Science NCERT Grade 8, Chapter 5, Coal and Petroleum introduces the students to the most commonly used fossil fuels. The chapters begin with an activity which groups different materials we use into natural and man-made. Furthermore, natural resources are classified into the following two types:

  • Inexhaustible natural resources

  • Exhaustible natural resources

Both types of natural resources are discussed along with their examples in chapter, Coal and Petroleum.

In this chapter, the main focus is given on some exhaustible natural resources like coal, petroleum and natural gas. The first section of the chapter, Coal and Petroleum talks about coal and some useful products obtained after it is processed like:

  • Coke

  • Coal tar

  • Coal gas

The second section talks about petroleum and its characteristics. Diagramatic representation of petroleum and natural gas deposits and a figure depicting a petroleum refinery further enhance the conceptual understanding of the topic. Information about various constituents of petroleum and its uses is presented in tabular form in the chapter, Coal and Petroleum. A note on natural gas is also provided. The last part of the discussion lays emphasis on the limited quantity of some natural resources. It discusses the negative effects of using fossil fuels as sources of energy. This section of the chapter also suggests some ways of conserving these fuels.

The topics covered in the chapter, Coal and Petroleum are - Coal, Petroleum, Natural Gas and Some Natural Resources are Limited.

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Question 1:

What are the advantages of using CNG and LPG as fuels?

Answer:

The advantages of using compressed natural gas (CNG) and liquified petroleum gas (LPG) as fuels are:

(i) They can be burnt directly.

(ii) They can be transported easily through pipe lines.

(iii) They are clean fuels and do not give smoke when burnt.

(iv) They give a lot of heat energy when burnt.

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Question 2:

Name the petroleum product used for surfacing of roads.

Answer:

Bitumen, a petroleum product, is used for surfacing roads.

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Question 3:

Describe how coal is formed from dead vegetation. What is this process called?

Answer:

Millions of years ago, dense forests got buried under the soil due to natural processes like storms, floods, and earthquakes. These got compressed as more and more soil got deposited over them. When they got buried deep in the soil, they were exposed to very high pressure and temperature. Under these conditions, these slowly got converted into coal. This process of formation of coal from dead vegetation is called carbonization.

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Question 4:

Fill in the banks.

(a) Fossil fuels are ________, ________ and _________.

(b) Process of separation of different constituents from petroleum is called _________.

(c) Least polluting fuel for vehicles is __________.

Answer:

(a) Fossil fuels are __coal__, __petroleum__ and __natural gas__.

(b) Process of separation of different constituents from petroleum is called __refining__.

(c) Least polluting fuel for vehicles is __compressed natural gas (CNG)__.

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Question 5:

Tick True/False against the following statements.

(a) Fossil fuels can be made in the laboratory. (T / F)

(b) CNG is more polluting fuel than petrol. (T / F)

(c) Coke is almost pure form of carbon. (T / F)

(d) Coal tar is a mixture of various substances. (T / F)

(e) Kerosene is not a fossil fuel. (T / F)

Answer:

(a) Fossil fuels can be made in the laboratory. (F)

(b) CNG is more polluting fuel than petrol. (F)

(c) Coke is almost pure form of carbon. (T)

(d) Coal tar is a mixture of various substances. (T)

(e) Kerosene is not a fossil fuel. (F)

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Question 6:

Explain why fossil fuels are exhaustible natural resources.

Answer:

Fossil fuels require millions of years to form from the dead vegetation and animals that get buried deep inside the Earth. They require high temperature and pressure for their formation, which cannot be provided in the laboratory. Thus, fossils are limited. Therefore, the use of fossil fuels at this rate will lead to their exhaustion.



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Question 7:

Describe characteristics and uses of coke.

Answer:

Characteristics of coke are:

(i) Tough

(ii) Porous

(iii) Black in colour

Uses of coke:

(i) In manufacture of steel.

(ii) In the extraction of metals (as a reducing agent).

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Question 8:

Explain the process of formation of petroleum.

Answer:

Petroleum was formed from dead organisms that got buried in the sea millions of years ago. These dead bodies got covered with layers of sand and clay. Lack of air, high temperature, and high pressure transformed these dead organisms into petroleum and natural gas.

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Question 9:

The following Table shows the total power shortage in India from 1991 − 1997. Show the data in the form of a graph. Plot shortage percentage for the years on the Y-axis and the year on the X-axis.

S. No.

Year

Shortage (%)

1

2

3

4

5

6

7

1991

1992

1993

1994

1995

1996

1997

7.9

7.8

8.3

7.4

7.1

9.2

11.5

Answer:



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