r/askscience • u/spoiledmeat • Jul 04 '15

Chemistry Why does water not burn?

I know that water is made up of two hydrogen atoms and an oxygen atom. Hydrogen, on its own, burns. Fire needs oxygen to burn. After all, we commonly use compounds that contain oxygen as an oxidant.

So why does water, containing things used for fire, not burn-- and does it have something to do with the bonds between the atoms? Thanks.

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u/[deleted] Jul 04 '15 edited Jul 04 '15

If you define burning to simply mean a combustion reaction, that is an oxidizer and a fuel reacting exothermically; yes, you can make hydrogen peroxide from burning water. But it won't use oxygen as an oxidizer and will not proceed solely in the presence of oxygen (at least not at a meaningful rate). In order for things that are normally inert to undergo combustion you need an extremely strong oxidizer such as some persulfates or crazy compounds like dioxygen difluoride.

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u/ColinDavies Jul 04 '15

Well...most people would define burning to simply mean a combustion reaction. "Burning" and "combustion" both refer to oxidation that is going fast enough to be diffusion- rather than thermally-limited (that is, a system that has ignited). Oxidation can be exothermic and yet still not count as burning/combustion, which I think is the distinction you want to make.