system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does oil not evaporate like water does?

My face gets really oily and when I touch my glasses in the morning (8 hours since warring them) the oil hasn't evaporated like water would have. Does it just take really really long to evaporate?
gpt
Yes, it takes a long time to evaporate. Oils are usually comprised of very big, rather heavy molecules, which is most of the reason that oil is liquid to begin with. So oils have high boiling points/low vapor pressure compared to water, but oils don't have *no* vapor pressure. Other organic molecules miscible with oils but closer in size to water molecules, like acetone or ethanol, have much much higher vapor pressures and evaporate even more quickly than water.