Osmosis Experiments (CIE IGCSE Biology: Co-ordinated Sciences (Double Award))

Immersing plant cells in solutions of different concentrations

• The most common osmosis practical involves cutting cylinders of root vegetables such as potato or radish and placing them into distilled water and sucrose solutions of increasing concentration
• The cylinders are weighed before placing into the solutions
• They are left in the solutions for 20 - 30 minutes and then removed, dried to remove excess liquid and reweighed

Potatoes are usually used in osmosis experiments to show how the concentration of a solution affects the movement of water, but radishes can be used too

• If the plant tissue gains mass:
  • Water must have moved into the plant tissue from the solution surrounding it by osmosis
  • The solution surrounding the tissue is more dilute than the plant tissue (which is more concentrated)
• If plant tissue loses mass:
  • Water must have moved out of the plant tissue into the solution surrounding it by osmosis
  • The solution surrounding the tissue is more concentrated than the plant tissue (which is more dilute)
• If there is no overall change in mass:
  • There has been no net movement of water as the concentration in both the plant tissue and the solution surrounding it must be equal
  • Remember that water will still be moving into and out of the plant tissue, but there wouldn’t be any net movement in this case