NCERT Class VIII Science Solutions: Chapter 6-Combustion and Flame Part 4 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Question 7:

Name the unit in which the calorific value of a fuel is expressed.


The calorific value of a fuel is expressed in a unit called kilojoule per kg.

Question 8:

Explain how is able to control fires.


, being heavier than oxygen, covers the fire like a blanket. Since the contact between the fuel and oxygen is cut off, the fire is controlled.

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Question 9:

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


The ignition temperature of green leaves is higher than that of the dry leaves, so dry leaves catch fire easily

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Question 10:

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


Goldsmith uses the outermost zone of the flame for melting gold and silver because it is the hottest zone (complete combustion) of the flame.

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