Fire needs air — Chemistry, 4–6 years
A flame is a fast chemical change that gives off heat and light. It needs something to burn and air around it, so a flame goes out when either is taken away.
What a flame needs
A flame keeps going when it has a fuel, such as a candle wax, and air around it. The fuel changes into new gases, while heat and light come out. Remove the fuel or block the air, and the flame stops.
Why this matters
People have long used fire for warmth, cooking and light, but fire can also spread and hurt things. Understanding its needs helps us control it: a candle wick supplies fuel, while a lid can cut off air. This idea came from watching flames grow, shrink and go out.
Covering a candle
An adult lights a small candle safely. First, the flame burns in the open air. Next, the adult places a glass over it without touching the hot wax. After a short time the flame becomes smaller and goes out, because the air inside is no longer being replaced.
The reasonable mistake
It is reasonable to think a flame is a little object that will keep glowing by itself, especially because air is invisible. But a flame is a process, not a solid thing. It needs a continuing supply of fuel and air, just as a person needs a continuing supply of food and air.
Controlling fire
A candle goes out when it has used its wax, and a cook turns down a gas flame by giving it less fuel. Firefighters often use water or a special covering to cool a fire or keep air away. Never test flames alone: an adult must handle candles, matches and hot objects.
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