You need some pieces of chalk rock for this activity.

Take a piece of chalk and place it in a glass dish. Add vinegar and see what happens.

Vinegar makes the change much faster than it would be in nature, but it shows how water can make chalk disappear. This happens to a rock called limestone, too.

Now soak a piece of chalk in water, put it in a plastic bag and put it in a freezer for several days.

Take it out and let it thaw. The chalk will fall apart. This is what happens on frosty days in nature. It shows you how frost can break up rocks when the water can get in.