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Exemplar Problems and Solutions for Class 8

Chapter 1: Crop Production and Management


1. Which one of the following condition is not essential to growmaize?
(a) High temperature   (c) Low temperature
(b) Humidity   (d) Rainfall

2. Propagation of ginger is generally done using
(a) seed   (c) root
(b) stem (rhizome)   (d) leaf

3. Which of the following statement is not true for organic manure?
(a) It enhances water holding capacity of soil.
(b) It has a balance of all plant nutrients.
(c) It provides humus to soil.
(d) It improves texture of soil.

4. The term used for the process of separation of grains from chaff is
(a) sieving   (c) winnowing
(b) threshing   (d) hand picking

5. Read the statements given below.

(i) Seeds require moisture for germination.
(ii) Plants can absorb nutrients mostly in dissolved form.
(iii) Irrigation protects crops from both frost and hot air currents.
(iv) Irrigation improves soil texture.
Choose the combination of statements which indicate the need to irrigate crops.
(a) i and ii
(b) i, ii, iii
(c) i, ii, iii, iv
(d) i and iii

6. Which of the following tools would a farmer use to remove weeds from the field?
(a) Hoe
(b) Plough
(c) Axe
(d) Cultivator

7. Which of the following is not true for fertilisers?
(a) They increase the yield.
(b) Their excessive use disturbs the balance of nutrients in soil.
(c) They are generally used in small quantity.
(d) They are environment friendly.

8. Given below are statements about the harmful effects of weeds on crop plants.
(i) They interfere in harvesting.
(ii) They help crop plants to grow healthily.
(iii) They compete with crop plants for water, nutrients, space and light.
(iv) They affect plant growth.
Choose the correct combination of statements.
(a) i, iii, iv (c) iii, iv
(b) iii only (d) i, ii, iii, iv

9. The process of loosening and turning of soil is called
(a) irrigation and manuring (c) tilling and ploughing
(b) digging and winnowing (d) harvesting and storage

10. The monsoon season in our country is during the months
(a) April to December (c) November to March
(b) June to September (d) January to May

11. The system of irrigation where in water is supplied drop by drop near the roots of plants, is called
(a) pulley system (c) sprinkler system
(b) drip system (d) lever system


12. Pick out the odd one from the following words given in the box
and give reason for it.
Plough, Seed Drill, Hoe, Chain Pump, Sickle

13. If you are given a dry piece of land for cultivation what will you do before sowing the seeds?

14. State whether the following statements are True or False. Correct the false statements.
(i) Using good quality seed is the only criterion to get high yield.
(ii) Growing different crops in different seasons in the same field will deplete the soil of nutrients.
(iii) All crop plants are sown as seeds in the field.
(iv) Cells of root nodules of leguminous plants fix nitrogen.
(v) Freshly harvested grains must be dried before storing.

15. During which months do farmers grow mustard in India?

16. Which activity of the farmer can promote growth of earthworms and microbes in the field?


17. Beera, wants to practice crop rotation in his field. Suggest a Rabi crop and a Kharif crop which will replenish his field with nitrogen. Which crop replenishes nitrogen and why?

18. Match the agricultural implements given in Column A with their use given in Column B.

Column I Column II
(i) Sickle (a) Ploughing
(ii) Hoe (b) Sowing
(iii) Seed Drill (c) Harvesting
(iv) Sprinkler (d) Irrigation

19. What are organic foods?

20. From the word puzzle given as Fig. 1.1 find atleast eight words which are ‘farmer’s friends.’ Classify them into living and non living.

21. (a) Name the tool used with a tractor for sowing seeds in a field.
(b) What are the advantages of using this tool?

22. (a) Name the practice followed for large scale rearing of farm animals.
(b) What facilities are provided to farm animals?

23. Clasify the following crops into Khariff and Rabi crops and write in the tabular column given below:
Maize, paddy, mustard, pea, gram, wheat, groundnut, cotton.


24. Despite favourable climatic conditions, a farmer’s crop failed to
give a good yield. Give the possible reasons for this.

25. As a part of eco-club activity, students were asked to raise a kitchen garden in the school premises. They were provided with some materials given in the box. List the other materials you would require. How will you plan the garden? Write the steps. khurpi, water-can, spade, shovel Note: You have been asked to use only environment friendly materials.

26. Paddy is a major cereal crop in our country.
(a) In which season is paddy cultivated?
(b) Discuss the method of sowing.
(c) What measures must be taken to prevent spoilage and insect attack of harvested grains.

27. Unscramble the words related to crop production and its management and write in the boxes given beneath them.
(iv) VERIR

28. Given below is a conversation between two farmers Heera and Beera.
Heera: Brother Beera, your maize crops looks beautiful! They
have grown pretty fast.
Beera: Yes, I have sprayed urea this time. What about you?
Heera: Well, I am still relying on good old cow dung. I am saving
money for buying a tractor.
Beera: That’s good. Tractor saves a lot of time and labour.
Heera: Yes, it’s been very labour intensive for me and now these
weeds have come up.
Beera: Try weedicides, they are very effective.
Now answer the following questions.
(i) List the practices which are not environment friendly and why?
(ii) What is the advantage of modern agriculture implements over traditional ones?
(iii) Name one weedicide and the precaution farmers must take during its application.

29. For discussion
Despite being one of the growing economies, our country still has a large section of population going hungry and malnourished. Do you think an efficient crop production mechanism is the only solution to this? Discuss in the class what else needs to be done to root out hunger and malnutrition from our country.

30. Terms related to agricultural practice are given below. Rearrange them in the correct sequence. harvesting,  owing, manuring, tilling and ploughing, irrigation, de-weeding.

Chapter 2: Microorganisms: Friend and Foe


1. Which of the following reproduces only inside a host cell?
(a) Bacteria (c) Amoeba
(b) Virus (d) Fungus.

2. A disease in human beings caused by virus is _______.
(a) typhoid (c) dysentry
(b) influenza (d) cholera

3. Pathogenic micro-organisms present in host cells are killed by medicines called
(a) pain killer (c) antibiotics
(b) antibodies (d) vaccines

4. The two micro-organisms which live in symbiotic association in lichens are
(a) fungus and protozoa (c) bacteria and protozoa
(b) alga and bacteria (d) alga and fungus

5. The gas released during the preparation of bread is
(a) oxygen (c) nitrogen
(b) carbon dioxide (d) sulphur dioxide

6. The disease caused by a protozoan and spread by an insect is _________.
(a) dengue (c) polio
(b) malaria (d) measles

7. Paheli dug two pits, A and B, in her garden. In pit A, she put a polyhtene bag packed with some agricultural waste. In pit B, she dumped the same kind of waste but without packing it in a polythene bag. She, then covered both the pits with soil. What did she observe after a month?

(a) Waste in pit A degraded faster than that in pit B.
(b) Waste in pit B degraded faster than that in pit A.
(c) Waste in both pits degraded almost equally.
(d) Waste in both pits did not degrade at all.


8. Unscramble the jumbled words underlined in the following statements.
(a) Cells of our body produce santiidobe to fight pathogens.
(b) curbossulite is an air-borne disease caused by a bacterium.
(c) Xanrhat is a dangerous bacterial disease.
(d) Yeasts are used in the wine industry because of their property of meronettinaf.

9. Suggest a suitable word for each of the following statements.
(a) Chemicals added to food to prevent growth of microorganisms.
(b) Nitrogen-fixing microorganism present in the root nodules of legumes.
(c) Agent which spreads pathogens from one place to another.
(d) Chemicals which kill or stop the growth of pathogens.

10. Match the names of scientists given in Column A with the discovery made by them given in Column B.

Column A Column B
a) Louis Pasteur 1) Penicillin
b) Robert Koch 2) anthrax bacterium
c) Edward Jenner 3) Fermentation
d) Alexander Fleming 4) small pox vaccine
5) Typhoid

11. Name one commercial use of yeast.

12. Name the process in yeast that converts sugars into alcohol.

13. In the soil, which nutrient is enriched by blue-green algae (cyanobacteria)?

14. Why should we avoid standing close to a tuberculosis patient while he/she is coughing?

15. Polio drops are not given to children suffering from diarrhoea.

16. Paheli watched her grandmother making mango pickle. After she bottled the pickle, her grand mother poured oil on top of the pickle before closing the lid. Paheli wanted to know why oil was poured? Can you help her understand why?


17. Match the microorganisms given in Column A to the group to which they belong in Column B.

Column A Column B
a) Lactobacillus (i) Algae
b) Aspergillus (ii) Protozoa
(c) Spirogyra (iii) Fungi
(d) Paramecium (iv) Bacteria

18. Classify the following into friendly and harmful microorganisms.

Yeast, malarial parasite, Lactobacillus, bread mould, Rhizobium, Bacillus anthracis

Friendly         Harmful
________   ________
________   ________
________   ________
________   ________

19. While returning from the school, Boojho ate chaat from a street hawker. When he reached home, he felt ill and complained of stomach ache and fell ill. What could be the reason?

20. What will happen to ‘pooris’ and ‘unused kneaded flour’ if they are left in the open for a day or two?

21. (a) Name two diseases that are caused by virus.
(b) Write one important characteristic of virus.


22. Observe the Fig.2.1 and answer the questions that follows.
(a) Write the name of the disease.
(b) Name the causative agent of this disease?
(c) How does the disease spread from one plant to another?
(d) Name any two plant diseases and the microbes that cause

23. How do vaccines work?

24. Observe the set up given in Fig. 2.2 and answer the following questions.
(a) What happens to the sugar solution in A?
(b) Which gas is released in A?
(c) What changes will you observe in B when the released gas passes through it?

25. Observe the Fig.2.3 and answer the following questions.

(a) Name the microorganism and the group to which it belongs.
(b) Name the food item on which the organism grows.
(c) Does it grow well in dry or in moist conditions?
(d) Is it safe to eat infected bread?

26. Give reasons for the following.
(a) Fresh milk is boiled before consumption while processed milk stored in packets can be consumed without boiling.
(b) Raw vegetables and fruits are kept in refrigerators whereas jams and pickles can be kept outside.
(c) Farmers prefer to grow beans and peas in nitrogen deficient soils.
(d) Mosquitoes can be controlled by preventing stagnation of water though they do not live in water. Why?

27. How can we prevent the following diseases?
(a) Cholera
(b) Typhoid
(c) Hepatitis A

28. Complete the following cycle given as Fig. 2.4 by filling the blanks (a), (b), (c) (d)

Chapter 3: Synthetic Fibres and Plastics


1. Pick the synthetic fibre out of the following?
(a) Cotton (c) Jute
(b) Nylon (d) Wool

2. Which of the following is a source of rayon?
(a) Wool (c) Wood pulp
(b) PET (d) Silk

3. Polycot is obtained by mixing
(a) nylon and wool (c) nylon and cotton
(b) polyester and wool (d) polyester and cotton

4. Which is a thermosetting plastic?
(a) Melamine (c) PVC
(b) Polythene (d) Nylon

5. The material similar to silk in appearance is
(a) Nylon (c) Polyester
(b) Rayon (d) Terylene

6. The most suitable material for the preparation of handles of cooking utensils is
(a) Polythene (c) Nylon
(b) PVC (d) Bakelite

7. Which of the following is not a common property of plastics?
(a) Non-reactive (c) Durable
(b) Light in weight (d) Good conductor of electricity

8. Which of the following represents the correct match for items in Column A with those in Column B.

Column A Column B
I. Nylon (i) Thermoplastic
II. PVC (ii) Thermosetting plastic
III. Bakelite (iii) Fibre

(a) I-(ii), II-(iii), III-(i) (c) I-(ii), II-(i), III-(iii)
(b) I-(iii), II-(i), III-(ii) (d) I-(iii), II-(ii), III-(i)

9. Which of the following groups contain all synthetic substances?
(a) Nylon, Terylene, Wool (c) PVC, Polythene, Bakelite
(b) Cotton, Polycot, Rayon (d) Acrylic, Silk, Wool

10. The material which is commonly used for making kitchen containers is
(a) PVC (c) Teflon
(b) Acrylic (d) PET


11. Cotton is a natural polymer. What is its chemical name?

12. A synthetic fiber which looks like silk is obtained by chemical treatment of wood pulp. It is, therefore, known as artificial silk. What is its common name?

13. Terrycot is made by mixing two types of fibres. Write the names the fibres.

14. Plastic articles are available in all possible shapes and sizes. Can you tell why?

15. Plastic is used for making a large variety of articles of daily use and these articles are very attractive. But it is advised to avoid the use of plastic as far as possible. Why?

16. Why is it not advisable to burn plastic and synthetic fabrics?

17. Select the articles from the following list which are biodegradable.
(a) paper (c) wood
(b) woolen clothes (d) aluminium can
(e) plastic bag (f) peels of vegetables

18. A bucket made of plastic does not rust like a bucket made of iron. Why?


19. Rohit took with him some nylon ropes, when he was going for rock climbing. Can you tell why he selected nylon ropes instead of ropes made of cotton or jute?

20. A lady went to the market to buy a blanket. The shopkeeper showed her blankets made of acrylic fibres as well as made of wool. She preferred to buy an acrylic blanket. Can you guess why?

21. PVC (polyvinyl chloride) is a thermoplastic and is used for making toys, chappals, etc. Bakelite is a thermosetting plastic and is used for making electrical switches, handles of various utensils, etc. Can you write the major difference between these two types of plastics?

22. Fill in the blanks.
(i) A polymer is a chain of many small units joined together which are called ______.
(ii) The synthetic fibres are also known as ______ fibres.
(iii) The first fully synthetic fibre was ______.
(iv) A fibre similar to wool is ______.
(v) A plastic used for making crockery is ______.

23. Match items in List A with the items of list B.

List A List B
a) Nylon 1) non-stick coating
b) PET 2)Electric switches
c) Rayon 3) Parachutes
d)Thermosetting Plastics 4) Polyester
e) Teflon 5) Artificial Silks

24. Unscramble the jumbled words given below, related to synthetic
(a) anory
(b) lopmery
(c) relyteen
(d) laspict
(e) yespolter
(f) felton


25. Indicate whether the following statements are True or False. Also write the false statements in their correct form.
(i) The fabric terywool is obtained by mixing terylene and wool.
(ii) Synthetic fibres do not melt on heating.
(iii) It is risky to wear synthetic clothes while working in the kitchen.
(iv) Most of the plastics are biodegradable.

26. Write the importance of synthetic polymers in our life.

27. Despite being very useful it is advised to restrict the use of plastic. Why is it so? Can you suggest some methods to limit its consumption?

28. Write an activity to show that synthetic fibres are stronger than the cotton fibres.

29. Complete the crossword given below with the help of clues.
1. Substance used as synthetic wool (7)
2. A plastic used for making containers and carry bags (9)
3. Substance made up of large number of smaller molecules (7)
4. Another name for this compound is artificial silk (5)

5. A type of fibre obtained naturally from cocoon (4)
6. A synthetic fibre classified as polyester (8)
7. A polymer used for making rope (5)

Chapter 4: Materials : Metals and Non-Metals


1. Which of the following is not a metal?
(a) copper (c) aluminium
(b) sulphur (d) iron

2. The substance that will be flattened on beating with a hammer is
(a) crystal of iodine (c) piece of coal
(b) lump of sulphur (d) zinc granule

3. Boojho has learnt that non-metals on beating with a hammer are generally broken into pieces. Which of the following is a nonmetal?
(a) iron nail (c) copper plate
(b) aluminium wire (d) piece of coal

4. Materials which can be drawn into wires are called ductile. Which of the following is not a ductile material?
(a) silver (c) sulphur
(b) copper (d) aluminium

5. Metals are generally hard. Which of the following metals is an exception and can be cut with a knife?
(a) iron (c) gold
(b) sodium (d) magnesium

6. Metals are generally solid. Which of the following metals is in the liquid state at room temperature?
(a) mercury (c) aluminium
(b) silver (d) sodium

7. Metals generally react with dilute acids to produce hydrogen gas. Which one of the following metals does not react with dilute hydrochloric acid?
(a) magnesium (c) iron
(b) aluminium (d) copper


8. Which of the following reacts with cold water vigorously?
(a) carbon (c) magnesium
(b) sodium (d) sulphur

9. The metal which produces hydrogen gas on reaction with dilute hydrochloric acid as well as sodium hydroxide solution is
(a) copper (c) aluminium
(b) iron (d) sodium

10. Which of the following non-metals reacts and catches fire on exposure to air?
(a) phosphorus (c) sulphur
(b) nitrogen (d) hydrogen

11. Generally metallic oxides are basic and non-metallic oxides are acidic in nature. Solution of which of the following oxides in water will change the colour of blue litmus to red?
(a) sulphur dioxide (c) iron oxide
(b) magnesium oxide (d) copper oxide

12. Which of the following property is not responsible for copper to be used as electrical conduction wires?
(a) ductility (c) good conductor of electricity
(b) colour (d) it is solid


13. Name two soft metals which can be cut with a knife.
14. Which non-metal is essential for our life and all living beings inhale it during breathing?
15. Name two major non-metals which are present in fertilisers and enhance the growth of plants.
16. Which non-metal is used to disinfect water?
17. A purple coloured non-metal forms a brown solution in alcohol which is applied on wounds as an antiseptic. Name the nonmetal.
18. Zinc sulphate forms a colourless solution in water. Will you observe any colour on adding copper turning in it?
19. Why are bells made of metals?
20. Which liquid metal is used for making thermometers?
21. Which of the following metals can displace the other two metals from their salt solutions?
zinc, iron, copper


22. Paheli bought a statue made of copper. To her surprise it acquired a dull green coating after a couple of months. Explain the reason.

23. In Fig 4.1 you find that the bulb glows when an iron nail is placed between two ends of wire. Complete the following sentences on the bases of this fact.

(a) __________ is a metal.
(b) Metals are good __________ of electricity.

24. If in Fig. 4.1 iron nail is replaced by a wooden stick, will the bulb glow or not? Justify your answer.

25. Paheli prepared a blue coloured solution of copper sulphate in beaker A and placed an iron nail in it. Boojho prepared a yellowish green solution of ferrous sulphate in beaker B and placed a copper wire in it. What changes will they observe in the two beakers after an hour?

26. A doctor prescribed a tablet to a patient suffering from iron deficiency. The tablet does not look like iron. Explain.

27. Match the substances in Column A with their applications given in Column B.

Column A ( Substance) Column B (Application)
a) oxygen 1) for making crackers
b) copper 2) for disinfecting water
c) sulphur 3) all living beings inhale during breathing
d) iron 4) for making electric wires
e) chlorine 5) for making rails


28. Some of the following statements are incorrect. Find the incorrect statements and correct them.
(a) The property of metals by virtue of which they can be drawn into wires is called ductility.
(b) Metals are good conductor of electricity but poor conductor of heat.
(c) Articles made of metals produce ringing sound when struck hard.
(d) Oxides of non-metals and metals are acidic in nature.
(e) A less reactive metal replaces a more reactive metal from its salt solution in water.

29. Iron is more reactive than copper. Can you write an activity to show this?

30. Fill in the blanks to complete the following paragraph.
The name of the product formed in the reaction of sulphur and _____________ is sulphur dioxide gas. When sulphur dioxide is dissolved in_________________, sulphurous acid is formed. The sulphurous acid turns _____________ litmus paper to ____________. Generally oxides of __________ are acidic in nature.
After completing the paragraph write two questions which you can raise on the basis of this information.

31. Find out the names of three metals and three non-metals from the box given as Fig 4.2.

32. Complete the crossword given in Fig. 4.3 with the help of the clues.
Fig 4.3

1. Which is generally hard, ductile, malleable and sonorous.
2. A metal is called so it can be drawn into wires.
3. Metal bells are used because of this property.
4. A metal generally used for making jewellery.
5. A metal which is liquid at room temperature.
6. A metal which reacts with acid as well as base to form hydrogen gas.
7. Substances used to enhance the growth of plants.
8. Property by virtue of which metals can be beaten into thin sheets.

Chapter 5: Coal and Petroleum

1. Various materials which are obtained from nature are called natural resources. Which of the following is not a natural resource?
(a) minerals (c) soil
(b) water (d) plastic

2. Air is a natural resource and cannot be exhausted by human activities. It is known as inexhaustible natural resource. Which of the following is another inexhaustible natural resource?
(a) coal (c) sun-light
(b) petroleum (d) minerals

3. Which of the following is a pair of exhaustible natural resources.
(a) coal and soil (c) water and petroleum
(b) air and sun-light (d) wild life and minerals

4. Coal is processed in industries to get some useful products. Which of the following is not obtained from coal?
(a) coke (c) coal gas
(b) coal tar (d) CNG

5. Exhaustible natural resources are:
(a) unlimited in quantity.
(b) not dependent on nature.
(c) limited in quantity.
(d) not exhausted by human activities.

6. Fossil fuels are obtained from:
(a) remains of non-living materials.
(b) dead remains of birds only.
(c) dead remains of insects only.
(d) dead remains of living organisms.

7. Coal is formed from the remains of
(a) vegetation only (c) both vegetation and animals
(b) animals only (d) neither vegetation nor animals

8. Which substance is formed by the carbonisation of dead vegetation?.
(a) coal (c) coal gas
(b) coke (d) coal tar

9. Naphthalene balls are obtained from coal tar and are used as
(a) mosquito repellant (c) moth repellant
(b) honey bee repellant (d) snake repellant

10. Which of the following is not a constituent of petroleum?
(a) paraffin wax (c) petrol
(b) lubricating oil (d) coke

11. Petroleum was formed from organisms:
(a) living on the land (c) living in the sea
(b) living on the plants (d) living on the rocks

12. Choose the correct statement from the following:
(a) It is difficult to transport natural gas through pipes.
(b) The disadvantage of natural gas is that it can not be used directly for burning in homes.
(c) Natural gas is stored under high pressure as compressed natural gas.
(d) Natural gas cannot be used for power generation.


13. You are provided with a mixture of petroleum and water. Can you suggest a method to separate the two?
14. What does CNG stand for and why is it considered to be a better fuel than petrol?
15. Name the petroleum product used as fuel for stoves, lamps and jet aircrafts.
16. Fill in the blanks in the following sentences.
(a) Coal is one of the ________ used to cook food.
(b) When heated in air, coal burns and produces mainly ________gas.
(c) Coal tar is a black, thick ________ with an ________ smell.
(d) Petroleum, ________ and ________ are fossil fuels.
(e) Forests and coal are ________ natural resources.

17. The underlined words in the following sentences have been jumbled up. Write them in their correct form.
(a) Loca is obtained from mines.
(b) Umpetlore is a fossil fuel.
(c) Rineryfe is a place where various fractions of peroleum are separated.
(d) Keenrose is a fuel used in jet crafts.
(e) Nutsgilh is an example of inexhaustible natural resources.

18. Fill in the blanks.
(a) The slow process of conversion of dead vegetation into coal is called__________.
(b) Coal and petroleum are formed from the dead remains of organisms and are known as __________.
(c) The black thick liquid with __________ smell is known as coal tar.
(d) During the processing of coal to get coke, coal tar and __________ are also obtained.
(e) The process of separating the various constituents of petroleum is known as __________.
(f) Excessive burning of fossil fuels is a major cause of __________.

19. Write True/False against the following statements.
(a) Oxygen in air is an exhaustible natural resource.
(b) Resources which are present in unlimited quantity in nature are called exhaustible natural resources.
(c) Wildlife is an exhaustible natural resource.
(d) Under high temperature and pressure, dead plants get slowly converted to coal.
(e) CNG is less polluting fuel than petrol and diesel.


20. Sunlight and air are inexhaustible natural resources. Comment.
21. Some natural resources are given in a box. Classify them into the exhaustible and inexhaustible natural resources.
air, coal, natural gas, sunlight, petroleum, minerals,
forests, oxygen.
22. Write two important uses of coke.
23. Write the characteristics and some important uses of coal.
24. Look at Fig. 5.1 where petroleum and natural gas deposits are shown. Why do we find oil layer above water layer?
25. Fill in the blanks and complete the story.
About 300 million years ago the earth had dense ________ in low lying wetland areas. Due to natural processes, like ______, these forests got burried under the ________. As more ________ deposited over them, they were compressed. The ________ also rose as they sank deeper and deeper. Under high ________ and high ________, dead plants got slowly converted into coal.

26. Match the items given in Column I with the items of Column II.

Column I Column II
a) Used for road surfacing 1) black gold
b) Natural Gas 2) Vaseline and candles
c) Petroleum 3) Bitumen
d) Paraffin wax 4) CNG


27. Name the products obtained and their uses when coal is processedin industry.
28. We say fossil fuels will last only for a few hundred years. Comment.
29. We read in newspapers that burning of fuels is a major cause of global warming. Explain why.
30. While driving what are the tips we must follow to save petrol/ diesel/natural gas?
31. Imagine that all the exhaustible natural resources are exhausted by human activities. Do you think survival of living beings would be possible.? If yes, why?, If not, why not?
32. Why petrol is exhaustible natural resource, whereas sunlight is not? Explain.
33. Write some important uses of the various constituents of petroleum.
34. Coal reserves are said to be enough to last for another hundredNyears. Do you think we need to worry in such case? Why or why not?
35. What steps would you suggest for the judicious use of fossil fuels?
36. Complete the crossword Fig. 5.2 with the help of the clues:
1. Fuels obtained form dead remains of living organisms. (6,5)
2. A process by which the various constituents of petroleum are
separated. (8)
3. A porous black substance obtained form coal. (4)
4. Another name for motor fuel. (6)
5. The substance obtained by carbonisation. (4)
6. Fuel for heavy motor vehicles. (6)
7. A petroleum product used for road surfacing. (7)
8. Dead remains of sea animals got converted into it. (9)

Chapter 6: Combustion and Flame

Chapter 7: Conservation of Plants and Animals

Chapter 8: Cell – Structure and Functions

Chapter 9: Reproduction in Animals

Chapter 10: Reaching the Age of Adolescence

Chapter 11: Force and Pressure

Chapter 12: Friction

Chapter 13: Sound

Chapter 14: Chemical Effects of Electric Current

Chapter 15: Some Natural Phenomenon

Chapter 16: Light

Chapter 17: Stars and Solar System

Chapter 18: Pollution of Air and Water


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