Teach children about the crystalline structure of many rocks by growing rock salt and rock candy. Salt crystals are the safest and easiest type of crystals to grow from a liquid, but sugar crystals are by far the most popular. Both can be grown at room temperature using easily available supplies. This activity can also be used in a Bible class to illustrate the concept of being "the salt of the earth."
Things You'll Need
- Small stick
- Glass pint jar
- Rock salt
- Foil pan
- Candy thermometer
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Prepare the Salt Crystal "Nursery"
Tie a piece of string to a small stick, such as a popsicle stick or pencil.
Place the stick over the mouth of a glass jar with the string hanging down in the center.
Tie a single piece of rock salt to the string. This will be the nucleus your crystal will grow on.
Grow Salt Crystals
Mix 3/4 cups salt and 2 cups water in a heavy saucepan.
Heat and stir until salt is dissolved.
Pour salt solution into prepared jar. Be sure the liquid completely covers the salt crystals.
Leave the jar in a dry place for several days and watch your crystals grow. The exact timing depends on the temperature and humidity.
Prepare Pan for Growing Sugar Crystals
Punch small holes along two opposite edges of the foil pan one inch apart and one inch above the bottom of the pan.
Cut a piece of cotton string 65 inches long. Knot the end with a large knot.
Thread the string through the holes back and forth across the pan.
Pull the string tight and knot the end.
Grow Sugar Crystals
Mix 2 cups sugar and 1 cup water in a heavy saucepan.
Cook until candy thermometer reads 250 degrees.
Pour the sugar solution into the prepared pan. Be sure the liquid completely covers the strings by at least a half-inch.
Leave the pan in a dry place for several days and watch your crystals grow. The exact timing depends on the temperature and humidity.