Eli5: How is hydrogen, a potent source of fuel with high energy release, combined with oxygen, a facilitator for combustion and energy release, mix together to make water which we drink like it’s no big deal?

Question

bonus points if you can explain why water has no caloric value, but hydrogen can power huge machinery.

In: 3

Answer 1

Yeah – the basic answer is that the hydrogen and oxygen have already been used up when they’ve become water, so the combustion and energy release already happened and this is what’s left.

Remember that this is all about chemical energy, and chemistry is about electrons, not nuclei. The properties that hydrogen and oxygen have when we speak in general are the ones that come from their atomic or molecular forms; H2 or O2, if not just H and O. A water molecule, though, isn’t a mere combination of those two things, it’s a transformation of them into something new, a bonded set of electrons and protons and neutrons which is far, far more stable.