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Thursday, January 12, 2012

Out, Out, Brief Candle!

In the last post, you learned how important the wax is to burning a candle. In this experiment, you will discover another requirement for burning - air. Burning wax is an example of a combustion reaction, in which carbon and hydrogen in the fuel (wax) combines with the oxygen in the air to form carbon dioxide and water. The more oxygen, the longer the candle will burn.

What you'll need:
Votive candle
Several drinking glasses of different sizes
Watch or other timer

Light one of the candles and cover it by inverting the smallest glass over the flame so that it is covered. See how long it takes for the candle to go out. Re-light the candle, and cover it with the next largest glass. Does the candle stay lit longer? Do the same thing for each size of glass.

You will generally find that, that larger the glass, the longer the candle stays lit. The explanation for this is pretty simple - larger glasses trap larger amounts of air (which contains oxygen), and it takes longer for the oxygen to get used up!

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