Diffusion

This simulation shows diffusion as the result of random motion. Every dye particle takes random steps, yet together they spread from the crowded side to the empty side until the concentration is even. Students set the temperature between 275 and 370 K and the particle diameter, then restart with the dye on the left. Readouts give the mixed percentage, the diffusion coefficient, elapsed time and the spread from the start. It helps teach diffusion, Brownian motion and why warm liquids mix faster.

• Press Restart and watch the Mixed percentage climb as the dye spreads from the left.
• Raise Temperature to 370 K and compare how quickly Mixed reaches a high value.
• Increase Particle diameter to 4 nm and read how the Diffusion coeff. D falls.
• Restart at 275 K and 300 K and compare the Spread from start after the same time.
• Ask students why no single particle is aiming anywhere, even though the dye ends up even.

1. 1Explain diffusion as the net movement from high to low concentration.
2. 2Describe Brownian motion as random movement caused by molecular collisions.
3. 3Predict how temperature and particle size affect the diffusion rate.
4. 4Interpret a mixing percentage as a measure of how even a spread is.

Questions teachers ask