This experiment guides you through the process of making rock candy by growing large sugar crystals from a solution. It's a fun, edible project that demonstrates the same principles of crystallization that form minerals and rocks in the Earth's crust.
If a wooden skewer is suspended in a supersaturated sugar solution, then large sugar crystals will form on the skewer as the water slowly evaporates, providing a model for how mineral crystals grow from solutions in the earth.
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Wet the wooden skewer and roll it in granulated sugar. Let this dry completely. This will give the crystals a surface to start growing on.
With adult help, bring the water to a boil in the saucepan.
Slowly stir in the sugar, one cup at a time, until no more sugar will dissolve. The solution should be clear.
Remove the pan from the heat and let it cool for about 20 minutes.
If desired, add a few drops of food coloring.
Carefully pour the warm sugar solution into the glass jar.
Use the clothespin to suspend the sugar-coated skewer in the middle of the jar, making sure it doesn't touch the bottom or sides.
Place the jar in a safe place where it won't be disturbed.
Observe the jar every day as the crystals grow. This will take about a week.
Once you are happy with the size of your crystals, remove the skewer and let it dry on a piece of wax paper.
Over the course of a week, large sugar crystals will grow on the skewer. This happens because you created a supersaturated solution, which is unstable. As the water cools and evaporates, the sugar molecules come out of the solution and attach themselves to the 'seed' crystals on the skewer, building up large, geometric crystal structures.
The slow cooling and evaporation of a supersaturated sugar solution.
The growth of sugar crystals on the skewer.
The ratio of sugar to water, the type of container, and the ambient temperature.
An adult must supervise the process of boiling water and making the hot sugar solution, as it can cause serious burns. Be patient and do not disturb the jar while the crystals are growing.
Display your finished rock candy skewer.
Explain the concept of a supersaturated solution and how it relates to crystal growth.
Draw parallels between your sugar crystals and the formation of mineral crystals like quartz or amethyst from hot, mineral-rich water inside the Earth.
The sugar crystals on the skewer act as 'seed crystals.' They provide a starting point, or nucleation site, for the sugar molecules in the solution to attach to. Without these seed crystals, the sugar might just crystallize on the bottom of the jar.
Crystal growing requires patience! If nothing is happening after a few days, your solution might not have been supersaturated enough. This means you may not have dissolved enough sugar in the hot water. You can try gently reheating the solution and dissolving more sugar.
Many beautiful mineral crystals, like the amethyst and quartz found in geodes, are formed in a similar way. They grow from hot, mineral-rich water that is trapped in underground cavities. As the water cools over thousands of years, the dissolved minerals slowly crystallize, creating the large, beautiful formations we see.
