Question

Why does water molecules require a semi - permeable membrane in the process of osmosis and why does the solute molecules do not in the process of diffusion ?

Answer 1

• Osmosis requires a semi-permeable membrane while diffusion does not. This means that osmosis is a special case of diffusion. Osmosis is the result of diffusion across a semi-permeable membrane. Without membrane also water can move. Then it is not said to be osmosis and it is diffusion.
• In diffusion, molecules intermingle as a result of their kinetic energy of random motion. Diffusion mainly occurs in gaseous state or within gas molecules and liquid molecules. But Osmosis occurs when the medium surrounding the cell has a higher water concentration than the cell. Diffusion does not need water for movement but osmosis need water.