Create Instant Ice
Learn how to make hot icicles!
Supercooling a liquid is a really neat way of keeping the liquid a liquid below the freezing temperature. Normally, when you decrease the temperature of a liquid below its freezing point, it turns into a solid. But if you do it gently and slowly enough, it will stay a liquid, albeit a really cold one!
In nature, you'll find supercooled water drops in freezing rain and also inside cumulus clouds. Pilots that fly through these clouds need to pay careful attention, as ice can instantly form on the instrument ports causing the instruments to fail. More dangerous is when it forms on the wings, changing the shape of the wing and causing the wing to stop producing lift. Most planes have de-icing capabilities, but the pilot still needs to turn it on.
We're going to supercool a substance called sodium acetate, and then disturb it to watch the crystals grow right before our eyes!
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. 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 136 deg F (58 deg C), so you can heat the solid sodium acetate in a saucepan of boiling water for about 10 minutes to liquify the crystals. Don't use your good saucepans - use an old one that's just intended for chemistry experiments.