Crystals are Cool: Making Rock Candy


January 25, 2010
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Wish I Had Noted the Name
Creative Commons License photo credit: biggertree

There are so many different kinds of crystals all around us, but just what are they anyway?

Put simply, a crystal is a grouping of molecules or atoms that is organized in a specific way.  Every crystal has a unique shape and properties that make it recognizable.  In today’s experiment, we will be working with sugar crystals which are oblong and slanted on the ends.

There are a couple of things going on that contribute to the growth of sugar crystals in this experiment.  First, you will be creating a supersaturated solution by heating a saturated sugar solution and allowing it to cool.

Supersaturated solutions are solutions that are so full (of sugar in this case), that they are unstable.  The solution you will create will contain more sugar (the solute) than it can hold in a liquid form.  Therefore, the sugar must come out of solution – forming what is called a precipitate (also known as yummy rock candy).  The second mechanism that helps to form the sugar crystals is evaporation.  Slowly, the water evaporates from your solution.  As this happens the solution becomes even more saturated with sugar and the sugar will continue to come out of the solution and form sugar crystals.

Blue Sugar
Creative Commons License photo credit: karsten.planz

What you are left with is a delicious science treat!  Make sure to only eat a little at a time and keep the rest sealed in a baggie.  Also, don’t forget to brush your teeth; it is pure sugar after all!  Have fun in your kitchen lab and don’t forget to be safe!  Always include an adult when trying new experiments.

Grab a handy adult; you will need one to do this activity!

Materials:
Granulated sugar – 1 cup
Water – ½ cup
Saucepan
Food coloring
Two canning jars
Spoon

What to do:
1. Dump one cup of sugar and ½ cup of water into your saucepan.  Don’t stir it!
2. Find your adult and have them help you put it onto the stove over medium-high heat.  Wait for the mixture to come to a boil and let it boil for one minute without stirring.  If you want colored rock candy, you may add some food coloring while it boils.
3. Instruct your handy adult to pour this mixture into the two canning jars.
4. Find a place on your counter that you can let the two jars sit undisturbed for two weeks.
5. Observe them once a day.  Slowly, crystals begin to form.  When you see a crust form on top of the jars, use a spoon to carefully break the crust so the water can continue to evaporate.  Don’t do anything else to your jars other than this!
6. When you feel like you have enough crystals of the right size, have an adult help you remove them from the jar using a dull table knife.
7. Eat and enjoy!  Don’t forget to brush your teeth, it is sugar after all!

Kat
Authored By Kat Havens

Kat has been both the spokesperson for the CSI: The Experience exhibit and project manager for the Imperial Rome exhibit and has a love of all things historical and cultural. She is responsible for the Xplorations summer camp program, coordinating weekday labs during the school year, writing department curriculum and presenting at teacher trainings. Kat has worked at the Museum since 1996.

3 responses to “Crystals are Cool: Making Rock Candy”

  1. Timanthia says:

    thanks this helped alot

  2. kate linning says:

    i actally really need the materials of makeing rock candy how fast can it grow?
    can anyone help me please?

  3. Kat says:

    Hi Kate:

    The only things you need to make rock candy are granulated sugar – 1 cup, water – ½ cup, a saucepan, food coloring (optional), two canning jars, and a spoon. It takes about two weeks to see good results. Good luck growing crystals! Let us know how it turns out.

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