Can you make a model cell swell, shrink, or stay the same size? Change the solution around it and investigate where water moves.
Illustrative simulation imagery
Learning target
I can use concentration data to explain the direction of net water movement across a selectively permeable membrane.
I know I am successful when…
I compare three outside solutions, record cell-volume changes, and explain each result using the inside and outside concentrations.
Your investigation
Predict what will happen when outside concentration is lower than, equal to, or higher than inside.
Test each outside solution for the same number of model steps. The starting cell and total water stay the same.
Compare the data. Explain why the net movement slows as the concentrations become closer.
Vocabulary: solute = dissolved particles; concentration = solute amount per volume; net movement = the overall difference between movement in opposite directions.
Experiment with the model
The membrane allows water through but keeps the modeled solute on its original side. Brown dots represent solute. Drawing shows a cross-section; use the numerical water-volume reading for comparisons.
Changing the outside solution starts a new trial; previous data stay in the table.
Selectively permeable membrane
Water crosses the membrane. Solute amounts remain fixed.
Model step 0Cell water volume 1.000Inside concentration 1.000Outside concentration 1.000
Blue line: current trial. All volumes and concentrations are relative model units.
Your recorded data
Trial
Outside start
Model step
Cell volume
Inside concentration
Outside concentration
Explain what your data show
Use your recorded results to connect a claim to evidence and a scientific explanation.
Your work stays in this tab. Download your report before leaving or reloading.
Model example, assumptions & science background
Model of a clear explanation: “When the outside solution started at 2.0 and inside at 1.0, cell volume decreased below 1.0. Water moved out overall toward the initially higher solute concentration.” Replace this example with your own recorded numbers.
This is an idealized model, not a calibrated real cell. It holds 1 solute unit inside, 4 × starting concentration outside, and 5 total water-volume units. Each step transfers 0.08 × (inside concentration − outside concentration) water units into the cell. It ignores membrane tension, pressure, cell rupture, active transport, and other solutes. Model steps are not real time. Only the latest 300 data rows are retained.
