One way that crystals form is from chemicals dissolved in water. If the water gets cooler, dissolves other chemicals, or evaporates, some of the dissolved chemicals can be deposited as crystals. Often, growing crystals can be a fairly long, involved process, but with this activity, we will grow some nice crystals quickly and easily.
I mentioned that I had a lot of fun experimenting with carbonated soda (and drinking it) and that I should do an experiment with chocolate. I got quite a few e-mails suggesting experiments with chocolate, but this one was the most common. It has to do with the white discoloration that you sometimes find on old chocolate.
The word rock means different things to different people. As with many words, its scientific meaning is different from many of the meanings used in everyday language, so lets start with a short video on the scientific definition of a rock.