Posts Tagged: "NCERT Science Solutions"

NCERT Solutions for Class 7th Science Chapter 1 : Nutrition in Plants

- - CBSE

CBSE NCERT Solutions for Class 7th Science Chapter 1 : Nutrition in Plants . NCERT Class 7 Science Solutions for Chapter 1. Class VII Science Solutions NCERT


NCERT Solutions for Class 7th Science Chapter 1 : Nutrition in Plants

Excercise

1. Why do organisms need to take food?

Answer

Organisms need to take food to get energy and perform life process. The life process include nutrition, respiration, growth, excretion, reproduction and response to stimuli which can only be done by intake of food.

2. Distinguish between a parasite and a saprotroph.

Answer

Parasite Saprotroph
The organism that grows on the body of another organism and derives nutrients from it is known as a parasite. The organism that obtains nutrients from the dead or decaying organic matter is called saprotroph.
They take the readymade food from the host. They take the digested and decayed food.
They directly feed on living organisms for their nutrition. They feed on dead and decaying organism.
Examples- Cuscuta and orchids. Examples- Fungi and some bacteria.

3. How would you test the presence of starch in leaves?

Answer

Steps to test the presence of starch in leaves :
Step 1: A fresh leaf is taken.
Step 2: The leaf is boiled in water for few minutes to kill the cells in the leaf.
Step 3: Now, dip this leaf in iodine solution.
Step 4: The color of the leaf will changes into blue black color when iodine is added to it which shows the presence of starch in it.

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

Answer

Photosynthesis is the process synthesis of food in the plants with the help of chlorophyll and carbon dioxide in the presence of sunlight.
Water and minerals present in the soil are absorbed by the roots and transported to the leaves by the vessels.
Carbon dioxide from air is taken through stomata present in leaves.
Leaves are the food factories of the plants which capture the energy of the sunlight with the help of chlorophyll. This energy is used to synthesize food from carbon dioxide and water.

http://4.bp.blogspot.com/-ZEJsXiSCaEM/Vccc5UIywgI/AAAAAAAAABs/49tuBxvJ_nE/s400/nutrtion-in-plants-photosynthesis.png

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

Answer

The food chain shows that the plant is the ultimate producer. Only plant can produce food and rest of other organisms are directly or indirectly dependent on it.

http://2.bp.blogspot.com/-64wh3MSvY6g/VccYa4kpsMI/AAAAAAAAABg/3C_0cQM36SE/s400/plants-is-the-ultimate-source-of-energy.jpg

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) Green plants are called autotrophs since they synthesise their own food.
(b) The food synthesised by the plants is stored as starch.
(c) In photosynthesis solar energy is captured by the pigment called chlorophyll .
(d) During photosynthesis plants take in carbon dioxide and releaseoxygen.

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 (Amarbel)
(ii) Pitcher plant
(iii) Stomata

8. Tick the correct answer:

(a) Amarbel is an example of:
(i) autotroph
(ii) parasite
(iii) saprotroph
(iv) host
► (ii) parasite

(b) The plant which traps and feeds on insects is:
(i) Cuscuta
(ii) china rose
(iii) pitcher plant
(iv) rose
► (iii) pitcher plant

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

Page No: 10

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

(i) Carbon dioxide is released during photosynthesis. (T/F)
► False
(ii) Plants which synthesise their food themselves are called saprotrophs. (T/F)
► False

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

(iv) Solar energy is converted into chemical energy during photosynthesis. (T/F)
► True
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
► (ii) Stomata

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
► (iv) leaves


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NCERT Solutions for Class 7th Science Chapter 2 : Nutrition in Plants

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CBSE NCERT Solutions for Class 7th Science Chapter 2 : Nutrition in Plants . NCERT Class 7 Science Solutions for Chapter 2. Class VII Science Solutions NCERT


NCERT Solutions for Class 7th Science Chapter 2 : Nutrition in Plants

Exercises

1. Fill in the blanks:

(a) The main steps of nutrition in humans are __________, __________, __________, _________ and __________.
(b) The largest gland in the human body is __________.
(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) The main steps of nutrition in humans are ingestion, digestion,absorption, assimilation and egestion.

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

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

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

(e) Amoeba digests its food in the food vacuole.

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) F
(b) T
(c) T
(d) T

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) Water from the undigested food is absorbed mainly in the
(i) stomach       (ii) foodpipe       (iii) small intestine      (iv) large intestine

Answer

(a) Fat is completely digested in the (iii) small intestine

(b) Water from the undigested food is absorbed mainly in the (iv) large intestine

Page No: 21

4. Match the items of Column I with those given in Column II:

Column I
Food Components
Column II
Product(s) of digestion
Carbohydrates Fatty Acids and Glycerol
Proteins Sugar
Fats Amino acids

Answer

Column I

Food Components

Column II

Product(s) of digestion

Carbohydrates Sugar
Proteins Amino acids
Fats Fatty acids and Glycerol

5. What are villi? What is their location and function?

Answer

Villi are small finger-like outgrowths present that help in the process of absorption. These are located in the inner walls of the small intestine. Its function is to increase the surface area of the small intestinal wall for absorption of the digested food.

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

Answer

The bile juice is secreted by the liver. Bile juice helps in the digestion of fats by breaking down the larger fat globules to smaller fat globules.

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

Answer

Cellulose is a type of carbohydrate that can be digested by ruminants and not by humans.
Ruminants have a large sac-like structure called rumen between the oesophagus and the small intestine. The cellulose of the food is digested here by the action of certain bacteria which are not present in humans.

8. Why do we get instant energy from glucose?

Answer

Glucose is simple sugar which is formed when carbohydrate get broken. Also, the carbohydrate get digested into glucose. Since, glucose does not have to be digested and thus acts as an instant source of energy.

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) absorption of food small intestine.

(ii) chewing of food buccal cavity.

(iii) killing of bacteria stomach.

(iv) complete digestion of food small intestine.

(v) formation of faeces large intestine.

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

Answer

Similarity:
Both Amoeba and human have holozoic type of nutrition.
Difference:
Human beings have complex structure for the ingestion, digestion and egestion of food while Amoeba has simple process in which it engulfs the with the help of pseudopodia and food get trapped in food vacuoles.

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
(e)Small intestine (v) Digestion is completed
(f)Large intestine (vi) Absorption of water

Page No: 22

12. Label Fig. 2.11 of the digestive system.

http://4.bp.blogspot.com/-EEgvjwW85kQ/VcjCVvmKjgI/AAAAAAAAACA/EcPUNJwOV3Y/s320/ch-2-science-class-7-ncert.JPG

Answer
http://2.bp.blogspot.com/-pFwSIqQA_V4/VcjHgsF1VpI/AAAAAAAAACQ/um0Y9_liBFU/s320/ch-2-science-class-7-ncert.JPG

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

Answer  

No, Humans cannot survive only on raw, leafy vegetables, or grass. It is because the grass is rich in cellulose, which is a type of carbohydrate that humans are not able to digest due to the absence of cellulose-digesting enzymes.


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NCERT Solutions for Class 7th Science Chapter 3 : Fibre to Fabric

- - CBSE

CBSE NCERT Solutions for Class 7th Science Chapter 3 : Fibre to Fabric. NCERT Class 7 Science Solutions for Chapter 3. Class VII Science Solutions NCERT


NCERT Solutions for Class 7th Science Chapter 3 : Fibre to Fabric

Page No: 32

Exercises
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 i.e. fleece of the black sheep have wool.

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

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

3. Which of the following does not yield wool?
(i) Yak           (ii) Camel           (iii) Goat            (iv) Woolly dog

Answer

► (iv) Woolly dog

4. What is meant by the following terms?
(i) Rearing             (ii) Shearing           (iii) Sericulture

Answer

(i) Rearing : It means taking care of herds of animals which includes feeding, grazing, breeding, etc. for economical purpose like meat and other useful products.

(ii) Shearing : The removal of fleece of the sheep along with a thin layer of skin from its body is called shearing.

(iii) Sericulture : The rearing of silkworms to obtain silk economically is called sericulture.

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, burrs picking, dying, rolling

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

http://1.bp.blogspot.com/-OZ-pYZWuXVM/VcuttsxAChI/AAAAAAAAACk/_SpUyJ-5Wv0/s320/lifecycle-silk-worm-class-7-ncert.jpg

The two stages in the life history of the silk moth which are directly related to the production of silk:

Spinning of cocoon of silk threads around caterpillar.
Changing of caterpillar into pupa.

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

Sericulture and moricultur

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 silk worm
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 silk worm
3. Yak (b) Wool yielding animal
4. Cocoon (a) Yields silk fibres

Page No: 33

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
http://i2.wp.com/farm9.staticflickr.com/8038/7998947480_3d8e693ae3_o.jpg
Answer:
http://i0.wp.com/farm9.staticflickr.com/8176/7998947448_0bff70920d_o.jpg


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NCERT Solutions for Class 7th Science Chapter 4 : Heat

- - CBSE

CBSE NCERT Solutions for Class 7th Science Chapter 4 : Heat. NCERT Class 7 Science Solutions for Chapter 4. Class VII Science Solutions NCERT


NCERT Solutions for Class 7th Science Chapter 4 : Heat

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

Answer

Similarities:
(i) both made up of uniform glass tube.
(ii) both contain mercury.
(iii) both have bulb at one end.
(iv) both generally have celcius scale.

Differences:
(i) Range of laboratory thermometer is from -10°C to 110°C whilerange of clinical thermometer is from 35°C to 42°C.
(ii) Laboratory thermometer is used to take the reading of temperature in laboratory while clinical thermometer is used to measure the temperature f human body.
(iii) Mercury level falls when removed from the source in case of laboratory thermometer while in case of clinical thermometer

2. Give two examples each of conductors and insulators of heat.

Answer

Examples of conductors : Iron, Copper
Examples of insulators : Plastic, Wood

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) The hotness of an object is determined by its temperature.

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

(c) Temperature is measured in degree Celsius.

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

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

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

Page No: 46
4. Match the following :

Column I Column II
(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

Column I Column II
(i) Land breeze blows during (d) night
(ii) Sea breeze blows during (c) day
(iii) Dark coloured clothes are preferred during (b) winter
(iv) Light coloured clothes are preferred during (a) summer

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

Answer

We wear more layers of clothing during winter to keeps us warmer than wearing just one thick piece of clothing because because air gets trapped in between the two layers of blankets. This air prevents the flow of heat from our body to the cold surroundings as air is bad conductor of heat.

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

http://3.bp.blogspot.com/-Pk6YTDHk70M/Vc8j4MJUMTI/AAAAAAAAADQ/GQ4jRxyqS48/s320/class-7-chapter4-science.JPG

Answer

 

http://4.bp.blogspot.com/-_hvxw_vUAlI/Vc8lGG1dP0I/AAAAAAAAADY/y7xwbMN6gV8/s1600/class-7-chapter4-science.JPG
Conduction: From pan to water.
Convection: Heat within water.
Radiation: From burner to pan.

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 that the outer walls of houses be painted white because white colour is absorb least heat. It reflects most of the heat and hence keeps the house cooler.

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) between 30°C and 50°C
Heat gained by cold water will be equal to the lost by hot wate.

Page No: 47

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) not flow from iron ball to water or from water to iron ball.
Both have the same temperature.

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) does not become cold.
Wood is a bad conductor of heat.

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


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NCERT Solutions for Class 7th Science Chapter 5 : Acids, Bases and Salts

- - CBSE

CBSE NCERT Solutions for Class 7th Science Chapter 5 : Acids, Bases and Salts . NCERT Class 7 Science Solutions for Chapter 5. Class VII Science Solutions NCERT


NCERT Solutions for Class 7th Science Chapter 5 : Acids, Bases and Salts

Exercises

1. State differences between acids and bases.

Answer

Acids Bases
(i) Acids are sour in taste. (i) Bases are bitter in taste.
(ii) It turns litmus paper red. (ii) It turns litmus paper blue.
(iii) It doesn’t change the colour of turmeric indicator. (iii) It changes the colour of turmeric indicator to red.
(iv) It doesn’t feel soapy on touching. (iv) It feels soapy on touching.

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

Answer

Ammonia turns red litmus blue so it is basic in nature.

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

Answer

Litmus solution is obtained from lichens dissolved in distilled water.
It is used to detect the acidic and basic characteristic of a substance as it changes its colour to red in acidic medium and into blue in basic medium.

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

Answer

The distilled water is neutral.
Litmus paper can be used to verify whether the distilled water acidic/basic/neutral.
Distilled water doesn’t changes the colour of blue or red litmus paper. So, it is neutral in nature.

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

Answer

When an acid solution and a base solution are mixed in suitable amounts both the solutions
neutralise the effect of each other and a new substance salt is formed. This process is called neutralisation.
When the solution of sodium hydroxide (a base) and hydrochloric acid (an acid) is mixed in test tube in proper ratio, both neutralize each other. In this reaction, a new substance sodium chloride is formed. The mixture obtain is neutral in nature which can be justified by litmus solution or phenolphthalein solution.
The reaction can be written as:
Hydrochloric acid(HCl) + Sodium hydroxide(NaOH) → Sodium Chloride(NaCl) + Water (H2O)

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) F
(ii) F
(iii) T
(iv) T
(v) F

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

Dorji will take red and blue litmus paper and dip it into every bottles of soft drink. The drink in which red litmus paper turnes blue is bottle of basic drink. The drink in which blue litmus paper turns red is bottle of acidic drink.The drink in which both litmus paper show no changes in colour is of neutral drink.

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) Excessive amount of acids in stomach causes pain and antacids prove relief from that pain. Antacids neutralises the effect of excessive acid as it is a base and acts against the acids.

(b) When an ant bites, it injects the acidic liquid (formic acid) into the skin. Calamine solution contains zinc carbonate which neutralises the effect of acid injected by the ant.

(c) Factory waste is neutralised before disposing it into the water bodies because these wastes contain chemicals and harmful acids which may be harmful for the aquatic life and also its leads to pollution of water.

Page No: 57


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

Dip the turmeric indicator in each liquids. The liquid in which the colour of turmeric indicator changes to red is basic in nature i.e. sodium hydroxide. Since, we already identified sodium hydroxide. We will pour the sodium hydroxide in other two bottles. The liquid which get warm after pouring the sodium hydroxide(base) in it is of hydrochloric acid as heat gets evolved in the neutralisation process. The last one which shows no effect is liquid of sugar solution.

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

Answer

The above solution could be a base or a neutral solution because blue litmus paper doesn’t change its colour in the neutral as well as basic solution.
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

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NCERT Solutions for Class 7th Science Chapter 6 : Physical and Chemical Changes

- - CBSE

CBSE NCERT Solutions for Class 7th Science Chapter 6 : Physical and Chemical Changes. NCERT Class 7 Science Solutions for Chapter 6. Class VII Science Solutions NCERT


NCERT Solutions for Class 7th Science Chapter 6 : Physical and Chemical Changes

Exercises

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) Photosynthesis → Chemical change

(b) Dissolving sugar in water → Physical change

(c) Burning of coal → Chemical change

(d) Melting of wax → Physical change

(e) Beating aluminium to make aluminium foil → Physical change

(f) Digestion of food → Chemical change

2. State whether the following statements are true or false. In case a statement is false, write the corrected statement in your notebook.
(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
Cutting a log of wood into pieces is a physical change.

(b) False
Formation of manure from leaves is a chemical change.

(c) True

(d) False

Iron and rust are different substances. Rust is oxide of iron (Fe2O3)

(e) True

Page No: 66

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) When carbon dioxide is passed through limewater, it turns milky due to the formation of calcium carbonate (CaCO3).

(b) The chemical name of baking soda is sodium hydrogen carbonate (NaHCO3).

(c) Two methods by which rusting of iron can be prevented aregalvanization and painting.

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

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

 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
When baking soda is mixed with lemon juice, the bubbles which are formed with the evolution of a gas is due to the evolution of carbon dioxide gas. Since, there is formation of a new substance in this reaction, it is a chemical change.
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 take place.
The melting wax is physical change as there is no formation of new product.
The burning of wax is chemical change as light is lit up by consuming the energy from wax.
Cooking of food is both physical and chemical because raw vegetables get cooked which is a chemical change and the water changes into steam which is a physical change.

6. How would you show that setting of curd is a chemical change?
Answer
The curd is formed from milk. Both curd and milk have different properties. Also, once the curd is formed it cannot be reversed back into milk. So, there is formation of new substance with different properties and also an irreversible process, setting of curd is a chemical change.
7. Explain why burning of wood and cutting it into small pieces are considered as two different types of changes.
Answer
When we burn wood, it turns into ashes which is a new substance and process is irreversible one, hence is a chemical change. While cutting the wood into small pieces no new substance is formed, hence is a physical change.
8. Describe how crystals of copper sulphate are prepared.
Answer
Crystals of copper sulphate are prepared by the method of crystallization.
The process is as followed:
Step 1: A cupful of water in a beaker is taken.
Step 2: Few drops of dilute sulphuric acid is added to it.
Step 3: Water is heated and when it starts boiling copper sulphate powder is added slowly while    stirring till no more copper sulphate powder dissolved in it.
Step 4: Solution is filtered and let it cool without disturbance. After some time the crystals of copper can be observed in it.
9. Explain how painting of an iron gate prevents it from rusting.
Answer
Painting of an iron gate prevents it from rusting because it cut the direct contact of iron from the environment and therefore there is no further exposure of iron to oxygen in moisture which is the causes for rusting.
10. Explain why rusting of iron objects is faster in coastal areas than in deserts.
Answer
Iron objects get rusted because of the reaction with oxygen present in moist air. In coastal areas, the presence of moisture is more because of sea or ocean while in deserts the air is dry and hot. Therefore, rusting of iron objects is faster in coastal areas than in deserts due to presence of moisture.
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.
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.
(iii) Both processes A and B are chemical changes.
(iv) None of these processes is a chemical change.
Answer
(iii) Both processes A and B are chemical changes.

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NCERT Solutions for Class 7th Science Chapter 7 : Weather, Climate and Adaptations of Animals to Climate

- - CBSE

CBSE NCERT Solutions for Class 7th Science Chapter 7 : Weather, Climate and Adaptations of Animals to Climate. NCERT Class 7 Science Solutions for Chapter 7. Class VII Science Solutions NCERT


NCERT Solutions for Class 7th Science Chapter 7 : Weather, Climate and Adaptations of Animals to Climate

Exercises

1. Name the elements that determine the weather of a place.

Answer

The elements that determine the weather of a place are:
(i) Temperature
(ii) Humidity
(iii) Rainfall
(iv) Wind speed

2. When are the maximum and minimum temperatures likely to occur during the day?

Answer

The maximum temperature during the day occurs at the afternoon while the minimum temperature occurs in the early morning.

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) The average weather taken over a long time is called climate.
(ii) A place receives very little rainfall and the temperature is high throughout the year, the climate of that place will be hot and dry.
(iii) The two regions of the earth with extreme climatic conditions are the polar region and the desert.

Page No: 78

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 wet
(b) Kerala → Hot and wet
(c) Rajasthan → Hot and dry
(d) North-east India → Wet

5. Which of the two changes frequently, weather or climate?

Answer

Weather changes frequently.

6. Following 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

(i) Diets heavy on fruits → Tropical rainforests

(ii) White fur → Polar regions

(iii) Need to migrate → Polar regions

(iv) Loud voice → Tropical rainforests

(v) Sticky pads on feet → Tropical rainforests

(vi) Layer of fat under skin → Polar regions

(vii) Wide and large paws → Polar regions

(viii) Bright colours → Tropical rainforests

(ix) Strong tails → Tropical rainforests

(x) Long and large beak → Tropical rainforests

No, these characteristics can’t be adapted for both regions as they are specific.

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

Answer

The tropical rainforest has a large population of animals due to favourable climatic conditions and easy availability of different kinds of foods. The regions is hot and humid  with ample rainfall which supports the growth of animals and plants.

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

Answer

We find animals of certain kind living in particular climatic conditions because every living organisms are adapted to live in the particular habitat. Every living things develop their feature according to the adaption area.
For example, penguins have thick skin to protect themselves from cold and webbed feet to swim in water. It can’t able to survive the hot climate of tropical regions as they developed thick skin for the protection from cold not from the hot and humid temperature.

9. How do elephant living in the tropical rainforest adapt itself?

Answer

Elephant living in the tropical rainforest are well adapted itself to this region.
(i) They have strong sense of smell and uses its trunk for smell.and to hold food.
(ii) They also use their trunk to hold food.
(iii) They have long ears which help them in keeping cool in hot and humid climate.
(iv) Long ears help them in hearing very soft sound.
(v) They have thick padded feet which help them in moving silently.

Choose the correct option which answers the following question:

10. 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

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

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

Page No: 79

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


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NCERT Solutions for Class 7th Science Chapter 8 : Winds, Storms and Cyclones

- - CBSE

CBSE NCERT Solutions for Class 7th Science Chapter 8 : Winds, Storms and Cyclones. NCERT Class 7 Science Solutions for Chapter 8. Class VII Science Solutions NCERT


NCERT Solutions for Class 7th Science Chapter 8 : Winds, Storms and Cyclones

Exercises

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) Wind is moving air.

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

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

(d) Air moves from a region of high pressure to a region of lowpressure.

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

Answer

Two methods to find out wind direction at a given place:
(i)Take some sand and release it from height. The direction in which the sand starts flowing is the direction of the wind.
(ii) Take an air balloon and releases it in the open space. The balloon will starts moving in one direction which will give you idea about the direction of the wind at that place.

3. State two experiences that made you think that air exerts pressure (other than those given in the text).

Answer

Two experiences are:
(i) Take mouthful of air and close the mouth tightly. Now, press the cheeks with the fingers. The air inside mouth put pressure on it.
(ii) Take a balloon and blew it. We observe that the balloon which was shrunk earlier got tighten due to air pressure.

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

Answer

No, I would not like to buy a house having windows but no ventilators because the room will not able to cool down properly. Warm air is lighter which rises up and exit from the ventilators. Cool air is heavier and thus move in through window making the room comfortable for living. Ventilators are important for the circulation of air.

5. Explain why holes are made in hanging banners and hoardings.

Answer

Holes are made in hanging banners and hoardings in order to tackle the air pressure. The air get passed through these holes made on the hoardings or banners and thus reduces the pressure of air on them. Therefore, the hoardings do not get blown away or torned due to air pressure.

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

Answer

Ways to help the neighbours in case cyclone:
(i) Providing first aid to the injured ones.
(ii) Keeping them informed about the weather forecast, alerts and warnings.
(iii) Helping them in moving to the shelter.
(iv) Arrangement of food and drinking water.
(v) Informing the rescue operators, agencies and forces about the affected area in the locality.

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

Answer

Planning required in advance to deal with the situation created by a cyclone are:
(i) Cyclone alert or Cyclone watch should be issued 48 hours in advance of any expected storm.
(ii) The message should be broadcasted every hour or half hour when a cyclone is nearer the coast.
(iii) Armies and Rescue forces should be kept on high alert at the sign of disaster.
(iv) Medical team should be always be prepared for providing the first aid.
(v) Arrangement of safe drinking water and food should be made in time.
(vi) Government should ready with rehabilitation plan.

8. Which one of the following place is unlikely to be affected by a cyclone.
(i) Chennai          (ii) Mangaluru (Mangalore)                 (iii) Amritsar               (iv) Puri

Answer

► (iii) Amritsar

Page No: 93

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.


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NCERT Solutions for Class 7th Science Chapter 9 : Soil

- - CBSE

CBSE NCERT Solutions for Class 7th Science Chapter 9 : Soil. NCERT Class 7 Science Solutions for Chapter 9. Class VII Science Solutions NCERT


NCERT Solutions for Class 7th Science Chapter 9 : Soil

Exercises

Tick the most suitable answer in questions 1 and 2.
1. 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

✓ (iii) minerals, organic matter, air and water

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

✓ (ii) clayey soil

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

4. Explain how soil is formed.

Answer

The soil is formed by the process of weathering in which the rocks break down by the action of wind, water and climate. It is a very slow process and big rocks get converted into soil.

5. How is clayey soil useful for crops?

Answer

Clayey soil is very useful for crops because:
(i) It has very good water retaining capacity.
(ii) This soil is rich in humus and is very fertile.
(iii) It contains useful organic minerals.
These properties of loamy soil is very suitable for growing crops.

6. List the differences between clayey soil and sandy soil.

Answer

Clayey Soil Loamy 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.
(iv) Particles are tightly packed (iv) Particles are loosely packed
(iv) Good for growing various crops. (iv) Not suitable for growing crops.

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

Answer

http://3.bp.blogspot.com/-4CueLdL3Fdg/VdYzURVC5JI/AAAAAAAAAEw/3iH1ayqpCI8/s320/Soil-profile-class7-science-ncert.JPG

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

Amount of water taken = 200 mL

Time taken by water to percolate = 40 min

∴ Rate of percolation = Amount of water taken/Time taken by water to percolate

= 200 mL/40 min = 5 mL/min

Page No: 106

9. Explain how soil pollution and soil erosion could be prevented.

Answer

Steps for preventing soil pollution and soil erosion:

(i) Plantation should be encouraged because plant roots firmly bind the soil and help in preventing erosion.

(ii) Methods like crop rotation and mixed farming should be followed.

(iii) Use of organic fertilizers and manure instead of synthetic.

(iv) Pesticides and insecticides should be used in limited quantity and find natural way to prevent it.

(v) Plastic bags should b banned and it doesn’t decompose and gives rise to soil pollution.

(vi) Industrial waste shouldn’t be dumped directly as it kill necessary micro organisms of soil.

Question 10: Solve the following crossword puzzle with the clues given:
http://i2.wp.com/farm9.staticflickr.com/8461/7999265906_51bf2c53e4_o.jpg
Across
2. Plantation prevents it.
5. Use should be banned to avoid soil pollution.
6. Type of soil used for making pottery.
7. Living organism in the soil.
Down
1. In desert soil erosion occurs through.
3. Clay and loam are suitable for cereals like.
4. This type of soil can hold very little water.
5. Collective name for layers of soil.
Answer:
http://i2.wp.com/farm9.staticflickr.com/8032/7999264007_71b37d7a9d_o.jpg


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NCERT Solutions for Class 7th Science Chapter 10 : Respiration in Organism

- - CBSE

CBSE NCERT Solutions for Class 7th Science Chapter 10 : Respiration in Organism . NCERT Class 7 Science Solutions for Chapter 5. Class VII Science Solutions NCERT


NCERT Solutions for Class 7th Science Chapter 10 : Respiration in Organism

Exercises

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.

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 plants cells. (iv) Examples: Human cells, yeast, Bacteria etc.

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.

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 COwill be utilized by the water plant for synthesizing food and hence there will be less concentration of COin these.

5. Tick the correct answer:
(a) In cockroaches, air enters the body through
(i) lungs             (ii) gills              (iii) spiracles             (iv) skin
 (iii) spiracles

(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
✓ (ii) lactic acid

(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
 (ii) 15 – 18

(d) During exhalation, the ribs
(i) move outwards             (ii) move downwards          (iii) move upwards         (iv) do not move at all
 (ii) move downwards

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 (iii) Alcohol
(b) Diaphragm (iv) Chest cavity
(c) Skin (i) Earthworm
(d) Leaves (v) Stomata
(e) Fish (ii) Gills
(f) Frog (vi) Lungs and skin

Page No: 119

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) F
(ii) F
(iii) T
(iv) F
(v) T

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.

http://4.bp.blogspot.com/-hZRfk7vLDu4/VdeBcPp2CYI/AAAAAAAAAFY/gkUC1C-lp98/s320/crossword-class7-science-chapter-10.JPG

(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

http://3.bp.blogspot.com/-FPmUm-1rTlU/VdeDriz9VxI/AAAAAAAAAFo/WDPPqFUrNmQ/s1600/crossword-class7-science-chapter-10.JPG
(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

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

The mountaineers carry oxygen with them because (b) The amount of air available to a person is less than that available on the ground


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