Candy Diffusion with M&Ms
Materials
- 1 bag of M&Ms (or Skittles)
- 1 white ceramic plate or shallow dish
- Room-temperature water
- Paper towels for cleanup
Steps
Place the plate on a flat surface.
Arrange several M&Ms in a circle around the edge of the plate (colors should touch but not overlap).
Slowly pour room-temperature water into the center of the plate until it just covers the bottom and touches all the candies.
Wait and watch—within a minute, the colors will begin to dissolve and spread toward the center.
Observe the sharp boundaries where different colors meet.
Optional: Try variations—use hot water, cold water, or sugar water and compare the results.
What’s Happening?
The candy coating is made of sugar and food coloring, both of which dissolve in water.
Once dissolved, the molecules spread out by diffusion—moving from areas of high concentration (near the candy) to lower concentration (in the water).
The clear lines between colors form because the dissolved dyes are similar in density and don’t mix immediately.
Extensions
Older students (Grades 5–6): Discuss how temperature affects the rate of diffusion.
