Osmosis: Water molecules from the beaker will move into the membrane sac through the process of osmosis. This is because the concentration of water molecules is higher outside the sac (in the beaker) than it is inside the sac (inside the oil). Osmosis will continue until the water concentrations on both sides of the membrane are equal.
Diffusion: The oil molecules inside the sac are too large to pass through the membrane, but some smaller molecules, such as oxygen and carbon dioxide, can diffuse across the membrane. This means that oxygen molecules from the water will diffuse into the oil, and carbon dioxide molecules from the oil will diffuse into the water.
Hydrostatic pressure: As water moves into the membrane sac by osmosis, the pressure inside the sac will increase. This is known as hydrostatic pressure. Hydrostatic pressure will oppose the movement of more water into the sac, eventually reaching a point where the inward force of osmosis is balanced by the outward force of hydrostatic pressure. This equilibrium state is known as osmotic equilibrium.
In summary, when a membrane sac filled with large molecules of oil is suspended in a beaker of water, osmosis and diffusion will occur, and hydrostatic pressure will develop inside the sac. Eventually, the system will reach osmotic equilibrium, where the net movement of water and molecules across the membrane will cease.
