Write an activity showing osmosis.

Take a peeled potato or carrot and scoop out a cavity in its center, ensuring the walls remain intact. Fill this cavity halfway with concentrated sugar solution or saturated salt solution and mark the initial level with a pen or by measuring. Place the potato in a beaker containing plain water, ensuring the water level outside is higher than the sugar solution level inside the cavity, but does not overflow into it. Leave this setup undisturbed for 3-4 hours or overnight. After this period, observe the level of solution in the cavity—you will notice it has risen significantly above the initial mark, and the solution has become more dilute.

This happens due to osmosis: water molecules from the beaker (higher water concentration) move through the semi-permeable potato cell membranes into the cavity (lower water concentration due to dissolved sugar/salt), attempting to equalize the concentration difference. The potato tissue acts as a semi-permeable membrane, allowing water to pass while restricting the passage of sugar molecules. The rise in solution level provides visible evidence of water movement across the membrane. A control setup using plain water in both the cavity and beaker would show minimal level change, confirming that the concentration difference drives the osmotic water movement. This simple experiment demonstrates the principle of osmosis that occurs constantly in living organisms—roots absorbing water from soil, kidneys filtering blood, and cells maintaining their water balance.