Thread: Why isn't water flamable?

Originally Posted by Bruno

Thanks. I was going to make the effort of explaining it scientifically, but you already did.
thanks man.

for all the good it did

It burns in Cleveland....

Originally Posted by Slartibartfast

It burns in Cleveland....

Yeah, I heard about that. My dad grew up near Cleveland.

Originally Posted by jockeys

burning = oxidation.

So when I have rust pits on my running boards of my SUV, I have actually burned them?

Matt

burn - to undergo combustion
combustion - a chemical reaction releasing heat and light.

Thus, to burn is to undergo a chemical reaction that releases heat and light.

Most but not all of these reactions are oxidation reactions where one chemical (fuel) is combines with oxygen. In common usage, the fuel is said to burn, in oxygen, but in truth one could also say that the oxygen burns in the fuel and be equally correct.

As has been mentioned by several others, water is the end product of combustion (between hydrogen and oxygen) and cannot burn further. This does not mean you cannot add oxygen to water, hydrogen peroxide is H2O2, thus 2H2O+O2 -----> 2H2O2. But this reaction is endothermic (i.e. it absorbs heat) so it is not combustion.

There are other reactions than oxydation that release heat and light. For example, the reaction between certain olefins and hydrogen to form a parrafins is exothermic.

Originally Posted by Seraphim

However, if you burn a piece of wood, you cannot reconstitute it to burn again. So, I'm suspicious of the answer of the hydrogen already being "burned" as a bit of sophistry and hand-waving from scientists who really don't want to answer my question or deal with the fact that when you pour water on a flame you are adding fuel to the fire.

There's obviously some sort of high-level cover-up going on here....

This bit about wood is not technically true. Any chemical reaction can go forwards or backwards. Backwards might not look the same as forwards (and it might not look the opposite either... if that makes sense and some might favor going one way, but both are possible.

I hope these photos post.

Originally Posted by Seraphim

The water isn't burning in that case, it is modifying the way the magnesium itself is burning.

Sort of like if you have a grease fire in a pot on a stove, if you put water on top of it, it causes an explosion. That is not due to the water bursting into flames, what happens is that the water contains the grease, which is still burning, which susequently super-heats due to the blanket of water on top, and then the grease rapidly expands into a big fireball.

Actually the case here is that the burning metal is able to seperate the componets, so in effect if you put water on a burning metal you are in effect fueling the fire. In firefighting training we where warned not to do this because of that effect. The method used by civilian firefighters (so we where told) with this type of fire is to keep away from it and let it burn itself out, In the navy we where to try and jetision the stuff if possible to keep it from spreading to other parts of the ship, or in my case on a submarine your pretty much screwed. (flashbacks to life in the service, run, run)

As for banning dihydrogen monoxide, I heard a rumor that as a joke someone started a bill in congress.... it almost got passed before people realized what it was

Originally Posted by errnest

As for banning dihydrogen monoxide, I heard a rumor that as a joke someone started a bill in congress.... it almost got passed before people realized what it was

The comedian Steve Allen used to do man on the street interviews. One of the best ones I remember was of him telling people that a local politician running for office was an admitted heterosexual and then he would ask what they thought about that. Most of the response were along the lines of "well, I don't think that's something that normal people should have to put up with and we certainly don't want our mayor to be a heterosexual!!!"