PITTSBURGH (KDKA) — Candles are neat, calming to some and full of science.
They are made of wax and a wick which seems pretty simple.
Once you light the candle, the wick burns. As the wick burns, it melts the wax.
That liquid wax is then pulled up the wick through what is called “capillary action.”
Capillary action is the process where liquids move up through a solid, like a tube or spongy material. In the case of candles, that spongy material is a wick.
According to the National Candle Association, as that liquid wax gets pulled up the wick, the flame vaporizes that liquid wax, turning it into a hot gas and starts to break down the hydrocarbons in it into hydrogen and carbon.
As this happens they create heat, light, water vapor and carbon dioxide when they interact with oxygen.
We are going to do an experiment that uses a flame, so make sure it is only done with a responsible adult.
If we were to drop a birthday candle into water, it would float, because the candle is less dense than the water.
We need it to float vertically though, so we will add some silly putty or clay to the bottom. Just enough so that it will still float, but upright.
Now we light it. Normally we watch a candle burn from the top down. We created a system here where the candle will burn up. Sort of the opposite that you would expect.
The wax at the top of the candle is melted by the flame, fueling the flame. If the candle remains less dense than the water, it will float. Once the candle can no longer hold up our silly putty, the flame will go out.
This shows us that the candle is, in fact, getting its fuel from the wax through capillary action, because it is pulling the wax up above the water through the wick!