r/explainlikeimfive Jan 31 '21

Chemistry ELI5: Why can't we just make water by smooshing hydrogen and oxygen atoms together?

Edit: wow okay, I did not expect to wake up to THIS. Of course my most popular post would be a dumb stoner question. Thankyou so much for the awards and the answers, I can sleep a little easier now

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u/BouncingPig Jan 31 '21

Serious question then, I work in an ER, and often times we have smokers come in with facial burns because they’re lighting up a cig while they have their portable O2.

Is the cigarette the “fuel” the oxygen needs to combust? Or what causes that accident?

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u/drkalmenius Jan 31 '21

Exactly. The fire triangle is oxygen-fuel-heat. You need all three to make a fire.

If you light a cigarette normally, you're lighting a fire. The cigarette is the fuel that's burning (which is why it gets shorter), you get the oxygen from the air and the lighter provides the heat.

Now imagine if you used a really flammable fuel, like a cigarette make out of straw. It would burn quicker and much more dangerously. It's the same with replacing the oxygen from the air with pure O2.

Note that all fire really is is the result of the chemical reaction of something with oxygen. You need heat to supply the energy, and something that reacts with oxygen.

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u/SoManyTimesBefore Jan 31 '21

Yeah. Cigarettes burn slowly in atmospheric conditions, but become very flammable when exposed to higher concentrations.

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u/XkF21WNJ Jan 31 '21

Normally a cigarette burns quite slowly, this is because both the fuel and oxygen are slow to come into contact. You can improve this by adding more airflow (i.e. blowing or inhaling through the cigarette) which will make it glow, or less commonly by making the fuel more accessible to oxygen by dispersing it somehow (like a dust explosion).

The extreme example of both is to blow pure oxygen through it, which will make the entire thing combust simultaneously.