Today, we’re going to make pretty crystals.

Take about a cupful of water and put it in a saucepan. Bring the water to the boil. When it’s boiling, start adding table salt. Keep putting more salt in until it stops dissolving.
Take your hot salty water and pour it into a clean glass or jam jar (carefully – boiling water and cold glass don’t always play nicely together, so you might want to warm the glass under the hot tap first). Dangle a thread from a cocktail stick into the liquid, and put the whole thing somewhere it won’t be disturbed.
Over the course of the next few hours, the salt will fall out of solution and precipitate onto any rough surfaces available to it – namely, the thread – forming crystals. Jostling the setup interrupts the crystal formation and results in smaller, more flawed crystals, so make sure it’s kept still and resist the urge to play with it.

Of course, dissolving and then precipitating something isn’t really a reaction. Except it is. Well, sort of. We’ll talk about it tomorrow.