NCERT Solutions for Class 8 Science Chapter 5 Materials Coal and Petroleum

NCERT Solutions for Class 8 Science Chapter 5 Materials Coal and Petroleum

NCERT Solutions for Class 8 Science Chapter 5 Materials Coal and Petroleum

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

Answer: The advantages of using CNG and LPG as fuels are:

a) They burn with a smokeless flame and so does not cause any pollution.

b) They leave no ash on burning.

c) They are easy to handle and convenient to store.

Q2. Name the petroleum product used for surfacing of roads.

Ans: Bitumen

Q3. Describe how coal is formed from dead vegetation. What is this process called?

Ans: Dense forests got buried under the soil due to natural processes, millions of years ago. More and more soil got deposited over them and they got compressed more. This led them to get exposed to very high temperatures and pressure. They slowly got converted coal under these extreme conditions. The whole process of the formation of coal from dead vegetation is known as carbonization.

Q4. Fill in the blanks.

(a) Fossils fuels are ____ , ____ and ____

Ans: coal, petroleum, natural gas

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

Ans: refining

(c) Least polluting fuel for vehicle is ______

Ans: CNG

Q5. Write True/False against the following statements.

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

Ans: False

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

Ans: False

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

Ans: True

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

Ans: True

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

Soln: False

Q6. Explain why fossil fuels are exhaustible natural resources.

Ans: The process of formation of fossil fuels requires millions of years. Dead vegetation and animals that get buried deep inside the earth require high temperature and pressure for the formation of fossil fuels, which cannot be done in the laboratory. Thus, fossils are limited. Therefore, the use of fossil fuels at a rapid rate will lead to their exhaustion.

Q7. Describe the characteristics and uses of coke.

Ans: Characteristics:

i) Coke is tough.

ii) Coke is porous.

iii) Coke is black in colour.


i) In the manufacture of steel.

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

Q8. Explain the process of the formation of petroleum.

Answer: Petroleum is formed by the burial of aquatic plants and animals below the sea bed. The marine animals and plants died thousands of years ago and settled down in the bottom of sea. In anaerobic conditions, microorganisms decompose this organic matter. Due to high pressure and heat, the dead remains of tiny plants and animals were slowly converted into petroleum.

see also: Extra Questions and Answers

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