NCERT solutions for class 8 Science Chapter 5 Coal And Petroleum

Solution for Exercise

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


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Answer :

The advantages of using CNG and LPG as fuels are:
They burn with a smokeless flame and so does not cause any pollution.
They leave no ash on burning.
They are easy to handle and convenient to store.
They give a lot of heat energy when burn.

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


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Answer :

Bitumen

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


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Answer :

Millions of years ago, trees, plants, ferns and forests got buried below the rocks, soil and sand due to natural processes like flooding, earthquake, etc. Slowly, as more soil deposited over them, they were compressed. This led to the conditions of high pressure and heat. These conditions along with the anaerobic conditions turned the carbon-enriched organic matter of wood into coal. This slow process of conversion of wood into coal is called carbonisation.

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 a vehicle is ______________ .


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Answer :

(a) Fossil fuels are __coal__, __Petroleum__ and __natural gas__.
(b) Process of separation of different constituents from petroleum is called __refining__.
(c) Least polluting fuel for a vehicle is __compressed natural gas___.

Q.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 the 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)


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Answer :

a) False
b) False
c) True
d) True
e) False

Q.6 Explain why fossil fuels are exhaustible natural resources.


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Answer :

Fossil fuels take millions of years to be formed.Dead vegetation and animals that get buried deep inside the earth require high temperature and pressure for the formation of fossil fuels, which cannot be done in the laboratory. Thus, fossils are limited. Therefore, the use of fossil fuels at a rapid rate will lead to their exhaustion.

Q.7 Describe the characteristics and uses of coke.


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Answer :

Characteristics:

i) Coke is tough.
ii) Coke is porous.
iii) Coke is black in colour.

Uses:

i) In the manufacture of steel.
ii) In the extraction of metals (as a reducing agent).

Q.8 Explain the process of the formation of petroleum.


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Answer :

Dead organisms that got buried in the sea millions of years ago got covered with layers of sand and clay. Due to lack of air, high temperature and high pressure, these dead organisms got transformed into petroleum and natural gas.

Q.9 The following table shows the total power shortage in India from 2004-2010. Show the data in the form of a graph. Piet shortage percentage for the years on the y-axis and the year on the x-axis.


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Answer :



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