Diffusion is defined as the spontaneous tendency of a substance to move down its concentration gradient from a more concentrated to a less concentrated area. This means that molecules move from an area of where there is a high concentration of them to where there is a low concentration. Osmosis is said to be the diffusion of water across a selectively permeable membrane. A membrane is said to be selectively permeable because it only allows some substances to cross more easily then others. …
