Our Very Own Science Inquiry!

In the past week, we have been doing science inquiries during class. It’s easy to make rock candy. All you need is a lot of sugar, some water, and a little patience. Pour three cups of sugar into one cup of water, and bring your mix to a boil while you stir. Once the mixture boils, the sugar will dissolve into the water. It quickly forms a clear solution. Repeat this procedure 5 times for maximum result. Pour the syrup-like mixture into a glass. Hang a stick or string in the mix. Make sure to prepare your string or stick by dipping it in the mixture you created, then in white granulated sugar. 

After a few days or a week, sugar crystals will have built upon the string, making a sticky-sweet candy. But the candy doesn’t look like the sugar you started with. The sugar molecules have instead become highly organised into a crystal structure.

Two different methods will contribute to the growth of the crystals on the string. You have created a supersaturated solution by first heating a saturated sugar solution (a solution in which no more sugar can dissolve at a particular temperature) and then allowing it to cool. A supersaturated solution is unstable—it contains more solute (in this case, sugar) than can stay in a liquid form—so the sugar will come out of solution, forming what’s called a precipitate. This method is called precipitation.

The other is evaporation—as time passes, the water will evaporate slowly from the solution. As the water evaporates, the solution becomes more saturated and sugar molecules will continue to come out of the solution and collect on the seed crystals on the string. The rock candy crystals grow molecule by molecule. Your finished rock candy will be made up of about a quadrillion (1,000,000,000,000,000) molecules attached to the string.

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