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

Coal and wood are pretty good fuel sources too, no? You can light them on fire and do things like power furnaces, steam engines, ovens, etc.

When the coal is burnt, it leaves behind some things. Ashes, carbon dioxide, and water vapor. Are any of *those* things good fuel sources? No, of course not, they’re already burnt. Spent. Used up.

Hydrogen and oxygen, in their pure forms, may be very reactive molecules, especially in the presence of each other. But after they combine into water, that’s it. They are no longer in their pure forms. They’re spent. Used up.

Water is effectively the “ash” of a reaction between oxygen and hydrogen.