P: diffusion and osmosis

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


  To investigate diffusion and osmosis using living and non-living systems.
• What equipment is needed for the living system experiment?

  • Plant tissue (e.g., potato)
  • Cork borer
  • Ruler
  • Measuring cylinder
  • Labels
  • Boiling tubes
  • Test tube rack
  • Paper towels
  • Sharp knife
  • White tile
  • Range of salt or sugar solutions
  • Distilled water
  • Top-pan balance
• What is the first step in the method for osmosis in a living system?


  Use a cork borer to cut 5 potato cylinders.
• How long should the potato cylinders be left in the boiling tubes?


  At least 15 minutes.
• Why is it important to accurately measure and record the mass of each potato cylinder?


  To calculate the percentage changes for each cylinder.
• What should be done after measuring the final mass of each potato cylinder?

  • Record measurements in a table.
  • Calculate the percentage changes for each cylinder.
  • Plot a graph of change in mass against the concentration of sugar solution.
  • Find the x-intercept to determine isotonic concentration.
• What is a potential source of error in the osmosis experiment using potato cylinders?


  Discs from different parts of the potato may have different water potentials.
• What safety precautions should be taken when handling the cork borer and sharp knife?


  Take care to avoid cuts and injuries.
• What equipment is needed for the non-living system experiment?

  • Beaker
  • Visking tubing
  • Capillary tube
  • Sucrose solution
  • Water
  • Marker
  • String
• What is the first step in the method for osmosis in a non-living system?


  Tie one end of a visking tube with a piece of string.
• How long should the visking tubing be left immersed in distilled water?


  15 minutes.
• What is the method for diffusion in a non-living system?


  1. Place potassium permanganate crystals in a beaker of water.
  2. Note the color of the water after 15 minutes.
  3. Note the color of the water after 1 hour.
• What happens to potassium permanganate molecules in water over time?


  They diffuse from a region of high concentration to a region of low concentration.
• What is the final color of the water after potassium permanganate reaches equilibrium?


  A uniform pale purple.
• What are the potential hazards associated with potassium permanganate?


  • Powerful oxidizing agent
  • Harmful if swallowed
  • Very toxic to aquatic life with long-lasting effects
  • Stains hands and clothing
• What is the initial step in the diffusion experiment using potassium permanganate?


  Place a few potassium permanganate crystals in a beaker of water.
• How does the color of the water change over time in the diffusion experiment?


  The color becomes more uniform as the potassium permanganate diffuses.