system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Where do the air bubbles on the bottom come from when you boil water?
gpt
It’s not air, it’s actually water vapour. When water boils, it turns from liquid water to gas water, but still just water.
Some of the bubbles may be from dissolved gases coming out of solution as the water warms (warm water can’t hold as much dissolved gas as cold water), but the big bubbles of boiling water is just water vapour.