218 The History of the Earth: Supplemental Guide
Making Rock Crystals
Note: This experiment must be done with adult supervision.
Materials
Small heatproof container or glass
String
Pencil
Paper Clip
Measuring spoons and a measuring cup
2 tablespoons sugar or salt
1 cup of water
Cooking pot
Heat source, such as a stove
Plastic wrap
Kitchen towel
Directions
First, tie the paper clip to the end of the string and the string to the pencil. Place the pencil
across the top of the container. The string should be long enough that the paper clip is able to
rest on the bottom of the glass container when tied to the pencil.
Next, place one cup of water into the pan. Have an adult place the pan on the stove or heat
source and cook the water on medium-high until the water begins to boil. Add two tablespoons
of sugar (or salt) and stir until the sugar (or salt) has dissolved into the water.
Last, have an adult pour the dissolved sugar water mixture into the container with paperclip
attached to the pencil. Place plastic-wrap over the top to keep dust out of the container. Wrap
the towel around the container to allow the solution to cool more slowly. Check your container
every day to see if crystals are forming on the string. Crystals should continue to form until there
is no liquid the jar.
If you are able, grow a second set of crystals by substituting salt for sugar in the recipe.
Compare the two different containers of crystals. Ask your child how the crystals are similar or
different.