2. What is Osmosis? Osmosis is a form of passive transport (no extra energy needs to be used) where water molecules move down their concentration gradient (from an area of high concentration to low concentration) and across a semipermeable membrane.

3. Concentration There are more molecules of a substance on one side of the membrane vs. the Other side of the membrane therefore one side of the membrane has a higher concentration of molecules than the other side.

4. Semipermeable membranes A semipermeable membrane is a membrane that is permeable to some molecules but not ALL molecules.

5. In the diagram below water will move from the right side of the semipermeable membrane to the left side. This is because the concentration of water is lower on the left side than it is on the right side. Therefore water will flow down the concentration gradient to bring the system to equilibrium.