View full lesson: http://ed.ted.com/lessons/how-do-cold-packs-get-cold-so-fast-john-pollard

If you stick water in the freezer, it will take a few hours to freeze into ice. How is it, then, that cold packs go from room temperature to near freezing in mere seconds? John Pollard details the chemistry of the cold pack, shedding light on the concepts of energetics and entropy along the way.

Lesson by John Pollard, animation by Karrot Animation.