system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does my glass of tap water fill with air bubbles if it sits still overnight?

ELI5: Why does my glass of tap water fill with air bubbles if it sits still overnight?
gpt
Atmospheric gases, Ike oxygen and nitrogen, come out of the water as time passes and as the water warms up.

 Your tap water isn't pure water, it's mixed with the air around it as it travels through the pipe and out the faucet. The bubbles forming are the gasses coming out of equilibrium with the water. Kind of like some sauces (or nail polish)  separating if you leave it alone for a while.