NCERT Class VIII Science Solutions: Chapter 5-Coal and Petroleum Part 2

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Question 3:

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

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 to coal.

As coal contains mainly carbon, the slow process of conversion of dead vegetation into coal is called carbonization.

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Question 4:

Fill in the blanks:

  1. Fossil fuels are ___________, __________ and ___________.

  2. Process of separation of different constituents from petroleum is called __________.

  3. Least polluting fuel for vehicle is ___________.

Answer:

  1. Fossil fuels are Natural Gas, Coal and Petroleum.

  2. Process of separation of different constituents from petroleum is called refining.

  3. Least polluting fuel for vehicle is CNG.

Question 5:

Tick True/False against the following statements:

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

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

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

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

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

Answer:

  1. Fossil fuels can be made in the laboratory. (False)

  2. CNG is more polluting fuel than petrol. (False)

  3. Coke is almost pure form of carbon. (True)

  4. Coal tar is a mixture of various substances. (True)

  5. Kerosene is not a fossil fuel. (False)

Question 6:

Explain why fossil fuels are exhaustible natural resources.

Answer:

Fossil fuels are formed over a period of millions of years, by the action of high temperature and high pressure on the remains of dead plants and animals. These fossil fuels are exhaustible natural resources because if these are exhausted by human activities, cannot be recreated in a short period of time.

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