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Comment by o11c | Hacker News Reader

That's literally the same as asking "how come hydrogen (flammable) + oxygen (enhances fire) = water (does not burn)?", but we probably have a better mental grasp of how water works.

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Oversimplifying, but you can explain that as "Because water is... the "ash" you get after burning hydrogen and oxygen."

I think the intent is that water is a byproduct of combustion.

I’m pretty sure the intent was that water is a byproduct of combustion.

It’s all about electrochemical potential. Adding or removing electrons from the outer shell of an atom involves a fair amount of energy, either being released or stored. Depending on the atom, they either want their shell filled or emptied. Noble gases have the same number of protons as a filled shell, so they are very stable. Why electron shells exist is a whole other matter.

Water is kind of like ash. Technically full combustion of any hydrocarbon outputs CO2 and Water. Since water isn’t a greenhouse gas it’s not mentioned when discussing combustion usually.

(boring not pick, water is not a green house gas as sea level, but in the upper atmosphere water vapour most certainly does help to trap heat in the system - https://science.nasa.gov/earth/climate-change/steamy-relatio...

This is one of the reasons why methane leaks are so impactful - not only is methane a terrible green house gas, when it decays in the upper atmosphere, it decays into water vapour and CO2)

Water absolutely is a green house gas, and the most significant one at that.

https://science.nasa.gov/earth/climate-change/steamy-relatio...

As a fun aside, there are plenty of rocket engines that run on hydrogen + oxygen. For instance the Space Shuttle Main Engine [1] was fueled by hydrogen + oxygen, which means its exhaust was literally water vapor.

[1] - https://en.wikipedia.org/wiki/RS-25

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