Many solids have a crystal structure, and different solutions can form various sizes and shapes of crystals. Two ways crystals can form is through precipitation and evaporation.
Precipitation
Precipitation happens when a solution has been heated, and more solute is dissolved than the solvent can normally hold at room temperature. This creates a supersaturated solution. Any additional solute that is added will cause excess to "fall" out of the solution and form a crystal precipitate. This procedure is suitable for all ages, but younger children will need an adult do the heating over the stove.
Materials
- Pan
- Stove or hot plate
- Two cups water
- Four to six cups granulated sugar
- Food coloring
- Large spoon
- Large canning jar
- String
- Pencil
- Tape
- Paper clip
- Plastic wrap
Procedure
- Wrap the string around the pencil a few times and hold it in place with a piece of tape.
- Place the pencil across the mouth of the canning jar and then cut the string so it is about an inch from the bottom of the jar.
- Tie the paper clip to the end of the string.
- Bring two cups of water to a boil in the pan on the stove.
- Adding about one-third cup of sugar at a time, stir in the sugar until it is dissolved. (Note: it will get more difficult to stir in the sugar as the solution nears saturation. Keep stirring until you cannot dissolve any more.)
- Remove the pan from the heat and add food coloring (darker colors work better).
- Let the solution cool for about five minutes.
- Carefully dip the string in the solution and then roll it in dry granulated sugar.
- Pour the solution into the canning jar and replace the pencil across the mouth with the string submerged into the jar.
- Cover the jar with plastic wrap and set aside to cool.
Crystals should begin to form on the string in a few hours, but they may take up to 10 days to fully form.
Evaporation
Crystal formation through evaporation will produce large crystals over a time span of about a week. Instead of the crystals falling out of the solution, the liquid part of the solution will evaporate leaving behind solid crystals. Different solutes will form differently shaped crystals. This procedure works for all ages.
Materials
- Five tablespoons Epsom salt
- Five tablespoons table salt
- 11 tablespoons hot water
- Red food coloring
- Blue food coloring
- Two plastic cups
- Two spoons
- Two baby food jars (or other small cups)
Procedure
- Put five tablespoons of Epsom salts into one of the plastic cups.
- Add five tablespoons of hot water and stir until the salt is dissolved.
- Add three to four drops of blue food coloring and set it aside.
- Put five tablespoons of table salt into the other plastic cup.
- Add six tablespoons of hot water and stir until it is dissolved.
- Add three to four drops of red food coloring.
- Pour one tablespoon of the Epsom salt solution into one baby food jar.
- Pour one tablespoon of the table salt solution into the other baby food jar.
- Set the jars aside and let the liquid evaporate for about a week.
The crystals should be visible within a couple of days, but it may take up to two weeks before the liquid has evaporated.
More Crystal Experiments
If you are looking for more fun ways to create crystals, there are many great experiments online. The procedures below use different materials and make for some beautiful science.
- Borax, a cleaning solution, makes interesting crystals. This particular procedure will yield crystals that make a snowflake shape.
- Alum makes large, single crystals. You can find alum in the spices section at the grocery store. With a little patience, a single, large, clear crystal will form from this recipe.
- Aragonite crystals will grow on the surface of the rocks with some white vinegar.
The Beauty of Crystals
Crystals make science come to life. With a little patience and the right technique, you can create beautiful crystals of different shapes and sizes.
