Did you know that supercooled liquids need to heat up in order to freeze into a solid? It’s totally backwards, I know…but it’s true! Here’s the deal:
A supercooled liquid is a liquid that you slowly and carefully bring down the temperature below the normal freezing point and still have it be a liquid. We did this in our Instant Ice experiment.
Since the temperature is now below the freezing point, if you disturb the solution, it will need to heat up in order to go back up to the freezing point in order to turn into a solid.
When this happens, the solution gives off heat as it freezes. So instead of cold ice, you have hot ice. Weird, isn’t it?
Sodium acetate is a colorless salt used making rubber, dying clothing, and neutralizing sulfuric acid (the acid found in car batteries) spills. It’s also commonly available in heating packs, since the liquid-solid process is completely reversible – you can melt the solid back into a liquid and do this experiment over and over again!
The crystals melt at 136oF (58oC), so you can pop this in a saucepan of boiling water (wrap it in a towel first so you don’t melt the bag) for about 10 minutes to liquify the crystals.
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Our hand warmers don’t have sodium acetate trihydrate in them. Where could I find some with that chemical in them, or should I make it myself?