How Does It Work
Keep in mind that this activity takes a lot of patience. You won’t see the color you’re adding right away. Just keep carefully squeezing the sugar water solution into its layer and you’ll see it begin to stack up.
Density is the measurement of how much “stuff” is packed into a measured space. That’s how we get the equation for density: Density = Mass (the stuff) ÷ Volume (a measured space). Nearly every substance and material imaginable has a different density. This is especially true for the sugar solutions you made.
By increasing the amount of sugar in solution but keeping the amount of water constant, you created solutions that have increasing densities. As you add sugar to the water, more and more sugar molecules take the available space between water molecules, making the solution more dense. The cup containing eight tablespoons of sugar will be the most dense and the cup with two tablespoons will be least dense. As you can see, a solution with a lower density stacks on top of a mixture with a higher density.
How did you make a supersaturated solution? When you dissolve sugar in water, there’s a point beyond which no more sugar can dissolve. This is called a saturated solution. The available water molecules have grabbed the most sugar molecules they can. However, if you heat this solution (add energy to it), the water molecules move much faster and more sugar can be dissolved. When this solution is cooled, the sugar remains in solution and it’s called a supersaturated solution. However, it’s very unstable and the sugar will crystallize very easily with very little effort. A stray sugar crystal, a bump, or a random nucleation site can spur very rapid crystal growth.
