Coal and Petroleum Class 8 Notes NCERT and MCQs

23-08-2023 17:13 PM IST Yadvendra Singh

The chapter defines exhaustible natural resources and exhaustible natural resources. Then, it discusses some exhaustible natural resources known as fossil fuels (coal, petroleum and natural gas). 

Natural Resources

Air, water, soil and minerals are obtained from nature and called natural resources. Natural resources can be broadly classified into two kinds. They are given below.

Fossil fuels

Exhaustible natural resources like coal, petroleum and natural gas are known as fossil fuels because these were formed from the dead remains of living organisms (fossils). 

Fig.1: Fossil Fuels

Coal

It is as hard as stone and is black in colour. Since coal was formed from the remains of vegetation, it is also called a fossil fuel. As coal contains mainly carbon, the slow process of conversion of dead vegetation into coal is called carbonisation. There are four types if Coal- Peat, Lignite, Bituminous and Anthracite.

Process of formation of coal

Fig.2: Process of Formation of Coal

Uses of Coal

• It is used as a fuel in cooking.
• It was used in railway engines to produce steam to run the engine.
• It is used in thermal power plants to produce electricity.
• Coal is also used as a fuel in different industries.

Coal is processed in industry to get some useful products such as coke, coal tar and coal gas. Coke is a tough, porous and black substance. It is an almost pure form of carbon. Coal tar is a black, thick liquid with an unpleasant smell.  Coal gas is obtained during the processing of coal to get coke. Uses of coke, coal gas and coal tar are given below.

Petroleum

Petrol and diesel are obtained from a natural resource called petroleum. Due to its commercial importance, petroleum is also called ‘black gold’. It is a dark oily liquid. It is mined from between the rocks under Earth as shown in figure given below. Layer containing petroleum oil and gas is above that of water as oil and gas are lighter than water and do not mix with it.

Petroleum was formed from organisms living in the sea.

Process of petroleum formation

• As organisms living in the sea died, their bodies settled at the bottom of the sea and got covered with layers of sand and clay.
• Over millions of years, absence of air, high temperature and high pressure transformed the dead organisms into petroleum and natural gas.

Petroleum refining

It is the process of separating the various constituents/ fractions of petroleum. Petroleum is a mixture of various useful constituents such as petroleum gas, petrol, diesel, lubricating oil, paraffin wax, kerosene and bitumen. Bitumen is nowadays used in place of coal tar for metalling the roads.

Uses of Constituents of Petroleum

Natural gas

Natural gas is easy to transport through pipes. It is stored under high pressure as compressed natural gas (CNG). CNG is used for power generation and as a less polluting cleaner fuel for transport vehicles.

The great advantage of CNG is that it can be used directly in homes and industries supplied through pipelines. It is also used in manufacturing chemicals and fertilisers. Natural Gas in India has been found in Tripura, Maharashtra, Rajasthan and Krishna Godavari delta.

Petrochemicals

Many useful substances are obtained from petroleum and natural gas. These are termed as ‘Petrochemicals’. These are used in the manufacture of detergents, fibres (polyester, nylon, acrylic etc.), polythene and other man-made plastics. Hydrogen gas obtained from natural gas is used in the production of fertilisers (urea).

Resources are Limited

Resources like Coal and Petroleum are limited as it takes millions of years for dead organisms to get converted into these fuels. We need to use them wisely. Judicious use of these fuels will result in better environment, smaller risk of global warming and their availability for longer duration.

MCQs based on NCERT Class 8 Chapter 5 Coal and Petroleum

1. Which of the following gas is obtained from natural gas and used in production of Urea?

a. Hydrogen

b. Nitrogen

c. Oxygen

d. Nitrogen oxide

Ans. a

Explanation:

Hydrogen gas obtained from natural gas is used in the production of fertilisers (urea).

2. Which of the following is used to obtain Naphthalene balls, which repel moths and other insects?

a. Coke

b. Coal gas

c. Coal tar

d. Petroleum

Ans. c

Explanation:

Products obtained from coal tar are used as starting materials for manufacturing of synthetic dyes, drugs, explosives, perfumes, plastics, paints, photographic materials, roofing materials, etc. Naphthalene balls used to repel moths and other insects are also obtained from coal tar.

3. Petroleum is mined from between the rocks under Earth. It was formed from-

a. Dense forests in low lying wetland areas

b. Organisms living in sea

c. Both a and b

d. Neither a nor b

Ans. b

Explanation:

Petroleum was formed from organisms living in sea. It is mined from between the rocks under the Earth. As organisms living in the sea died, their bodies settled at the bottom of the sea and got covered with layers of sand and clay. Over millions of years, absence of air, high temperature and high pressure transformed the dead organisms into petroleum and natural gas.