When a cell gains water, what happens to its size and weight

 Water will move across the semi-permeable membrane in order to balance both sides until they are neutral.

"Osmosis is the net movement of water across a selectively permeable membrane driven by a difference in solute concentrations on the two sides of the membrane. A selectively permeable membrane is one that allows unrestricted passage of water, but not solute molecules or ions."

Or

When a cell gains water it becomes much bigger and heavier which could possibly lead to its explosion.

"Water moving into a cell can make the cell swell, or even burst! This happens when cells are placed into a hypotonic solution. Like the egg in distilled (pure) water. Water leaving a cell can make it shrivel up"

When a cell gains water, the size will expand, making the cell bigger, and the weight will increase, depending on the type of cell as well as the amount of water.

i think that it is plants