How does those heat packs with a tiny metal disc inside work?
In: Chemistry
The sodium acetate inside has a melting / freezing point of 58 C (138 F), and is super-cooled because it’s very pure. When you click the disk, it sets off a freezing reaction. When it freezes, it releases all that “stress” of being super-cooled as heat and returns to its freezing point temperature. Sodium acetate is used because it is non-toxic (it’s the stuff used for salt and vinegar flavor chips), easy to make, can be super-cooled easily, and has a nice freezing point that’s warm but not too hot for us to handle.
Latest Answers