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SAI International School
Class – VIII
Subject – Chemistry

Topic – Coal and Petroleum
Sub-Topic – Fossil Fuel, Coal, Types of Coal, Uses of Coal

LESSON NOTES

Coal:

It is a hard, black combustible mineral that consists mainly of carbon. It can be found in deep coal
mines under the surface of the earth. In India, coal is mainly found in Bihar, West Bengal, Orissa
and Madhya Pradesh. Coal is the most important source of energy in our country.

How Coal was formed:

Coal was formed by the decomposition of large land plants and trees buried under the earth about
millions of years ago.

Due to natural processes like earthquakes, volcanoes etc., these forests were buried under the
surface of the earth. As more soils deposited over them, they were compressed. The temperature
also rose as they sank deeper and deeper. Due to high pressure and high temperature inside the
earth, and in the absence of air, the wood of buried forest plants and trees was slowly converted
into coal. The slow process by which the dead plants buried deep under the earth have
become coal is called Carbonisation.

Types of coal:

Classification of coal depends upon the carbon content in the coal. If a type of coal has more amount
of carbon, then it can produce more amount of heat and it is a good quality of coal and is also a
good fuel.

Depending upon the carbon content, coal can be classified into the following types.

1. Peat: it is the first step in the coal formation. It contains less than 60% of carbon. It has high
water content. It is soft and brown in colour. It is used for house hold cooking.

2. Lignite: eventually over time, with increasing pressures and temperatures, peat changes into
coal’s next stage, lignite.
It contains 60% to 70% of carbon. It is brown in colour and still contains a high amount of
water. Lignite has a higher heat content than peat. It is used in thermal power plants.

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