Chapter Notes - Coal & Petroleum Class 8 Notes | EduRev

Science Class 8

Class 8 : Chapter Notes - Coal & Petroleum Class 8 Notes | EduRev

The document Chapter Notes - Coal & Petroleum Class 8 Notes | EduRev is a part of the Class 8 Course Science Class 8.
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Natural Resources

  • Resources supplied by nature are called natural resources. The sun, air, water, soil, trees and forests, wildlife, coal, petroleum, natural gas and minerals are all natural resources. Many industries, like fishing, mining, hunting, agriculture and forestry, revolve around the sensible use of natural resources.
  • Natural resources are classified as renewable and non-renewable resources. Renewable resources are those that are present in unlimited quantity in nature or those that will replace themselves over time. These resources are not likely to be exhausted by human activities. As they are unlimited, they are also called inexhaustible resources.
    Examples: Sunlight, water, wind, etc.Chapter Notes - Coal & Petroleum Class 8 Notes | EduRevRenewable Sources of Energy
  • Non-renewable resources are those that are limited in nature and will not replace themselves. They can be exhausted by human activities. As they are limited, they are also called exhaustible resources.
  • Coal, petroleum and natural gas are exhaustible fossil fuels, which cannot be prepared in the laboratory. It takes millions of years for dead organisms to get converted into these fuels.Chapter Notes - Coal & Petroleum Class 8 Notes | EduRevNon-renewable Sources of Energy
  • Studies show that the known reserves of these fuels are fast depleting. Burning of these fuels is also a major cause for air pollution and along with the cutting down of trees is contributing to global warming. 

The Petroleum Conservation Research Association (PCRA) of India has some tips for people on how to save petrol/ diesel while driving:

  • Drive vehicles at a constant and moderate speed.
  • While waiting or at a traffic junction, switch off the engine.
  • Ensure correct tyre pressure.
  • Ensure regular maintenance checks of the vehicle.

Tips for conserving energy at home and school:

  • Switch off lights and electrical appliances when not in use.
  • Turn off air conditioning when leaving the room.
  • Do not let the tap run while you brush your teeth or soap your hands.
  • Check all leaky taps.
  • Take shorter showers.
  • Buy rechargeable batteries and a charger for them.
  • Avoid plastic bags.
  • Recycle your newspapers.

1. Coal

  • It is hard like stone substance and black in colour. It has many uses since old times like it was used as heat source to cook food, to produce steam to run train and other engines, in thermal power plants to produce electricity, etc.Chapter Notes - Coal & Petroleum Class 8 Notes | EduRevCoal
  • During the carboniferous age, the earth had large amounts of plant life and dense forests in swampy and low-lying wetland areas. Plants and other life forms, after their death, drifted down to the bottom of the swamps where they were compressed and decomposed to form peat. 
  • Coal was formed due to the compression of the peat at high temperature and pressure. As coal was formed from the remains of vegetation, it is called a fossil fuel. Carbonisation is the slow process of conversion of dead vegetation into coal.

Some products obtained from coal:
(a) Coke 

  • It is hard, porous and black in colour. It is the purest form of carbon.
  • Applications: In manufacturing of steel, extraction of metals, etc.Chapter Notes - Coal & Petroleum Class 8 Notes | EduRev

(b) Coal Tar

  • It is thick black coloured liquid having foul smell. It is mixture of about 200 substances.
  • Applications: The by-products obtained from coal tar are used in manufacturing of synthetic dyes, drugs, explosives, perfumes, etc. Interestingly, naphthalene balls used to repel moths and other insects are also obtained from coal tar.

(c) Coal Gas

  • It is obtained when coal is processed to obtain the coke. Coal gas was used for street lighting for the first time in London in 1810 and in New York around 1820. Nowadays, it is used as a source of heat rather than light.
  • Applications: It is mainly used as fuel in many industries. Bitumen, a petroleum product, is now used in place of coal tar for surfacing roads. Coal gas is obtained during the processing of coal to get coke. It is mainly used as a fuel in industries around coal processing plants.

➢ Uses of Coal

  • Coal is the largest source of fuel used to generate electricity world-wide.
  • Coal is used in manufacturing industries for heat and power applications.
  • Coal is used to make steam for heating.
  • It is also used as coke in steel making.

2. Petroleum

  • Petroleum, a natural resource formed from organisms living in the sea, is a dark and oily liquid mixture with a very unpleasant odour. 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.

Chapter Notes - Coal & Petroleum Class 8 Notes | EduRevOil Well

  • The first oil well in the world was drilled in Pennsylvania, USA. Oil in India is found in Assam, Gujarat and Mumbai High, and in the river basins of Godavari and Krishna.
  • 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.
    Chapter Notes - Coal & Petroleum Class 8 Notes | EduRevOil Refinery
  • 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 UsesChapter Notes - Coal & Petroleum Class 8 Notes | EduRevOil Refinery Working

  • 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.

➢ Steps to Reduce Consumption of Petrol/ Diesel

  • Use public transport.
  • Combine many errands into one trip.
  • Carpooling 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.

3. Natural Gas

  • Natural gas is another fossil fuel, like coal and petroleum. It is a non-renewable fuel. Natural gas is used for waste treatment and incineration. Gases like butane, ethane and propane may be extracted from it and used as feedstock for products such as fertilisers and pharmaceutical products.

Chapter Notes - Coal & Petroleum Class 8 Notes | EduRev

  • Natural gas is one of the most useful, clean and safe energy sources. It is a colourless and odourless gas in its pure form and is made up of many gases, of which methane is the most prominent. The chemical formula for methane is CH4.
  • When natural gas burns, it gives off a great deal of energy, and unlike other fossil fuels, leaves no ash. It causes very little air pollution, as methane burns almost completely.
  • It is one of the cleanest burning fuels and produces mostly heat, carbon dioxide and water vapour. Thus, it is said that it contributes to a cleaner and greener environment. 
  • Natural gas is odourless. To detect gas leaks, a harmless but pungent odorant that smells like rotten eggs is added to it, as a safety measure. It can be smelt in case of even a small leak.
  • Natural gas is measured in British Thermal Units (BTU).
  • Natural gas is compressed to high pressure and stored in hard cylindrical or spherical containers, for distribution. It is then known as Compressed Natural Gas or CNG.
    Chapter Notes - Coal & Petroleum Class 8 Notes | EduRev
  • CNG is also distributed to homes and industries through pipes. For example, in India, such a network of pipelines exists in Vadodara in Gujarat and some parts of Delhi. CNG is now used as a fuel for transport vehicles - from light-duty trucks, auto rickshaws and taxi cabs to delivery vans and heavy-duty vehicles like buses.

➢ Uses of Natural Gas 

  • Natural gas is used for cooking. 
  • To run central heating and cooling systems, and cloth dryers.
  • For electricity generation through the use of gas turbines and steam turbines. 
  • In the manufacture of fabrics, glass, steel, plastics, paint and other products.

➢ Limitations of Natural Resources

  • Fossil fuels like coal, petroleum, etc. need millions of years to get transformed from dead bodies to fuels. But currently, their demands are so high that after few hundred years there will be scarcity of these resources.
  • In addition, too much air pollution is caused when these fuels are burnt. And these fuels are also responsible for the problems associated with global warming. Hence, it is very much important to use these fuels wisely.
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