Chapter 5: Coal and Petroleum

Choose the correct Answers :

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

Answer: (d) plastic
[ Plastic is a synthetic material made by humans, not obtained directly from nature.]

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         (b) petroleum     (c)  sun-light    (d) minerals

Answer:  (c) sun-light
[ Sunlight is an inexhaustible natural resource as it is continuously available and cannot be depleted by human activities. ]

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

Answer: (d) wildlife and minerals
[ Both wildlife and minerals are exhaustible natural resources because they can be depleted by human activities and take very long to form or cannot be renewed quickly. ]

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

Answer:  (d) CNG
[ CNG (Compressed Natural Gas) is obtained from natural gas, not from coal. Coke, coal tar, and coal gas are all obtained from coal processing.]

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

Answer: (c) limited in quantity.
[ Exhaustible natural resources are present in limited amounts and can be depleted by human activities over time.]

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.

Answer:  (d) dead remains of living organisms.
[ Fossil fuels are formed from the dead remains of plants and animals buried under the earth over millions of years.]

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

Answer: (a) vegetation only
[ Coal is formed from the remains of plants (vegetation) that lived millions of years ago, buried under soil and heat over time.]

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

Answer: (a) coal

[ Coal is formed when dead vegetation undergoes carbonisation under high pressure and temperature over millions of years.]
9. Naphthalene balls are obtained from coal tar and are used as
(a) mosquito repellant     (b) honey bee repellant    (c) moth repellant   (d) snake repellant

Answer:  (c) moth repellant
[ Naphthalene balls obtained from coal tar are used to repel moths and protect clothes from insects.]

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

Answer: (d) coke
[ Coke is obtained from coal, not from petroleum. Paraffin wax, lubricating oil and petrol are all constituents of petroleum.]

11.Petroleum was formed from organisms

(a) living on the land    (b) living on the plants (c) living in the sea     (d) living on the rocks

Answer: (c) living in the sea
[ Petroleum was formed from the dead remains of tiny sea organisms (like zooplankton and algae) buried under sea sediments over millions of years.]

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.

Answer: (c) Natural gas is stored under high pressure as compressed natural gas.
[ CNG is stored under high pressure to increase its storage capacity and make transport and use easier.]

VERY SHORT ANSWER QUESTIONS

13. You are provided with a mixture of petroleum and water. Can you suggest a method to separate the two?

Answer: Using a separating funnel, as petroleum and water are immiscible and form separate layers.

14. What does CNG stand for and why is it considered to be a better fuel than petrol?

Answer: CNG stands for Compressed Natural Gas. It is a better fuel than petrol because it burns more cleanly, produces less pollution, and is more environmentally friendly.

15. Name the petroleum product used as fuel for stoves, lamps and jet aircrafts.

Answer: Kerosene is 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.

Answer: (a) Coal is one of the fuels used to cook food.
(b) When heated in air, coal burns and produces mainly carbon dioxide gas.
(c) Coal tar is a black, thick liquid with an unpleasant smell.
(d) Petroleum, coal and natural gas are fossil fuels.
(e) Forests and coal are exhaustible 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.

Answer: (a) Coal is obtained from mines.
(b) Petroleum is a fossil fuel.
(c) Refinery is a place where various fractions of petroleum are separated.
(d) Kerosene is a fuel used in jet crafts.
(e) Sunlight 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 __________.

Answer: (a) The slow process of conversion of dead vegetation into coal is called carbonisation.
(b) Coal and petroleum are formed from the dead remains of organisms and are known as fossil fuels.
(c) The black thick liquid with unpleasant smell is known as coal tar.
(d) During the processing of coal to get coke, coal tar and coal gas are also obtained.
(e) The process of separating the various constituents of petroleum is known as refining.
(f) Excessive burning of fossil fuels is a major cause of air pollution.

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.

Answer: (a) Oxygen in air is an inexhaustible natural resource. – False
(b) Resources present in unlimited quantity are called inexhaustible natural resources.– False
(c) Wildlife is an exhaustible natural resource.– True
(d) Under high temperature and pressure, dead plants get slowly converted to coal. – True .
(e) CNG is less polluting fuel than petrol and diesel.– True.

SHORT ANSWER QUESTIONS

20. Sunlight and air are inexhaustible natural resources. Comment.

Answer: Sunlight and air are inexhaustible natural resources because they are present in unlimited quantity in nature and cannot be exhausted by human activities. They are continuously available and will last forever, unlike exhaustible resources like coal and petroleum.

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.

Answer: Exhaustible natural resources: coal, natural gas, petroleum, minerals and forests .

Inexhaustible natural resources: air, sunlight and oxygen .

22. Write two important uses of coke.

Answer: Two important uses of coke are:

(i) It is used in the manufacture of steel.

(ii) It is used as a fuel in industries and for heating purposes.

23. Write the characteristics and some important uses of coal.

Answer: The characteristics of coal:

(i) It is hard, black, and combustible.

(ii) It burns in air to produce carbon dioxide and releases heat.

(iii) It is an exhaustible fossil fuel.

Important uses of coal:

(i) Used as a fuel to cook food and generate electricity.

(ii) Used in industries to manufacture steel (through coke).

(iii) Coal tar and coal gas obtained from coal are used in various products like medicines, dyes, and as fuel.

24. Look at Fig. 5.1 where petroleum and natural gas deposits are shown. Why do we find oil layer above water layer?

 

Answer: Oil sits above water because it is less dense (lighter) than water. Since oil and water do not mix , the lighter oil floats on top of the heavier water. Similarly, natural gas is the lightest and sits above the oil.

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.

Answer: About 300 million years ago the earth had dense forests in low lying wetland areas. Due to natural processes, like flooding, these forests got buried under the soil. As more soil deposited over them, they were compressed. The temperature also rose as they sank deeper and deeper. Under high pressure and high temperature, 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  (i) Black gold
(b) Natural gas                       (ii) Vaseline and candles
(c) Petroleum                        (iii) Bitumen
(d) Paraffin wax                    (iv) CNG

Answer: (a) Used for road surfacing → (iii) Bitumen
(b) Natural gas → (iv) CNG
(c) Petroleum → (i) Black gold
(d) Paraffin wax → (ii) Vaseline and candles

LONG ANSWER QUESTIONS

27. Name the products obtained and their uses when coal is processed in industry.

Answer: When coal is processed in industry, the following products are obtained along with their uses:

(i) Coke 

It is a tough, porous, and black substance. It is used in the manufacture of steel and as a fuel in industries (e.g., in blast furnaces).

(ii) Coal tar 

It is a black, thick liquid with an unpleasant smell. It is used to make synthetic dyes, drugs, perfumes, paints, naphthalene balls, and roofing materials.

(iii) Coal gas

It is a gaseous fuel. It was used for lighting streets and homes earlier. Nowadays, it is used as a fuel in industries and for heating.

28. We say fossil fuels will last only for a few hundred years. Comment.

Answer: Fossil fuels like coal, petroleum, and natural gas are exhaustible natural resources formed from the dead remains of living organisms over millions of years. Since they are being used at a very fast rate for energy, transportation, and industries, and their formation is extremely slow, they cannot be replenished quickly. Therefore, scientists estimate that fossil fuels will last only for a few hundred years if consumed at the current rate. This highlights the need to use them wisely and switch to renewable energy sources like sunlight, wind, and water.

29. We read in newspapers that burning of fuels is a major cause of global warming. Explain why.

Answer: Burning of fuels like coal, petroleum and natural gas releases carbon dioxide (CO₂) and other gases into the air. Carbon dioxide traps heat from the sun and does not allow it to escape into space, causing the Earth's temperature to rise gradually. This rise in temperature is called global warming. Excessive burning of fossil fuels increases the amount of CO₂ in the atmosphere, making global warming worse. Global warming can lead to melting of polar ice, rise in sea levels and changes in weather patterns.

30. While driving what are the tips we must follow to save petrol/ diesel/natural gas?

Answer: To save petrol, diesel, or natural gas while driving, we should follow these tips:

(i) Drive at a constant and moderate speed : Frequent acceleration and braking consume more fuel.

(ii) Switch off the engine at traffic lights or when waiting : Idling wastes fuel unnecessarily.

(iii) Keep the vehicle properly maintained : Regular servicing, clean air filters, and correct tyre pressure improve fuel efficiency.

(iv) Reduce the use of air conditioners : AC increases fuel consumption.

(v) Carry only necessary load : Extra weight in the vehicle makes it burn more fuel.

(vi) Use public transport or carpool whenever possible : This reduces individual fuel use.

(vii) Plan your route in advance : Avoid congested roads and unnecessary trips.

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?

Answer: No, survival of living beings would not be possible if all exhaustible natural resources are exhausted. Because of :

(i) No energy for daily needs : Exhaustible resources like coal, petroleum, and natural gas are the main sources of energy for cooking, transportation, electricity, and industries. Without them, modern life would come to a standstill.

(ii) No raw materials for essential products : Petroleum provides petrol, diesel, kerosene, plastics, medicines, and fertilizers. Coal gives coke for steel, and coal tar for dyes and drugs. Without these, making everyday items would be impossible.

(iii) Forests would be gone : Forests (exhaustible) provide oxygen, wood, food, shelter to animals, and maintain rainfall. Without forests, many animals would die, and the air would become polluted.

(iv) Minerals would be missing : Minerals are used to make tools, machines, buildings, and vehicles. Without them, even basic farming and shelter would be difficult.

32. Why petrol is exhaustible natural resource, whereas sunlight is not? Explain.

Answer: Petrol is an exhaustible natural resource because it is obtained from petroleum, which is formed from the dead remains of sea organisms over millions of years. Its formation is very slow, and it gets depleted faster than it can be replenished. On the other hand, sunlight is an inexhaustible resource because it is continuously available in unlimited quantity from the sun and will never run out, regardless of how much we use

33. Write some important uses of the various constituents of petroleum.

Answer: Petroleum is refined to obtain several useful constituents. Their important uses are:

(i) Petrol : Used as fuel for light vehicles like cars, motorcycles, and scooters.

(ii) Diesel : Used as fuel for heavy vehicles like trucks, buses, trains, and generators.

(iii) Kerosene : Used as fuel for stoves, lamps, and jet aircrafts.

(iv) Lubricating oil : Used to reduce friction in machine parts and engines.

(v) Paraffin wax : Used to make candles, ointments, cosmetics, and polishes.

(vi) Bitumen : Used for road surfacing and making waterproof roofs.

(vii) Petroleum gas (LPG) : Used as cooking gas in homes.

34. Coal reserves are said to be enough to last for another hundred years. Do you think we need to worry in such case? Why or why not?

Answer: Yes, we still need to worry even if coal reserves last for another hundred years. Due to:

(i) Coal is exhaustible : Once used up, it cannot be renewed quickly. Future generations will be left with no coal.

(ii) Burning coal causes pollution : It releases harmful gases like carbon dioxide and sulphur dioxide, leading to air pollution, acid rain, and global warming.

(iii) Over-dependence is risky : If we don't start using renewable energy sources like sunlight, wind, and water now, we will face an energy crisis later.

(iv) It takes millions of years to form : Even if new coal forms, it will take far too long to be useful for humans.

So, even though coal may last a hundred years, we must use it wisely, reduce wastage, and shift to cleaner, inexhaustible resources.

35. What steps would you suggest for the judicious use of fossil fuels?

Answer: To use fossil fuels judiciously, we should:

(i) Use public transport, carpool, or cycle instead of personal vehicles.

(ii) Switch off engines at traffic lights or when waiting.

(iii) Keep vehicles properly serviced and maintain correct tyre pressure.

(iv) Use solar heaters, pressure cookers, and renewable energy sources.

(v) Avoid unnecessary burning of fuels and spread awareness about conservation.

(vi) Promote use of CNG and electric vehicles.

36. Complete the crossword Fig. 5.2 with the help of the clues:

Across
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)
Down
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)

Answer: Across
1. Fuels obtained form dead remains of living organisms. (6,5) → Fossil Fuels
2. A process by which the various constituents of petroleum are separated. (8) → Refining
3. A porous black substance obtained form coal. (4) → Coke
4. Another name for motor fuel. (6) → Petrol .
Down
5. The substance obtained by carbonisation. (4) →Coal
6. Fuel for heavy motor vehicles. (6) → Diesel .
7. A petroleum product used for road surfacing. (7) → Bitumen
8. Dead remains of sea animals got converted into it. (9) → Petroleum.