why fire burns better in air than pure oxygen?

Question

why fire burns better in air(21% oxygen) than pure oxygen?

Answer 1

Ok, I have to pipe in here. Although the right answer is already up, I thought I'd actually explain it.

Any combustion process involves a reductant and an oxidizer. Even if you haven't taken chemistry to know what that means, the reductant is usually the "fuel," and the oxidizer, as you may have guessed, it usually "oxygen." In almost every situation--fires, explosions, etc. the limiting factor is how fast the oxygen can get to the fuel. This is why something very light and porous, like toilet paper, will burn faster than regular paper, which will burn faster than cardboard, which will burn faster than wood. Wood has more energy to give out if you burn it than paper, but it's denser so the oxygen can't get in there as fast.

So since the oxygen is basically the limiting factor in burning, if the atmosphere consisted of 100% oxygen instead of 21% oxygen, everything would burn much faster. I don't know that the "light a match, blow up the world" thing would actually happen, but let's just say firefighters would have an even more miserable job than they do now, and by far.

If you want a strange example regarding the whole oxygen is the limiting factor thing, consider this: the fastest way to burn anything is with liquid oxygen. Liquid oxygen is 200 degrees colder than regular ice. Yet, being liquid oxygen, it is ~1000 times denser than even a 100% pure oxygen atmosphere would be. So despite the fact that it is so cold, it will instantaneously burn anything in its path.

Also, in case you care, since the slow access of oxygen to the material being burned is what usually slows down a fire, explosives are made using chemical groups like nitro (NO2) that already contain oxygen in the molecule. So all the molecule has to do in order to burn is just rearrange itself, instead of waiting for external oxygen. That's why explosives "burn" so fast, they already have their oxygen with them.

So fire burns better in pure oxygen because it needs the oxygen and the other components of air (nitrogen, carbon dioxide) totally don't matter to the fire.

Answer 2

fire burns better in 100% oxygen than in 21% oxygen.

what the other guy said is true. if the atmosphere was 100% O2 and someone lit a match, the entire world will blow up. when you light the match, only the head burns. in 100% oxygen, the flame grows so large it can ignite the entire match stick, including your skin, muscle and bone. basically everything containing carbon will catch fire, causing the flame to grow ridiculously large, and burn all organic material in the vicinity.

Answer 3

the fact is that oxygen only aids in combustion but does not really burn on its own... i mean oxygen does not burn like hydrogen or nitrogen.. so when a match is lit in a room of oxygen it does not light up the whole room.. it extinguishes soon.. but when other flammable gasses are around, oxygen helps other gases to combust and hence is the reason that fire burns better in air than pure oxygen.

Answer 4

well if u lit a match in 100% oxegen the whole world would be full of fire and everything would burn reason:fire breathes in oygen to survive and to grow

Answer 5

Massive increase in heat produced.

Answer 6

You may find the opposite is true!

Answer 7

It doesn't. Please let us know if you have disproved a law of physics.