Science Question Answer (2 Marks)

When heated in air, coal burns and produces mainly carbon dioxide gas. Coal can be processed in industry to get some useful products such as coke, coal tar and coal gas. Coal is used as a fuel in industries and was used to cook food. It was used in railway engines to produce steam to run the engine. It is used in thermal power plants to produce electricity.

CNG is compressed natural gas. Natural gas is a very important fossil fuel because it is easy to transport through pipes. Natural gas is stored under high pressure as compressed natural gas (CNG). It can be used as a fuel in homes and factories. It is also used as a starting material for the manufacture of a number of chemicals and fertilizers.

1. Kerosene is used as a fuel for stoves, lamps and for jet aircrafts.
2. Paraffin wax is used in ointments, candles and Vaseline etc.

Carbonisation is the process by which plant material or vegetation buried deep under the earth was slowly converted into coal. Since, coal was formed from the remains of vegetation, it is also known as fossil fuel.

The three useful products of coal are following:

1. Coke: It is a tough, porous and black substance. It is almost pure form of carbon.
2. Coal tar: It is a mixture of about 200 substances. It is a black, thick liquid with unpleasant smell.
3. Coal gas: It is obtained during the processing of coal to get coke.

The exhaustible natural resources which are formed from the dead remains of living organisms or fossils are known as fossil fuels. For example, coal, petroleum and natural gas are fossil fuels. The resources are present in limited amount in nature and are known as exhaustible natural resources. They can be exhausted by human activities.

Substances used in everyday life which are manufactured starting from the products of coal tar are following:
Synthetic dyes, drugs, perfumes, plastics and paints. Naphthalene balls used to repel moths and other insects are also obtained from coal tar.

Coke is a very useful product of coal. It is a tough, porous and black substance. It is almost pure form of carbon. It is used as a reducing agent in the extraction of metals. It is also used in the manufacture of steel and in the extraction of many metals.

India has huge reserves of natural gas. It has been found in Tripura, Rajasthan, Maharashtra and in the Krishna Godavari delta. It is advantageous to use CNG as a fuel because it is less polluting than petrol. It is a clean burning fuel. It produces 45% less hydrocarbons than petrol. The great advantage of CNG is that it can be used as fuel in homes and factories where it can be supplied through pipes.

Many useful substances are obtained from petroleum and natural gas. These are termed as ‘Petrochemicals’. These are used in the manufacture of detergents, fibres (polyester, nylon, acrylic etc.), polythene and other man-made plastics. Hydrogen gas obtained from natural gas, is used in the production of fertilisers (urea).

The resources which are present in unlimited quantity in nature and are not likely to be exhausted by human activities are known as inexhaustible natural resources. For example, sunlight and air are inexhaustible natural resources.

The fossil fuel such as petroleum is formed from the dead animals under the sea. As these organisms died, their bodies settled at the bottom of the sea. They got covered with layers of sand and clay. Over millions of years, in the absence of air, with high temperature and high pressure, these the dead organisms were transformed into petroleum and natural gas.