PURPOSE: To demonstrate diffusion.

DESCRIPTION: A drop of food coloring is placed gently into a beaker of water. In a few minutes the food coloring will diffuse through the entire beaker of water. It might be argued that residual currents in the water account for much of this "diffusion." Maybe so, but it gets the point across even if you mention this.

SUGGESTIONS:

REFERENCES: (PIRA unknown.)

EQUIPMENT: Beaker of water, food coloring.

SETUP TIME: None.