Gas diffusion mixer

Diffusion is the net movement of particles from high to low concentration, driven by random motion. This simulation lets you release two gases and watch them mingle, then test how temperature and particle mass change the mixing speed. Learning goals: explain diffusion in terms of random particle motion; use Graham's law to compare diffusion rates of gases; explain why temperature increases the rate of diffusion.

Particles move randomly from high to low concentration — diffusion, the basis of smell spreading across a room.

Controls

Temperature slider: Sets the average kinetic energy of the particles.
Particle mass: Chooses the gas; heavier choices move more slowly at the same temperature.
Barrier control: Opens the divider so the two gases can mix by diffusion.
Graph view: Switches the view between particle animation and a concentration graph.

The chemistry

\frac{\text{rate}_1}{\text{rate}_2} = \sqrt{\frac{M_2}{M_1}}

Graham's law of effusion and diffusion

KE_{avg} = \frac{3}{2}RT

Average kinetic energy per mole of gas

Assumptions

Particles are identical except for mass and move in two dimensions.
Collisions are perfectly elastic.
No attractions exist between particles.

Guided activity

Open the barrier at low temperature and time how long mixing takes.
Raise the temperature and compare the mixing time.
Run hydrogen versus oxygen particles and compare their spreading speeds.
Predict which gas effuses faster through a pinhole, then test it.

Challenge questions

Explain why lighter gases mix faster using kinetic energy, not just speed.
Use Graham's law to predict the rate ratio for two gases, then verify.
Describe how a real perfume spreading across a room differs from this ideal model.