Osmosis

• What is osmosis?

  Osmosis is the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane
• What happens when a plant cell is placed into water?

  Water will move into the cell and the cell will expand
• What happens when a plant cell is placed into a concentrated solution?

  Water will move out the cell and the cell will shrink
• How do you set up the osmosis practical?

  Use a cork borer to produce three cylinders of potato of the same diameter and trim them to the same length (around 3cm)

  Weigh and measure the cylinders and mark down the measurements

  Place each cylinder into a test tube, one with 0.5 molar sugar solution, one with 0.25 molar sugar solution and one with distilled water
• What happens in the practical?

  Leave the potato cylinders overnight so that osmosis has taken place and then remove the potato cylinders and gently pat dry to remove surface moisture

  Measure and weigh them again and find the percentage change compared to the original values

  Plot this on a graph
• What should the results of the osmosis practical be?

  The potato cylinders in the concentrated sugar solution should lose the most mass as water moves out by osmosis.

  The potato cylinder in the distilled water should gain mass as water moves in by osmosis
• What are safety precautions in this experiment?

  Sharp knife - cut on a chopping board and keep fingers away from the blade

  Chemicals/solutions - wear safety goggles so that nothing comes into contact with your eyes
• Why do the potatoes have to be peeled?

  The potato skins prevent osmosis from happening