CBSE Class 8 Science Chapter 5 Revision Notes

Chapter 5: Coal And Petroleum Revision Notes

NATURAL RESOURCES: Natural resources are all that nature provides and are highly beneficial to humans.

Source

NATURAL RESOURCE TYPES:

(i) Inexhaustible: Some natural resources are limitless and will not be depleted even if they are utilised indefinitely. Sunlight and air are two examples.

(ii) Exhaustible: These resources are limited, and they will quickly diminish if they are used excessively. Examples include forests, wildlife, minerals, coal, petroleum, and other natural resources.

FOSSIL FUELS

• Fossil fuels are finite natural resources that cannot be replenished.
• Fossil fuels included coal, petroleum, and natural gas and were formed from the remains of living organisms that had died.
• Burning these fuels leads to air pollution linked to global warming.

COAL

• Coal is used to manufacture coke, coal tar, and coal gas.
• They are used as an industrial fuel and in thermal power plants.

1. COKE

Black, porous substance used in steelmaking and metal extraction.

2. COAL TAR

Black, thick liquid, utilised as starting materials to manufacture a variety of common and industrial compounds.

3. COAL GAS

Obtained from coal and is used as a fuel source.

PETROLEUM

• Refining petroleum {Petra (rock) and oleum (oil)} yields petroleum gas, petrol, diesel, kerosene, paraffin wax, and lubricating oil.
• It was formed millions of years ago by transformed dead sea organisms (absence of air, high temperature, and high pressure).
• The availability of coal and petroleum is limited, and hence we should use them with caution.

REFINING OF PETROLEUM

• Dark oily liquid with a foul odour.
• Petroleum is a mixture of different ingredients such as petroleum gas, gasoline, diesel, lubricating oil, paraffin wax, etc.
• The process of separating the various elements or fractions of petroleum is known as refining.
• It is carried out in a petroleum refinery.

NATURAL GAS

• Natural gas is a valuable fossil fuel because it is easy to distribute via pipelines.
• As compressed natural gas, natural gas is held under high pressure (CNG).
• CNG is utilised to generate electricity. Because it is less polluting/cleaner, it is used as a transportation fuel.
• CNG has the advantage of being able to be burned directly in homes and factories where it can be delivered via pipes.
• Natural gas is also employed as a raw material in producing a wide range of chemicals and fertilisers.

Source: Chapter-5.pmd (ncert.nic.in)

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