system
Given the following post, respond as if you're commenting on Reddit:
human
Why does water evaporate even when it is at room temperature?

I have always been taught that water evaporates at 100 degrees Celsius.Yet when one leaves a cup of water for a few days, it will evaporate, why is this? Excuse me if this has been asked before.
gpt
>that water evaporates at 100 degrees Celsius

No, water *boils* at 100 degrees C.

The temperature of a material is the *average* thermal energy of the particles in that material. In liquid water, while the *average* temperature is at room temperature, *some* particles are hot enough to break out of the intermolecular bonds keeping them in the liquid, while others are *less* than average and remain inside.

At boiling temperatures, most of the particles begin to escape, rapidly.