Summer Science Experiments for Kids- Rock Candy

What could be better than summer, kids, science…and candy!  This week, we’re going to examine the science behind Rock Candy, but first, the fun part- making the candy!

This candy is so easy to prepare.  The hard part is seeing how long you can wait before eating it!  So, what materials do you need?

• 1- small glass jar (must be glass)
• 1- craft stick
• 1- clothes pin (optional)
• 4 cups- granulated sugar (plus 1 tbs)
• 2 cups- water
• food coloring
• flavor oil or extract
• plastic wrap or paper towel
• adult supervision

What do I need to do?

1. Clean out the jar with hot water.  Make sure sure it is rinsed thoroughly.
2. Put 2 cups of water in a medium pot and bring to a boil.  Add 4 cups of sugar a little at a time, stirring in between.
3. Once all 4 cups of sugar has been added and dissolved, remove the pot from the stove and add food coloring and flavoring if desired.  Stir to incorporate.
4. Let the liquid cool for about 10 minutes.  Then, carefully pour it into the jar.
5. Wet the craft stick and coat it with the remaining sugar.  Place the sugar covered stick into the jar and secure with the clothes pin if needed.
6. Cover the jar with plastic wrap or paper towel and set in a cool place.
7. Crystals should appear in about 3 hours and continue to form for a couple of days.

Where’s the Science?

First, we dissolved a lot of sugar (4 cups) into a little bit of water (2 cups).  Creating a situation where no more sugar can be dissolved in the water at a particular temperature is called a supersaturated solution.  A supersaturated solution is very unstable because it can  only “hold” the sugar for so long since there is so much of it.   When it falls out of the solution, the sugar will begin to cling to the craft stick because it is more porous than the glass jar (and because it already has sugar on it).  In addition, the water will evaporate over time, leaving more sugar behind.  This sugar will continue to cling to the sugar on the craft stick and build up over time.

Need something like this for your classroom?  Read the Two Best Design Challenges to Start the Year!