Uhm, IIRC it does not radiate heat. It is cold. As soon as you introduce it to heat (touching it), it causes a chain reaction.

I gave it a 4 even though I still don't buy it. My guess? It looks like ice but I bet it's just precipitate falling out of an unstable solution.

It's not a precipitate, and it does release heat. What they're showing is how to make a metastable supersaturated solution of sodium acetate. You can dissolve more sodium acetate into nearly boiling water than you can at room temperature. When you do that and let it cool (assuming the container is clean and there's no dust or contaminates in the container or solution), it can cool to room temperature or below without forming crystals.

As soon as you introduce an appropriate surface to induce crystallization (your finger, or a "seed" crystal of sodium acetate), the solution will suddenly crystallize (one sodium ion, one acetate ion, and three water molecules will come together forming sodium acetate trihydrate, the whitish translucent solid). The crystal form is in a lower energy configuration than the individual ions in solution, thus the heat that gets released.

...a total nerd and share this... :-)

If you're horribly bored, & you'd like to take a shot at making sodium acetate from scratch, take a look at:

http://www.instructables.com/id/Crystallization-of-homemade-sodium-acetate/

;-)

The music in this video is bitchin'.