Place the Skittles in a circle around the edge of the plate.
If you’re feeling adventurous, add some Skittles to the center of the plate too!
Fill the measuring cup with warm water. Then, pour the water into the center of the plate until the Skittles are halfway submerged in water. Be careful to not to disturb the Skittles!
The colorful rainbow effect comes as the candy coating dissolves into the water. The coating is made up almost entirely of sugar with a little bit of food coloring. When the coating dissolves, the sugar and food coloring mix into the water to form a solution, or a chemical mixture with the water.
Solutions like this like to be balanced — if there’s a lot of sugar and food coloring in one part of the water, but not a lot in another, that’s unbalanced. To get balanced, the solution will gradually spread out from areas with more of it (around the candy) to areas with less of it (in the center of the dish) so all parts of the water have about the same amount of sugar and food coloring. That’s what you see happening as the rainbow starts to move away from the candy! Scientists call this process diffusion.
But as you saw, the colors will spread towards each other and then stop, forming a line where they meet. That’s because the spots where they meet have the same overall amount of sugar and food coloring, even though the colors are different. Diffusion won’t mix those solutions together. Well, not right away, at least. Eventually, the food coloring will separate from the sugar to diffuse on its own, and the whole dish will become the same brownish color.
There are lots of variations you can try to explore what's going on is this experiment. Try placing a single candy in a dish of hot water and one in a dish of cold water. Which candy coating dissolves first? How does the color spread?
Or, try placing just a few candies in the dish, and see where the color goes. How long does it take for the colors combine if you don't disturb the dish? You can also try the same experiment using something other than water, like rubbing alcohol or vegetable oil.
Have some fun and play with other confectioneries like M&M's or peppermints, for some holiday-themed fun!
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