Osmosis

• Osmosis is the diffusion of water molecules, from a region where the water molecules are in higher concentration, to a region where they are in lower concentration, through a partially permeable membrane.
• A partially permeable membrane :

  • allows small molecules such as water to go pass through it
  • does now allow ions or larger molecules such as sucrose to pass through it
• Cell membranes are partially permeable water can diffuse across them but sugars cannot
• A dilute solution contains a high concentration of water molecules, while a concentrated solution contains a low concentration of water molecules.
• Osmosis refers to the movement of water molecules only.