Osmosis Required Practical 3

• What is the aim of the investigation described in the study material?

  To investigate the movement of water by osmosis into or out of plant tissue
• What equipment is needed for the investigation of osmosis in plant tissue?

  • Plant tissue (e.g., potato)
  • Cork borer
  • Ruler
  • Measuring cylinder
  • Labels
  • Boiling tubes
  • Test tube rack
  • Paper towels
  • Sharp knife
  • A range of salt or sugar solutions
  • Distilled water
  • Top-pan balance
• How should the potato cylinders be prepared for the experiment?

  Cut 5 potato cylinders using a cork borer and trim them to about 3 cm in length
• What should be measured and recorded for each potato cylinder?

  The length and mass of each cylinder
• What is the first step in preparing the sugar solutions for the experiment?

  Measure 10 cm³ of the 1.0M sugar solution and transfer it to the first boiling tube
• What should be done after preparing the sugar solutions?

  Add one potato cylinder of known mass and length to each boiling tube
• How long should the potato cylinders be left in the boiling tubes?

  Overnight
• What should be done after removing the potato cylinders from the boiling tubes?

  Blot them dry with paper towels and measure their length and mass
• What calculations should be performed after measuring the potato cylinders?

  Calculate the percentage changes for each cylinder
• What graphs should be plotted based on the experiment's results?

  • Change in mass (in g) against the concentration of sugar solution
  • Change in length (in mm) against the concentration of sugar solution
• What are some sources of error in the experiment?

  Discs taken from different parts of the potato may have different water potentials
• How can the surface area of potato discs affect the experiment?

  Different surface areas can affect the rate of osmosis
• What safety precautions should be taken during the experiment?

  Take care when handling the cork borer and sharp knife