How do I compare the processes of diffusion and osmosis?

Firstly, think of similarities between the processes. For example, neither process requires energy, so they are passive processes. This means that in both processes, molecules must move from a high concentration to a low concentration, ‘down a concentration gradient’. Now think of what could be different between the processes. Only water moves by osmosis whereas all gases and liquids move by diffusion. Finally, the most important feature of osmosis is that it occurs across a partially permeable membrane. (Show diagrams to compare).