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NCERT Solution for Class 8 Science Chapter 5 Coal and Petroleum
Natural Resources: The resources, that are obtained from nature are called natural resources, for example, air, water, soil and minerals.
Inexhaustible Natural Resources: The resources, that are present in unlimited quantity in nature, and cannot be exhausted by human activities, for example, air, sunlight etc.
Exhaustible Natural Resources: The resources, that are present in limited quantity in nature, and can be exhausted by human activities, for example, coal, petroleum, minerals, forests etc.
Fossil: The remains of the part of plants or animals transformed over time, is called fossil.
Some exhaustible natural resources from the dead remains of living organisms are known as fossil fuels, for example, coal, petroleum and natural gas.
Coal is a fossil fuel, that was formed by the decay of vegetation, which existed millions of years ago. It is a non-crystalline form of carbon.
Carbonisation: The slow process of conversion of dead vegetations into coal is called carbonisation.
Coke is an amorphous form of carbon, which is harder and denser than charcoal and is used as a fuel. It is obtained by heating soft coal in the absence or little supply of air. It is black in colour. It is used in the manufacture of steel.
Destructive Distillation: The process of heating coal in the absence of air is called destructive distillation.
Coal Tar is a black thick liquid, i.e., a mixture of about 200 substances and is used to get various materials of everyday life/industry, like; drugs, dyes, plastics, perfumes, paints, naphthalene balls etc.
Coal Gas is a by-product, that is obtained during the processing of coal to form coke, and is used as a fuel.
Petroleum is a fossil fuel, that is obtained by the decomposition of dead animals and plants due to geological changes under the earth. It means oil from the rocks. It is a dark oily liquid that is insoluble in water.
Various constituents of petroleum and their uses are as follows:
| S. No. | Constituents of Petroleum | Uses |
| 1. | Petroleum Gas in Liquid form (LPG) | Fuel for home and industry |
| 2. | Petrol | Motor fuel, aviation fuel, solvent for dry cleaning |
| 3. | Kerosene | Fuel for stoves, lamps and for jet aircrafts |
| 4. | Diesel | Fuel for heavy motor vehicles, electric generators |
| 5. | Lubricating oil | Lubrication |
| 6. | Paraffin wax | Ointment, candles, vaseline etc. |
| 7. | Bitumen | Paints, road surfacing |
Petroleum Refining: The process of separating the different constituents/fractions of petroleum is known as petroleum refining.
Natural Gas is a very important fossil fuel, that is stored under high pressure and is easy to transport through pipes and referred to as CNG (compressed natural gas). It is a non-polluting fuel. It helps in the manufacture of a number of chemicals and fertilizers.
Coal: Coal is a fossil fuel, formed by the decay of vegetation which existed millions of years ago.
Coal Gas: Coal gas is obtained as a by-product during the processing of coal to form coke, and is used as a fuel.
Coal Tar: It is a black thick liquid with an unpleasant smell obtained by the processing of coal.
Coke: It is tough, porous and black substance obtained by the processing of coal.
Fossil Fuel: Dead remains of living organisms and buried over millions of years, like coal, petroleum and natural gas are fossil fuels.
Natural Gas: Natural Gas is a very important fossil fuel. It is a cleaner fuel.
Petroleum: It is a dark oily liquid with an unpleasant odour. It is a source of petrol and diesel.
Petroleum Refinery: Petroleum refinery is a place where the process of separating the various constituents of petroleum is carried out.
NCERT Solution for Class 8 Science Chapter 5 Coal and Petroleum Important Question
Types of natural resources
1. Inexhaustible natural resources
These sources are present in unlimited quantity in nature and are not likely to be exhausted by human activities.
Examples: Sunlight, air, etc.
2. Exhaustible natural resources
The amount of these resources in nature is limited, they can be exhausted by human activities.
Examples: Forests, coal, petroleum. minerals, wild life, natural gas, etc.
What are the characteristics of an ideal fuel?
(1) It should have a high calorific value.
(2) It should not cause any pollution or should not produce harmful gases on combustion.
(3) It should be of low cost and easily available.
(4) It should be easy to handle, store and transport.
(5) It should have moderate ignition temperature.
(6) It should have moderate rate of combustion.
what is Fossil fuels
Exhaustible natural resources like coal, petroleum and natural gas were formed from the dead remains of living organism (fossils). So, these are called fossil fuels. Coal and petroleum are very important natural resources and play a vital role in modem society. They are found in the earth’s crust.
How many types of coal are there?
(1) Peat
(2) Lignite
(3) Bituminous coal
(4) Anthracite coal
What is petroleum used for?
(1) Petroleum products are used as fuels.
(2) Lubricating oils, and vaseline are used as lubricants.
(3) Paraffin wax, products of petroleum, is used for manufacturing candles, polishes, waxed paper, water proofing, etc.
(4) Some of the by-products of petroleum after purification are used in the preparation of medicines, ointments, face creams and cosmetics.
How to conserve fossil fuels?
It is believed that it took millions of years for the dead organisms to change into coal, petroleum or natural gas. Furthermore, their known reserves are limited.
Another problem with fossil fuels is that they are steadily increasing air . pollution, their use is linked to global warming. So, it is important that we use fuels only when it is absolutely necessary. tri this way, we can save these fuels for the Manufacture of many substances which are dependent on petrochemicals.
For energy purpose, we must look for alternative sources, such as solar energy, tidal energy, wind energy, etc. Furthermore, fossil fuels will be available to future generations for more useful products.
In India, the Petroleum Conservation Research Association (PCRA) offers the following tips to conserve petrol & diesel while driving.
(1) Drive at a constant & moderate speed as far as possible. Driving at a high speed or slow speed wastes a lot of fuel.
(2) Switch off engine if you have to wait at traffic lights or for any other reason.
(3) Check the tyre pressure regularly, low pressure or too high pressure waste fuel.
(4) Make sure that you send your vehicle to garage for regular maintenance.
