NCERT Book Class 8 Science Coal And Petroleum

COAL AND PETROLEUM

We use various materials for our basic needs. Some of them are found in nature and some have been made by human efforts.

Can air, water and soil be exhausted by human activities? You have already studied about water in Class VII. Is water a limitless resource? In the light of the availability of various resources in nature, natural resources can be broadly classified into two kinds: Inexhaustible Natural Resources These resources are present in unlimited quantity in nature and are not likely to be exhausted by human activities. Examples are: sunlight, air. Exhaustible Natural Resources The amount of these resources in nature is limited. They can be exhausted by human activities. Examples of these resources are forests, wildlife, minerals, coal, petroleum, natural gas etc.

5.1 Coal

You may have seen coal, or heard about it (Fig. 5.1). It is as hard as stone and is black in colour Coal is one of the fuels used to cook food. Earlier, it was used in railway engines to produce steam to run the engine. It is also used in thermal power  plants to produce electricity. Coal is alsoused as a fuel in various industries.

Story of Coal:

About 300 million years ago the earth had dense forests in low lying wetland areas. Due to natural processes like flooding, these forests got buriedunder 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. Since it was formed from the remains of vegetation, coal is also called a fossil When heated in air, coal burns and produces mainly carbon dioxide gas.

Coal is processed in industry to get some useful products such as coke, coal tar and coal gas.

A. Coke

It is a tough, porous and black substance. It is almost pure form of carbon. Coke is used in the manufactureof steel and in the extraction of manymetals.

B. Coal tar

It is a black, thick liquid (Fig. 5.3) with unpleasant smell. It is a mixture of about 200 substances. 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 fromcoal tar.

C. Coal gas

Coal gas is obtained during the processing of coal to get coke. It is used as a fuel in many industries situated near the coal processing plants.

5.2 Petroleum

You know that petrol is used as a fuel in light automobiles such as motor cycles/ scooters and cars. Heavy motor vehicles like trucks and tractors run on diesel. Petrol and diesel are obtained from a natural resource called petroleum. Do you know how petroleum is formed? 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.

Exercises

1. What are the advantages of using CNG and LPG as fuels?

2. Name the petroleum product used for surfacing of roads.

3. Describe how coal is formed from dead vegetation. What is this process called?

4. Fill in the blanks :

(a) Fossil fuels are , and .

(b) Process of separation of different constituents from petroleum is called .

(c) Least polluting fuel for vehicle is .

5. Tick True/False against the following statements :

(a) Fossil fuels can be made in the laboratory. (T/F)

(b) CNG is more polluting fuel than petrol. (T/F)

(c) Coke is almost pure form of carbon. (T/F)

(d) Coal tar is a mixture of various substances. (T/F)

(e) Kerosene is not a fossil fuel. (T/F)

6. Explain why fossil fuels are exhaustible natural resources. COAL AND PETROLEUM 

7. Describe characteristics and uses of coke.

8. Explain the process of formation of petroleum.

Extended Learning — Activities and Projects

1. Get an outline map of India. Mark the places in the map where coal, petroleum and natural gas are found. Show the places wherepetroleum refineries are situated.

2. Choose any five families of your neighbourhood. Enquire whether their energy consumption (coal, gas, electricity, petrol, kerosene) has increased or decreased in the last five years. Enquire also about the measures they adopt to conserve energy.

3. Find out the location of major thermal power plants in India. What could be the reasons for their being located at those places?

Please refer to attached file for NCERT Class 8 Science Coal And Petroleum