If the membrane allows the passage of water but not the solute the water will move into the compartment with the greatest solute concentration in order to establish an equilibrium in which the energy of the system is at a minimum.
Se a membrana permite o paso de auga pero non o do soluto, ocorre que a auga flúe cara ao compartimento máis concentrado en soluto, coa fin de establecer un equilibrio no cal a enerxía do sistema sexa mínima.