Solute (blocked by membrane)
Water (crosses membrane)
This 2D companion draws a schematic cross-section of two compartments joined by a semipermeable membrane: an orange solute that cannot cross, and blue water molecules that can. Set the solute concentration on each side and watch water diffuse from the dilute compartment into the concentrated one, raising its liquid level, exactly as van 't Hoff's law π = MRT predicts. Membrane permeability changes only how fast the system settles; raising or lowering either concentration changes where it settles, and the readouts track the live osmotic pressure on each side, the pressure difference driving flow, and the level gap until hydrostatic back-pressure brings the system to osmotic equilibrium.