Hot Ice?

OK, this is something cool I did a while ago. "Hot Ice" is is sodium acetate, you get it as a white mush from the volcano baking soda and vinegar reaction along with carbon dioxide (maybe I'll do that sometime), that is supercooled. Supercooling is where you take a liquid and cool it down to lower its normal freezing point without its phase changing (the state of matter it's in, solid, liquid, gas, and plasma). You do this by making the liquid totally pure. When a liquid turns into a solid, it becomes a crystal. There is the exception of amorphous solids like glass, that are physically solids, but have no order between the atoms and do flow, they are just very viscous, so it takes hundreds of years. For a crystal to form, it needs an object to grow off of. 

When water is completely pure, it has no dust in it to start growing crystals. Water normally it freezes at 0 °C (32 °F), but when it's pure, it freezes at -42 °C (-43.6 °F). It's able to do this because the water molecules start clumping together so tightly that they form an unstable crystal that melts at a temperature higher than -42° C. That allows the water to form crystals. 

Sodium acetate does the same thing. Since it is not a liquid at room temperature, it has to be dissolved in a liquid. You have to have a lot of sodium acetate in the solution, so you have to supersaturate it by heating up the liquid and dissolving the sodium acetate so more of it is in the liquid than you normally could dissolve. It's like rock candy, you dissolve as much sugar as you can in boiling water, supersaturating it, and then place a starter crystal and after about a week, it forms a giant sugar crystal. So after supersaturating the sodium acetate at around 58 °C (136.4 °F), and then heating it up to 100 °C (212 °F), you cool it down to room temperature. There you have it, all you have to do it touch it and it will crystalize and heat up in an exothermic reaction (it does this because of electron spacing allows atoms not to hold as much energy, so they release it as heat. I'll explain it in another experiment). 

You can get powdered sodium acetate online to do this but you can also just go buy some hand warmers (I got a couple at REI). They're plastic bags filled with a clear liquid (sodium acetate) with a metal coin that you flex to start the reaction. I tried to make some, concentrating the white mush from the baking soda and vinegar experiment. The proportions weren't correct so there was left over vinegar and baking soda so that most of it decomposed when I concentrated making it brown and the rest of the impurities made it crystallize. Well, I hope you thought this was cool, I have a video posted of one of the hand warmers, and if I ever make my own sodium acetate I'll post that too. Oh, also here's a recipe for making the sodium acetate with baking soda and vinegar.