Coal and Petroleum Question Answers: NCERT Class 8 Science

The advantages of using compressed natural gas (CNG) and liquefied petroleum gas (LPG) as fuels are as follows:

1. They can be burnt easily.
2. They can be transported easily through the pipes.
3. They are clean fuels and do not give smoke when burnt.
4. They give a lot of heat energy when burnt.

Bitumen is used for the surfacing of roads because it provide better grip to the tyres of the vehicles while coal tar gets heated up very easily.

Millions of years ago, dense forest got buried under the soil due to natural processes like storms, floods and earthquakes etc. These got compressed or more and more layer of soil got deposited over them. When they got deep burried in the layers of soil, they were exposed to very high pressure and high temperature. Under these conditions they slowly got converted into coal. This process of formation of coal from dead and decay vegetation is called carbonization.

(a) Coal, petroleum, natural gas

Fossil fuels are made up of dead vegetation and animals. This process takes years to make petroleum.

(b) Refining

For purifying the petroleum, refining process is done. It separates the different constituents from petroleum which is known as refining.

(c) CNG

CNG is a clean fuel. It does not produce any harmful gases. The use of CNG in vehicles make our environment clean.

(a) False

This statement is false because the fossil fuels are made up of natural processes.

(b) False

This statement is false because CNG is a clean fuel. It does not produce any harmful gases behind whereas the petrol does.

(c) True

This statement is true because coke is the pure form of the carbon. Carbon is found in many forms like coal, petroleum and coke.

(d) True

This statement is true because coal tar is not the pure form of carbon. It is made up of the mixing of different substances.

(e) False

This statement is false because kerosene oil is also a fossil fuel. The process of making fossil fuel takes much time. Ti is made up of dead vegetation which burried deep in the soil by the natural activities.

In the formation of the fossil fuel, million years are required. Fossil fuels are formed from the dead vegetation and animals which get burried deep inside the soil layers. Due to higher temperature and high pressure, they get converted into the fuel. That is why these are known as fossil fuels. Fossil fuels are limited. We should avoid the use of fossil fuels because they cannot be formed by the human beings. Therefore, the fossil fuels are the exhaustible natural resources.

Coke is the purest form of carbon. Characteristics of coke are as follows:

1. It is very tough.
2. It is very parous is appearance.
3. It is black in colour.

Uses of coke are as follows:

1. It is used in manufacturing of steel.
2. It is used as a reducing agent in the extraction of metals.

Petroleum was formed from the dead and decay organisms that got buried deep in the sea, millions of years ago. These dead and decay bodies got covered by layer of sand and clay. Lack of air, high temperature and high pressure, transformed these dead organisms into petroleum natural gas.