Osmosis and Diffusion

The process by which plants draw in water through their roots is called osmosis. During osmosis water passes through a semi-permeable membrane. The water molecules always move from areas of lower concentration into areas of higher concentration. This causes the more concentrated solution to become less concentrated.

Some molecules cannot pass through the semi-permeable membrane because they are too big.

During diffusion particles move from an area of high concentration into areas of low concentration. Diffusion is the process that causes carbon dioxide and oxygen to pass in and out of leaves.