– Why does putting the top on a pot of boiling pasta make it frothy and boil over?

Question

– Why does putting the top on a pot of boiling pasta make it frothy and boil over?

In: Chemistry

Answer 1

Changing boiling-temp water into steam takes a ton of energy, at least as much as heating liquid water up to boiling temp. The phase change itself needs huge energy input.

If the steam is free to escape, it carries all that energy away with it.

If the steam is trapped by a lid, then when it condenses back into liquid it dumps all that energy right back into the pot. It’s like doubling your element’s heat setting!