Grow Your Own Rock Candy
Hosted by: UT Austin INFORMS Student Chapter
Visit our Booth: Sunday, February 28, 2021, 12 p.m. - 4 p.m.
Recommended Grades: All
The Challenge: Did you know that you can grow your own rock candy at home? All it takes is a little water, a lot of sugar, heat, and some patience. If you've got a bit of a sweet tooth, this activity is for you.
Share a video of your process and/or your final product on Flipgrid.
Recommended Materials: a measuring cup, a medium saucepan, 1 cup of water, 2 2/3 cups of sugar, cotton cooking string like this one from HEB (the natural fibers facilitate crystal growth), a pencil or pen for suspending your candy while it grows, a quart-sized mason jar, such as an empty pasta sauce jar, or similar sized glass for growing the crystals, food coloring (optional)
- Measure and cut an approximately 8 in. piece of the cooking twine. Tie one end around the pencil or pen. The other end should dangle with about 1 inch of clearance from the bottom of the jar with the pencil or pen resting across the lip of the jar. Too long, and your rock candy will connect to the bottom of the mason jar. Too short, and not much of your rock candy will be submerged and the resulting candy will be short.
- Add the 2 cups of sugar and the 1 cup of water to the saucepan. Heat over medium heat. Stir until the sugar solution boils and all the sugar is dissolved. Then add the remaining 2/3 cup sugar one spoonful at a time. Notice that as you add more and more sugar, it takes longer for the new sugar to dissolve. This is because the solution is reaching its saturation point or the point where the water cannot dissolve any more sugar. By dissolving more and more sugar into the heated water, you are creating a solution that has as much solute (sugar) as the solvent (water) can hold. Heat raises this saturation point. Then, as the water cools, the sugar will recrystallize out of the water and onto the string! You can make sure that all sugar is dissolved by lifting a spoonful of the sugar solution from the pan and looking in the liquid for remaining undissolved sugar crystals. There may be some bubbles, but the solution should be clear, not cloudy.
- (Optional): For colored rock candy, dissolve 5 drops of food coloring into the sugar solution, or enough to reach your desired color.
- Place the jar in an out-of-the-way location so it won't be jostled while the crystals grow (this can distrub growth). Place the string into the jar. Carefully poor the (HOT!) sugar syrup into the jar. Take a clean spoon (you don't want to get any sugar crystals in the solution now) and straighten the string in the liquid as needed. After 3 days, you should start to see tiny crystals beginning to grow along the string. Leave the jar undistrubed for 1-2 weeks while the rock candy grows.
- After the candy has reached the desired size, take out your rock candy and let it dry. Enjoy!
How does this activity connect to STEM and today's Girl Day theme of Innovating Food and Fashion?
In this activity, you will experiment with crystalization, dilution, and solutions. The connection to today's theme of Innovating Food and Fashion is pretty clear: you can eat what you create! Did you know that you do science every day that you cook or bake a meal? Chemical reactions help cake rise, help bananas ripen and even determine how your food tastes and smells. These reactions you see in your home aren't all that different from ones performed in labs by scientists and engineers across the world. Engineers use similar reactions to help make your drinking water safe to drink!
We are the University of Texas at Austin’s INFORMS student chapter. Our membership consists primarily of students in the Operations Research and Industrial Engineering graduate programs in the Cockrell School of Engineering. From alumni panelist seminars to Friday night puzzle socials, our chapter hosts a variety of events that bring students, alumni, and faculty together. Moreover, we use social media to share and celebrate the news of our peers’ successes, to inform of upcoming events, and to get to know each another beyond just the scope of our research. Building from our shared interests, we act to foster individual growth, encourage one another, and develop true community.
For more information, please visit our website: https://connect.informs.org/universityoftexasaustin/home