Petroleum : Science Ncert / Cbse Revision Notes

Petroleum, a natural resource formed from organisms living in the sea, is a dark and oily liquid mixture with a very unpleasant odour. The word petroleum comes from the Latin words ‘petro’ meaning rock and ‘leum’ meaning oil. Petroleum and natural gas are formed from compressed organic matter.

As petroleum and natural gas are lighter than water, the deposits of petroleum and natural gas occur above that of water.

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The first oil well in the world was drilled in Pennsylvania, USA in the year 1859. After eight years, in the year 1867, oil was struck at Makum in Assam. Oil in India is found in Assam, Gujarat and Mumbai High, and in the river basins of Godavari and Krishna.

Petroleum, Science Ncert / Cbse Revision Notes, Class 8 Science
Petroleum is a mixture of various constituents like petroleum gas, petrol, diesel, lubricating oil, paraffin wax, etc., and the process of separating its many constituents is called refining. It is refined in a petroleum refinery. At the refinery, the crude oil mixture is 'fractionated' into different components by fractional distillation.

At the refinery, this crude oil mixture is separated or 'fractionated' into different components by fractional distillation. Light gases are the topmost fraction, followed by petrol and kerosene. Diesel is the heaviest. The other heavier fractions are not useful and are usually used to make asphalt to surface roads.

Constituents of petroleum and their uses: 

  • LPG or petroleum gas is used as a fuel for home and industry.
  • Petrol is used as a motor fuel, aviation fuel and a solvent for dry cleaning.
  • Kerosene is used as a fuel for stoves and lamps and also in jet aircraft.
  • Diesel is used as a fuel for heavy motor vehicles and electric generators.
  • Lubricating oil is used for many lubricating purposes.
  • Paraffin wax is used in ointments, candles and Vaseline.
  • Bitumen is used in paints and also to surface roads.
  • Petrochemicals are used in the manufacture of detergents, polyester and nylon fibres, polythene and other man-made plastics.

Simple steps to reduce consumption of petrol/diesel:

  • Use public transport.
  • Combine many errands into one trip.
  • Car pooling to school and work.

Burning petroleum releases carbon dioxide into the air, which contributes to global warming.
Oil spills at sea are devastating to the animal and plant life in and around the sea.

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