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.
REFERENCES: (PIRA unavailable.)
EQUIPMENT: Beaker of water, food coloring.
SETUP TIME: None.
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