system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why does soda or other carbonated beverages foam up when poured over ice?
gpt
Common ice cubes have uneven surfaces. When carbonated water touches those bumpy surfaces, it gives something for the carbon dioxide to cling to. The bubble eventually grows large enough that the upward pull causes it to lose hold of the icecube, float to the surface and break! Before it breaks, it causes the foam you see.