system
Given the following post, respond as if you're commenting on Reddit:
human
What's the difference between water drying and boiling on a molecular level? Is the reaction same between different types of liquid?

I've always thought that water turns into gas only after boiling because the molecules spread out. How does water that's just sitting there dry out?
gpt
On the surface of any liquid, there will be a few molecules with more energy than the others, simply due to random jostling. If one gets jostled hard enough, it will leave the surface and evaporate. 

Boiling is a more extreme form of this process. The jostling is so intense that molecules _throughout_ the liquid, not just on the surface, have a chance to be jostled into high speed. If they're under the surface, they join with other fast-moving molecules to form a bubble, effectively creating a new surface for more boiling (homogeneous nucleation).

Incidentally, the creation of a new bubble is helped if there is any speck or flaw in the vessel where fast-moving molecules can agglomerate. This is called heterogenous nucleation, and it's why tossing salt into a pot of boiling water will make it seem to boil more fiercely.