I know the question sounds simple enough, and to be honest I hesitated asking it because it would seem so easy…But I was wondering if a fire needs three things to burn (Heat, fuel and oxygen) it would seem that blowing on a match would only make it flame more if you are increasing the oxygen. So I was hoping one of the chemists-types or physics guru’s would swing on in and answer this simple question for me.
Why does a match go out when you blow on it? Is it lack of fuel? Velocity of the blown air? Is it the CO[sub]2[/sub] coming out of your mouth that does it?
Traf Michael Faraday’s classic text a Chemical History of a Candle – great, accessible science delivered originally as Christmas lectures with demonstrations almost 200 years ago.
The important part, for this question, is that flame is supported by gases liberated by heating the wax of the candle or the wood of the match. It’s these gases that burn, not the wood or the wick, really. The gases burn with a blue flame. The carbon liberated forms small particles of soot, which heat up and glow , giving off blackbody radiation that form the yellow part of the flame. (Your gas birner on your stove doesn;'t form soot, if adjusted properly, so it nurn just blue, and the bottom of your pots doesn’t get covered with soot.)
When you blow out a candle or a match, your immense whirlwind of a breath blows away the weak flow of gases to the flame, so the flame goes out, as it lack fuel.
if you blow on a camp fire or other large fire, your puny breath isn’t enough to blow away all the gases being liberated. Even if you did, they’re being replenished much fastwer than with a small candle or atch flame. So you can;t blow out a camp fire. What you do, however, id inject a lot of air into the fire (even though we say you exhale carbon dioxide, your beathe actuall only contains excess of carbon dioxide. It still contains oxygen, although proportionally less than ambient air). The flame in a camp fire needs oxygen, so you actually cause a campfire to burn more rapidly and intensely by blowing on it.
A persistent flame on a piece of wood such as a match is reliant upon its own heat releasing the volatile combustible components from the wood, and the already-incandescent volatiles currently under combustion still being there to ignite them when they are released.
When you blow on a match, you’re displacing the flame until it cannot ignite the continuing supply of volatiles(there might also be an aspect in which you are dispersing the emitted unburned volatiles), and it goes out.
Residual heat continues to drive off volatiles, but with nothing to ignite them, they appear as smoke; if a new source of ignition (doesn’t have to be hot enough to start the volatiles being driven off again - that is still ongoing - say, a spark from a flint or a piezo crystal device) is introduced to the stream of smoke in short order, it will relight and the process will resume.
