CBSE NCERT Solutions for Class 8 Science Chapter 5

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CBSE NCERT Solutions for Class 8 Science Chapter 5:

Question-1:

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

Solution:

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

Question-2:

Explain why fossil fuels are exhaustible natural resources.

Solution:

Fossil fuels require millions of years to form from the dead vegetation and animals that get buried deep inside the Earth. They require high temperature and pressure for their formation, which cannot be provided in the laboratory. Thus, fossils are limited. Therefore, the use of fossil fuels at this rate will lead to their exhaustion.

Question-3:

Describe characteristics and uses of coke.

Solution:

Characteristics of coke are:
→ Tough
→ Porous
→ Black in color
Uses of coke:
→ In manufacture of steel.
→ In the extraction of metals (as a reducing agent).

Question-4:

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

Solution:

The advantages of using compressed natural gas (CNG) and liquefied petroleum gas
(LPG) as fuels are:
→ They can be burnt directly.
→ They can be transported easily through pipe lines.
→ They are clean fuels and do not give smoke when burnt.
→ They give a lot of heat energy when burnt.