Osmotic activity is the phenomenon that occurs when one solution, usually lower in conductivity or minerals content, passes through a semi-permeable barrier for the purpose of diluting the concentration of the solution on the other side, usually containing a higher conductivity or minerals content.
In my 8th grade science lab, we dissolved the shell of a common egg using vinegar. We then removed the yoke and albumen. First we filled the egg sack (i.e., semi-permeable membrane) with water to prove that water would not pass through on its own at atmospheric pressure. We then drained the egg sack and partially filled it with molasses. Then we submerged the sealed egg sack in water. Over a period of time, the water passed through the membrane by way of "osmosis" to effectively dilute the molasses solution on the other side. This is an excellent example of "osmotic activity".
