Rock Candy

What you need:

• 1 glass cup

• Wooden skewer

• Clothespin

• A large pot

• 1 cup of water

• 4 cups of sugar

• A plate

• Food coloring

What you do:

1. Run your wooden skewer under a sink so it's wet.

2. Pour one cup of sugar onto a plate and then roll the wet skewer in the sugar.

3. Let the sugared skewer dry.

4. While the skewer is drying, boil one cup of water.

5. When the water is boiling, add one cup of sugar and stir until it dissolves. Add the remaining cups of sugar to the water and stir until fully dissolved.

6. Remove the pot from the stove and allow it to cool for 20 minutes.

7. While it's cooling, add your food coloring to the water and sugar mixture.

8. Once the 20 minutes have passed, pour the mixture into your glass cup.

9. Place your clothespin across the top of your glass cup.

10. Stick your skewer through the middle of your clothespin to hold the skewer in place while it's in the cup.

11. Now, it's time to wait. Over the next few days, you'll see crystals forming on the skewer. Once you're happy with what your crystals look like, you can take the skewer out and enjoy your candy.

Questions to ask:

1. Where do you think the sugar crystals come from?

2. What do you think would happen if you used less sugar?

3. What could you change to grow bigger crystals?

What's the science:

When you mix sugar with hot water, something sweet starts to happen. Hot water can dissolve more sugar than cooler water can, creating a supersaturated solution, which is a solution holding more dissolved sugar than it normally can. 

As the sugar water cools, it can’t hold onto all the sugar anymore. That means the extra sugar comes out of the solution and sticks together, forming the crystals you see growing on the skewer. 

The sugar that you added to the skewer at the beginning acts like seed crystals. They give the sugar a place to start growing, helping your candy crystals grow.