Some extra information on diffusion: In living things, substances move in and out of cells by diffusion. For example: Respiration produces waste carbon dioxide, causing the amount of carbon dioxide to increase in the cell. Eventually, the carbon dioxide concentration in the cell is higher than that in the surrounding blood. The carbon dioxide then diffuses out through the cell membrane and into the blood. Water diffuses into plants through their root hair cells. The water moves from an area of high concentration (in the soil) to an area of lower concentration (in the root hair cell). This is because root hair cells are partially permeable. The diffusion of water like this, is called osmosis.
