Fuels & Fire
Tell a fuel from a non-fuel — and what burning needs.
What this lesson covers
Why it matters
Strike a match and a fuel bursts into flame, giving out heat and light. But hold water or a stone to the fire and nothing happens — some things simply are not fuels at all.
Predict first
Which of these is a FUEL — something that burns to give useful energy?
A fuel is a substance that burns in air to release heat and light. Wood, coal, petrol and cooking gas are fuels; water, sand, glass and stone do not burn, so they are not fuels.
- Sand
- LPG (the gas in cooking cylinders) — correct
- Water
- Glass
What you do
Sort each item: is it a fuel that burns to give energy, or not a fuel?
Check yourself
What must be present from the air for a fuel to burn?
Burning is a reaction with oxygen from the air. Cut off the oxygen and the flame goes out.
When a fuel like wood or petrol burns completely, what does it mainly produce?
Most common fuels contain carbon and hydrogen. Burning them in oxygen gives carbon dioxide and water, and releases heat energy.
Which fuels burn cleaner, with less smoke?
Gaseous fuels like LPG and CNG burn cleanly with very little smoke, so they are better for the air than smoky solid fuels such as wood and coal.
- Oxygen — correct
- Nitrogen
- Carbon dioxide
- Water vapour
- Carbon dioxide, water and heat — correct
- Only pure oxygen
- Ice and salt
- Gold
- LPG and CNG — correct
- Wood and coal
- Only wet leaves
- Sand and stone