Hydrogen is inflammable and oxygen is supporter of fire but still water does no gets fire instead it extinguish fire WHY?

Answer 1

Hydrogen burns because it has a very high stored chemical energy. It has few outer electrons and needs to share some to become stable. Oxygen supports fire because it has a very high stored chemical energy. But this stored energy is due to oxygen having many outer electrons and only needing a few to become stable. All this chemical energy is released when the two combine. Less energy remains, you can never get to zero energy, and thus water will not burn nor will it normally support fire. There are a few substances that, when 'burning', water will not put out the fire.

I believe thermite is one of those substances, and a large piece of magnesium metal possibly as well.

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Okay...

Water does NOT burn because "burning" is also called oxidation; in oxidation a chemical combines with oxygen. Depending on the speed of the oxidation heat may be released. (Think of rust; rust is oxidized iron, but iron oxidizes so slowly no heat is formed. Now think of carbon. When carbon oxidizes it does so at a fast rate so a lot of heat is formed, and the oxidation products leap off the surface of the carbon so fast with so much energy they produce light...the oxidation reaction is known as "a fire.") But water is already oxidized, so it can't be oxidized again.

Water puts out fires for two reasons. It absorbs heat, and fires must have heat if they are to continue. And it keeps oxygen, which fires need, from getting to the fuel.