osmosis

• What is osmosis?

  Osmosis is the net movement of water molecules across a partially permeable membrane from a high to low water potential
• What is the direction of water movement during osmosis?

  Water moves from a region of higher water potential to a region of lower water potential.
• What characterizes a partially permeable membrane?

  A partially permeable membrane has very small holes in it.
• What is the procedure to investigate osmosis using potato cylinders?

  1. Prepare sucrose solutions of varying concentrations.
  2. Cut potatoes into cylinders of about 1 cm diameter.
  3. Measure the mass of groups of three cylinders.
  4. Place each group in different sucrose solutions.
  5. Leave for at least 40 minutes.
  6. Weigh the cylinders again and record results.
  7. Calculate the % change in mass.
  8. Plot a graph of the results.
• How do you calculate the percentage change in mass?

  Percentage change = (final mass - initial mass) / initial mass x 100
• What happens to potato cylinders in solutions with a higher water potential?

  They will draw in water by osmosis, becoming longer and increasing in mass.
• What happens to potato cylinders in solutions with a lower water potential?

  They will lose water and shrink in size, decreasing in mass.
• What occurs when the water potential of the sucrose solution is the same as that of the potato cylinders?

  There will be no net water loss or gain, so they will stay the same size and mass.