What name is given to the process by which water moves across a membrane?

The process by which water moves across a membrane is called Osmosis.

Here are the steps of how osmosis works:

1. Osmosis is the movement of water from an area of low solute concentration to an area of high solute concentration through a semi-permeable membrane.

2. The semi-permeable membrane allows the passage of water molecules but not the solute molecules.

3. Initially, when there is a concentration gradient (i.e., one side of the membrane has a high concentration of solute and the other side has a low concentration), water will start to move from the low concentration side to the high concentration side.

4. This movement continues until the concentration of solute is equal on both sides of the membrane. At this point, the system is said to be in equilibrium.

5. However, water molecules will continue to move across the membrane in both directions. But the rate of water movement will be the same in both directions, so there is no net movement of water.

6. This process helps in maintaining the cell's turgidity and shape, and also in the transportation of molecules in living organisms.