Test: Combustion & Flame- 1 - UPSC MCQ

To explain why "B: Fuel" is the correct answer:

- Fuel:
- Fuels are substances that can undergo combustion to release heat and light.
- During combustion, chemical energy stored in the fuel is converted into heat and light energy.
- This process is essential for generating energy in various forms, like in engines, stoves, or power plants.
- Examples of fuels include wood, coal, oil, gas, and gasoline.

Therefore, fuel is the substance that gives heat and light after combustion.

As water is denser than that of oil if you pour water on burning oil it set down permitting the petrol or oil to rise up to the surface and enhance the burning in a continued manner.

Air is needed for fire to burn. By cutting off the supply of air, you can control or put out a fire. This stops the fire from getting the oxygen it needs to keep burning.

LPG is a better domestic fuel as it burns cleanly without producing smoke or unburnt carbon particles, which can cause respiratory problems.

• A candle does not burn without a flame. When you light a candle, the wax melts and the liquid wax is drawn up into the wick by capillary action.
• The heat of the flame vaporizes the liquid wax and starts to break down the hydrocarbons into molecules.
• These vaporized molecules are then drawn up into the flame where they react with oxygen in the air, producing heat, light, water vapor, and carbon dioxide.
• This is why a candle produces light and heat when it burns.

The amount of heat energy released on complete combustion of 1 kg of fuel is called calorific value of that fuel. Higher the calorific value better the fuel is considered.

The lowest temperature at which substance catch fire is called ignition temperature. The fuel with moderate temperature is considered better fuel for domestic use.

Carbon dioxide gas is used in fire extinguisher to cut the oxygen supply.
Option A is correct.

Aluminium absorbs heat, lowering the temperature of the paper wrapped around it and preventing it from reaching its ignition temperature, so it does not catch fire easily.

The three essential requirements for producing fire are fuel, air (to supply oxygen), and heat (to raise the temperature of the fuel beyond the ignition temperature). Fire can be controlled by removing one or more of these requirements.