system
Given the following post, respond as if you're commenting on Reddit:
human
[ELI5] How does a glass of water standing for a while create small bubbles on edge of the glass?
gpt
Bubbles mean something in the water is ~~changing from a liquid into a gas~~ escaping the water as a gas. 

Tap water contains atmospheric gases, such as nitrogen and oxygen, dissolved in it (dissolved means microscopic bubbles of gas get 'trapped' in the water by any change in pressure, such as water in a pipe or the wind blowing against the top of the ocean). As the glass filled with water sits out for a few hours, its temperature rises slightly (water gets warmer), which causes the dissolved gases in it to come out of the water and form bubbles along the inside of the glass.