Does Mom ever get angry because a moth has eaten a hole in her clothes? What does she do to keep moths out? Some people buy moth crystals or mothballs. Moth stuff is really a chemical called "naphtha." (Say "NAFF-tha.")

Put some moth crystals into a saucer, and smell the pieces. After awhile, you will notice that you can smell it quite a distance from the saucer. It really is not a very pleasant smell, is it? How can it be that the smell is noticed over "here," when the crystals are over "there?"

You will begin to realize that the crystals are changing from a solid into a gas that cannot be seen but which can be detected by smell. It is similar to evaporation, isn't it?

Now, we'll place some naphtha crystals into a test tube, and use a test tube holder, to hold the tube over a candle flame. [Young students should not be allowed to do this, as naphtha crystals can burst into flame.]

We must rotate the test tube in the flame to keep it from becoming overheated in one spot, and catching on fire.

When we see fernlike crystals form, we'll realize that the solid crystals changed into a gas (sublimed), then changed back into a solid (frosted).

[Here's a bit of word play: "sublime" can be an adjective that means "really wonderful," or it can be a verb that means "to change."]

We can sublime dry ice, also, by causing it to change from crystals into a gas.