Notes of Ch 5 Coal and Petroleum| Class 8th Science

Study Material and Notes of Ch 5 Coal and Petroleum Class 8th Science

Topics in the Chapter

• Introduction
• Inexhaustible Natural Resources
→ Renewable Resources
• Exhaustible Natural Resources
→ Non-renewable resources
• Coal
→ Story of Coal
→ Uses of coal
• Products from coal
→ Coke
→ Coal tar
→ Coal gas
• Petroleum
→ Petroleum and its uses
• Cracking
• Natural Gas


→ There are two types of resources:
(i) Inexhaustible Natural Resources (Renewable sources of energy)
(ii) Exhaustible Natural Resources (Non-renewable sources of energy)

Inexhaustible Natural Resources

→ They are renewable sources of energy that are replenished at a rate faster than that at which they are consumed.

→ These resources are present in unlimited quantity in nature and are not likely to be exhausted by human activities.


→ Tidal energy, wave energy, ocean thermal energy.

→ Solar energy: Solar cooker, solar water heater (very efficient for small scale electricity production)

→ Geothermal energy: Heat energy inside the earth

→ Nuclear energy: Not dependent on solar energy, never-ending source, very efficient source, more environment friendly.

Exhaustible Natural Resources

They are non-renewable sources of energy are those that are consumed at a rate faster than that at
which they are replenished. The amount of these resources in nature is limited which can be exhausted by human activities.


→ Forests, wildlife, minerals, coal, petroleum, natural gas etc.

→ Fossil fuels: Coal, petroleum and natural gas
Advantages of using fossils fuels:
Easy availability
Generate heat that is easily converted into electricity.

→ Coal, petroleum, and natural gas were formed from the dead remains of living organisms. Hence, they are known as fossil fuels

→ Resources such as coal and petroleum are limited. Burning of such fuels is the major cause of air pollution. Therefore, these fuels should be used only when necessary.

→ Burning of fossil fuels releases gases like carbon dioxide which cause greenhouse effect.


→ It is a fossil fuels which is hard solid and black in colour.

• Story of Coal

→ Due to natural processes, the dense forests got buried under the soil.

→ Under high temperature and high pressure, dead plants got slowly converted to coal.

→ The slow process of conversion of dead vegetation into coal is called carbonisation.

• Uses of Coal

→ It is used as fuel to cook food. Earlier, it was used in railway engines to produce steam.

→ It is used in thermal power stations to generate electricity.

→ Coke, coal tar, and coal gas are the products of coal.

Products from coal


→ It is a tough, porous and black substance.

→ It is the pure form of carbon and is used in the extraction of steel and many other metals.

Coal tar

→ It is black, thick liquid with unpleasant smell.

→ It is the mixture of about 200 substances.

→ The products obtained from coal tar are used as starting materials for dyes, drugs, paints, perfumes, etc.

Coal gas

→ It is obtained during the processing of coal to obtain coke.

→ It is used as a fuel in many industries situated near the coal processing plants.


→ Petroleum was formed from the dead organisms present in the sea.

→ Petrol, diesel, kerosene, paraffin wax, lubricating oil, and petroleum gas are the products of petroleum.

→ The process of separating various constituents of petroleum is known as refining.

→ Refining of petroleum is done in fractionating column.

→ Components with higher boiling points are collected at the bottom of the fractionating column.

→ Components with lower boiling points are collected at the top of the column.

Petroleum and its uses

Constituents of Petroleum
Petroleum Gas in Liquid form (LPG)Fuel for home and industry.
PetrolMotor fuel, aviation fuel, solvent for dry cleaning
Paraffin waxCandle, Vaseline, Ointments etc.
DieselFuel for heavy motor vehicles, electric generators
KeroseneFuel for stoves, lamps.
Lubricating oilLubrication.
BitumenPaints, road surfacing

→ Complete combustion of hydrocarbons lead to formation of carbon dioxide and water, while incomplete combustion of hydrocarbons yield carbon monoxide and water.

→ Carbon dioxide as well as carbon monoxide are responsible for pollution in our environment.

→ The test used to determine the amount of carbon monoxide in vehicle's exhaust gases is known as emission test.

→ Gas analyzer is used in detection of carbon monoxide in exhaust gases.

→ Petroleum is a natural resource

→ The formation of petroleum takes place over a period of millions of years.

→ Petroleum reserves are limited i.e. they are found only in a few places on the Earth.

→ The ever increasing population has further increased the demand for petroleum and its products.

→ In India, the Petroleum Conservation Research Association (PCRA) advises people on the various methods that can be adopted to conserve petrol/diesel.


→ Heating higher alkanes to sufficiently high temperatures in absence of oxygen, in order to obtain lower hydrocarbons is known as cracking or pyrolysis.

Natural Gas

→ Natural gas is formed from dead organisms which decompose in the absence of air under conditions of high pressure and temperature.

→ It is stored under high pressure as compressed natural gas (CNG). It is used as a fuel for vehicles because it is a cleaner fuel (less polluting).

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