system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are things that are hot to the touch, not so hot to the mouth i.e. Coffee?

I've always wondered why I can drink a really hot cup of coffee and the cup is really hot to the touch, to the point where I have to put it down if I'm not holding by the handle, but when I sip it, it doesn't burn my mouth.
gpt
Two reasons mostly.  The first is that your mouth is actually built to handle somewhat warmer temperatures than your skin.  So something that is just a little too hot to stick a finger into is probably okay to drink.

The second is that you usually aren't taking big gulps of really hot coffee - you're taking sips.  And when you sip, you're mixing the fluid with air and spattering it across your mouth - this spreads out the heat and minimizes the amount of coffee that's actually in contact with your mouth.  If you took a straw and swept a few drops of coffee across the back of your hand, it'd burn much less than that same amount all in one spot - that's what's happening inside of your mouth.