If fire feeds off of oxygen(O), and there is oxygen in water (H2O), how does water extinguish fire?



If fire feeds off of oxygen(O), and there is oxygen in water (H2O), how does water extinguish fire?

In: Chemistry

In water. The oxygen is already bonded to hydrogen, so it isn’t in the water “free” to bond with any other chemicals, in order to burn it.

Basically, the hydrogen blocks the oxygen from being useful.

So when you pour water on a fire, you are smothering it with useless oxygen, so that useful oxygen can’t get to it.

guess that fire feeds off oxygen in nature (O2, not the element O) so H2O is a completely different thing

The way fire “feeds” off of oxygen is by converting volatile 02 into more stable compounds (usually H20 and C02). In other words, if oxygen is (one part of) fuel, H20 is *spent* fuel.

Now, in a more direct answer to your question: fire needs 3 things to survive: heat, fuel, and oxygen. Dumping water on fire accomplishes both to move heat away quickly, and to starve it of 02 by “drowning” it.

Also, some fires can feed off of water. Your common fire gets extinguished because you need a lot of heat to unbind the hydrogen from the oxigen and the water suffocates the combustion before that happens.
Oil fires burn hotter and they can unbind the elements that form water. The oxigen in water feeds the fire as does hydrogen which is very combustible.

If sodium is highly caustic and chlorine is a deadly poison, how can we eat salt?

A molecule isn’t a combination of the properties of its constituent atoms, it has its own unique properties that might be nothing like them. One of water’s properties is it doesn’t burn easily. In, water is the opposite of burning, it is one of the things that is produced when anything containing hydrogen burns.

Common Fire is the rapid oxidization of material (fuel) as a chemical reaction of O2 and said fuel. The O in H2O is already strongly bonded to its hydrogen atoms, and will not as easily react.

Water extinguishes fire in two ways. It takes away the oxygen, and it cools down the fuel to the point it will no longer ignote.

ITT: Lots of people saying that the bonds between hydrogen and oxygen prevent water from being an oxidizer (as opposed to, say, HO, which is an oxidizer). But that’s not what puts out a fire.

Water has a vaporization temperature way lower than the temperature needed for combustion. Every time a water molecule vaporizes it takes energy from its surroundings. The combination of these two facts means that if you put a match into water, the intense heat gets absorbed by the vaporizing water, until the temperature of the match is too low to vaporize any more water, at which point the match has long since stopped burning.

This explains why dropping a match into water has the same effect as pouring water over top of it. Even if the water capillaries upwards a bit, it’s not effectively blocking oxygen to the match head. But it is drawing heat away very quickly and efficiently.