Ans. Characteristics of petroleum
i. It is a dark oily liquid.
ii. It has an unpleasant odour.
iii. It is a mixture of various constituents such as petroleum gas, petrol, diesel, lubricating oil, paraffin wax, etc.
Ans. Petroleum was formed from organisms living in the sea. As these organisms died, their bodies settled at the bottom of the sea and got covered with layers of sand and clay. Over millions of years, absence of air, high temperature and high pressure transformed the dead organisms into petroleum and natural gas.
Ans. Products obtained from coal tar are used as starting materials for manufacturing various substances used in everyday life and in industry, like synthetic dyes, drugs, explosives, perfumes, plastics, paints, photographic materials, roofing materials, etc. Interestingly, naphthalene balls used to repel moths and other insects are also obtained from coal tar.
Ans. Uses of coal
i. Coal is one of the fuels used to cook food.
ii. Earlier, it was used in railway engines to produce steam to run the engine.
iii. It is also used in thermal power plants to produce electricity.
iv. Coal is also used as a fuel in various industries.
Ans. The advantages of using CNG and LPG as fuels are:
i. They can be transported easily through pipes.
ii. They can be used directly for burning in homes and factories where it can be supplied through pipes.
iii. They are clean fuels and do not give smoke when burnt.
iv. They are less polluting.
Ans. Their tips are:
i. Drive at a constant and moderate speed as far as possible,
ii. Switch off the engine at traffic lights or at a place where you have to wait,
iii. Ensure correct tyre pressure, and
iv. Ensure regular maintenance of the vehicle.
Ans. About 300 million years ago the earth had dense forests in low lying wetland areas. Due to natural processes, like flooding, these forests got buried under the soil. As more soil deposited over them, they were compressed. The temperature also rose as they sank deeper and deeper. Under high pressure and high temperature, dead plants got slowly converted to coal. As coal contains mainly carbon, the slow process of conversion of dead vegetation into coal is called carbonisation.
Inexhaustible Natural Resources
Exhaustible Natural Resources
1. These resources are present in unlimited quantity in nature and are not likely to be exhausted by human activities.
1. The amount of these resources in nature is limited. They can be exhausted by human activities.
2. Examples of these resources are sunlight and air.
2. Examples of these resources are forests, wildlife, minerals, coal, petroleum, natural gas etc.
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