Question

hydrogen is combustible oxygen helps combustion but water helps to extiguish fire

(scientific reasons)

Answer 1

We know that hydrogen can cause fire, as it is combustible.

We also know that it thier exists alone, means it is thier in elemental form.

So, it shows its all properties.

Since, water is a compound consists of H and O, since it is a compund so it will losse all properties of its constituents.

So, water shows properties of $\textbf{extinguishing }$fire.

Answer 2

Water actually absorbs heat to evaporate. so when we put water on fire, some of the water absorbs heat and evaporate (known as latent energy) . But your question might be that why don't hydrogen and oxygen then burn to produce more heat? Simple answer is that in a compound , molecules are bonded (attached) together so that the don't move freely .Hence they can't be broken down that easily (Case specific- it depends on type of bond and structure and bond strength). In water, this strength b/w atoms are so high that it is tough to dissociate water into H²and O². So it basically, Explaining for a noobie I can say.
Hydrogen and oxygen are loving couples in H²O. But there are a lot of water molecules in which a hydrogen attracts other oxygen atoms(affair) and vice-versa. But truly love the oxygen they're bonded to. So in crucial situation (heating) they actually break their affairs and go on to live a happy life together (as water vapour) .Happily Ever After.....
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