NCERT Solution for Class 8 Science Chapter 5 : Coal and Petroleum

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NCERT Solution for Class 8 Science Ch 5 : Coal and Petroleum

Question 1: What are the advantages of using CNG and LPG as fuels?
Answer

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

(a) They can be burnt directly.

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

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

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

Question 2: Name the petroleum product used for surfacing of roads.

Answer

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

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.

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).

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)

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.

Question 7: Describe characteristics and uses of coke.
Answer

Characteristics of coke are:

(i)  Tough

(ii)  Porous

(iii) Black in color

Uses of coke:

a)  In manufacture of steel.

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

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.

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.YearShortage (%)
119917.9
219927.8
319938.3
419947.4
519957.1
619969.2
7199711.5

Answer

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