Make a Collection
Younger investigators may want to make a collection of crystals and work out their own method for grouping the crystals into categories. Common crystals include salt, sugar, snowflakes, and quartz. What other crystals can you find? What are the similarities and differences between these crystals? What materials look like crystals, but really aren't? (Hint: Glass doesn't have an ordered internal structure, so it isn't crystal.)
Make a Model
Prevent Crystal Growth
Your project can involve ways you might prevent crystals from forming. For example, can you think of a way to keep crystals from forming in ice cream? Does the temperature of the ice cream matter? What happens as a result of freezing and thawing cycles? What effect do different ingredients have on the size and number of crystals that form?
Growing crystals is a fun way to explore your interest in chemistry and geology. In addition to growing crystals from kits, there are lots of types of crystals that can be grown from common household substances, such as sugar (sucrose), salt (sodium chloride), epsom salts, borax, and alum. Sometimes it's interesting to mix different materials to see what types of crystals result. For example, salt crystals look different when they are grown with vinegar. Can you figure out why?
If you want a good science fair project, it would be better if you tested some aspect of growing crystals rather than simply growing pretty crystals and explaining the process. Here are some ideas of ways to turn a fun project into a great science fair or research project:
- How does the rate of evaporation of the crystal-growing medium affect the final size of the crystals? You can change the rate of evaporation by sealing the container (no evaporation at all if there is no air space) or by blowing a fan over the liquid or enclosing the jar of medium with a dessicant. Different places and seasons will have different humidities. The crystals grown in a desert may be different from those grown in a rain forest.
- You will usually heat water or another liquid to dissolve a solid to grow your crystals. Does the rate at which this liquid is cooled affect the way the crystals grow? You can compare crystals allowed to cool at room temperature to those formed from cooling the liquid in a refrigerator.
- What effect do additives have on the crystals? You could add food coloring, flavorings, or other 'impurities'. How do crystals grown from uniodized salt compare with those grown from iodized salt?
- What steps can you take to maximize crystal size? Developing a procedure is a form of experimental science. You can affect parameters such as vibration, humidity, temperature, rate of evaporation, purity of your growth medium, and time allowed for crystal growth. The type of container used to grow your crystals may make a difference, as could the type of string used to suspend a seed crystal (or other method used to grow a crystal). Are you changing containers when crystals start to grow that could compete with your seed crystal? There are lots of things to think about! Some may have a major effect on crystal growth and others may be negligible. Does light/dark affect growth? Probably not for a salt crystal, but it could for a substance that is degraded by visible radiation.
- If you are up for a challenge, you can make predictions about the shapes of crystals before you grow them, based on their molecular structures and molecular geometry.