Information
Osmosis: A semipermeable membrane has pores so fine that the small water particles can pass through, while larger dissolved particles such as sodium ions (Na⁺) and chloride ions (Cl⁻) cannot. Water therefore moves net towards the side with the higher concentration of dissolved particles. In the U-tube, the water level on that side keeps rising until the hydrostatic pressure of the higher water column balances the osmotically driven water flow. The incoming water dilutes the saltier side, so its concentration drops — but the concentrations can never fully equalise, because the dissolved particles cannot pass through the membrane.
Tasks:
- Task 1: Add salt to one side of the U-tube, start the simulation and describe the change in the two water levels.
- Task 2: Compare the two concentration bars before and after the water flow. Explain why the bars move closer together.
- Task 3: Show the particle level and describe which particles can pass through the membrane and which cannot.
- Task 4: Add the same amount of salt to both sides and explain your observation.