Diffusion & Osmosis Lab
Explore how particles move across a semipermeable membrane driven by concentration gradients. Adjust concentrations on each side, set membrane permeability, and watch diffusion drive the system toward equilibrium through Fick's First Law.
Guided Experiment: Observing Diffusion Across a Membrane
If you create a large concentration difference between left and right sides, what do you predict will happen to particle movement over time?
Write your hypothesis in the Lab Report panel, then click Next.
Controls
Results
Concentration vs Time
Press Run to simulate concentration equilibration over time.
Data Table
(0 rows)| # | Trial | Time(s) | Conc Left(mol/L) | Conc Right(mol/L) | Gradient(mol/L) | Flux(mol/(m²·s)) |
|---|
Reference Guide
Diffusion
Diffusion is the net movement of particles from a region of high concentration to a region of low concentration. It requires no energy and continues until equilibrium is reached.
The driving force is the concentration gradient — the steeper the gradient, the faster the net diffusion. At equilibrium, particles still move, but with no net flow in either direction.
Fick's First Law
Fick's First Law relates diffusion flux to the concentration gradient.
Where J is flux (mol/m²·s), D is the diffusion coefficient (m²/s), and dc/dx is the concentration gradient. The negative sign means flux flows from high to low concentration.
Osmosis
Osmosis is the movement of solvent (water) molecules through a semipermeable membrane from a region of low solute concentration to high solute concentration.
The membrane allows small solvent molecules to pass but blocks larger solute molecules. Water moves to dilute the more concentrated solution, generating osmotic pressure.
Osmotic Pressure
The Van't Hoff equation gives the osmotic pressure of a dilute solution.
Where π is osmotic pressure (atm), M is molarity (mol/L), R is 0.08206 L·atm/(mol·K), and T is temperature in Kelvin. Higher concentration or higher temperature means greater osmotic pressure.