system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If water is made out of Hydrogen and Oxygen why isn't it the perfect fuel?

I mean its all you need for a fire so why does it put fire out instead of make it gargantuan?
gpt
Because water is essentially the ash of combustion of hydrogen and oxygen. It's already had the energy extracted, and to convert it back into fuel, you'd first have to add a lot of energy to separate the two elements again.