A tube of sugar solution sits in pure water, the two separated by a semipermeable membrane that lets water through but not sugar. Water flows into the solution, and its level climbs — until the weight of the raised column pushes back just hard enough to stop it. That balancing push is the osmotic pressure.
Water crosses toward the concentrated sideThe level rises until flow stopsMore solute → higher rise → more osmotic pressure
Set the concentration, then press Start.
Concentration
More dissolved particles pull in more water before the column grows heavy enough to stop the flow.
What is happening
Osmotic pressure
Osmosis is the flow of solvent through a semipermeable membrane from the dilute side to the concentrated side. The osmotic pressure is the exact extra pressure you would need to apply to the solution to stop that flow. It depends on the number of dissolved particles — Π = CRT — which makes it a colligative property.
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