Decoding the Science of Candles: From the Flame to the Chemistry
Candles have been a source of light and beauty for centuries, but did you know that there’s a lot of science behind the flame? From Faraday’s lectures in the 1800s to NASA’s space shuttle experiments in the late 20th century, scientists have been studying candles to understand the principles of heat, light, and combustion.
When a candle burns, the heat of the flame melts the wax near the wick. This liquid wax is then drawn up the wick by capillary action. The heat of the flame vaporizes the liquid wax and starts to break down the hydrocarbons into molecules of hydrogen and carbon. These vaporized molecules are drawn up into the flame, where they react with oxygen from the air to create heat, light, water vapor, and carbon dioxide. About 25% of the energy created by a candle’s combustion is given off as heat, and the rest is used to maintain the combustion process until the fuel is used up.
A well-burning candle flame is a very efficient combustion machine, with a steady and quiet teardrop shape. However, if the flame gets too little or too much air or fuel, it can flicker or flare and unburned carbon particles (soot) will escape from the flame before they can fully combust.
When looking closely at a candle flame, you can see different zones. The blue zone at the base of the flame is where the hydrocarbon molecules vaporize and start to break apart into hydrogen and carbon atoms. The dark or orange/brown region has relatively little oxygen, and this is where the various forms of carbon continue to break down and small, hardened carbon particles start to form. The yellow region at the top of the flame is where the carbon particles ignite and emit the full spectrum of visible light.
The study of candles offers a fascinating glimpse into the worlds of chemistry and physics. From the properties of wax and wicks, to the behavior of candle flames, scientists continue to uncover new insights and understanding about these ancient sources of light. Try making your own candles and let us know hoe you got on!
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