Diffusion & Osmosis Simulator
See solute and water move across a membrane and find out why water follows the higher concentration.
About the Diffusion & Osmosis Simulator
Free diffusion and osmosis simulation. Set solute amounts on each side of a membrane, choose whether the solute can pass, and watch water levels and particles move. Built for biology, the diffusion & osmosis simulator runs instantly in your browser: change a setting or drag an object and the result updates at once, so you learn by trying things out rather than only reading about them.
See solute and water move across a membrane and find out why water follows the higher concentration. Use it to explore biology ideas at your own pace, then check what you found against the key ideas further down this page.
How to use the Diffusion & Osmosis Simulator
- Use the controls to change Solute on the left, Solute on the right, Membrane lets solute through?. The simulation reacts instantly.
- Pick an option such as No (water only), Yes to switch modes or load an example.
- Press "Pause", "Reset" to start, reset or change what is happening.
- Where you see a glowing handle, object, weight or atom, drag it with your mouse or finger. Everything responds in real time.
- Watch the readouts and graphs update as you experiment, and compare what you see with the key ideas below.
Things to try
- Put more solute on the left and watch the water move.
- Make the membrane let solute pass.
- Balance both sides.
- Reset and try the opposite.
Key ideas you can learn
- Diffusion moves particles from high to low concentration.
- Osmosis is the diffusion of water across a semipermeable membrane toward the side with more solute.
- If the solute can cross the membrane, it diffuses until both sides match, and osmosis fades.
Where this is used in the real world
Osmosis and diffusion move nutrients into cells, keep plants firm, and are used in kidney dialysis, food preservation and water purification.
Who is this simulation for?
Biology students and teachers who want to explore living systems, populations and genetics interactively and safely.
For teachers: project it on the board, let students predict what will happen, then run it together. For students: change one thing at a time and write down what changes.
Frequently asked questions
What is the difference between diffusion and osmosis?
Diffusion is any movement of particles from high to low concentration. Osmosis is the special case of water moving across a semipermeable membrane.
Which way does water move in osmosis?
Toward the side with the higher solute concentration, which has the lower water concentration.
Is the Diffusion & Osmosis Simulator free to use?
Yes. It is completely free, with no signup, no download and no ads inside the simulation. It runs in your web browser.
Does the Diffusion & Osmosis Simulator work on a phone or tablet?
Yes. It uses touch as well as the mouse, so you can drag objects with your finger. A larger screen makes the controls easier to see.