NCERT SOLUTIONS CLASS 7 SCIENCE

NCERT Solutions for Class 7 Science is provided here. Students can download the complete NCERT Solutions for Class 7 Science here. This page provides the complete solution for all Chapters of Class 7 Science. Download the NCERT Solutions for Class 7 Science PDF for free on this page. Get the solutions for all chapters and exercises of Class 7 Science.

Last modified:2019-10-19

Chapter 1 - Nutrition in Plants

Question 1

Why do organisms need to take food?

Answer

All organisms need to take food to get energy for the growth, development and maintenance of their bodies.

 

Question 2

Distinguish between a parasite and a saprotroph.

Answer

Parasite

Saprotroph

Organisms derive nutrition from the body of other living organisms (host) are parasites.

Plants which derive nutrition from dead and decaying organisms are called saprotrophs.

Example: Cuscuta (Amar bel)

Example: Mushrooms

 

Question 3

How would you test the presence of starch in leaves?

Answer

  • Take a potted plant with variegated leaves — for example, money plant or crotons.
  • Keep the plant in a dark room for three days so that all the starch gets used up.
  • Now select a leaf cover its portion with a black strip paper and keep the plant in sunlight for about six hours.
  • Pluck the leaf from the plant.
  • Mark the uncovered area in it and trace them on a sheet of paper.
  • Dip the leaf in boiling water for a few minutes.
  • After this, immerse it in a beaker containing alcohol.
  • Carefully place the above beaker in a water-bath and heat till the alcohol begins to boil.
  • Now dip the leaf in a dilute solution of iodine for a few minutes.
  • Take out the leaf and rinse off the iodine solution.
  • You observe that the presence of starch in various areas of the leaf which was uncovered.

 

Question 4

Give a brief description of the process of synthesis of food in green plants.

Answer

Leaves are the food factories of plants. The synthesis of food in plants occurs in leaves. Therefore, all the raw materials (Water, Carbon dioxide and sunlight) must reach there. Water and minerals are transported to the leaves by the vessels which run like pipes throughout the root, the stem, the branches and the leaves. The leaves have a green pigment called chlorophyll which helps leaves to capture the energy of the sunlight. This energy is used to synthesise (prepare) food from carbon dioxide and water.

 

Question 5

Show with the help of a sketch that the plants are the ultimate source

of food.

Answer

 

 

Question 6

Fill in the blanks:

(a) Green plants are called _________________ since they synthesise their own food.

(b) The food synthesised by the plants is stored as _________________.

(c) In photosynthesis solar energy is captured by the pigment called ___________.

(d) During photosynthesis plants take in ______________________ and release __________________.

Answer

(a) autotrophs

(b) starch

(c) chlorophyll

(d) carbon dioxide, oxygen

 

Question 7

Name the following:

(i) A parasitic plant with yellow, slender and tubular stem.

(ii) A plant that has both autotrophic and heterotrophic mode of nutrition.

(iii) The pores through which leaves exchange gases.

Answer

(i) cuscuta (ii) Insectivorous plant (iii) Stomata

 

Question 8

Tick the correct answer:

(a) Amarbel is an example of:

(i) autotroph (ii) parasite (iii) saprotroph (iv) host

(b) The plant which traps and feeds on insects is:

(i) Cuscuta (ii) china rose (iv) pitcher plant (iv) rose

Answer

(a) (ii) Parasite (b) (iii) Pitcher plant

 

Question 9

Match the items given in Column I with those in Column II:

 

Column I

Column II

Chlorophyll

Bacteria

Nitrogen

Heterotrophs

Amarbel

Pitcher plant

Animals

Leaf

Insects

Parasite

Answer

 

Column I

Column II

Chlorophyll

Leaf

Nitrogen

Bacteria

Amarbel

Parasite

Animals

Heterotrophs

Insects

Pitcher Plant

 

Question 10

Mark ‘T’ if the statement is true and ‘F’ if it is false:

(i) Carbon dioxide is released during photosynthesis. (T/F)

(ii) Plants which synthesise their food themselves are called saprotrophs. (T/F)

(iii) The product of photosynthesis is not a protein. (T/F)

(iv) Solar energy is converted into chemical energy during photosynthesis. (T/F)

Answer

(i) False

(ii) False

(iii) True

(iv) True

 

Question 11

Choose the correct option from the following:

Which part of the plant takes in carbon dioxide from the air for photosynthesis?

(i) Root hair (ii) Stomata (iii) Leaf veins (iv) Sepals

Answer

(ii) Stomata

 

Question 12

Choose the correct option from the following:

Plants take carbon dioxide from the atmosphere mainly through their:

(i) roots (ii) stem (iii) flowers (iv) leaves

Answer

(iv) Leaves

 

 

Chapter 2 - Nutrition in Animals

Question 1

1. Fill in the blanks:

(a) The main steps of nutrition in humans are __________, __________, __________, _________ and __________.

(c) The stomach releases hydrochloric acid and ___________ juices which act on food.

(d) The inner wall of the small intestine has many finger-like outgrowths

called _________.

(e) Amoeba digests its food in the ____________ .

Answer

(a) ingestion, digestion, absorption, assimilation, egestion

(b) Liver

(c) digestive

(d) villi

(e) food vacuole

 

Question 2

Mark "T" if the statement is true and "F" if it is false:

(a) Digestion of starch starts in the stomach. (T/F)

(b) The tongue helps in mixing food with saliva. (T/F)

(c) The gall bladder temporarily stores bile. (T/F)

(d) The ruminants bring back swallowed grass into their mouth and chew it for some time. (T/F)

Answer

(a) False

(b) True

(c) True

(d) True

Question 3

Tick () mark the correct answer in each of the following:

(a) Fat is completely digested in the __________.

(i) stomach (ii) mouth (iii) small intestine (iv) large intestine

(b) The largest gland in the human body is __________.

(i) stomach (ii) food pipe (iii) small intestine (iv) large intestine

Answer

(a) (iii) Small Intestine

(b) (iv) Large Intestine

Question 4

 

Match the items given in Column I with those in Column II:

Column I

Column II

Food Components

Product (s) of Digestion

Carbohydrates

Fatty Acids and Glycerol

Proteins

Sugar

Fats

Amino Acids

Answer

Column I

Column II

Food Components

Product (s) of Digestion

Carbohydrates

Sugar

Proteins

Amino Acids

Fats

Fatty Acids and Glycerol

 

Question 5

What are villi? What is their location and function?

Answer

The finger like projections in the inner walls of the small intestine is called villi. These are found in small intestine.

Function: The villi increase the surface area for absorption of the digested food

 

Question 6

Where is the bile produced? Which component of the food does it help to digest?

Answer

Bile is produced in liver. The bile juice stored in sac called the gallbladder. It helps in the digestion of fats.

 

Question 7

Name the type of carbohydrate that can be digested by ruminants but not by humAnswer Give the reason also.

Answer

Cellulose is the carbohydrate that can be digested by ruminants. Ruminants have large sac like structure between the small intestine and large intestine. The cellulose of the food is digested by the action of certain bacteria which are not present in humAnswer

 

Question 8

Why do we get instant energy from glucose?

Answer

Because it easily breaks down in the cell with the help of oxygen which provides instant energy to the organism. Glucose does not need digestion, it is directly absorbed into the blood.

 

Question 9

Which part of the digestive canal is involved in:

(i) Absorption of food ________ .

(ii) Chewing of food ________ .

(iii) Killing of bacteria ________ .

(iv) Complete digestion of food ________ .

(v) Formation of faeces ________ .

Answer

(i) Small intestine (ii) Mouth (iii) Stomach (iv) Small intestine (v) Large intestine

 

Question 10

Write one similarity and one difference between the nutrition in amoeba and human beings.

Answer

Similarity: The digestive juices in amoeba are secreted into food vacuole and in human beings the digestive juices are secreted in stomach and small intestine. Then the juices convert complex food into simpler soluble and absorbable substances.

Difference: Amoeba captures the food with help of pseudopodia and engulf it. In human beings food is taken by the mouth.

 

Question 11

Match the items of Column I with suitable items in Column II.

 

 

Column I

Column II

(a) Salivary Gland

(i) Bile Juice Secretion

(b) Stomach

(ii) Storage of undigested food

(c) Liver

(iii) Saliva Secretion

(d) Rectum

(iv) Acid release

(e) Small Intestine

(v) Digestion is completed

(f) Large Intestine

(vi) Absorption of water

 

(vii) Release of Faeces

 

Answer

 

Column I

Column II

(a) Salivary Gland

(iii) Saliva Secretion

(b) Stomach

(iv) Acid release

(c) Liver

(i) Bile Juice Secretion

(d) Rectum

(ii) Storage of undigested food, faeces

(e) Small Intestine

(v) Digestion is completed

(f) Large Intestine

(vi) Absorption of water

 

Question 11

Label Fig. 2.11 of the digestive system.

Answer

 

Question 12

Can we survive only on raw, leafy vegetables/grass? Discuss.

Answer

We know that the animals, fungi, bacteria, non-green plants and human being do not have the ability to make their own food. They depend on autotrophs for their food directly or indirectly. The green plant (leafy vegetables/grass) trap solar energy and make their own food in the form of glucose. So, we can say that leafy vegetables and grass can provide sufficient energy to help us survive.

 

 

Chapter 3 - Fibre to Fabric

 

Question 1

You must be familiar with the following nursery rhymes:

(i) ‘Baa baa black sheep, have you any Wool.’

(ii) ‘Mary had a little lamb, whose fleece was white as snow.’

Answer the following:

(a) Which parts of the black sheep have wool?

(b) What is meant by the white fleece of the lamb?

Answer

(a) The hairy skin called fleece has wool in black sheep.

(b) White fleece of the lamb means the white coloured hairy skin.

 

Question 2

The silkworm is (a) a caterpillar (b) a larva. Choose the correct option.

(i) (a) (ii) (b) (iii) both (a) and (b) (iv) neither (a) nor (b)

Answer

(iii) both (a) and (b).

 

Question 3

Which of the following does not yield wool?

(i) Yak (ii) Camel (iii) Goat (iv) Woolly dog

Answer

(iv) Woolly dog

 

Question 4

What is meant by the following terms?

(i) Rearing (ii) Shearing (iii) Sericulture

Answer

(i) Rearing: The process of keeping, feeding, breeding and medical care of useful animals is called rearing of animals. These animals produce one or more useful products for human beings.

(ii) Shearing: The process of removing the fleece of the sheep along with thin layer of skin is called shearing.

(iii) Sericulture: The rearing of silkworms for obtaining silk is called sericulture.

 

Question 5

Given below is a sequence of steps in the processing of wool. Which are the missing steps? Add them.

Shearing, ________ , sorting,________, __________

Answer

Shearing, scouring, sorting, picking out of burrs, colouring, rolling.

 

Question 6

Make sketches of the two stages in the life history of the silk moth which are directly related to the production of silk.

Answer

 

Question 7

Out of the following, which are the two terms related to silk production? Sericulture, floriculture, moriculture, apiculture and silviculture.

Hints: (i) Silk production involves cultivation of mulberry leaves and rearing silkworms. (ii) Scientific name of mulberry is Morus alba.

Answer

(i) Sericulture (ii) Moriculture

 

Question 8

Match the words of Column I with those given in Column II:

 

Column I

Column II

(1) Scouring

(a) Yields Silk fibres

(2) Mulberry Leaves

(b) Wool yielding animal

(3) Yak

(c) Food of Silkworm

(4) Cocoon

(d) Reeling

 

(e) Cleaning sheared skin

 

Answer

 

Column I

Column II

(1) Scouring

(e) Cleaning sheared skin

(2) Mulberry Leaves

(c) Food of Silkworm

(3) Yak

(b) Wool yielding animal

(4) Cocoon

(a) Yields Silk fibres

 

Question 9

Given below is a crossword puzzle based on this lesson. Use hints to fill in the blank spaces with letters that complete the words.

Down                                                   Across

(D) 1 : Thorough washing                 (A) 1 : Keeps warm

      2 : Animal fibre                                  2 : Its leaves are eaten by silkworms

      3 : Long thread like structure           3 : Hatches from egg of moth

Answer

Image

Image

 

Chapter 4 - Heat

 

Question 1

State similarities and differences between the laboratory thermometer and the clinical thermometer.

Answer

Similarities:

(i) Both clinical and laboratory thermometers have long, narrow, uniform glass tubes.

(ii) The bulbs of both the thermometers have mercury in them.

Differences:

(i) The temperature range of clinical thermometers is from 350C to 420C while that of laboratory thermometer is from —100C to 1100C.

(ii) Clinical thermometer is used to measure the temperature of a human body. However, laboratory thermometer cannot be used to measure the temperature of a human body.

(iii) The least count of both the thermometers differs.

(iv) Unlike clinical thermometer that can be tilted, laboratory thermometer is kept upright while reading the temperature values.

 

Question 2

Give two examples each of conductors and insulators of heat.

Answer

Two examples of conductors of heat are:

(i) Aluminium

(ii) Iron

Two examples of insulators of heat are:

(i) Wood

(ii) Plastic

 

Question 3

Fill in the blanks :

(a) The hotness of an object is determined by its __________.

(b) Temperature of boiling water cannot be measured by a _____________ thermometer.

(c) Temperature is measured in degree ______________.

(d) No medium is required for transfer of heat by the process of __________.

(e) A cold steel spoon is dipped in a cup of hot milk. It transfers heat to its other end by the process of ______________.

(f ) Clothes of ______________ colours absorb heat better than clothes of light colours.

Answer

(a) temperature

(b) Clinical

(c) Celsius

(d) radiation

(e) Conduction

(f) dark

 

Question 4

Match the following :

 

(i) Land breeze blows during

(a) summer

(ii) Sea breeze blows during

(b) winter

(iii) Dark coloured clothes are preferred during

(c) day

(iv) Light coloured clothes are preferred during

(d) night

 

Answer

 

(i) Land breeze blows during

(a) Night

(ii) Sea breeze blows during

(b) Day

(iii) Dark coloured clothes are preferred during

(c) Winter

(iv) Light coloured clothes are preferred during

(d) Summer

 

Question 5

Discuss why wearing more layers of clothing during winter keeps us warmer than wearing just one thick piece of clothing.

Answer

More layers of clothing keep us warm in winters as they have a lot of space between them. This space gets filled up with air. Air is a bad conductor, it does not allow the body heat to escape out.

 

Question 6

Look at Fig. 4.13. Mark where the heat is being transferred by conduction, by convection and by radiation.

Answer

 

(i) Transfer of heat from hot plate to pan is by conduction.

(ii) Transfer of heat within water is by convection.

(iii) Transfer of heat from hot bodies like pan, plate, burner etc. to the surroundings is by radiation.

 

Concept insight: There are three methods of heat transfer - conduction, convection and radiation. Conduction and convection need material medium but radiation does not need any material medium.

 

Question 7

In places of hot climate it is advised that the outer walls of houses be painted white. Explain.

Answer

In places of hot climate, it is advised to paint the outer walls of houses as white because a light colour such as white reflects back most of the heat that falls on it. We can say that it absorbs less amount of heat and keeps the house cool.

 

Concept insight: White colour is a poor absorber of heat and very good reflector of heat.

 

Question 8

One litre of water at 30°C is mixed with one litre of water at 50°C. The temperature of the mixture will be

(a) 80°C (b) more than 50°C but less than 80°C

(c) 20°C (d) between 30°C and 50°C

Answer

(d) The temperature of the mixture will be between 30°C and 50°C.

 

Concept insight: Heat gained by cold water will be equal to the lost by hot water such that the final temperature of the mixture will be between 30°C and 50°C.

 

Question 9

An iron ball at 40°C is dropped in a mug containing water at 40°C.

The heat will

(a) flow from iron ball to water.

(b) not flow from iron ball to water or from water to iron ball.

(c) flow from water to iron ball.

(d) increase the temperature of both.

Answer

(b) The heat will not flow from iron ball to water or from water to iron ball as both the substances have same temperature.

 

Concept insight: Heat flow takes place from a hot body to a cold body. As both water and iron ball have the same temperature, so there is no temperature difference between the two for heat flow to take place.

 

Question 10

A wooden spoon is dipped in a cup of ice cream. Its other end

(a) becomes cold by the process of conduction.

(b) becomes cold by the process of convection.

(c) becomes cold by the process of radiation.

(d) does not become cold.

Answer

(d) Its other end does not become cold as wood is a bad conductor of heat.

Concept insight: A bad conductor does allow heat to pass through it.

 

Question 11

Stainless steel pans are usually provided with copper bottoms. The reason for this could be that

(a) copper bottom makes the pan more durable.

(b) such pans appear colourful.

(c) copper is a better conductor of heat than the stainless steel.

(d) copper is easier to clean than the stainless steel.

Answer

(c) The reason for this is that copper is a better conductor of heat than stainless steel.

 

Concept insight: As copper is better conductor of heat than stainless steel so the heat from the flame is transferred quickly and more effectively through the copper bottom to the contents of the pan.

 

 

Chapter 5 - Acids, Bases and Salts

Question 1

State differences between acids and bases.

Answer

 

Acids

Bases

These are sour to taste

These are bitter to taste

Acids turn blue litmus red

Bases do not change the colour of blue litmus

Acids do not change the colour of red litmus

Bases turn red litmus blue

 

 

With china rose indicator, these give dark pink colour

Bases give green colour with china rose indicator

Acids do not change the colour of turmeric indicator

Bases turn the colour of turmeric indicator to red

 

Question 2

Ammonia is found in many household products, such as window cleaners. It turns red litmus blue. What is its nature?

Answer

Ammonia is basic in nature as it turns the colour of red litmus paper to blue.

Question 3

Name the source from which litmus solution is obtained. What is the use of this solution?

Answer

Litmus solution is obtained from lichens. A natural dye extracted from lichens is dissolved in distilled water to obtain litmus solution. It is used as an indicator to distinguish between acids and bases.

 

Solution

Colour of litmus Solution

Acidic

Red

Basic

Blue

Neutral

No Change

 

Question 4

Is the distilled water acidic/basic/neutral? How would you verify it?

Answer

Distilled water is neutral in nature. The same can be verified by using red and blue litmus papers. Neither will show a colour change with distilled water. This proves that distilled water is neutral.

Question 5

Describe the process of neutralisation with the help of an example.

Answer

The reaction between an acid and a base is known as neutralisation. Salt and water are produced in this process with the evolution of heat.

Antacids like milk of magnesia (magnesium hydroxide), baking soda, etc. which contain a base are used for reducing acidity in stomach when excessive acid released by glands.

 

Question 6

Mark ‘T’ if the statement is true and ‘F’ if it is false:

(i) Nitric acid turn red litmus blue. (T/F)

(ii) Sodium hydroxide turns blue litmus red. (T/F)

(iii) Sodium hydroxide and hydrochloric acid neutralise each other and

form salt and water. (T/F)

(iv) Indicator is a substance which shows different colours in acidic

and basic solutions. (T/F)

(v) Tooth decay is caused by the presence of a base. (T/F)

Answer

(i) Nitric acid turns red litmus blue. (F)

(ii) Sodium hydroxide turns blue litmus red. (F)

(iii) Sodium hydroxide and hydrochloric acid neutralise each other and form salt and water. (T)

(iv) Indicator is a substance which shows different colours in acidic and basic solutions. (T)

(v) Tooth decay is caused by the presence of a base. (F)

Question 7

Dorji has a few bottles of soft drink in his restaurant. But, unfortunately, these are not labelled. He has to serve the drinks on the demand of customers. One customer wants acidic drink, another wants basic and third one wants neutral drink. How will Dorji decide which drink is to be served to whom?

Answer

Since the drinks are edible, Dorji can take the decision by tasting the drinks. Acidic drinks will be sour to taste whereas basic drinks will be bitter to taste and neutral drinks will have no taste. If Dorji has litmus indicator (solution or paper), then he can take its help. He should put one drop of each drink on blue litmus paper. If the colour of the litmus paper changes to red, then it is an acidic drink. Out of the remaining drinks, some are basic and some are neutral. Again, he should put one drop of the remaining drinks on red litmus paper. If the colour changes to blue, then it is basic and the others are neutral. In this way, he can serve all the three customers their respective drinks.

Question 8

Explain why:

(a) An antacid tablet is taken when you suffer from acidity.

(b) Calamine solution is applied on the skin when an ant bites.

(c) Factory waste is neutralised before disposing it into the water bodies.

Answer

(a) This is because during acidity, an excess of acids is produced in the stomach. An antacid contains base, such as milk of magnesia. These bases react with excess of acids and neutralize their effect, thus giving us relief.

(b) When an ant bites, it injects formic acid into the skin. Calamine solution contains zinc carbonate which is basic in nature. Therefore, it is applied on the skin to neutralize the effect of formic acid.

(c) Factory wastes contain acids. Therefore, these wastes, when thrown directly to water bodies, harm aquatic lives. Hence, these wastes are neutralised with basic chemicals before disposing to water bodies.

Question 9

Three liquids are given to you. One is hydrochloric acid, another is sodium hydroxide and third is a sugar solution. How will you identify them? You have only turmeric indicator.

Answer

Name of the substances Effect on turmeric indicator

1. Hydrochloric acid - Yellow to blue

2. Sodium hydroxide - Yellow to red

3. Sugar solution - No change

 

 

Question 10

Blue litmus paper is dipped in a solution. It remains blue. What is the nature of the solution? Explain.

Answer

We know that basic and neutral solutions do not change the colour of blue litmus paper. Since blue litmus remains blue after dipping in the solution, the solution is either basic or neutral in nature. Put a drop of this solution on a red litmus paper. If it turns blue, then the above solution is basic in nature and if no colour change occurs, then it is neutral.

 

Question 11

Consider the following statements:

(a) Both acids and bases change colour of all indicators.

(b) If an indicator gives a colour change with an acid, it does not give a change with a base.

(c) If an indicator changes colour with a base, it does not change colour with an acid.

(d) Change of colour in an acid and a base depends on the type of the indicator.

Which of these statements are correct?

(i) All four (ii) a and d (iii) b and c (iv) only d

Answer

(iv) Only d

 

Chapter 6 - Physical and Chemical Changes

Question 1

Classify the changes involved in the following processes as physical or chemical changes:

(a) Photosynthesis

(b) Dissolving sugar in water

(c) Burning of coal

(d) Melting of wax

(e) Beating aluminium to make aluminium foil

(f) Digestion of food

 

Answer

(a) Chemical change

(b) Physical change

(c) Chemical change

(d) Physical change

(e) Physical change

(f) Chemical change

 

Question 2

(a) Cutting a log of wood into pieces is a chemical change. (True/ False)

(b) Formation of manure from leaves is a physical change. (True/ False)

(c) Iron pipes coated with zinc do not get rusted easily. (True/ False)

(d) Iron and rust are the same substances. (True/ False)

(e) Condensation of steam is not a chemical change. (True/ False)

Answer

(a) False

(b) False

(c) True

(d) False

(e) True

 

Question 3

Fill in the blanks in the following statements:

(a) When carbon dioxide is passed through lime water, it turns milky due to the formation of _________.

(b) The chemical name of baking soda is _________.

(c) Two methods by which rusting of iron can be prevented are _________ and _________.

(d) Changes in which only _________ properties of a substance change are called physical changes.

(e) Changes in which new substances are formed are called _________ changes.

Answer

(a) Calcium carbonate

(b) Sodium hydrogen carbonate

(c) painting or greasing, galvanisation

(d) physical

(e) chemical

 

Question 4

When baking soda is mixed with lemon juice, bubbles are formed with the evolution of a gas. What type of change is it? Explain.

Answer

The reaction between baking soda and lemon juice can be given as below:

Lemon juice + Baking soda ———> C02 (bubbles) + Other substances

(Citric acid)                                    (Sodium hydrogen carbonate)  (Carbon dioxide)

 

It is a chemical change

 

Question 5

When a candle burns, both physical and chemical changes take place. Identify these changes. Give another example of a familiar process in which both the chemical and physical changes take place.

Answer

When a candle burns, both physical and chemical changes occur:

(i) Physical change: melting of wax, vapourisation of melted wax.

(ii) Chemical change: Burning of vapours of wax to give carbon dioxide, heat and light.

LPG is another example in which physical change occurs when LPG comes out of cylinder and is converted from liquid to gaseous state and a chemical change occurs when gas burns in air.

 

Question 6

How would you show that setting of curd is a chemical change?

Answer

We can say that setting of curd is a chemical change because we can not get the original substance, i.e., milk back and a new substance is formed with different taste, smell and other chemical properties.

 

Question 7

Explain why burning of wood and cutting it into small pieces are considered as two different types of changes.

Answer

Burning of wood is a chemical change because in burning new substances are formed as

Wood + Oxygen ———–> Charcoal + Carbon dioxide + Heat + Light

But cutting it into small pieces is physical change because no new substance is formed. We can only reduce the size of wood.

 

Question 8

Describe how crystals of copper sulphate are prepared.

Answer

Take a cupful of water in a beaker and add a few drops of dilute sulphuric acid. Heat the water. When it starts boiling, add copper sulphate powder slowly. Continue to add copper sulphate powder till no more powder can be dissolved. During this process continuously stir the solution. Filter the solution. Leave it for cooling. Look it after some time, you can see the crystals of copper sulphate.

 

Question 9

Explain how painting of an iron gate prevents it from rusting.

Answer

It is known that for rusting the presence of oxygen and moisture is essential. Painting prevents the iron gate from coming in contact with oxygen and moisture.

Question 10

Explain why rusting of iron objects is faster in coastal areas than in deserts.

Answer

As content of moisture in the air in coastal areas is higher than in the air in deserts. So, the process of rusting is faster in coastal areas.

 

Question 11

The gas we use in the kitchen is called liquified petroleum gas (LPG). In the cylinder it exist as a liquid. When it comes out from the cylinder it becomes a gas (Change – A) then it burns (Change – B). The following statements pertain to these changes. Choose the correct one.

(i) Process – A is a chemical change.

(ii) Process – B is a chemical change.

(iii) Both processes A and B are chemical changes.

(iv) None of these processes is a chemical change.

Answer

(ii) Process - B is a chemical change.

Question 12

Anaerobic bacteria digest animal waste and produce biogas (Change – A).

The biogas is then burnt as fuel (Change – B). The following

statements pertain to these changes. Choose the correct one.

(i) Process – A is a chemical change.

(ii) Process – B is a chemical change.

Answer

(iii) Both processes A and B are chemical change

 

Chapter 7 - Weather, Climate and Adaptations of Animals of Climate

 

Question 1

Name the elements that determine the weather of a place.

Answer

The temperature, humidity, rainfall, wind-speed, etc. are called the elements that determine the weather of a place.

 

Question 2

When are the maximum and minimum temperature likely to occur during the day?

Answer

The maximum temperature of the day occurs generally in the afternoon and the minimum temperature occurs in the early morning.

 

Question 3

Fill in the blanks

(i) The average weather taken over a long time is called __________

(ii) A place receives very little rainfall and the temperature is high throughout the year, the climate of that place will be ________ and _________

(iii) The two regions of the earth with extreme climatic conditions are __________ and ____________

Answer

(i) climate of the place (ii) hot, dry (iii) polar, tropical regions

 

Question 4

Indicate the type of climate of the following areas:

(a) Jammu and Kashmir:

(b) Kerala:,

(c) Rajasthan:

(d) North-east India:

Answer

(a) Jammu and Kashmir—moderately hot and moderately wet climate.

(b) Kerala—very hot and wet climate.

(c) Rajasthan—hot and dry climate.

(d) North-east India—The north eastern India receives rain for a major part of the year, hence wet climate.

 

Question 5

Which of the two changes frequently, weather or climate?

Answer

Weather

 

Question 6

Followings are some of the characteristics of animals:

(i) Diets heavy on fruits , (ii) White fur (iii) Need to migrate (iv) Loud voice

(v) Sticky pads on feet (vi) Layer of fat under skin

(vii) Wide and large paws (viii) Bright colours

(ix) Strong tails (x) Long and large beak

For each characteristic indicate whether it is adaptation for tropical rainforests or polar regions. Do you think that some of these characteristics can be adapted for both regions?

Answer

Characteristics of Animals

Adaption for

Diets heavy on fruits

Tropical rainforests

White fur

Polar regions

Need to migrate

Polar regions

Loud voice

Tropical rainforests

Sticky pads on feet

Tropical rainforests

Layer of fat under skin

Polar regions

Wide and large paws

Polar regions

Bright colours

Tropical rainforests

Strong tails

Tropical rainforests

Long and large beak

Tropical rainforests

 

Question 7

The tropical rainforests has a large population of animals. Explain why it is so.

Answer

Because of continuous warmth and rain, the tropical region supports an enormous number and a wide variety of animals

 

Question 8

Explain with examples, why we find animals of certain kind living in particular climatic conditions.

Answer

Animals are adapted to survive in the conditions in which they live. Features and habits which help them to adapt to their surroundings are the result of evolution. So, to survive in a particular type of climate the animals must have certain adapted features. This is the reason we find animals of certain kind living in particular climatic conditions. For example, animals in the polar region are adapted to the extremely cold climate. They have special characteristics, such as white fur, strong sense of smell, a layer of fat under the skin, wide and large paws for swimming and walking in snow etc.

 

Question 9

How do elephants living in the tropical rainforests adapt themselves?

Answer

The elephant has adapted to the conditions of rainforest in many remarkable ways. It has a trunk that it uses as a nose because of this it has a strong sense of smell. The trunk is also used by it for picking up food. Its tusks are modified teeth. These can tear the bark of trees that an elephant loves to eat. So, the elephant is able to handle the competition for food very well. Large ears of the elephant help it to hear even very soft sounds. They also help the elephant to keep cool in the hot* humid climate of the rainforest.

 

Question 10

Choose the correct option which answers the following question:

A carnivore with stripes on its body moves very fast while catching its prey. It is likely to be found in:

(i) polar regions (ii) deserts

(iii) oceans (iv) tropical rainforests

Answer

(iv) tropical rainforests

 

Question 11

Which features adapt polar bears to live in extremely cold climate?

(i) A white fur, fat below skin, keen sense of smell.

(ii) Thin skin, large eyes, a white fur.

(iii) A long tail, strong claws, white large paws.

(iv) White body, paws for swimming, gills for respiration.

Answer

(iv) A white fur, fat below skin, keen sense of smell.

 

Question 12

Which option best describes a tropical region?

(i) hot and humid

(ii) moderate temperature, heavy rainfall (iii) cold and humid (iv) hot and dry

Answer

(i) Hot and humid

 

Chapter 8 - Winds, Storms and Cyclones

Question 1

Fill the missing word in the blank spaces in the following statements:

(a) Wind is ___________air.

(b) Winds are generated due to _________ heating on the earth.

(c) Near the earth’s surface _________ air rises up whereas _________ air comes down.

(d) Air moves from a region _________of pressure to a region _________of pressure.

Answer

(a) moving (b) uneven

(c) warm, cooler (d) high, low

 

Question 2

Suggest two methods to find out wind direction at a given place.

Answer

(i) Take a piece of a paper in your hand. Allow it to fall from your hand. It will flow in the direction in which wind is blowing.

(ii) You can also use a wind-pane which helps us to know accurate wind direction.

 

Question 3

State two experiences that made you think that air exerts pressure.

Answer:

(i) Balloons and balls can be used only when they are inflated with air. When balloon is overfilled with air it bursts due to excessive air pressure.

(ii) Compressed air is used in the brake system for stopping trains.

 

Question 4

You want to buy a house. Would you like to buy a house having windows but no ventilators? Explain your answer.

Answer:

No, a house which has no ventilators is not a safe or healthy house to live in. The air circulation is not there in such a house. So, it has no fresh air. Because warm air rises up and goes out through ventilators and fresh air comes in through windows.

 

Question 5

Explain why holes are made in hanging banners and hoardings.

Answer:

Air exerts pressure. Due to this pressure banners and hoarding flutter and torn when wind is blowing fast. Holes are made in banners and hoardings so that wind passes through the holes and they do not become loose and fall down.

 

Question 6

How will you help your neighbours in case cyclone approaches your village/town?

Answer:

(i) I will make them aware of cyclone forecast and warning service.

(ii) Rapid communication of warning to the government agencies and all the important places.

(iii) Construction of cyclone shelters in the cyclone prone areas.

(iv) Helping them to shift essential goods, domestic animals etc. to safer places.

 

Question 7

What planning is required in advance to deal with the situation created by a cyclone?

Answer:

To deal with cyclone, it is important to follow the following points :

(i) carefully listening the warnings transmitted on T.V. and radio.

(ii) moving to the safer places.

(iii) keeping an emergency kit ready.

(iv) store food in waterproof bags. .

(v) not venturing into sea.

(vi) keeping all the emergency numbers.

 

Question 8

Which one of the following places is unlikely to be affected by cyclone?

(i) Chennai (ii) Mangalore

(iii) Amritsar (iv) Puri

Answer:

(iv) Amritsar

 

Question 9

Which of the statements given below is correct?

(i) In winter the winds flow from the land to the ocean.

(ii) In summer the winds flow from the land towards the ocean.

(iii) A cyclone is formed by a very high-pressure system with very high-speed winds revolving around it.

(iv) The coastline of India is not vulnerable to cyclones.

Answer:

(i) In winter the winds flow from the land to the ocean.

 

Chapter 9 - Soil

Question 1

Tick the most suitable answer in question 1 and 2.

In addition to the rock particles, the soil contains

(i) Air and water

(ii) Water and plants

(iii) Minerals, organic matter, air and water

(iv) Water, air and plants

Answer:

In addition to the rock particles, the soil contains

(iii) Minerals, organic matter, air and water.

 

Question 2

The water holding capacity is the highest in

(i) Sandy soil

(ii) Clayey soil

(iii) Loamy soil

(iv) Mixture of sand and loam

Answer:

The water holding capacity is the highest in

(ii) Clayey soil

 

Question 3

Match the items in Column I with those in Column II:

 

Column I

Column II

(i) A home for living organisms

(a) Large particles

(ii) upper layer of the soil

(b) All kinds of soil

(iii) Sandy Soil

(c) Dark in Colour

(iv) Middle layer of the soil

(d) Small Particles and packed tight

(v) Clayey soil

(e) Lesser amount of humus

 

Answer:

Column I

Column II

(i) A home for living organisms

(b) All kinds of soil

(ii) upper layer of the soil

(c) Dark in Colour

(iii) Sandy Soil

(a) Large particles

(iv) Middle layer of the soil

(e) Lesser amount of humus

(v) Clayey soil

(d) Small Particles and packed tight

 

Question 4

Explain how soil is formed.

Answer:

Soil is formed through the process of weathering. Weathering is a process of physical breakdown and chemical decomposition of rocks and minerals near or at the surface of the earth. This physical and chemical decomposition is primarily done by wind, water, and climate. As a result of these processes, large rock pieces are converted into smaller pieces and eventually to soil.

 

Question 5

How is clayey soil useful for crops?

Answer:

Following are the properties of clayey soil:

 

  • It has very good water holding capacity.
  • It is rich in organic matter.
  • For growing crops such as wheat, gram, and paddy, the soil that is good at retaining water and rich in organic matter is suitable. Therefore, clayey soils having these characteristics are useful for such kind of crops.

 

Question 6

List the differences between clayey soil and sandy soil.

Answer:

 

Clayey Soil

Sandy Soil

(i) It has much smaller particles

(i) It has much larger particles

(ii) It can hold good amount of water

(ii) It cannot hold water

(iii) It is fertile

(iii) It is not fertile

(iv) Air content is low

(iv) Air get trapped between the particles

(v) Particles are tightly packed

(v) Particles are loosely packed

(vi) Good for growing various crops

(vi) Not suitable for growing crops

 

Question 7

Sketch the cross section of soil and label the various layers.

Answer:

 

 

Question 8

Razia conducted an experiment in the field related to the rate of percolation. She observed that it took 40 min for 200 mL of water to percolate through the soil sample. Calculate the rate of percolation.

Answer:

 

Question 9

Explain how soil pollution and soil erosion could be prevented.

Answer:

Prevention of soil pollution:

The persistent build-up of toxic compounds in the soil is defined as soil pollution. To prevent soil pollution, its causes must be controlled.

 

Reduce the use of plastics: Plastics and polythene bags destroy the fertility of soil. Hence, these should be disposed off properly and if possible, their use should be avoided.

Industrial pollutants: Some waste products from industries and homes pollute soil. These pollutants should be treated chemically to make them harmless before they are disposed off.

Insecticides: Other pollutants of soil include pesticides and insecticides. Therefore, excessive use of these substances should be avoided.

Prevention of soil erosion:

Removal of the upper fertile layer of the soil (top soil) by strong wind and flowing water is known as soil erosion. Following steps can be taken to reduce soil erosion:

 

  1. Mass awareness to reduce deforestation for industrial purposes.
  2. Helping local people to regenerate degrading forest.
  3. Planting trees.

 

Chapter 10 - Respiration in Organisms

 

Question 1

Why does an athlete breathe faster and deeper than usual after finishing the race?

Answer:

During the run, the demand of energy is high but the supply of oxygen to produce energy is limited. Therefore, anaerobic respiration takes places in the muscle cells to fulfill the demand of energy. After finishing the race, an athlete breathe faster and deeper than usual so that more oxygen is supplied to the cells.

 

Question 2

List the similarities and differences between aerobic and anaerobic respiration.

Answer:

Similarity:

(i) In both aerobic and anaerobic respiration, food is broken down to release energy.

(ii) Both takes place inside cells.

(iii) Both produces byproducts.

 

Differences:

 

Aerobic Respiration

Anaerobic Respiration

(i) It takes place in the presence of oxygen

(i) It takes place in the absence of oxygen

(ii) Energy is released in higher amount

(ii) Energy is released in lesser amount

(iii) Carbon dioxide and water are produced as byproducts

(iii) Carbon dioxide and water are produced as byproducts

(iv) It is a slow process

(iv) It is a fast process

(v) Examples: Animals and Plant cells

(v) Examples: Human cells, yeast, Bacteria etc.

 

Question 3

Why do we often sneeze when we inhale a lot of dust-laden air?

Answer:

We often sneeze when we inhale a lot of dust-laden air to expel out these foreign particles. These particles get past the hair in the nasal cavity and irritate the lining of the cavity which results in sneezing.

 

Question 4

Take three test-tubes. Fill each of them with water. Label them A, B and C. Keep a snail in test-tube A, a water plant in test-tube B and in C, keep snail and plant both. Which test-tube would have the highest concentration of CO2?

Answer:

Test-tube A will have the highest concentration of CO2 because snail will take in oxygen and gives out CO2.

In test-tubes B and C, the CO2 will be utilized by the water plant for synthesizing food and hence there will be less concentration of CO2 in these.

 

Question 5

Tick the correct answer:

(a) In cockroaches, air enters the body through

(i) lungs

(ii) gills

(iii) spiracles

(iv) skin

(b) During heavy exercise, we get cramps in the legs due to the accumulation of _______

(i) carbon dioxide

(ii) lactic acid

(iii) alcohol

(iv) water

(c) Normal range of breathing rate per minute in an average adult person at rest is:

(i) 9 – 12

(ii) 15 – 18

(iii) 21 – 24

(iv) 30 – 33

(d) During exhalation, the ribs

(i) move outwards

(ii) move downwards

(iii) move upwards

(iv) do not move at all

 

Answer:

(iii) spiracles

(ii) lactic acid

(ii) 15 – 18

(ii) move downwards

 

Question 6

Match the items in Column I with those in Column II:

 

Column I

Column II

(a) Yeast

(i) Earthworm

(b) Diaphragm

(ii) Gills

(c) Skin

(iii) Alcohol

(d) Leaves

(iv) Chest Cavity

(e) Fish

(v) Stomata

(f) frog

(vi) Lungs and skin

 

(vii) Tracheae

 

Answer:

Column I

Column II

(a) Yeast

(i) Earthworm

(b) Diaphragm

(ii) Gills

(c) Skin

(iii) Alcohol

(d) Leaves

(iv) Chest Cavity

(e) Fish

(v) Stomata

(f) frog

(vi) Lungs and skin

 

(vii) Tracheae

 

 

Question 7

Mark T if the statement is true and F if it is false:

(i) During heavy exercise the breathing rate of a person slows down. (T/ F)

(ii) Plants carry out photosynthesis only during the day and respiration only at night. (T/ F)

(iii) Frogs breathe through their skins as well as their lungs. (T/ F)

(iv) The fishes have lungs for respiration. (T/ F)

(v) The size of the chest cavity increases during inhalation. (T/ F)

Answer:

(i) False

(ii) False

(iii) True

(iv) False

(v) True

 

Question 8

Given below is a square of letters in which are hidden different words related to respiration in organisms. These words may be present in any direction – upwards, downwards, or along the diagonals. Find the words for your respiratory system. Clues about those words are given below the square.

Image

(i) The air tubes of insects

(ii) Skeletal structures surrounding chest cavity

(iii) Muscular floor of chest cavity

(iv) Tiny pores on the surface of leaf

(v) Small openings on the sides of the body of an insect

(vi) The respiratory organs of human beings

(vii) The openings through which we inhale

(viii) An anaerobic organism

(ix) An organism with tracheal system

 

Answer:

 

Image

 

(i) The air tubes of insects → Trachea

(ii) Skeletal structures surrounding chest cavity → Ribs

(iii) Muscular floor of chest cavity → Diaphragm

(iv) Tiny pores on the surface of leaf → Stomata

(v) Small openings on the sides of the body of an insect → Spiracles

(vi) The respiratory organs of human beings → Lungs

(vii) The openings through which we inhale → Nostrils

(viii) An anaerobic organism → Yeast

(ix) An organism with tracheal system → Ant

 

Question 9

The mountaineers carry oxygen with them because:

(a) At an altitude of more than 5 km there is no air.

(b) The amount of air available to a person is less than that available on the ground.

(c) The temperature of air is higher than that on the ground.

(d) The pressure of air is higher than that on the ground.

Answer:

(b) The amount of air available to a person is less than that available on the ground.

 

Chapter 11 - Transportation in Animals and Plants

Question 1

Match structures given in Column I with functions given in Column II.

 

Column I

Column II

(i) Stomata

(a) Absorption of water

(ii) Xylem

(b) Transpiration

(iii) Root hairs

(c) Transport of food

(iv) Phloem

(d) Transport of water

 

(e) Synthesis of carbohydrates

Answer:

Column I

Column II

(i) Stomata

(b) Transpiration

(ii) Xylem

(d) Transport of water

(iii) Root hairs

(a) Absorption of water

(iv) Phloem

(c) Transport of food

 

Question 2

Fill in the blanks :

(i) The blood from the heart is transported to all parts of the body by the _____________

(ii) Haemoglobin is present in ___________ cells.

(iii) Arteries and veins are joined by a network of ___________ .

(iv) The rhythmic expansion and contraction of the heart is called ___________

(v) The main excretory product in human beings is ___________

(vi) Sweat contains water and .

(vii) Kidneys eliminate the waste materials in the liquid form called ______ .

(viii) Water reaches great heights in the trees because of suction pull caused by ______

Answer:

(i) arteries

(ii) red blood cells

(iii) capillaries

(iv) heartbeat

(v) urea

(vi) salts

(vii) urine

(viii) transpiration

 

Question 3

Choose the correct options:

(a) In plants, water is transported through

(i) Xylem (ii) Phloem (iii) Stomata (iv) Root hair

(b) Water absorption through roots can be increased by keeping the plants

(i) In the shade (ii) in dim light (iii) under the fan (iv) covered with a polythene bag

Answer:

(a) (i) Xylem

(b) (iii) under the fan

 

Question 4

Why is transport of materials necessary in a plant or an animal? Explain.

Answer:

Transport of materials is necessary for plants or animals because due to it the nutrients and oxygen are made available to all the parts of the body. If the transport of necessary nutrients and oxygen does not take place in the body, the body will not be able to survive.

 

Question 5

What will happen if there are no platelets in the blood?

Answer:

The blood platelets are responsible for the clotting of the blood. When some injury occurs blood starts flowing. But it clots on its own. If there are no platelets, the blood will not be able to clot and keep on flowing. Huge loss of blood ultimately causes death.

 

Question 6

What are stomata? Give two junctions of stomata.

Answer:

There are small openings on the lower surface of the leaves. These pores are called stomata. These openings are surrounded with guard cells.

Functions of stomata:

1. It helps in the transpiration of water, i.e., the loss of excess water from the plant.

2. Loss of water from the stomata creates an upward pull, i.e., suction pull which helps in absorption of water from the roots.

3. They help in exchange of gases.

 

Question 7

Does transpiration serve any useful function in plants? Explain.

Answer:

(i) It helps to enhance the absorption of water and dissolved minerals by creation of a suction pull.

(ii) It helps in getting rid of the excess water.

(iii) It helps in transport of water and minerals to leaves and leaves use the water for photosynthesis. ‘

(iv)It produces a cooling effect on the plant

 

Question 8

What are the components of blood?

Answer:

There are four components of blood:

(i) Plasma is a liquid part of blood which is yellowish in colour and contain 90% water. It contains food, enzymes, wastes and proteins etc

(ii) Red blood cells are disc shaped cells containing red coloured pigment called haemoglobin in it. Haemoglobin helps in transportation of oxygen.

(iii) White blood cells are the fighting cells which protect us against bacteria and foreign materials causing infections.

(iv) Platelets help in clotting of the blood

 

Question 9

Why is blood needed by all the parts of a body?

Answer:

Blood is needed by all the parts because it contains the digested food and oxygen in it. It supplies the oxygen and digested food to various parts of the body to provide essential energy to them which helps the body to perform various functions

 

Question 10

What makes the blood look red?

Answer:

A red pigment called haemoglobin gives the blood its red colour. This pigment helps in carrying oxygen to various parts of the body by blood.

 

Question 11

Describe the function of the heart.

Answer:

The right auricle and ventricle receive blood with carbon dioxide from all parts of the body. The collected blood is then pumped to the lungs for the purification. In lungs, the exchange of gases takes place and purified blood is sent back to left auricle. It pumps it to the left ventricle, which in turn pumps off the purified blood to all parts of body through arteries

 

Question 12

Why is it necessary to excrete waste products?

Answer:

Certain waste and toxic products are formed during functioning of body cells. The waste products like urea etc. are toxic. When these toxic materials are not removed from the body, they get mixed with blood and can damage the cells of body. It is necessary to remove such poisonous waste materials from our body.

 

Question 13

Draw a diagram of the human excretory system and label the various parts.

Answer:

 

Chapter 12 - Reproduction in Plants

 

Question 1

Fill in the blanks:

(a) Production of new individuals from the vegetative part of parent is called ___________.

(b) A flower may have either male or female reproductive parts. Such a flower is called _______.

(c) The transfer of pollen grains from the anther to the stigma of the same or of

another flower of the same kind is known as __________.

(d) The fusion of male and female gametes is termed as ____________ .

(e) Seed dispersal takes place by means of ________ and __________.

Answer

(a) vegetative reproduction

(b) unisexual flower

(c) pollination

(d) fertilization

(e) wind, water

 

Question 2

Describe the different methods of asexual reproduction. Give examples.

Answer

Different methods of asexual reproduction are:

(a) Binary Fission: This process takes place in unicellular organisms. Parent cell elongates and gets divided into two identical daughter cells. Each daughter cell grows into an independent adult.

(b) Endospore Formation: In this method the spore wall is formed around a bacterial cell to form an endospore. This endospore germinates to form an active bacterium under favourable conditions.

(c) Fragmentation: In this process, body of the organism breaks up into two parts. Then each part grows into a new filament thus forming two organisms from a single one.

(d) Spore Formation: The spores are tiny spherical unicellular structures protected by thick wall. The spores are stored in a hard outer covering and this is called sporangium. Under favourable conditions the hard cover breaks and spores spread for germination.

(e) Budding: In yeast, new organisms are produced by the bud formation from the parent organism. After growing to full size, the bud gets detached and forms a new independent individual.

(f) Vegetative propagation: When vegetative parts of a plant like stems, leaves and root etc., give rise to new ones, it is.called vegetative propagation.

 

Question 3

Explain what you understand by sexual reproduction.

Answer

Sexual reproduction means involvement of two parents in the process of reproduction. It is found mainly in higher plants where male gamete and female gamete fuse to form a zygote. These zygotes develop into individuals which are not identical. Offsprings inherit the characteristics of both the parents. In sexual reproduction both parents survive after the process of reproduction.

 

Question 4

State the main difference between asexual and sexual reproduction.

Answer

Asexual Reproduction

Sexual Reproduction

(i) Only one parent plant is involved

(i) Both male and female parents are involved

(ii) Occurs in unisexual plants

(ii) Occurs in bisexual plants

(iii) Occurs in lower plants

(iii) Occurs in higher plants

(iv) Reproductive organs are not present

(iv) Fully developed reproductive parts are present

(v) In most of the methods the original parent disappears

(v) Original parents remain alive after process of reproduction

(vi) Process like gamete formation or fertilization is not seen

(vi) Fertilization of gametes give rises to Zygote

(vii) Characteristics of only one parent is inherited

(vii) Characteristics of both parents are inherited

(viii) No need of seeds.

(viii) Seeds are used to get new plants from a flower

 

Question 5

Sketch the reproductive parts of a flower.

Answer

Image

Question 6

Explain the difference between self-pollination and cross-pollination.

Answer

Self-pollination

Cross-pollination

(a) Pollen grains are transferred to the stigma of the same flower.

(a) Pollen grains are carried to stigma of another flower

(b) Occurs in bisexual plants having anther and stigma maturing at same time

(b) Occurs in bisexual flowers having anther and stigma maturing at different times

(c) It takes place in plants like wheat, peas, etc.

(c) It takes place in plants like lady-finger, tomato, brinjal, etc.

 

Question 7

How does the process of fertilization take place in flowers?

Answer

When the pollen grain reaches the stigma of a same species flower, it starts

growing out into the pollen tube of the stigma. This tube continues to grow inside the style till it reaches the ovule. Male cells are released into the ovule for the fertilization with the female egg cell and thus the zygote is formed. After this process of fertilization, the ovary develops into fruit and ovule into seeds.

 

Question 8

Describe the various ways by which seeds are dispersed.

Answer

Following are the ways in which the seeds are dispersed:

(i) Some light seeds like that of madar, which are hairy, dry and small are carried away by the wind to different places.

(ii) Spiny seeds and fruits like that of xanthium and urena, stick to the clothes of passers by and animals. These seeds are carried away by these agents to different places.

(iii) In some plants having heavy seeds like that of coconut, water acts as the dispersing agents.

(iv) Some seeds are dispersed with the fruit burst like in case of balsam and castor.

 

Question 9

Match items in Column I with those in Column II

Column I

Column II

(a) Bud

(i) Maple

(b) Eyes

(ii) Spirogyra

(c) Fragmentation

(iii) Yeast

(d) Wings

(iv) Bread mould

(e) Spores

(v) Potato

 

(vi) Rose

 

Answer

Column I

Column II

(a) Bud

(iii) Yeast

(b) Eyes

(v) Potato

(c) Fragmentation

(ii) Spirogyra

(d) Wings

(i) Maple

(e) Spores

(iv) Bread mould

 

Question 10

Tick (✓) the correct answer:

(a) The reproductive part of a plant is the

(i) leaf (ii) stem (iii) root (iv) flower

(b) The process of fusion of the male and the female gametes is called

(i) fertilisation (ii) pollination (iii) reproduction (iv) seed formation

c) Mature ovary forms the

(i) seed (ii) stamen (iii) pistil (iv) fruit

(d) A spore producing plant is

(i) rose (ii) bread mould (iii) potato (iv) ginger

(e) Bryophyllum can be reproduced by its

(i) stem (ii) leaves (iii) roots (iv) flower

Answer

(a) (iv) flower

(b) (i) fertilisation

(c) (iv) fruit

(d) (ii) bread mould

(e) (ii) leaves

 

Chapter 13 - Motion and Time

Question 1

Classify the following as motion along a straight line, circular or oscillatory motion:

(i) Motion of your hands while running.

(ii) Motion of a horse pulling a cart on a straight road.

(iii) Motion of a child in a merry-go-round.

(iv) Motion of a child on a seesaw.

(v) Motion of the hammer of an electric bell.

(vi) Motion of a train on a straight bridge.

Answer

(i) Oscillatory motion

(ii) Linear motion

(iii) Circular motion

(iv) Oscillatory motion

(v) Oscillatory motion

(vi) Linear motion

 

Question 2

Which of the following are not correct?

(i) The basic unit of time is second.

(ii) Every object moves with a constant speed.

(iii) Distances between two cities are measured in kilometers.

(iv) The time period of a given pendulum is not constant.

(v) The speed of a train is expressed in m/h

Answer

(ii), (iv), (v)

 

Question 3

A simple pendulum takes 32s to complete 20 oscillations, what is the time period of the pendulum?

Answer

Time taken to complete 20 oscillations = 32 s

Time taken to complete 1 oscillation = 32/20 s = 1.6 s

Time period of a pendulum is time taken by it to complete 1 oscillation.

Time period of pendulum is 1.6 seconds.

 

Question 4

The distance between two stations is 240 km. A train takes 4 hours to cover this distance. Calculate the speed of the train.

Answer

Distance = 240 km

Time taken = 4 hours

Speed =Distance covered/time taken = 240km/4 hammer

=60 km/h

Speed of train =60 km/h

 

Question 5

The odometer of a car reads 57321.0 km when the clock shows the time 08:30 AM. What is the distance moved by the car, if at 08:50 AM, the odometer reading has changed to 57336.0 km? Calculate the speed of the car in km/min during this time. Express the speed in km/h also.

Answer

Distance = 57336.0 km – 57321 km =15 km

Speed in km/min =15km/20 min = 3/4 km/min

 

Speed in km/hr =15 km/1/3 hr

=(15 x 3) km/hr

=45 km/hr.

 

Question 6

Salma takes 15 minutes from her house to reach her school on a bicycle. If the bicycle has a speed of 2 m/min, calculate the distance between her house and the school.

Answer

Time taken =15 min

Speed = 2 m/min .

Distance = speed x time = 2 x 15 = 30 m

Distance between Salma’s school and her house is 30 m.

 

Question 7

Show the shape of the distance-time graph for the motion in the following cases:

(i) A car moving with a constant speed.

(ii) A car parked on a side road

 

 

Image

 

Question 8

Which of the following relations is correct?

(i) Speed = Distance Time

(ii) Speed = Distance/Time

(iii)Speed – Time/Distance

(iv)Speed = 1/Distance Time

Answer

(ii) Speed = Distance/Time is correct

 

Question 9

The basic unit of speed is:

(i) km/min (ii) m/min (iii) km/h (iv) m/s

Answer

(iv) m/s

 

Question 10

A car moves with a speed of 40 km/h for 15 minutes and then with a speed of 60 km/h for the next 15 minutes. The total distance covered by the car is:

(i) 100 km (ii) 25 km (iii) 15 km (iv) 10 km

Answer

(ii) 25 km

 

Question 11

Suppose the two photographs, shown in fig. 13.1 and fig. 13.2 of NCERT had been taken at an interval of 10 seconds. If a distance of 100 metres is shown by 1 cm in these photographs, calculate the speed of the blue car.

Answer

0.1 cm/s or 10 m/s

 

Question 12

Fig 13.10 shows the distance-time graph for the motion of two vehicles A and B. Which one of them is moving faster?

 

Image

Answer

A’ is moving faster

 

Question 13

Which of the following distance-time graphs shows a truck moving with speed which is not constant?

Answer

(iii)

Chapter 14 - Electric Current and its Effects

Question 1

Draw in your notebook the symbols to represent the following components of electrical circuits: connecting wires, switch in the ‘OFF’ position, bulb, cell, switch in the ‘ON’ position and battery.

Answer

 

Image

 

 

Question 2

Draw the circuit diagram to represent the circuit shown in fig. 14.9.

 

Image

Answer

Image

Question 3

Fig. 14.11 shows four cells fixed on a board. Draw lines to indicate how you will connect their terminals with wires to make a battery of four cells.

Image

 

Answer

Image

 

Question 4

The bulb in the circuit shown in fig. 14.13 does not glow. Can you identify the problem? Make necessary changes in the circuit to make the bulb glow.

 

Image

 

Answer

Problem in this circuit is the combination of two cells. In the circuit positive terminal of one cell should be connected with negative terminal of other to make the bulb glow.

 

Image

 

 

 

Question 5

Name any two effects of electric current.

Answer

Electric current has the following effect :

(i) Electric current can give rise to heating and lighting.

(ii) Electric current can convert a straight conductor into a temporary magnet.

 

Question 6

When the current is switched on through a wire, a compass needle kept nearby gets deflected from its north-south position. Explain.

Answer

When current is passed through the wire, it deflects the compass near it from its north-south position like a magnet. This is called magnetic effect of the current. As we know that needle of the compass is made up of a thin magnet. When this needle comes in contact with another magnet then the like poles of the magnet repel each other and opposite poles attract each other. So the deflection is seen in the needle. In this case the wire behaves like a magnet and causes deflection in needle of the compass.

 

Question 7

Will the compass needle show deflection when the switch in the circuit shown by fig. 14.15 is closed?

 

Image

Answer

No, because there is no source of electric current in this circuit, i.e., there is no battery.

 

Question 8

Fill in the blanks:

(a) Longer line in the symbol for a cell represents its ___________terminal

(b) The combination of two or more cells is called a ____________.

(c) When current is switched ‘on’ in a room heater, it ___________.

(d) The safety device based on the heating effect of electric current is called a _____________.

Answer

(a) positive (b) battery (c) becomes red hot and emits heat (d) fuse.

 

Question 9

Mark ‘T’ if the statement is true and ‘F’ it is a false:

(a) To make a battery of two cells, the negative terminal of one cell is connected to the negative terminal of the other cell. [T/F]

(b) When the electric current through the fuse exceeds a certain limit , the fuse wire melts and breaks. [T/F]

(c) An electromagnet does not attract a piece of iron. [T/F]

(d) An electric bell has an electromagnet. [T/F]

Answer

(a) F

(b) T

(c) F

(d) T

 

Question 10

Do you think an electromagnet can be used for separating plastic bags from a garbage heap? Explain.

Answer

No, the plastic bags do not get attracted by the magnet, so they cannot be separated by an electromagnet. Plastic bags are not magnetic materials, only magnetic materials like iron can be attracted by the magnet.

 

Question 11

An electrician is carrying out some repairs in your house. He wants to replace a fuse by a piece of wire. Would you agree? Give reasons for your response.

Answer

No, we would not agree to allow to replace the fuse by a wire. Wires in the fuses are of specific melting points. So we should always use ISI marked fuses in our houses to prevent short circuits.

 

Question 12

Zubeda made an electric circuit using a cell holder shown in fig. 14.16, a switch and a bulb. When she put the switch in the ‘ON’ position, the bulb did not glow. Help Zubeda in identifying the possible defects in the circuit.

 

Image

 

Answer

It is important to put the cells in right series. The positive terminal of the first cell should be connected with negative terminal of the second cell. The switch should be closed properly and bulb should not be fused. If Zubeda will check these then the bulb will certainly glow.

 

Question 13

In the circuit shown in fig. 14.17.

 

Image

 

Would any of the bulb glow when the switch is in the ‘OFF’ position?

What will be the order in which the bulbs A, B and C will glow when the switch is moved to the ‘ON’ position?

Answer

No bulb will glow.

All bulbs will glow simultaneously.

 

Chapter 15 - Light

Question 1

Fill in the blanks:

(a) An image that cannot be obtained on a screen is called ___________ .

(b) Image formed by a convex is __________ always virtual and smaller in size.

(c) An image formed by a __________ mirror is always of the same size as that of the object.

(d) An image which can be obtained on a screen is called a __________ image.

(e) An image formed by a concave __________ cannot be obtained on a screen.

Answer

(a) virtual image

(b) mirror

(c) plane

(d) real

(e) lens

 

Question 2

Mark ‘T’ if the statement is true and ‘F’ if it is false:

(a) We can obtain an enlarged and erect image by a convex mirror. (T/F)

(b) A concave lens always form a virtual image. (T/F)

(c) We can obtain a real, enlarged and inverted image by a concave mirror. (T/F)

(d) A real image cannot be obtained on a screen. (T/F)

(e) A concave mirror always form a real image. (T/F)

Answer

a) False

(b) True

(c) True

(d) False

(e) False

 

Question 3
Match the items given in Column I with one or more items of Column II

 

Column I

Column II

(a) A plane mirror

(i) used as a magnifying glass

(b) A Convex mirror

(ii) Can form image of objects spread over a large area

(c) A convex lens

(iii) Used by dentists to see enlarged image of teeth

(d) A concave mirror

(iv) The image is always inverted and magnified

(e) A Concave lens

(v) The image is erect and of the same size as the object

 

(vi) The image is erect and smaller in size than the object

Answer

 

Column I

Column II

(a) A plane mirror

(v) The image is erect and of the same size as the object

(b) A Convex mirror

(ii) Can form image of objects spread over a large area

(c) A convex lens

(i) used as a magnifying glass

(d) A concave mirror

(iii) Used by dentists to see enlarged image of teeth

(e) A Concave lens

(vi) The image is erect and smaller in size than the object

 

Question 4

State the characteristics of the image formed by a plane mirror.

Answer

(i) Plane mirror forms an erect image.

(ii) It forms a virtual image.

(iii) Size of the image is same as that of the object.

(iv)Image is formed at the same distance behind the mirror as the object stands in front of it.

(v) Image formed is a laterally inverted image i.e., right hand side of the object seems to be the left hand side and vice-versa.

 

Question 5

Find out the letters of English alphabet or any other language known to you in which the image formed in a plane mirror appears exactly like the letter itself. Discuss your findings.

Answer

Letters like A, H, I, M, O, T, U ,V, W etc. appear same when seen through a plane mirror

 

Question 6

What is a virtual image? Give one situation where a virtual image is formed.

Answer

The image which cannot be taken on a screen is called virtual image. When some object is placed very close to the concave mirror we don’t get any image on the white screen placed behind the mirror. Such image is called virtual image.

 

Question 7

State two differences between a convex and a concave lens.

Answer

Convex lens

Concave lens

(i) Convex lens can form both real and virtual images

(i) Concave lens always forms a virtual image

(ii) It can form magnified image

(ii) Image is always diminished in size

 

Question 8

Give one use each of a concave and a convex mirror.

Answer

Use of concave mirror:

Concave mirror is used by dentists to examine the teeth.

Use of convex mirror:

Convex mirror is used as side view mirror in vehicles

 

Question 9

Which type of mirror can form a real image?

Answer

Concave mirror can form a real image.

 

Question 10

Which type of lens forms always a virtual image?

Answer

Concave lens always forms a virtual image.

 

Choose the correct option in Questions 11-13:

 

Question 11

A virtual image larger than the object can be produced by a

(i) concave lens (ii) concave mirror (iii) convex mirror (iv) plane mirror

 

Answer

(ii) concave mirror

 

Question 12

David is observing his image in a plane mirror. Die distance between the mirror and his image is 4 m. If he moves 1 m towards the mirror, then the distance between David and his image will be

(i) 3 m (ii) 5 m (iii) 6 m (iv) 8 m

 

Answer

(iii) 6 m

 

Question 13

The rear view mirror of a car is a plane mirror. A driver is reversing his car at a speed of 2 m/s. The driver sees in his rear mew mirror the image of a truck parked behind his car. The speed at which the image of the truck appears to approach the driver will be

(i) 1 m/s (ii) 2 m/s (iii) 4 m/s (iv) 8 m/s

 

Answer

(ii) 4 m/s

 

Chapter 16 - Water: A Precious Resource

Question 1

Mark ‘T’ if the statement is true and ‘F’ if it is false:

(a) The freshwater stored in the ground is much more than that present in the rivers and lakes of the world. (T/F)

(b) Water shortage is a problem faced only by people living in rural areas. (T/F)

(c) Water from rivers is the only source for irrigation in the fields. (T/F)

(d) Rain is the ultimate source of water. (T/F)

 

Answer

(a) True

(b) False

(c) Fale

(d) True

 

Question 2

Explain how groundwater is recharged.

Answer

The groundwater gets recharged through the process of infiltration. Infiltration means seeping of water from rivers and lakes into the empty spaces and cracks deep below the ground.

 

Question 3

There are ten tubewells in a lane of fifty houses. What could be the long-term impact on the water table?

Answer

The effect on the water table depends on the replenishment of underground water. Only five families will share a tubewell, the water used for daily domestic purposes will not affect the water table. But if there is shortage of rains, the water used by the family will not replenished and water table will fall down.

 

Question 4

You have been asked to maintain a garden. How will you minimise the use of water?

Answer

To minimise the wastage of water we will use the drip irrigation which throws the water at the base of plants. We will check the leakages in the water pipes and arrange small pits for rainwater harvesting. The collected rainwater will be used later.

 

Question 5

Explain the factors responsible for the depletion of water table.

Answer

Various factors responsible for the depletion of water table are:

(i) Increased population: Demand of water has been increased by the increased population. As the number of humans increase, the consumption of water also increases.

(ii) Increasing industries: All industries need water. As the number of human population increase, the number of industries are also increased which definitely increases the consumption of water.

(iii) Lack of water conservation techniques: Main source of water on earth and for the underground water is rain. The water of the rain, if conserved can increase the ground water level. But this is not done due to lack of water conservative techniques.

(iv) Agricultural activities: India is a country which depends on agriculture. The land used for cultivation has increased. So, the consumption of water for agriculture has increased. Irregular rainfall has increased the consumption of groundwater. This has increased the depletion of groundwater.

 

Question 6

Fill in the blanks with the appropriate answers:.

(a) People obtain groundwater through_____ and _____.

(b) Three forms of water are solid _____, _____ and _____.

(c) The water bearing layer of the earth is ______.

(d) The process of water seepage into the ground is called ______.

Answer

(a) wells, hand pumps

(b) liquid, gas

(c) aquifer

(d) infiltration

 

Question 7

Which one of the following is not responsible for water shortage?

(i) Rapid growth of industries

(ii) Increasing population

(iii) Heavy rainfall

(iv) Mismanagement of water resources

Answer

(iii) heavy rainfall

 

Question 8

Choose the correct option. The total water

(i) in the lakes and rivers of the world remains constant.

(ii) under the ground remains constant.

(iii) in the seas and oceans of the world remains constant.

(iv) of the world remains constant.

Answer

(iv) of the world remains constant.

 

Question 9

Make a sketch showing groundwater and water table. Label it.

Answer

Image

 

Chapter 17 - Forests: Our Lifeline

Question 1

Explain how animals dwelling in the forest help it grow and regenerate.

Answer

Animals help in growing and regenerating forests in many ways. Animals work as the cleaning agents in the forest. Microorganisms work on dead bodies of plants and animals and degenerate them. Animals also help in pollination which helps in growing a number of plants. Herbivores helps the carnivores to grow as they serve as food for them. Thus flora and fauna mutually grow in the forest.

 

Question 2

Explain how forests prevent floods.

Answer

Forests can absorb a lot of water. The roots of the trees absorb the water and prevent it from flowing away. Roots of trees also help in percolation of water into the soil. This helps in preventing floods.

 

Question 3

What are decomposers? Name any two of them. What do they do in the forest?

Answer

Decomposers are the organisms which feed on the dead bodies of plants and animals. They clean the forests decaying dead bodies and replenishing the nutrients back to the forest soil, e.g.„ beetles and grubs.

 

Question 4

Explain the role of forest in maintaining the balance between oxygen and carbon dioxide in the atmosphere.

Answer

Plants release oxygen in the atmosphere during the process of photosynthesis. This oxygen is inhaled by the animals for respiration. During respiration, they release carbon-dioxide which is absorbed by plants. In this way the oxygen and carbon dioxide cycle goes on. Since forests contain a large number of plants, they help much in this cycle and maintain balance in nature.

 

Question 5

Explain why there is no waste in a forest.

Answer

There is no waste in the forest because decomposers convert all the dead bodies of the plants and animals into the humus which gets added to the soil. Thus, no waste remains.

 

Question 6

List five products we get from forests.

Answer

(i) We get medicines from forests.

(ii) We get gum from forests.

(iii) We get wood which is used for many purposes like making furniture, paper etc.

(iv) We get food for animals from forests.

(v) We get sealing wax from forests.

 

Question 7

Fill in the blank:

(a) The insects, butterflies, honeybees and birds help flowering plants in ______ .

(b) A forest is a purifier of and ______.

(c) Herbs form the layer in the forest ______.

(d) The decaying leaves and animal droppings in a forest enrich the  ______.

Answer

(a) pollination (b) water, air (c) lowest (d) soil as humus.

 

Question 8

Why should we worry about the conditions and issues related to forests far from us?

Answer

We should be worried about deforestation as it would lead to floods, increase in earth’s temperature, decreasing animals habitats and soil erosion. Damage to forests directly or indirectly affects human habitat and environment so it must be a matter of concern among us.

 

Question 9

Explain why there is a need of variety of animals and plants in a forest.

Answer

All plants and animals sustain the forest life and also C02 – 02 cycle goes on due to animals and plants. Animals convert the dead and decaying matters into humus and increase the fertility of soil, thus enhancing plant growth. All food chains and food webs need variety of plants and animals.

 

Question 10

In fig. 1 7.15 the artist has forgotten to put the labels and directions on the arrows. Mark the directions on the arrows and label the diagram using the following labels: clouds, rain, atmosphere, carbon dioxide, oxygen, plants, animals, soil, roots, water table.

 

Image

 

Answer

 

Image

 

Question 11

Which of the following is not a forest product?

(i) Gum (ii) Plywood (iii) Sealing wax (iv) Kerosene

Answer

(iv) Kerosene

 

Question 12

Which of the following statements is not correct?

(i) Forests protect the soil from erosion.

(ii) Plants and animals in a forest are not dependent on one another.

(iii) Forests influence the climate and water cycle.

(iu) Soil helps forests to grow and regenerate.

Answer

(ii) Plants and animals in a forest are not dependent on one another.

 

Question 13

Micro-organisms act upon the dead plants to produce

(i) sand (ii) mushrooms (iii) humus (iu) wood

Answer

(i) Humus

 

Chapter 18 - Wastewater Story

Question 1

Fill in the blanks:

(a) Cleaning of water is process of removing __________

(b) Wastewater released by houses is called __________.

(c) Dried __________ is used as manure.

(d) Drains get blocked by __________ and __________.

Answer

(a) pollutants (b) sewage (c) sludge (d) (d) chemicals, kitchen waste

 

Question 2

What is sewage? Explain why it is harmful to discharge untreated sewage into rivers or seas.

Answer

Sewage is a liquid containing wastes which is disposed by households, industrial and agricultural activities in water. It is harmful to discharge untreated sewage into rivers or seas because it can pollute the whole sources of water. Sewage contains harmful substances and disease causing organisms. It is therefore dangerous to release untreated sewage in water.

 

Question 3

Why should oils and fats be not released in the drain? Explain.

Answer

Oils and fats should not be released in drains because they harden the soil in the pipes and block them. Fats get clogged in holes of the soil in the drain and block it. It does not allow the water to flow.

 

Question 4

Describe the steps involved in getting clarified water from wastewater.

Answer

Following steps are involved in the purification of water:

(i) Firstly all the physical impurities like stones, plastic bags, cans etc. are to be removed. It is done by passing the water through bar screens.

(ii) Then water is taken to grit and sand removal tank where impurities are removed by sedimentation.

(iii) Solid impurities and faeces etc. are collected from bottom of water. These impurities collected are called sludge.

(iv) Clarified water is cleaned of other impurities by aerator. All disease causing bacteria are removed by chlorination.

 

Question 5

What is sludge? Explain how it is treated.

Answer

Sludge is the collected solid waste from the wastewater during the treatment in water treatment plant. Sludge is decomposed in a separate tank by the anaerobic bacteria. Activated sludge is used as manure.

 

Question 6

Untreated human excreta is a health hazard. Explain.

Answer

Untreated human excreta can cause a lot of health related problems. It pollutes water, air and soil. The polluted water contain disease causing bacteria which can spread epidemics like cholera, meningitis etc.

 

Question 7

Name two chemicals used to disinfect water.

Answer

Chlorine and ozone

 

Question 8

Explain the Junction of bar screens in a wastewater treatment plant.

Answer

Bar screens clear the wastewater of all the physical impurities. Large size waste like napkins, plastics, cans etc. are removed from the wastewater through the bar screens.

 

Question 9

Explain the relationship between sanitation and disease.

Answer

Sanitation and disease are related to each other. Sanitation involves proper disposal of sewage and refuse from house and public places. If sanitation is there, no disease will occur, but if sanitation is not there various types of disease will occur and spread. So sanitation should be kept to avoid disease.

 

Question 10

Outline your role as an active citizen in relation to sanitation.

Answer

As active citizen we should take care of our personal environmental sanitation. We should make people aware of the benefits of sanitation. We should help municipal corporations to cover all the open drains and remove disease causing substances thrown in open.

 

Question 11

Here is a crossword puzzle. Good luck!

 

Image

 

Across:

3. Liquid waste products

4. Solid waste extracted in sewage treatment

6. A word related to hygiene

8. Waste matter discharged from human body

Down:

1. Used water

2. A pipe carrying sewage

5. Micro-organisms which cause cholera

7. A chemical to disinfect water

 

Answer

Image

 

Question 12

Study the following statements about ozone:

(a) It is essential for breathing of living organisms.

(b) It is used to disinfect water.

(c) It absorbs ultraviolet rays.

(d) Its proportion in air is about 3%.

Which of these statements are correct?

(i) (a), (b) and (c) (ii) (b) and (c) (iii) (a) and (d) (iv) All four

Answer

(ii) (b) and (c)


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