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?

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

How does Carbon dioxide extinguish fire?

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

What is the SI unit of calorific value?