Online Test — Combustion and Flame
15 Questions • 15 min • Chapter MCQ
15:00
Question 1 of 15
Combustion is the burning of a substance in:
Nitrogen
Oxygen
Water
Carbon dioxide
Explanation: Combustion is a reaction with oxygen that gives heat and usually light.
Question 2 of 15
Which of these is a combustible substance?
Glass
Stone
Wood
Iron rod
Explanation: Wood burns, so it is combustible; glass, stone and iron do not burn easily.
Question 3 of 15
The three conditions for combustion are fuel, ignition temperature and:
A supporter of combustion (oxygen)
Water
Sound
Light only
Explanation: Fuel, oxygen and the ignition temperature make up the fire triangle.
Question 4 of 15
The lowest temperature at which a substance catches fire is its:
Boiling point
Calorific value
Ignition temperature
Melting point
Explanation: This is the ignition temperature.
Question 5 of 15
Substances with a very low ignition temperature that catch fire easily are:
Non-combustible
Inflammable
Metals
Supporters of combustion
Explanation: Inflammable substances catch fire easily, like petrol and LPG.
Question 6 of 15
Burning of LPG when a stove is lit is an example of ___ combustion.
Spontaneous
Rapid
Slow
Explosion
Explanation: LPG burns quickly when lit, which is rapid combustion.
Question 7 of 15
A substance bursting into flames on its own without a flame being brought near is ___ combustion.
Rapid
Spontaneous
Explosion
Incomplete
Explanation: Catching fire on its own is spontaneous combustion.
Question 8 of 15
The sudden reaction releasing heat, light, sound and gas, like a firecracker bursting, is an:
Explosion
Rapid combustion
Spontaneous combustion
Slow burning
Explanation: A firecracker bursting is an explosion.
Question 9 of 15
A flame is produced only when the burning substance gives off:
Vapours (gases)
Water
Ash only
Sound
Explanation: A flame forms when the substance produces vapours that burn.
Question 10 of 15
Which zone of a candle flame is the LEAST hot?
Dark innermost zone
Yellow middle zone
Blue outer zone
All are equally hot
Explanation: The dark innermost zone has unburnt vapour and little oxygen, so it is least hot.
Question 11 of 15
Goldsmiths heat metals with the outer part of a flame because it is the:
Coldest part
Hottest part
Darkest part
Yellow part
Explanation: The outer blue zone is hottest due to complete combustion.
Question 12 of 15
The amount of heat produced on completely burning 1 kg of a fuel is its:
Ignition temperature
Calorific value
Boiling point
Density
Explanation: Calorific value is measured in kJ/kg.
Question 13 of 15
Incomplete combustion of fuels can produce the poisonous gas:
Oxygen
Carbon monoxide
Nitrogen
Hydrogen
Explanation: Incomplete combustion produces poisonous carbon monoxide.
Question 14 of 15
Water should NOT be used to put out fires caused by:
Paper
Wood
Electrical equipment or oil
Dry leaves
Explanation: Water conducts electricity and oil floats on it, so water is unsafe for these fires.
Question 15 of 15
A carbon dioxide extinguisher puts out a fire by:
Adding more oxygen
Cutting off the oxygen supply
Adding fuel
Raising the temperature
Explanation: CO2 blankets the fire and cuts off oxygen, stopping the combustion.