Osmosis Demonstration LabObjectivesThe student will: 1) Observe the effects of different concentrations of salt solutions on potato cores. 2) Infer the relationship between weight loss and rate of osmosis. 3) Use a line graph to display data and draw conclusions. 4) Observe plasmolysis in Elodea.BackgroundOsmosis is the process whereby water moves across a cell membrane by diffusion. Diffusion takes place when the molecules of a substance tend to move from areas of higher concentration to areas of lower concentration. The process of osmosis must be tightly controlled by cells, otherwise they will die. For example, if you place a red blood cell in pure (distilled) water, it will quickly take up water until it bursts. That is why plasma, the liquid portion of our blood is made of water with proteins and salts dissolved in it, preventing the unnecessary gain of water by our blood cells.In plants, osmosis is just as important. Plants with too little water will wilt. This happens when water moves out of the cells by osmosis. Without this water there is little pressure inside the cells and the plant can no longer support itself against the pull of gravity. However, after watering the plant, the cells become reinflated with water and the plant stands upright. The effect of water loss on plant cells is shown in the diagram below.