CBSE Class 9 Answered

Exosmosis: Movement of water molecules out of a cell when the cell is placed in hypertonic solution.

Endosmosis: Movement of water molecules into the cell when the cell is placed in hypotonic solution.

If the medium/solution surrounding the cell has a higher water concentration than the cell, the solution is known as a hypotonic solution. Here the cell will gain water by osmosis. Example - distilled water

If the medium has exactly the same water concentration as the cell, the solution is known as an isotonic solution. There will be no net movement of water across the cell membrane and the cell will stay the same size. Example - Isotonic saline

If the medium has a lower concentration of water than the cell, meaning that it is a very concentrated solution, the solution is known as a hypertonic solution. The cell will lose water by osmosis. Example - Concentrated salt solution.