Final answer:
When salt is added to an eggplant, it leads to osmosis where water moves from the inside of its cells to the outside, resulting in visible water droplets on the surface, a process known as plasmolysis.
Step-by-step explanation:
The phenomenon where water rises to the top of an eggplant when salt is added can be explained by the principle of osmosis. Osmosis is the diffusion of water across a semipermeable membrane from a region of lower solute concentration to one of higher solute concentration. When salt is sprinkled on an eggplant, it creates a hypertonic environment on the surface of the eggplant's cells. As the interior of the cells is less salty, or hypotonic, compared to the surface, water moves from inside the cells to the outside to balance the solute concentration, a process called plasmolysis. This movement of water results in droplets forming on the surface of the eggplant. In cooking, this technique is often used to draw out moisture, as with salting eggplants to reduce bitterness and improve texture.