Why does combining hydrogen with oxygen cause heat and energy???

Question

I need to write an essay and explain it so I need to understand your answer.

Answer 1

That is really a chemistry question, and I don't know chemistry that well, so you might want to post this question again in the chemistry section.

Basically, the chemical energy of the hydrogen and oxygen atoms separately is higher than the chemical energy of the water molecule, so when the atoms combine, the extra energy is released.

Answer 2

The exchange of atomic components=work=heat.