What you need:
- A candle
- Some matches
Flames are involved so best make sure there is a sober adult present.
What to do.
1) Light the candle and let it burn for a minute or until the wick is surrounded by a puddle of liquid wax.
2) Blow out the candle.
3) Hold a lit match in the candle's smoke a couple of centimetres above the wick.
4) Bingo, the candle should suddenly reignite.
What's going on?
To set things alight you need oxygen (which comes from the air), an ignition source (the flaming wick) and some fuel (the paraffin wax in the candle). The flame melts the wax which is then drawn up the wick and so provides the flame with a ready source of fuel. When you blow the candle out the wick contains some of this liquid wax and the glowing end of the wick heats the wax still further so that it vaporises (to a gas) and drifts off with the smoke. The gaseous wax is flammable so when you put a match in the smoke you ignite the gas, the flame travels down the smoke trail and then reignites the wick. It all happens too fast for you to see so it looks like the candle spontaneously relights when you hold a match above it.