Coal and Petroleum - Class 8 : Notes


This chapter on coal and petroleum for class 8 science focuses on the study of nonrenewable energy sources such as coal, petroleum, and natural gas. These are also classified as non-renewable energy sources which we will define later in this page.

Resources- Various materials which are used to fulfill or accomplish needs of a human. In other words, we can say that
A 'resource' is anything in the environment that can be used.
Resources can be broadly divided into following two categories

1. Natural Resources

  • Natural gas which can be obtained naturally.
  • Some of the examples of natural resources includes Air, Soil, Water, Sunlight, Coal etc.

2.Man-made Resources

  • These are the resources which are made by man.
  • Some of its examples includes Table, Chair, Car, Bus, Plastic etc.
Types of resources
Types of resources
Question: Can we use all our natural resources forever?
Answer: No, as all-natural resources would vanish or exhaust.

Classification Of Natural Resources

Depending upon the availability of resources, they can be classified into two types which are as follows-

A. Inexhaustible Natural Resources

  • This type of resources is also known as Renewable source of energy.
  • These are resources which are not exhausted by human activities.
  • They can be used over and over again. They last forever.
  • Air, Water, Sunlight are the examples of this type of resources.

B. Exhaustible Natural Resources

  • This type of resources is also known as Non-renewable source of energy.
  • Resources which can be exhausted by human activities and will deplete after a few hundred years.
  • So, the exhaustible natural resources do not last forever.
  • Forests, Wildlife, Mineral, Coal, Petroleum, Natural gas are the examples of this type of resources.

Difference between exhaustible and inexhaustible resources

difference between exhaustible and inexhaustible resources
Exhaustible Vs. Inexhaustible Resources

Fossil Fuels

  • Fossil fuels are renewable fuels produced from the remains of long-dead living organisms buried beneath the earth.
  • Coal, petroleum, and natural gas are examples of fossil fuels.
  • They were created by the decomposition of prehistoric plant and animal remains (fossils) which were buried under the earth a long time ago.
  • These are exhaustible natural resources.

How Fossil Fuels were Formed

How Fossil Fuels were Formed
How Fossil Fuels were Formed

Coal-The Exhaustible Natural Resource

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  • Coal- A black or brownish-black sedimentary rock with a huge amount of carbon but also contains hydrogen, sulphur, oxygen and nitrogen.
  • Coal is an exhaustible natural resource as it's one of the fuel used to cook food, producing electricity.
  • Coal is as hard as stone.
  • Coal is found in deep coal mines under Earth's surface.
    Coal Mine
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  • It is most important source of energy in our country.
  • Coal is found in abundance in India in states like Bihar, Orissa, West Bengal, Madhya Pradesh.

Story Of Coal : How it was formed?

  • Decomposition of dense forests in low-lying wetland areas about 300 million years ago caused the formation of coal by the natural processes.
  • The natural processes like flodding, forests got burried under the soil.
  • The action of heat and pressure on the burried forests resulted in the formation of coal.
  • Coal is classified as a fossil fuel as coal is formed from remains of dead plant matter under high pressure and temperature. These dead plants were slowly converted to coal over a large period of time.


  • Carbonisation refers to the gradual process by which dead plants buried deep underneath the earth have turned into coal.
  • The process of converting dead vegetation into coal is a very slow process
  • Coal is classified as a fossil fuel because it was made from the remains of plants.
Question: What happens when coal is heated in presence of air?
Answer: When heated in air,coal burns and produces mainly carbon dioxide gas.

Uses Of Coal

Coal is significant because it can be consumed directly as a source of heat energy (by burning it) or converted into other sources of energy such as coal gas, coke, or electricity.

  1. Coal is used as a source of energy in both homes and businesses.
  2. Thermal Power Plants use coal as a fuel to produce electricity.
  3. Coal is used to produce coal gas, a valuable industrial fuel.
  4. Previously, coal was used as a source of ‘energy,' which was used to power steam locomotives. 
  5. Organic chemicals were also derived from coal.

Three useful products of coal

  1. Coke
  2. Coal Tar
  3. Coal Gas

These products are formed by processing of coal. When coal is heated in the absence of air, these products are generated. This is because when coal is heated in the presence of air, it burns primarily to create carbon dioxide gas and no other useful items. The method of rapidly heating coal in the absence of air is known as destructive distillation of coal.


  • A fuel with a high carbon content.
  • Coke is formed by heating coal in the absence of air.
  • Coke are grey,hard and porous.
  • Coke is used to manufacture steel and many other materials.
  • Coke is preffered over coal sometimes during burning as coke produces very little smoke.
  • Coke is used in the extraction of many metals like Iron.

  • A derivative of coal.
  • Coal tar is a by-product of the production of coke,a solid fuel that contains mostly carbon.
  • Coal tar is black , viscous liquid heavier than water, with a napthalene like odour.
  • Coal tar has both medicinal and industrial uses.
  • Coal tar is used to make dyes,drugs and perfumes.
  • Napthalene balls which are used to repel moths and other insects are also obtained from coal tar.

  • A mixture of gases obtained by the destructive distillation of coal
  • Coal gas is used for lightning and for heating
  • This gas is not used for cooking
  • Coal gas is used as a fuel in many industries situated near the coal processing plant
  • Coal gas earlier was used for street lightning for the first time in London in 1810 and in New York around 1820. But nowadays , it's used as a source of heat rather than light.
  • Petroleum

    • It's also referred to as black gold because to a large extent Nation's economy depends on its petroleum welth.
    • Petroleum or crude oil is a sticky liquid with a foul smell because of the presence of compounds containing Sulphur
    • It's formed from the dead remains of land and sea creatures,that got burried under the ocean or sea millions of years ago.
    • As more and more sediments deposited on top of them,the heat and pressure gradually changed the layers at the bottom into petroleum and natural gas.
    • Petroleum is taken out using an oil rig with the evolution of natural gas .

    Digramatic representation of Petroleum and Natural Gas Deposits

    Uses Of Petroleum

  • It is used as a fuel for aeroplanes and automobiles.
  • It's also used for dry cleaning,making printing inks and medicines.
  • Paraffin wax that we get from petroleum is used to make polish,candles and waterproof cartons.
  • How Is Petroleum Refined?

    • Originally, petroleum was a mixture of several different substances, including gas, gasoline, petroleum, paraffin wax, lubricating oil, and so on.
    • It is an industrial process that removes crude oil from the earth and converts it into usable items such as LPG, Kerosene and Diesel.
    • The main purpose of petroleum refining aimed at transforming crude oil into useful products.This process is carried out in petroleum refinery.The products made from petroleum are called petrochemicals.
    • This procedure is carried out in a petroleum refinery.

    Natural Gas

    • It is a gaseous , abundant and a clean fossil fuel as compared to petroleum and coal. . Natural gas is found along with crude petroleum in oil wells.
    • Natural gas was formed by the decomposition of dead plants and animals and got buried under sand .In the absence of oxygen these dead plants and animals changes to gas.
    • Natural gas is compressed under high pressure to form CNG-Compressed Natural Gas.

    Advantages of CNG

    • It is used as an ideal automobile fuel instead of petrol or diesel.
    • It is also used as a starting material for the manufacture of a number of chemicals and fertilizers.
    Question: What makes natural gas an excellent fuel for domestic and industrial use?
    Answer: As natural gas burns readily in the presence of air to liberate a large amount of heat which makes a natural gas an excellent fuel for domestic and industrial use.

    Conservation of Resources

    Conservation is the sustainable use and protection of natural resources. The main aim of conservation is to maintain an adequate supply of these resources so that they are available in the future also.

    • PCRA(Petroleum Conservation Research Association) is an agency which helps in the conservation and preservation of fossil fuels.This agency suggested some ways to save diesel or petrol.
    • Avoid excessive braking .
    • Turn off the engine when not in use.
    • Vehicle should be checked and serviced regularly.

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