Every year around this time, the students want to make Borax crystal snowflakes! This activity is really about saturated solutions.
Students mix Borax crystals into boiling water, which holds more Borax than cold water. That’s because heated water molecules move farther apart, making room for more of the borax crystals to dissolve. When no more of the solution can be dissolved, you have reached saturation. As this solution cools, the water molecules move closer together again. Now there’s less room for the solution to hold onto as much of the dissolved Borax. Crystals begin to form and build on the snowflake shape made of pipe cleaners and string as the water lets go of the excess.