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STEM concept: Crystal formation
Ingredients to make rock candy :
- glass jars
- large saucepan
- string or small skewers
- food coloring (optional)
- candy flavoring (optional)
Follow the steps to make rock candy :
Safety reminder: This experiment requires the use of fire for heating the solution. It also involves pouring the solution into jars. Children need adult supervision when doing these steps.
- In a saucepan, mix equal parts of water and sugar, and cook over low heat until all the sugar is dissolved.
- Slowly add more sugar while continuously stirring the mixture. Keep adding sugar to the mixture until the sugar stops dissolving in the water. You’ll know you’ve reached this state when the mixture starts looking cloudy instead of clear.
- Add candy flavoring and color if desired.
- Remove the mixture from the heat and allow it to cool.
- Prepare candy sticks by wetting them with a little bit of water and dipping them in sugar.
- Let the candy sticks dry.
- Transfer the sugar mixture to jars.
- Put the candy sticks into the jars, making sure that the sticks do not touch the jar’s sides or bottom.
- Wait for 5–7 days until rock crystals form on the sticks.
- Enjoy your rock candies!
The science behind the rock candy experiment:
The sticks dipped in sugar provide surfaces for the crystals to grow. This serves as the seed crystal. As water evaporates from the jar, the sugar molecules will bump into one another and stick together. As the sugar molecules stick together, small crystals will form on the sticks.