The Skittles experiment is a simple demonstration that illustrates fundamental scientific principles. This activity transforms colorful candy into a display of how substances interact with water. It is an accessible project, requiring only common household items, making it a favorite for exploring basic chemistry.
Materials and Procedure
To begin, gather a pack of Skittles, a shallow white plate or dish, and warm tap water. The white background of the plate is preferable as it allows the colors to be seen clearly as they spread. The water should be warm, but not boiling, because heat affects the speed of the eventual reaction.
The procedure starts by carefully arranging the candy pieces around the outer edge of the plate. A common arrangement is a full circle, with the pieces touching or nearly touching, often alternating colors.
Once the candies are positioned, slowly pour the warm water into the center of the plate. Pouring gently prevents the candies from shifting and ensures the color spreads evenly toward the center. Add just enough water to barely cover the bottom half of the Skittles.
If too much water is added, the candies may float and disrupt the pattern. The colors should begin spreading almost immediately, but a full display takes a few minutes of observation.
Understanding Diffusion and Dissolution
The visual effect is a result of two distinct scientific processes: dissolution and diffusion. Dissolution occurs first, as the warm water contacts the candy’s outer shell, which is composed of sugar and food coloring. Since both the sugar and the dye are water-soluble, they quickly dissolve into the surrounding water.
As the sugar and dye dissolve, they create a highly concentrated solution immediately next to each Skittle. This leads to the second process, diffusion, which is the movement of particles from an area of high concentration to an area of lower concentration.
The dissolved molecules naturally attempt to spread out and equalize the concentration across the entire plate. The colored water moves toward the center, which initially contains pure, uncolored water, representing the area of lowest concentration.
The distinct colored paths remain separate because the sugary solution is denser than the pure water, creating a form of water stratification. Additionally, as the different colors meet, their similarly high sugar concentration acts as a barrier, preventing them from mixing completely.
Experiment Troubleshooting and Extensions
When conducting the experiment, rapid mixing often results in a murky, brown center. This occurs if the water used is too hot, as increased heat accelerates the movement of molecules, speeding up dissolution and diffusion. Ensure the plate is placed on a level surface before adding the water.
The setup allows for several variations to further explore the underlying science. Testing the reaction time with cold water versus warm water demonstrates how temperature affects the rate of molecular movement. Other liquids, such as milk or vinegar, can be substituted for the water to observe how different solvents interact with the candy coating.
Varying the arrangement of the candies, like creating clusters instead of a continuous circle, can lead to different and unexpected color patterns.