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Thursday, January 12, 2012

Blowin' In The Wind

How do you usually extinguish a candle? Not by putting a glass over it, but rather, by blowing it out. Why does this work?

Maybe it's that carbon dioxide again. Your exhaled breath contains more carbon dioxide than the air you breathe in. When you blow out a candle, do you reduce the amount of oxygen around the flame so that it goes out? No - there's still more oxygen (about 15%) in your exhaled breath than CO2 (4-5%). That's not enough to snuff out the flame. The real explanation is actually simpler. The candle will go out if you blow hard enough to separate the flame from the wick. If the molten wax isn't actually on fire, it can't continue to burn.
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