Heat Packs

[den]

I bought a couple of these Geni heat packs for keeping young animals warm during a rescue. I can't stop playing with them! I wish it didn't take so long to reset the sodium acetate. I've discovered that if you wait until the reaction is finished after you pop the disc then vigorously scoosh them between your hands to break up the crystal, the heat given off by the reaction is almost to much to touch. I'll have to wrap them in soft cloth so the babies don't get burned.

Comments

[tropism.livejournal.com]

Hah, I love the Sodium Acetate demonstration of supersaturation. What really happens there is that the salt is extremely hygroscopic -- there're a lot of extra water molecules stuck to the Sodium Acetate molecules. When you heat it up, the water is released and the salt dissolves in its own water of hydration. When it cools back down -- if there're no other acetate crystals around, and if no dust drops in it -- you get this clear liquid which then 'freezes' upon the introduction of friction or a crystal of sodium acetate.

The thing that amazed me about these packs is how -slow- the reaction occurs in them. I've seen a quart jar full of sodium acetate go from liquid to solid in a split second.