CBSE NCERT Solutions for Class 8 Science Chapter 6

These NCERT solutions helps students to know the best answers to all the respective exercise-wise questions and thus, help them to prepare in a more efficient way for their exams.

CBSE NCERT Solutions for Class 8 Science Chapter 6:

Question-1:

Explain how the use of CNG in automobiles has reduced pollution in our cities.

Solution:

Combustion of fuels like petroleum causes formation of un-burnt carbon particles
along with carbon monoxide gas. These harmful pollutants enter the air and cause respiratory diseases. Compressed Natural Gas (CNG) produces these harmful products in very less quantity. It is a comparatively cleaner fuel. Therefore, the use of CNG has reduced pollution in our cities.

Question-2:

Give reasons.
(a) Water is not used to control fires involving electrical equipment.
(b) LPG is a better domestic fuel than wood.
(c) Paper by itself catches fire easily whereas a piece of paper wrapped around an
aluminium pipe does not.

Solution:

(a) Water is a conductor of electricity, so it can easily conduct electric current
and cause danger of electric shocks or short-circuits. Therefore, water cannot be used to control the fire involving electrical equipment.
(b) LPG is a better domestic fuel as it does not produce smoke and un-burnt carbon
particles, which cause respiratory problems.
(c) Paper by itself catches fire easily because it has low ignition temperature but
when wrapped around an aluminum pipe its temperature is lowered due to aluminum metal absorbing the heat supplied to paper. So it does not catch fire.

Question-3:

It is difficult to burn a heap of green leaves but dry leaves catch fire easily.
Explain.

Solution:

Green leaves have a lot of moisture in them. This moisture does not allow them to
catch fire easily. However, dry leaves have no moisture in them. Therefore, they catch fire easily.

Question-4:

Which zone of a flame does a goldsmith use for melting gold and silver and why?

Solution:

A goldsmith uses the outer part of the candle flame for melting gold and silver
because in this zone the temperature is the highest which helps to melt these metals easily.