Osmosis always involves:
- A selectively permeable membrane
- A difference in solvent concentration
- Diffusion
Osmosis is the process by which solvent molecules move through a selectively permeable membrane from a region of lower solute concentration to a region of higher solute concentration. This movement occurs to equalize the solute concentrations on both sides of the membrane. The selectively permeable membrane allows only certain molecules to pass through, while blocking others. The difference in solvent concentration drives the movement of solvent molecules, and this process is a form of diffusion, which is the movement of molecules from an area of higher concentration to an area of lower concentration.