Expert: Walter Hintz - 10/2/2006

Question
If you peel a raw egg without breaking the membrane or "melt" away the shell in vinegar. If you place it in a glass distilled deioinized water. It will swell in size untill it breaks. Why is the flow one way?

Answer
Water diffuses from an area of high concentration to a area of lower concentration (osmosis)  Water inside the egg is less concentrated than the water outside(pure water) so water flows in.  Actually osmosis occurs in both directions but in the case you mention more flows in than out.