system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does a glass of water get little bubbles in it after sitting for a while?

I poured a glass of water this morning and didn't finish it. When I got back from class later, it has bubbles on the side of the glass. Why?
gpt
When you pour the glass of water, there will be some gasses actually dissolved in the liquid. Oxygen for example, dissolves better as the water gets colder.

While you leave the glass sitting the water warms up and the gasses can no longer remain dissolved so they form small bubbles in the water, float to the top and escape. However, if the bubbles are on the side of your cup they will get stuck on tiny imperfections in the glass which is why you are able to come back and see them.