Osmosis

• What is the main objective of the practical investigation?

  To investigate the effect of salt or sugar concentrations
• What apparatus is needed for the practical investigation?

  • Potato
  • Cork borer
  • Ruler
  • Measuring cylinder
  • Labels
  • 3 boiling tubes
  • Test tube rack
  • Paper towels
  • Scalpel
  • White tile
  • 1 M sugar solution
  • 0.5 M sugar solution
  • Distilled water
  • Top-pan balance
• What should be measured before and after soaking potato samples?

  Mass and length of the samples
• How do you calculate the percentage change in mass of plant tissue?

  Use initial and final mass measurements
• What does a positive percentage change in mass indicate?

  The potato gained water by osmosis
• What does it mean if results lie above 0 on the X-axis?

  The potato has increased in mass
• What does it mean if results lie below 0 on the X-axis?

  The potato has decreased in mass
• What safety risks are associated with the practical?

  • Sharp equipment (cork borers, scalpels)
  • Electric shock from balance near water
• What should be done to ensure accurate results in the practical?

  Prepare samples carefully and record measurements accurately
• How many different concentrations should be used in the practical?

  At least five different concentrations
• What is the independent variable in this practical?

  The concentration of salt or sucrose solution
• What is the dependent variable in this practical?

  Mass and length of potato cylinders
• What are important control variables in this practical?

  Type and volume of solute, temperature, time
• How long can the potato cylinders be left in the solution?

  30 minutes in a water bath at 30 °C
• What are the steps involved in analyzing osmosis in the practical?

  1. Measure mass and length before soaking
  2. Soak in different concentrations
  3. Measure mass and length after soaking
  4. Calculate percentage change in mass
  5. Plot and interpret graphs