NCERT Class VIII Science Solutions: Chapter 6-Combustion and Flame Part 4

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Question 7:

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

Answer:

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

Question 8:

Explain how is able to control fires.

Answer:

, 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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Corban Dioxide Able to Control Fires

Question 9:

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

Answer:

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

Image result for burn a heap of green leaves but dry leaves …

Burn a Heap of Green Leaves but Dry Leaves Catch Fire Easily …

Question 10:

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

Answer:

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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Goldsmith Use for Melting Gold and Silver

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