COMBUSTION AND FLAME

The hottest zone of a candle flame is

• Non-luminous zone

• Luminous zone

• dark zone

• blue zone at the base of the wick.

Which poisonous gas is formed as a result of incomplete combustion?

• Coal gas

• carbon monoxide

• carbon dioxide

• nitrogen oxide

Good fuels have

• low ignition temperature and high calorific value

• high ignition temperature and high calorific value

• low ignition temperature and low calorific value

• high ignition temperature and low calorific value

Which one of the following gases is used in combustion?

• CO

• Carbon dioxide

• Oxygen

• Nitrogen

A temperature at which the substance burns is called

• melting

• boiling temperature

• ignition temperature

• evaporation

Why is the innermost zone of a flame black in colour?

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What are the characteristics of good fuel? (Write any 4)

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How does Carbon dioxide extinguish fire?

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All combustible substances must be heated to the same temperature to make them burn. True or false?

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What is the SI unit of calorific value?

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