If fire burns because of oxygen, how come candles don’t lit up when we blow on them, but instead they go out?
In: Chemistry
Because you don’t exhale pure oxygen, you exhale air filled with carbon dioxide.
The carbon dioxide surrounds the flame blocking the oxygen in the air causing the flame to die.
There’s moisture in your breath. But also, you are blowing away the wax vapors (which are what’s actually burning) No fuel, no fire.
Now blowing on a fire is a great way to help light one, so your premise is completely valid.
Because they also need heat. As you blow the air carries away the hot gas that is burning replacing it with cool air from your lungs. Eventually this effect will over come the fires ability to heat the air, boil more wax, and keep burning. This is why gentle blowing doesn’t work.
How much O2 are you exhaling? I, for one, try to *inhale* O2 and exhale CO2.
Fire also needs fuel (in this case wax+wick) to combust there isn’t enough fuel for that oxygen to be used so the cool moist air from your breath extinguishes the flame.
They do if you blow lightly, but if you blow too hard you will cool them below their combustion temperature and without added energy, it will go out
Fire needs 3 things, oxygen, burning material and heat.
If you blow on a candle, you are blowing the heat away. Oxygen and burning material are left, the candle and atmosphere.
Take away any of those 3 and it will go out.
You can try it yourself. Light a match without a candle. Yes, oxygen and heat are present. Candle is not lit.
Try it with a candle in a vacuum. No, it wont lit.
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