Which part of the living system did you change?
Labs / Biology
Membrane Diffusion
A tank is split down the middle by a semipermeable membrane. Tiny water molecules slip through the pores, but the larger solute cannot — so water drifts toward the saltier side until both concentrations match. Move the sliders, or drag inside a chamber to sprinkle in more solute, and watch the levels shift.
Labs / Biology / Membrane Diffusion
Membrane Diffusion
A tank is split down the middle by a semipermeable membrane. Tiny water molecules slip through the pores, but the larger solute cannot — so water drifts toward the saltier side until both concentrations match. Move the sliders, or drag inside a chamber to sprinkle in more solute, and watch the levels shift.
Why it matters
Why explore this?
Living systems are connected and constantly changing. This model makes one biological process visible so you can test how its parts affect one another.
Explore
Try the model
CL —CR —flow —
Investigate
Questions to test
Predict first, try it in the model, then use what you observe to answer.
What to try
- Make the left side much saltier than the right. Which way does the water go, and why does the level rise where the salt is?
- Can you find solute settings where the two levels stay perfectly even? What do the concentrations read then?
- What happens if one side starts as nearly pure water? How high can osmosis push the other side?
- Turn permeability down low. Does the tank still reach the same final levels — just slower, or somewhere different?
- Once it settles, sprinkle solute into the lower chamber. Can you reverse the direction of flow?
Explain
Make sense of what happened
Explain the process as a chain: a change happens, the system responds, and that response affects what happens next. Use an observation from the model as evidence.
Check
Before you leave
How did the system respond?
How would you explain that response?
If you can answer all three using evidence from the model, you understand the main idea. If not, return to Explore and change one setting at a time.