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CBSE Class 8 Chemistry Notes for Chapter 3 Coal and Petroleum

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                        CHAPTER 3 COAL AND PETROLEUM
 
INEXHAUSTIBLE NATURAL RESOURCES
The resources present in unlimited quantity and will not be exhausted by human use are called inexhaustible natural resources. E.g. Air
 
EXHAUSTIBLE NATURAL RESOURCES
The resources present in limited quantity and will be eventually exhausted by human use are called exhaustible human resources. E.g. Crude oil
 
COAL
Formation of coal:
When plant matter got buried under the soil a long time ago, it got converted into coal under high temperature and pressure. Coal is black, stone-hard and mainly contains carbon and therefore the formation of coal is called carbonisation. Coal is a fossil fuel.
Processing of coal:
Processing of coal gives many useful products like:

  • Coke: It is almost pure form of carbon and is tough, porous and black. It is used in steel manufacturing and metal extraction.

 

  • Coal tar: It is a mixture of 200 substances which make it a black, thick liquid having an unpleasant smell. It is used in synthetic dyes, explosives, etc.

 

  • Coal gas: It can be used as a fuel for industries.


 
PETROLEUM
Formation of petroleum:
As the organisms under the sea died they got buried under layers of sand and clay. Over millions of years, under high temperature and pressure and in the absence of air, these dead organisms transformed into petroleum and natural gas.
Refining of petroleum:
Petroleum is a dark oily liquid having an unpleasant odour. Various constituents of petroleum are separated in petroleum refinery. The following are the constituents of petroleum:

  • Liquid Petroleum Gas (LPG)
  • Petrol
  • Kerosene
  • Diesel
  • Lubricating oil
  • Paraffin wax
  • Bitumen

 
NATURAL GAS
Natural gas is a major fossil fuel. It is stored under high pressure as Compressed Natural Gas (CNG). It is used for power generation and as fuel in vehicles. Compared to other fuels available, natural gas is a cleaner fuel as it is less polluting.
 
Coal and petroleum are exhaustible resources. The rate at which these fuels are being consumed, we will run out if them in a few hundred years.  Therefore, these fuels must be conserved.

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