Candles are amazing sources of light, which have been used for centuries. They are deceptively simple - a candle appears to be a string (the wick) stuck into a chunk of wax. You might think that any old piece of string will act as a wick, but that won't work. If you tried using the wrong kind of string (or the wrong kind of wax), you would find that the flame would go out quickly, and the candle wouldn't continue to burn. If you watch a candle for a while as it burns, you will notice that the wick doesn't actually burn away, and it's the wax that disappears. The wax must melt into a fairly thin liquid that can be soaked up by the absorbent wick. Two kinds of wax that do this are paraffin and beeswax. Paraffin is made from crude oil; beeswax comes from bee hives. The wax is absorbed into the wick where it vaporizes, then burns. If you watch a candle closely, you'll see that the wick burns much, much slower than the wax. When you blow out the candle, you see a white stream of smoke; this is cooling wax vapor. Ask an adult to touch a match to this white stream; you should see that the candle relights as the flame travels down the column of wax vapor.
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