 ( l – Wavelength)
Scattering of light decreases with increase in wavelength

Q. If there is no earth’s atmosphere? What will happen to scattering

phenomenon?
Ans. There will be no scattering and sky will appear dark.
(3) Colour of the Sun of Sunrise and Sunset
While sunset and sunrise, the colour of the sun and its surrounding appear
red.
During sunset and sunrise, the sun is near horizon, and therefore the sunlight
has to travel larger distance in atmosphere. Due to this most of the blue light
(shorter wavelength) are scattered away by the particles. The light of longer
wavelength (red colour) will reach our eye. This is why sun appear red in
colour.
(4) Why the danger signal or sign are made of red colour.
Red colour scattered the least when strikes the small particle of fog and
smoke because in has the maximum wavelength (visible spectrum). Hence
at large distance also, we can see the red colour clearly.
(4) At noon sun appear white–
At noon the, sun is overhead and sunlight would travel shorter distance
relatively through the atmosphere. Hence, at noon, the Sun appear while as
only little of the blue and violet colours are scattered.
(In the afternoon)
(In the early morning (Less blue
or evening) Light travel less scattered)
distance in atmosphere.
(Blue scattered away
sun appear reddish
.............................................
.............................................
.............................................
.............................................
Light Travel large distance
.............................................
.............................................
in atmosphere
Sun near
.............................................
.............................................
Atmosphere
horizon .............................................
.............................................
EARTH

122 X-Science
 EXERCISE
(Question Bank)
Very Short Answers (1 Mark)
1. What is the phenomenon responsible for the blue colour of sky?
2. What is the near and far point of a normal eye?
3. Name the component of eye that is responsible for the adjustment of
eyelens?
4. To an astronaut why does the sky appear dark instead of blue?
5. How can your remove the defect of vision ‘Presbyopia’.
6. Name three primary colour? (Ans. RED, BLUE, GREEN)
7. Write the nature of image formed by our eye?
8. What do you understand by Dispersion of light?
9. What is Tyndall Effect?
10. A student has difficulty reading the black board while sitting in the last row.
What is the defect of vision and how it can be corrected?
Short Answers (2 Marks)
1. Name the phenomenon responsible for formation of rainbow? Explain it
with the help of diagram?
2. What is power of accommodation. How ciliary muscles helps in
accommodation?
3. Why the sun appear red while sunset and sunrise. Explain?
4. Why the star twinkle but not earth?
5. Explain the function of
(i) Iris (ii) Pupil (iii) Retina
6. Explain the refraction of light through glass prism with the help of diagram.
Show angle of emergence and angle of deviation?
Long Answer Type Questions (5 Marks)
1. What is myopia. State the two causes of myopia? With the help of labelled
ray diagram show
(1) Eye defect
(2) Correction of myopia
2. What is hypermetropia. State the two causes? With the help of labelled ray
diagram show
(1) Eye defect
(2) Correction of hypermetropia.
3. Draw the labelled diagram of human eye and explain the image formation?

123 X-Science
 CHAPTER – 12
ELECTRICITY
Think life without “electricity” in this modern society. Is it possible to survive
without electrical energy in world of technology. Since we are science student, so it
is necessary to understand the basic concept behind the word “electricity”
Charge®
(q)
It is a very small particles present in an atom it can be either negative (electron) or
positive (proton)
“Coulomb” is the SI unit of charge, represented by C.
Net charge (Q)– Total charge
1018
IC Net charge is equivalent to the charge contained in nearly electrons 6´

Q = ne (n is no: of electron)
–19
If Q = 1C, e = 1.6 ´
10 C (negative charge on electron)
Q 1
n= =
e 1.6 ´ 10
–19

100 18 18
= ´ 10 = 6.2 ´
10
16
18
n=6´
10 electron

Current (I)
Rate of flow of net charge is called current. Denoted by (I)

Q
I = t is time
t

SI unit of current is “Ampere” rep. by A.

Ampere ®
Defined as one coulomb of charge following per second.

1C
1A =
1s

124 X-Science
In an electric circuit the electric current flow in the opposite direction of the flow of
electron (–ve charge) conventionally. It flows from the +ve terminal of battery or
cell to –ve terminal.
Small quantity of current are expressed in
–3
mA (milli Ampere) = 10 A
–6
uA (micro Ampere) = 10 A
Ammeter– It is an instrument used to measure the electric current in a circuit.
It is always connected in series m a circuit
It is represented by the symbol ––––––––+ A – ––––––– in an electric circuit. It has
low resistance.
Electric Circuit– It is a closed path along which an electric current flow.

Bulb
The arrow shows the direction
of electric current in circuit.
–
Ammeter A
+
Key In this circuit ammeter is
+ – connected in series.

Battery
(Having 3 cells)
The electron can only flow when there is difference of electric pressure. For
example “water flowing through a tube” It is only possible when there high
pressure at one side and low at another side, then it will move from high pressure to
low pressure.
In case of electric current, the flow of charge is made possible due to chemical
action with in a cell that generates the potential difference across the terminals of
the cell.
8. Electric potential Difference– It is defined as the work done in carrying a unit
charge from one point to another between the two points of an electric circuits.
V – Potential Difference
W
V= W – Work
Q
Q – Net Charge
SI unit of potential difference – Volts rep. by “V”

125 X-Science
One Volt ® When 1 Joule of work is done to carry one coulomb (1C) of charge
from one point to another of a current carrying conductor then the potential
difference is send to be IV.

1J
IV =
1C

Voltmeter ® It is an instrument, used to measure the potential difference and

represented by the symbol +V – in an electric circuit. It is always
connected in parallel across the points between which the potential difference is to
be measured. It has high resistance.
Symbols for some commonly used instrument in circuit diagrams

(1) Cell + –

(2) Battery + –

(3) Key (switch) open OR

(4) Key (Close) OR

(5) Joint wire

(6) Wires with no join

(7) Bulb

+ –
(8) Ammeter A

+ –
(9) Voltmeter V

126 X-Science
Georg Simon Ohm (physicist) 1787 – 1854
Found the relationship between the current (I) flowing through a conductor and
potential difference (V) across the terminals of a conductor using the circuit
diagram.
+ V– GRAPH

–
A
+ V Va
I
(V)
O I (A)
+ –

In this circuit diagram we come across two new symbols

RESISTANCE (R)

OR RHEOSTAT (Variable Resistance)

Ohm’s Law ® He stated that the electric current flowing through a conductor is
directly proportion at to the potential difference across its ends, provided the
temperature remain constant
Va I
V = IR
Where “R” is the proportionality constant for the given metal at given temperature
and is said to be resistance, the graph between V and I is always straight line.
Resistance– It is the property of a conductor that opposes the flow of current. It is
represented by ‘R’ and symbol is
SI unit of resistance “Ohm” OR W
1 Ohm – The resistance of a conductor is said to be one Ohm, when the potential
difference across the conductor is 1V and the current flowing through it is 1A.
V = IR
\ R= V
I
1 Ohm or 1 W = 1V
1A

127 X-Science
Rheostate–
As we know that
V = IR
1= V
\
R {
Shows that current through
conductor resistor is inversely
proportional is its resistance }
So to increase or decrease the current accordingly in the circuit a component is
used is called “Rheostat”, that regulates the current without changing potential
difference. Represented by “Rh”

Its symbol is OR

it a conductor has less Resistance, then more current will flow through it.

FACTORS ON WHICH RESISTANCE OF A CONDUCTOR DEPENDS–

(1) On its length (l)
(2) On its cross sectional area (A)
(3) On the nature of material

(Resistance) Ral (Directly prop. to length)

1 (inversely prop to cross-sectional area)
Ra
A
Ra l
A
R= l
A
Where “ ” (rho) is a proportionality constant known as resistivity of the material
of conductor.
11. Resistivity ( ) – the resistance offered by a wire of unit length and unit cross-
sectional area is called resistivity.
l
Its SI unit is W m Since R =
A
R.A W .m2
\ ==
l m
\
SI unit of =
W
m.

For a material irrespective of length and area, the resistivity is a constant.

128 X-Science
Resistantly of a material vary with temperature
Resistivity of an alloy (homogeneous mixture of metals) is generally higher than
of its constituent metals. Example Constantan (alloy of Cu & Ni)
Alloys have high resistivity and do not oxidise (burn) readly at high temperature,
for this reason they are commonly used in electrical heating devices, like electric
iron, heater, toasters etc. For example “Tungsten” as filament of electric bulb.
Resistance in Series– (Maximum Effective Resistance)
Let us take three resistance R1, R2 and R3 that are connected in series in a circuit.
R1 R2 R3

V1 V2 V3
I

+ –

V
Ohm’s low stated
V = IR
The current (I) flowing through the resistance in series will remain same, where as
the potential difference (V) across each resistor will be different.
V = IR
V1 = IR1 , V2 = IR2 , V3 = IR3
Total potential difference (V) = V1 + V2 + V3
V = IR1 + IR2 + IR3
} Putting the value of
V, V , V & V
1 2 3

I R = I (R1 + R2 + R3)
Reff = R1 + R2 + R3

Thus, we conclude that effective Resistance of the several resistors joined in series
is equal to the sum of their individual resistance.
Resistance in Parallel (Minimum Effective Resistance)
Let us take three R1, R2 and R3, that are connected in parallel in the electric circuit.
R1
I1
I2 R2
I1 R3
I3

+ –

129 X-Science
 Now,
I1 = V , I2 = V , I3 = V
R1 R2 R3
Total current (I) = I1 + I2 + I3
substitute the value of I1 , I2 , I3 and I
V = V + V + V
R R1 R2 R3
V = V 1 + 1 + 1
R R1 R2 R3

1 = 1 + 1 + 1
Reff R1 R2 R3
Thus, we conclude that the reciprocal of total effective resistance of the several
resistors connected in parallel is equal to the sum of the reciprocals of the
individual resistance.
Disadvantage of series connection in on electric circuit :–
1. In series connection if any of the component fail to work, the circuit will break
and then none of the component (ex. TV, bulb, fan..) will work.
2. It is not possible to connect a bulb and a heater in series, because they need
different value of current to operate properly.
Hence, to overcome this problem we generally use parallel circuit.
Heating effect of Electric Current :
Explanation® Battery or a cell is a source of electrical energy.

Battery or Cell Electron

(Chemical reaction in will come in motion
it will produce potential to flow current
difference at its through resistor
two terminals)

Rest of energy of source is Part of this energy is To maintain this current,

converted into heat, that consumed in useful the source has to keep
raises the temperature work expending its energy
of gadget. (like rotating of fan)

This is known as heating This effect is utilized in

effect of electric current devices such as electric
heater, iron etc.

130 X-Science
Mathematical Expression :–
Let us suppose that current (I) is flowing through a resistor of resistance (R) for the
time (t). The potential difference across the resistance is (V).
W
V= Q

\
Work done in morning the charge Q will be
W = VQ
W
Then power, P = t [Rate of change of work done]
VQ
= t
Q
P = VI I= t – (1)

Heat energy supplied by the source for time t will be

Energy or Work
H=P´ t P= – (2)
time
Put equation (i) in equation (2)
H = VIt
= (IR) It \
V = IR Ohm’s Law]
2
H = I Rt
This is known as Joule’s Law
The law stated that the heat produced in a resistor is
(i) directly proportional to square of the current(I)
(ii) directly proportional to resistance (R) for given current
(iii) directly proportional to time (t) for which current flow through resistor.
Application of Heating Effect of Electric Current :–
(1) Used in electric iron, toaster, oven, heater etc.
(2) It is also used in bulb to produce light.
(Filament of bulb is made of strong metal with high melting point such as
tungsten (m.pt = 3380°C). This filament can retain as much of the heat
generated as possible, to become very hot and emit light)
(3) It is also used in the “fuse connected in an electric circuit {Fuse a safety
device, protect the circuits and appliance by stopping the flow of high current.
The wire of fuse is made of an alloy of metals for ex Aluminium Copper, Iron

131 X-Science
 lead etc. The alloy should be of low m.pt and high resistivity, fuse is always
connected in series circuit. When large current flow through the circuit, the
temperature of fuse wire will increase. This melts the fuse wire and break the
circuit.
“ Fuses” used for domestic purposes are rated as 1A, 2A, 3A, 5A, 10A etc. for
various operation depending upon the power of appliance using.
Example- let us consider an appliance “electric Iron” which consume 1KW
electric power, at 220V
P = VI
I = P = 1KW = 1000W
V 220V 220V
I = 4.54A

In this case a 5A fuse is required.

Electric Power :– In case of electricity, it is defined as the rate of change electrical
energy dissipated or consumed in an electric electrical energy dissipated or
consumed in an electric circuit.
P = VI
or P = I2R ( V = IR Ohm’s Law)
2
V ( I= V )
or P =
R R
or P = Electrical Energy (E)
time (t)
SI unit of electric power is “Watt” (W).
1 Watt® Defined as the power consumed by a device, when 1A of current passes
through it at the potential difference of 1V.
P = VI
1 Watt = 1 Volt ´
1 Ampere

29 Electrical Energy– E – Electrical Energy

P= E t – time
t
\
E=P´
t

132 X-Science
SI unit of electrical energy = Ws or J
Commercial unit of electrical energy = KWh or One unit

E=P´
t
\
KWh = 1KW ´
h
= 1000W ´ 3600 s
5
= 36 ´10 Ws
= 3.6 ´106J (SI unit Ws = J)
\
1 106J
KWh = 3.6 ´

One horse power = 746W

133 X-Science
 EXERCISE
(Question Bank)
Very Short Answers (1 Mark)
1. Define the SI unit of (one mark each)
(a) Current
(b) Potential Difference
(c) Resistance
(d) Electric Power
(e) Electric Energy (Commercial)
2. What is the conventional direction of flow of current?
3. Define the term resistivity?
4. On what factors does the resistance of a conductor depend?
5. How is the voltmeter and ammeter connected in the electric circuit.
6. Heating effect of current carrying conductor is due to –
(Ans : loss of kmectic energy of electron)
7. Why the filament of bulb has high melting point?
8. How does use of a fuse wire protect electrical appliance?
9. What is the relationship between power, current and potential difference
(Ans : P = VI)
10. How many joules are there in 1KWh?
Short Answer (2-3 marks) type Questions
1. Draw a schematic diagram of a circuit consisting of a battery of six cell of
1.5V each, three resistor each of 3W
in series and a plug key.
2. State Ohm’s law. Draw the graph between V&I?
3. What is joule’s Heating effect of current, derive its expression?
4. A wire of length L and R is stretched so that its length’s doubled and the area
of cross section is halved. How will its
(i) Resistance change
(ii) Resistivity change.

134 X-Science
5. An electrical appliance of power 2KW works at potential difference of 220V.
Does it require fuse of 5A, give reason?
6. Calculate the total effective resistance between points A and B
1W 1W
(i)
1W 1W 1W
A 1W 1W B

3W 3W

(ii)
A B

3W 3W

2W
(iii)
A 2W

2W 2W

2W
B

Long Answer (5 Marks) type Questions

1. On what factor the resistance of conductor depends give its mathematical
expression. Give the SI unit of resistivity?
Calculate the resistivity of a metal of length 2m at 20°C having the resistance
of 20W and diameter 0.3mm?
2. In a circuit below, calculate
4W 2W

6W

+ –

6W

135 X-Science
 (1) Calculate total effective resistance
(2) The total current through the circuit.
(3) Potential difference across 4W
and 2W
.
3. Three resistance of 2W
, 3W
and 5W
are connected in the electric circuit.
Calculate the
(1) Maximum effective resistance
(2) Minimum effective resistance

136 X-Science
 CHAPTER – 13
MAGNETIC EFFECTS OF
ELECTRIC CURRENT
In this chapter, we will study the effects of electric current :
1. Hans Christian Oersted (1777-1851)
Oersted showed that electricity and magnetism are related to each other. His
research later used in radio, television etc.
The unit of magnetic field strength is name Oersted in his honour.
2. Oersted Experiment

R K
X

XY is conductor (Cu wire)

through which current is passed

Y
– +
On passing the current through the copper wire XY in the circuit, the compass
needle which is placed near the conductor gets deflected. If we reverse the
direction of current, the compass needle deflect in reverse direction. If we
stop the flow of current, the needle comes at rest.
Hence, it conclude that electricity and magnetism are linked to each other. It
shows that whenever the current will flow through the conductor, then
magnetic field around. it will developer
3. Magnetic Field – It is the region surrounding a magnet, in which force of
magnet can be detected. It is a vector quantity, having both direction &
magnitude.
4. Compass needle– It is a small bar magnet, whose north end is pointing
towards north pole and south end is pointing towards south pole of earth.
5. Magnetic field lines–
When a bar magnet is placed on a card board and iron fillings are sprinkled,
they will arrange themselves in a pattern as shown below.

137 X-Science
 N S

The lines along which the iron filling align themselves represent magnetic
field lines.
Hence, magnetic field line is a path along which a hypothetical free north pole
tend to move towards south pole.
6. Characteristics of Magnetic field lines :
(1) The direction of magnetic field lines outside the magnet is always from
north pole to south pole of bar magnet and are indicated by an arrow.
Inside the magnetic, the direction of field lines is from its south pole to north
pole
Thus magnetic field lines are closed curve
(2) The strength of magnetic field is expressed by the closeness of magnetic
field lines. Closer the lines, more will be the strength and farther the lines, less
will be the magnetic field strength.
(3) No two field lines will intersect each other.
If they intersects, then at point of intersection the compass needle will show
two direction of magnetic field which is not possible.

Tangent at the
point of intersection
shows two direction.

7. Magnetic field due to Current Carrying Conductor

N N
x S y x S y
Cu wire Cu wire

+ – – +

(a) (b)

138 X-Science
 The above electric circuit in which a copper is placed paralled to a compass
needle, shows the deflection in needle gets reversed, when the direction of
current reversed. Hence electricity and magnetism are related to each other.
8. Right Hand Thumb Rule :–
It is a convenient way of finding the direction of magnetic field associated
with current carrying conductor.
Hold the straight were carrying current in your right hand such that thumb
points towards the direction of current, then your folded fingers around the
conductor will show the direction of magnetic field.

Direction of magnetic
field lines.

This rule is also called Maxwell’s corkscrew rule.

9. Magnetic Field due to Current through a Straight Conductor
+ –
A
Direction of Direction can be
Current explained using
Right Hand Thumb
Rule

on c + –
ecti i
Dir agnet Pheostat
f
o dm
fiel
10. Magnetic Field due to Current through a circular Loop
S
Z

–
+

139 X-Science
 Every point on the wire carrying current give rise to the magnetic field,
appearing as a straight line at the centre of loop. By applying Right hand
Thumb rule, we can find the direction of magnetic field at every section of the
wire.
11. Solenoid– A Coil of many circular turns of insulated copper wire wrapped
closely in the shape of a cylinder is called solenoid.
12. Magnetic field due to a current in a solenoid–

S N

+ –

– Using R.H. Thumb Rule, we can draw the pattern of magnetic field lives
around a current carrying solenod.
– One end of the solenoid behaves as a magnetic north pole, white the other
end behave as the South Pole.
– The filed lines inside the solenoid are in form of parallel straigh lines, that
implies that magnetic field inside the solenoid is same at all points i.e. Field is
uniform.
13. Electromagnet– Strong magnetic field inside the solenoid can be used to
magnetise a magnetic material for example soft iron, when it is placed inside
the coil. The magnet so formed is called electromagnet.
14. Force on a current carrying conductor in a magnetic field.
Andre Marie Ampere (1775-1836) suggested that the magnet also exert an
equal and opposite force on the current carrying conductor.
Iron Stand
Experiment®

+ S

rod Current Carrying

–

N Aluminium rod should lie

between the two poles
of magnet

Horse shoe magnet

140 X-Science
 We will observe that the rod will displace i.e. the rod will experience a force,
when it is placed in magnetic field, in a perpendicular direction to its length.
– The direction of the exert force will be reversed if the direction of current
through the conductor is reversed.
– If we change the direction of field by inter changing the two poles of the
magnet, again the direction of exert force will change.
– Therefore the direction of exerted force depends on
(1) direction of current
(2) direction of magnetic field lines.
15. Left Hand Fleming Rule
M other F ather C hild

(Force) ®
Motion Field Current
T humb Fore finger Middle finger
Thrust (force)
Three of them perpendicular to each other.

– According to this rule, stretch thumb, forefinger and middle finger

of your left hand such that they are mutually perpendicular to each
other.
If fore finger represent direction of magnetic field & middle finger
represent direction of current, then thumb will point in the direction
motion or force acting on the conductor.
– Functioning of electric motor is based on this rule. It convert electrical
energy into mechanical energy.
16. Michael Faraday– Gave the law of Electro magnetic Induction
17. Galvanometer® It is an instrument that can detect the presence of a current
in a circuit. If pointer is at zero (the centre of scale) the there will be no flow of
current.
If the pointer deflect on either side right or left, this will show the direction of
current. Represented by
o
G

141 X-Science
18. Electro Magnetic Induction – Can be explained by two experiments
(a) FIRST EXPERIMENT ®
“SELF INDUCTION”

N S
G G

In this experiment, when the north pole of bar magnet is brought closes to the
coil or away from the coil, we see momentary deflection in the needle of
galvanometer on either side of null point. First right and then left.
Similarly, if we keep the magnet stationary and coil is made to move towards
or away from the north pole of magnet. Again we will observe deflection in
the needle of galvanometer.
If both bar magnet and coil kept stationary, there will be no deflection in
galvanometer.
This experiment can also be done with the south pole of magnet, we will
observe the deflection in galvanometer, but it would be in opposite direction
to the previous case.
Þ It concludes that motion of magnet with respect to coil or vice-versa,
changes the magnetic field. Due to this change in magnetic field lines,
potential difference is induced in the same coil, which set up an induced
current in the circuit.
(b) SECOND EXPERIMENT – Mutual Induction
Primary Coil Secondary Coil

+ – G
Coil 1 Coil 2

In this experiment plug in the key that is connect coil with battery and observe
the deflection in galvanometer. Now plug out the key that is disconnect the
coil-1 from battery and observe the deflection in galvanometer, which will be
in reverse direction.
Hence, we conclude that potential difference is induced in secondary coil
(coil-2), whenever there is a change in current, in primary coil (coil-1) (by on
and off of key).

142 X-Science
 This is because, whenever there is change in current in primary coil
¯
Magnetic field associated with it also changes
¯
Now, magnetic field lines around the secondary coil (coil-2) will change and
induces the electric current in it (observed by the deflectionof needle of
Galvanometer in secondary circuit)
This process, by which changing of strength of current in primary coil,
induces a current in secondary coil is called Electromagnetic Induction”
The induced current is found to be highest when the direction of motion of coil
is at right angles to the magnetic field.
19. Fleming’s Right Hand Rule
(1) (2) (3)
M other F ather C hild

Motion Field Current

(movement of conductor) (Magnetic) (Induced)

Thumb Fore finger Middle finger

Three of them perpendicular to each other.
Rule can be defined at–
Stretch thumb , forefinger and middle finger of right hand, so that they
are perpendicular to each other. The forefinger indicates direction of magnetic
field, thumb shows the direction of motion of conductor, then the middle
finger will shows the direction of induced current.
Electrical generator is based on the principle of electro magnetic induction.
It convert mechanical energy into electrical energy.
Current

Alternate Current (AC) Direct Current (DC)

(1) Changes the direction Does not change its
periodically after equal direction with time it is
interval of time unidirectional

143 X-Science
 Current

I
I
(A)
(A) time
time (s)
(s)
It has frequency It has frequency
50Hz in India OHz
60 Hz in America

21. Advantages of Alternate Current (AC) over Direct Current (DC)

Electric power can be transmitted to longer distances without much loss of
energy. Therefore cost of transmission is low.
In India the frequency of AC is 50Hz. It means after every 1/100 second it
changes its direction.
22. Domestic Electric Circuits :–
In our homes, the electric power supplied is of potential difference V = 220V
and frequency 50Hz.
It consist of three wires :–
(1) Wire with red insulation cover – LIVE WIRE (POSITIVE)
Live wire is at high potential of 220V
(2) Wire with black insulation cover – NEUTRAL WIRE (NEGATIVE)
Neutral wire is at zero potential
Therefore, the potential difference between the two is 220V.
(3) Wire with Green insulation cover – EARTH WIRE
it is connected to a copper plate deep in the earth near house.
The metallic body of the appliances is connected with the earth wire as a
safety measure.
Function–
Earth wire provide a low resistance to the current hence any leakage of
current to the metallic body of the appliances, keep its potential equal to
that of earth. That means zero potential and the user is saved from severe
electric shock.

144 X-Science
23. Distribution Box
containing main
Earth wire switch & fuse
for each
current
Live wire
Ueutral wire

Electrical Electricity
Fuse board meter

Point to be noted in domestic circuit

(1) Each appliance has a seperate switch of ON/OFF
(2) In order to provide equal potential difference to each appliance, they should
be connected parallel to each other. So that they can be operated at any time.
One consist of current of 15A
for high power appliances
(3) We have two electric circuit in our home
Other circuit consist of current 5A
for low power appliances.

24. Short Circuiting –

Due to fault in the appliances or damage in the insulation of two wires, the
circuit will offer zero or negligible resistance to the flow of current. Due to
low resistance, large amount of current will flow.
I2) heat is produced in live wire
According to Joule’s law of heating effect (Ha
and produces spark, damaging the device and wiring.
25. Overloading–
Overloading can be caused by (1) Connecting too many appliances to a single
socket or (2) accidental rise in supply voltage if the total current drawn by the
appliances at a particular time exceeds the bearing capacity of that wire, it will
get heated up. This is known as overloading.
Fuse a safety device can prevent the circuit from overloading and short
circuiting.

145 X-Science
 EXERCISE
(Question Bank)
Very Short Answers (1 Mark)
1. What is the frequency of AC used in India?
2. Name the point where the iron filling are collected more?
3. Who discovered electro magnetic induction?
4. Why does a compass needle get deflected when brought near the bar
magnet?
5. If both the coil and the magnet are stationary, will there be deflection in
galvanometer?
6. Why magnetic field lines do not intersect each other?
7. What is the advantage of Alternate Current over Direct current?
8. What do you understand by short circuiting?
9. When the force experienced by a current carrying conductor placed in a
magnetic field is maximum?
10. Write the factors affecting the magnetic field due to a straight conductor?
Short Answers (2 Marks)
1. A charged particles enters at right angles into a uniform magnetic field. What
is the nature of charge particle, if it experiences a force in a direction pointing
vertically out of the page.
Magnetic field

Charge particle (use left hand flemings rule)

2. Name the Rule–
(1) Force experience by a current - carrying conductor placed in a
magnetic field.
(2) Direction of magnetic field lines associated with a current carrying
conductor.
(3) Direction of induced current in a coil due to its rotation in magnetic
field.

146 X-Science
3. What is solenoid? Where the magnetic field is uniform in solenoid?
4. Draw the pattern of magnetic field lines due to current carrying straight
conductor?
(5) Name two safety measures commonly used in electric circuit and
appliances?
(6) What is overloading?
Long Answer (5 Marks)
1. Explain the phenomenon of Electro magnetic Induction with the help of an
activity. Write its one application.
2. Draw the schematic diagram of domestic circuit. Write the colour and
function of Neutral wire, Live wire and Earth wire.

147 X-Science
 CHAPTER – 14
SOURCES OF ENERGY
Energy comes in different forms and one form can be converted to another.
?
For example if we drop a plate from a height, the potential energy of the plate
is converted mostly to sound energy when it hits the ground.
If we light a candle, the process is highly exothermic so that the chemical
?
energy of the wax is converted into heat energy and light energy on burning.
A Good Source of Energy would be one
§which has high calorific value
§be easily accessible
§be easy to store and transport
§be economical
SOURCES OF ENERGY

Conventional Source of Energy Non-Conventional Source of Energy

§
Fossil Fuels §
Solar Energy
Eg. Coal & Petroleum Eg. Solar Cooker, Solar Cell Panel
§Thermal Power Plant §Energy From the Sea
§Hydro Power Plants Eg. Tidal & wave energy, O.T.
Energy
§Bio-Mass® bio gas plant
§Geothermal Energy
§Wind Energy
§Nuclear Energy.

Amont the sources of energy, some of them get exhausted (Non-Renewable)

?
While some of them do not get exhausted, therefore called as Renewable
source of energy. Examples
1. Non Renewable source of energy®
Coal, Petroleum, Natural Gas
2. Renewable Source of energy®
Air, Water, Solar radiation, Geothermal
Energy, ocean waves etc.

148 X-Science
CONVENTIONAL SOURCE OF ENERGY
1. Fossil Fuels : Fuels developed from the fossils. Eg. Coal & Petroleum.
? Formed over million of years ago have only limited reserves
? These are non-renewable source of energy
? India has about 6% share in the world reserved coal, that may last 250 years
more at the present rate of consumption.
Disadvantages of Burning Fossil Fuels
? released oxides of Carbon, Nitrogen, Sulphur (acidic in nature) cause Air
pollution & Acid rain & green-house effect.

Bulb
Dynamo
Pressure
Cooker
Tennis Ball
Heat fitted with metal plate
(Fossil Fuel)

A Model of Thermo Electric Production.

This is our Turbine for generating electricity. Actually the steam/fluid impart
?
energy to rotor of turbine which can move shaft of the generator to produce
electricity. A very large amount of fossil fuels are burnt in Thermal Power
Plant to heat up water to produce steam.
Hydropower Plants Convert the Potential energy of falling water into
?
Electricity since there are few water-falls which could be used a source of
potential energy, hence this is the reason, a large number of DAMS are built
all over the world.
Around 25% of our country’s energy requirement is met by Hydro Power
?
Plants

149 X-Science
Dams are constructed to :
Prevent flooding of river, provide water for irrigation & to generate
?
hydroelectricity.
Disadvantages of construction of Big Dams
1. Submerging/Loss of large variety of Flora fauna and human settlements &
roting of submerged vegetation release green house gas (CH4).
2. They pose dangers of earthquakes, landslides etc.
3. Biomass is Agricultural & animal wastes that can be used as a fuel. Eg. of
Biomass – Firewood, cattle dung, sewage, dry leaves, stems & bagasse.
Normally biomass has low calorific value & produce lot of smoke when they
?
are burnt. Their efficiency as a good fuel has been increased tremendously
with the application of technology. For Eg. cowdung becomes efficient &
cheap good fuel in a Bio-gas plant.
Charcoal is better fuel than wood because it do not contain water & other
?
volatile material which are present in wood.
Limited
Wood Charcoal
Supply of O2
Charcoal burns without smoke, flames & has high calorific value.
Bio-gas is an excellent fuel & contain 75% of Methane (CH4). It burns
?
without smoke, leaves no reciters like ash, with high heat capacity.
Biogas is produced by anerobic decomposition of the slurry (cowdung +
?
water mixture) by microbes. This process is applied in a Bio gas plant.
Gas Outlet
SLURRY
Manure

Digestel

150 X-Science
The Biogas is stored in the gas tank from which they are drawn through pipes
?
for use in a Bio-gas plant
Bio gas is used for lighting, cooking in the rural areas. While the slurry left
?
behind is used as excellent manure, rich in nitrogen and phosphorous
The large scale use of Bio-wastes & sewage material provide a safe and
?
efficient method of waste-disposal besides supplying energy and manure.
WIND ENERGY
Unequal heating of the landmass and water bodies by solar radiation
?
generates air movement & causes winds to blow. This kinetic energy of the
wind can be used to do work.
This energy is utilised to lift water from the well & to generate electricity in
?
the wind mill.
Actually the rotatory motion of the windmill is used to turn the rotor of the turbine
which then generate electricity through Dynamo.
The output of a single windmill is quite small so a number of windmills are erected
over a large area - called wind energy farm.
India Ranked Fifth in the world in harnessing wind energy for the production of
electricity. It is estimated that nearly 45,000 MW of electric power can be
generated if India’s wind potential is fully exploited.
The minimum wind speed for wind mill to serve as a source of energy is
?
20KMPH.
Advantages of Wind Energy
1. Eco friendly
2. Efficient source of renewable energy.
3. No recurring expenses for production of electricity
Limitations of Wind Energy
1. Wind energy farms need large area of land
2. Difficulty in getting regular wind speed of 15-20 KmPH.
3. Initial cost of establishing wind energy farm is very high.
4. High level of maintenance of blades of wind mill.
Non Conventional Sources of Energy
Solar Energy :
The energy imitted by the sun in form of heat and light is called solar energy.

151 X-Science
 2
Solar Constant = 1.4kJ/s m
2
Outer edge of the earth receives solar energy equal to 1.4 kJ/sm which is known as
solar constant.
Solar energy devices :
A large number of devices that utilize solar energy directly like :
(i) Solar Cooker
(ii) Solar furnaces
(iii) Solar cells
(iv) Solar water heaters
Solar heating devices :
Use black painted surface because black surface absorbs more heat as
?
compared to white or other surface.
Use of glass plate because it allows shorter infrared radiations to pass through
?
it but doesn’t allow the longer wavelength infrared radiations to through it,
that results in increase in temperature.
Solar Cooker :
Box type solar Cooker
It consists of a rectangular box which is made up of material such as plastic or
?
wood.
Box is covered with black sheet and its inner walls are painted black to
?
increase heat absorption.
Solar cookers are covered with glass plate and have mirros to focus the rays of
?
the sun and achieve a higher temperature.

PLANE MIRROR

INNER METALLIC
BOX

GLASS COVER

BLACK CONTAINER

WOODEN BOX

SOLAR COOKER (Box Type)

152 X-Science
Advantages :
1. Use energy which is available in plenty (Solar Energy)
2. Is pollution free.
3. More than one food can be cooked simultaneously
Disadvantages :
1. Cannot be used for frying or baking purpose.
2. Food cannot be cooked at night or on a cloudy day.
3. Direction of reflector of solar heating has to be changed from time to time to
keep it facing the sun
Solar Cells :
? Solar cells are device that convert Solar energy into electricity.
? Develops a voltage of 0.5 – IV and can produce about 0.7W of electricity.
Advantages of Solar Cell
1. Require a little maintenance
2. Have no moving part.
3. No focussing device is required
4. Can be set up in remote areas.
5. Environment - friendly i.e. do not cause pollution.
Disadvantage of Solar Cells
1. It require high cost
2. Efficiency is low
3. Initial cost of installation is quite high.
Uses of Solar Cell
1. Used in calculators, watches etc.
2. Used in artificial satellites and space probes.
3. It is used in radio or wireless transmission system.
Solar Panel
A large number of Solar Cells connected to each other in an arrangement is called
solar panel.
Material used for making solar cells
? Silicon
Silver is used for inter connection of cells.

153 X-Science
 Energy from the Sea or Ocean
The energy from the sea is available in the following forms.
(i) Energy of sea waves
(ii) Tidal energy
(iii) Ocean Thermal Energy.
(i) Energy of Sea Waves
The waves are generated by the strong winds that blows across the sea.
?
The kinetic energy of this moving water rotates the turbine of a generator
?
Limitation
When strong winds stop blowing, the generator stops producing electricity
(iii) Tidal Energy
The tidal energy possessed by water during tides.
?
The tides are caused due to gravitational force of attraction exerted by the
?
moon on the water of the ocean.
This form of energy is harnessed by constructing a dam across a narrow
?
opening to the sea.
A turbine fixed at the opening of the dam converts tidal energy to electricity.
?
(iii) Ocean Thermal Energy
The power plants used to harness the ocean thermal energy is known as “Ocean
Thermal Energy Conversion plant) (OTEC)
Temperature difference between surface water and water at the depth of 2km
?
should be 20°C or more.
The warm surface water is used to boil ammonia (liquid)
?
The vapours of the liquid are used to run the turbine of generator.
?
The cold water (from deeper layers) is pumped up to condense the vapour into
?
liquid.
Geothermal Energy
1. Energy stored as heat inside the earth
2. The steam of underground water is taken out by sinking pipes through holes
drilled in the earth’s crust. The steam under high pressure is used to rotate the
turbines of the generator to produce electricity.

154 X-Science
 Nuclear Energy
Nuclear energy is the energy which is stored in the nucleus of an atom.
?
Nuclear energy is of two types
?

(i) Nuclear fission ® nucleus of a heavy atom (Uranium) when bombarded with
low energy neutron split (break down) into lighter nuclei and huge amount of
energy is released
(ii) Nuclear Fusion® When two lighter nucleic join up to form heavy nucleus
and tremendous amount of energy is released.
Nuclear fission process is utilized in nuclear reactors to produce electricity.
?
Major Nuclear power plants : Tarapur, Rana Pratap Sagar, Kalpakkam.
?
Advantages of Nuclear Energy :
1. Large amount of energy is released.
2. In nuclear power plant, the nuclear fuel is inserted once to get energy over a
long period of time.
Disadvantages of Nuclear Energy :
1. High cost of installation.
2. Environmental contamination may occur due to imporper nuclear waste
disposal.
Environmental Consequences
1. Energy sources should be used judiciously otherwise it would disturb the
environment.
2. Use of clean fuels like CNG (compressed natural gas) because burning of
fossil fuel causes green house effect.
3. Assembly of devices like solar cell (otherwise renewable source of energy)
would have caused environmental damage.
How long will energy source last
the sources of energy can be divided into two catagories :
(i) Renewable sources of energy eg wind, sun, biogas
(ii) Non renewable sources of energy eg. Coal, Petroleum, Natural Gas.
Continuous use of non renewable source of energy is a matter of concern because
ultimately the deposit of these sources will be completely finished on the other
hand renewable sources of energy will last forever eg sun as a source of energy will
be available for a very long period of time.

155 X-Science
 EXERCISE
(Question Bank)
Very Short Answers (1 Mark)
1. What is a good source of energy.
2. Expand CNG and LPG
3. What is the minimum wind velocity required to obtain useful energy with a
wind mill?
4. Name the main constituent of biogas.
5. Giv two examples of fossil fuels
6. Name the device which directly converts solar energy into electric energy.
7. What does “OTEC” stand for?
8. What is nuclear energy?
9. Which one out of these is renewable source of energy solar energy, coal,
petroleum, bio gas.
10. Which source of energy would you use to heat your food and why?
Short Answers (2 or 3Marks)
1. State two disadvantages of using fossil fuels as a source of energy.
2. Write two disadvantages of constructing high rising dams.
3. Give (i) two limitations and (ii) two advantages of wind mill.
4. Name any three forms of energy of the oceans which can be converted into
usable energy forms. Describes how it is done in each case.
5. Explain the working of biogas plant with the help of labelled diagram
6. Explain the principle on which the solar cooker works.
7. Write the advantages and disadvantages of using a solar cooker.
8. How does hydro electric power plant operate? Draw diagram
Long Answer Type Questions (5 Marks)
1. (a) Why is the solar cooker box covered with plane glass plate?
(b) Why is nuclear fission reaction considered better.
(c) Use of wood as a domestic fuel is not considered as good. State two
reasons for it
2. Distinguish between renewable and non renewable sources of energy?
Which one of them you consider as better? Why?

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 CHAPTER – 15
OUR ENVIRONMENT
Environment means everything which surrounds us. It may include living
?
(biotic) and non-living (abiotic) components. So, it may includes besides all
creatures, water & air also.
Environment affect the life and development of an organism in its natural
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habitat & vice a versa.
Substances that are decomposed are called bio-degredable. Eg. organic
?
wastes while some substances like plastics, some chemicals (DDTs &
fertilizers) are inert and can’t be decomposed, are called Non-biodegradable
Actually non-biodegradable persist in the environment for a long time or may
?
harm the various members of the eco system.
ECO SYSTEM & ITS COMPONENT
All the interacting organisms in an area together with non living components form
an ecosystem. So an ecosystem consists of both biotic (living creatures) and
abiotic components like temperature, rainfall, wind, soil etc.
Ecosystem

Man-made Ecosystem Natural Ecosystem

Eg. Cropland, Aquarium etc.

Aquatic Ecosystem Terrestrial Ecosystem

land Ecosystem
Eg. Forest,
Marine Fresh water Desert, Grassland etc.
Ecosystem Ecosystem
Eg. Sea, Oceans River, Lake,
Pond, pool

All living organisms are classified on the basis of the manner in which they
?
survive in the Ecosystem. These groups include
I Producers– All green plants, blue green algae can produce their food (Sugar
& starch) from in organic substance using light energy (Photosynthesis)

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II Consumers– Include organisms which depend on the producers either
directly or indirectly for their sustenance. In other word consumers consume
the food produced by producers.
CONSUMERS

Parasite
Herbivores Carnivores Live & feed Omnivores
– Gross eaters Flash Eaters on the host body Feed on both plant
and flesh.
Eg. Cow, dear Lion, Tiger Plasmodium Eg. Crow

III DECOMPOSERS– Fungi & Bacterias which break down (decompose) the
dead plant, animals complex compounds into the simpler one. Thus
decomposers help in the replenishment of the natural resources.
Food chain refers to an arrangement of different biotic groups in a sequence of
enery transfer. These biotic groups are producer herbivores, carnivores.
For Eg. T1 T2 T3
Grass DearA Lion
A 3-setp Food chain
In a food chain, these biotic components where transfer of energy takes place
?
is called a trophic level.
The green plants capture 1% of sunlight falls on their leaves.
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The flow of energy is unidirectional in a food chain
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There is gradual decrease in the amount of energy transfer from one trophic
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level to next trophic level in a food chain
Tertiary
consumers
1kJ
Secondary ­
Consumer 10kJ
Primary ­
Consumer 100kJ
Producer
­
Energy Flow 1000 kJ TROPHIC LEVEL
Energy

So only 10% of Energy is transferred to next trophic level while 90% of energy is
used by present trophic level in its life processes.

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While the conc. of harmful chemical increases with every next trophic level in
?
a food chain. It is called Bio-magnification For Eg.
Grass Dear Lion
(10 ppm) (200 ppm) (5000ppm)
DDT DDT DDT
Maximum concentration of such chemicals accumulated in human bodies.
?
Naturally the food chains are inter-connected with each other forming a web
?
like pattern, which is known as FOOD WEB.
The loss of energy at each step (trophic level) is very high, so very little
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amount of energy remains after four trophic levels.
There are gnerally a big population at lower trophic levels of an ecosystem.
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For Eg. the population of the producer is higher than the consumer carnivore
(lion) population.
ENVIRONMENTAL PROBLEMS
Changes in environment affect us and our activities change the environment
?
around us. This led to the slow degreadation of environment that arose many
environmental problems. Eg. depletion of the Ozone Layer and waste
disposal.
I Depletion of Ozone Layer
Ozone (O3) layer is largely found in the stratosphere which is a part of our
?
atmosphere from 12 km – 50km above sea level.
Ozone is a deadly poison at the ground level.
?
Ozone is formed as a result of a following photochemical reaction.
?

O2 hv O+O (Splitting of
(1800°A to 2000°A) molecular oxygen)
O2 + O O3 (Ozone)

Ozone layer is a protective blanket around earth which absorbs most of the
?
harmful U.V. (Ultraviolet) radiation of the Sun, thus protecting the living
beings of the earth from health hazards like skin cancer, cataract in eyes,
weaken immune system, destruction of plants etc.
The decline of Ozone layer thickness is Antartica was first discovered in 1985
?
and was termed as OZONE HOLE.

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Reason of Ozone Depletion :
Excessive use of CFCs (Chloro Flouro Carbon) a synthetic, inert chemical Eg.
Freon which are used as refrigerants and in fire extinguishers, caused Ozone
depletion in the upper atmosphere. A single chlorine atom can destroys 1,00,000
Ozone molecules. U.N.E.P. (United Nation Envrionment Programme) did an
excellent job in forging an agreement to freeze CFC production at 1986 levels
(KYOTO Protocol) by all countries.
Garbage Disposal
Industrialization and rise in demand of consumer goods have created a major
problem in the form of wastes/garbage accumulation and its disposal especially in
urban area.
The different methods of solid wastes disposal commonly used around the world
are.
1. Open dumping : A conventional method in which solid wastes dumped in
selected areas of a town. It actually cause pollution
2. Land fillings : Wastes are dumped in low living area and are compacted by
rolling with bulldozers
3. Composting : Organic wastes are filled into a compost pit (2m x 1m x 1m). It
is then covered with a thin layer of soil. After about three months the same
garbage filled inside the pit changes into organic manure.
4. Recycling : The solid wastes is broken down into its constituent simpler
materials. These materials are then used to make new items. Even non-bio
degradable solid wastes like plastic, metal can be recycled.
5 Reuse : A very simple conventional technique of using an item again & again.
For Eg. paper can be reused for making envelops etc.

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 EXERCISE
(Question Bank)
Very Short Answers (1 Mark)
1. Define Biomagnification
2. Expand the term CFC & U.N.E.P.
3. Define Ozone hole
4. Which of the following is/are Biodegradable plastic cups, cowdung,
Aluminium foil, cotton.
5. Define food web
6. Define Ecosystem
7. Differentiate between Biodegradable and non biodegradable wastes.
8. Use of Kulhads was not environment friendly idea. Why?
9. Draw an Energy Pyramid showing different trophic level.
10. What is the advantage of disposable paper cup use over plastic cups?
11. How can we help in reducing the the problem of waste disposal? Give any
two methods.
12. What is role of decomposer in Ecosystem.
13. Give any two ways in which non biodegradable substance would affect the
environment.
14. What are trophic levels? Give an example of a food chain and state the
different trophic levels in it.
15. What will happen if we kill all the organisms in one trophic level?
16. Study the food chain given below.
I Grass ®
Grasshopper ®
Frog
II Wheat ®
Rat ®
Snake ®
Hawk
Which of the two consumers frog/hawk will get more available energy and why?

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 CHAPTER – 16
MANAGEMENT OF NATURAL
RESOURCES
Natural Resources
? Resources provided to us by nature
Soil, air, water, forests
wildlife, coal and petroleum are used by man for his survival.
?
Management of natural resources is needed for conservation of natural
resources.
There are national and international laws and Acts to protect the environment.
?
Ganga Action Plan : Multi Crore Project came in 1985 to improve the quality
?
of Ganga
Accordingly a survey was conducted and a data was collected of total
?
coliform ( a group of bacteria found in human intestine) between 1993-1994
which was as below
1993-94 Total Coliform (MPN/100ml)

Minimum found Minimum desired level Maximum found in Kannauj

in Rishikesh 450MPN/100ml 1400MPN/100ml
600-650MPN/100ml

MPN ®
? Most probable number.
National Award for wildlife conservation – In the memory Amrita Devi
?
Bishnoi who lost her life in the protection of Khejri trees in Rajasthan
alongwith 363 other people.
Chipko Andolan – Movement originated in Garhwal in early 1970S that was
?
the result of a grassroot level effort to end the alienation of people from their
forest.
Protection of Sal forest in West Bengal in 1972.
?
Three R’s to save the environment
?

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 Reduce means use less Recycle Reuse
Save the resource Segregate the waste that use the things again
by not wasting them can be recycled and use to make and gain.
required things.

Reuse is better than recycling as it saves energy.

?
Management of Natural Resources is necessary so that these may last for the
?
generations to come and are not exploited for short term gains. Also see the
damage they cause to the environment when they are used or mixed.
Forest and wild life conservation – Forests are biodiversity hot spots
?
Biodiversity of an area is the number of species of different life forms like
bacteria, fungi, powering plants insects, birds etc.
Hotspot means an area full of biological diversity.
?
– loss of diversity may lead to a loss of ecological stability/ecological
imbalance
Stake holders
A person having interest or concern for some thing called as stake holder.
Stakeholders : their dependence on forests

Local People Forest Department Industrialists Wild life

(dependent on (Govt. who owns (Who use various enthusiasts
forests for their the land and controls forest products) (who want to
survival) resources conserve nature)

Sustainable management – Management of forest resources Wisely to make it

?
available for future generations.
Water as a Resource
?
Water is a basic necessity for all terrestrial forms of life.
?
Regions of water scarcity are closely correlated to the regions of acute
?
poverty.
Failure to sustain water availability has resulted in loss of vegetation cover,
?
diversion for high water demanding crops and pollution from industries and
urban wastes and less rain.
Irrigation methods like dams, tanks and coals have been used in various part
?
of India.
Dams
?
Advantages of Dams – Ensures of adequate water for irrigation.
?

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Generate electricity.
?
Continuous supply of water in regions.
?
Disadvantages :
?
No equitable distribution of water.
?
Large no. of people displaced without compensation.
?
Involves huge amount of Public money without giving proper benefits.
?
Causes deforestation and loss of biological diversity.
?
Water Harvesting – Aim is to develop primary resources of land and water
?
and to produce secondary resources of plants and animals for use in a manner
which will not cause ecological imbalance.
? Various ancient methods of water harvesting
? Method State
Khadin, tanks, nadis Rajasthan
Bandharas, tals Maharasthra
Bundhis Madhya Pradesh and U.P.
Pyhes Bihar
Kulhs Himachal Pradesh
Ponds Jammu Region
Eris (tanks) Tamilnadu
Bawlis – old method of water harvesting in Delhi and near by region.
? These techniques are locale specific to ensure the mismanagement and
over-exploitation of these resources
? Advantages of Khadin System :
– Water does no evaporate
– Recharge wells and moisture for vegetation.
– does no provide breeding ground for mosquito
– Ground water is protected from human and animal waste.
Coal and Petroleum
? Generally called fossil fuel.
? Formed from the disintegration of bio-mass millions of years ago.
? They will get exhausted in the future no matter how carefully we use them.
? Petroleum will last us for about 40 years and the coal resources will last for
another two hundred years.
? These contain hydrogen, nitrogen and sulphur.
? Why to use fossil fuels judiciously?
– By using public transport enstead of private one, by using C.F.L. tubes, by
using stairs instead of lift, by saving electricity as much as possible.

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 EXERCISE
(Question Bank)
Very Short Answers (1 Mark)
1. Why is it necessary to conserve our environment?
2. Define sustainable development
3. Name any two exhaustible resources
4. What is the most conductive PH range for the life of fresh water plants?
5. List two advantages of water harvesting.
6. Why reuse is better than recycle?
7. What are Dhadin? Where there found?
8. List two steps you would take to conserve electricity in your house.
9. Who are called stake holders?
10. Name some traditional water harvesting systems in India.
Short Answers (2 Marks)
1. How mining is a cause of pollution?
2. Make a list of four forests products that we use.
3. How burning of fossil fuels is effecting our environment?
4. Suggest two weasures for controlling CO2 levels in atmosphere.
5. Why should we conserve forest and wild life?
(3 Marks)
1. What are three main problems from dams?
2. How can you reduce energy consumption at your level. Suggest at least three
points.
3. Explain the maximum of ‘Reduce’, ‘Recycle’ and ‘Reuse’ in your own
words.
(5 Marks)
1. What is the main objective of water harvesting techniques? Name & ancient
water harvesting structures used in India. Mention 3 causes for failure to
sustain water availability under ground?
2. Discuss the damage caused to forest by the following activities:
(a) Building rest houses for 10% tourists in national parks.
(b) Grazing domestic animals on National Parks.
(c) Tourists throwing plastic bottles, covers and other litter in National
Parks.

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