Osmosis

• Osmosis is the movement of water across a semi permeable membrane - passive (not requiring energy)
• Osmosis practical - find the water potential of a potato cylinder
• 1. cut of peices of potato using cork borer
• 2. using a mass balance scale messure the mass of the cylinders

  its okay if not all the same size, and we will do percentage change at the end
• 3. prepare sucrose solutions of varying concerntrations
• 4. place and FULLY SUBMERGE different potato samples into each beaker
• 5. leave potaos for same amout of time
• 6. take out and pat them dry to remove surface water.
• 7. reweigh all potatoes to find new mass
• 8. calculate percentage change in mass =

  FINAL MASS - ORIGINAL MASS / ORIGINAL MASS X 100
• 9. plot graph of percentage of sucrose solution against percentage change in mass
• 10. point that crosses x axis is isotonic point, and is the concentration inside the cell
• Summary

  1. cut out and measure masses of potato using balance
  2. prepare sucrose solution of varying concentration
  3. place potato samples in solutions, fully submerged
  4. take out after same time, and pat dry to remove surface water
  5. take new mass using balance
  6. find percentage change in mass final- original / original x 100
  7. plot graph of sucrose concentration against change in mass
  8. find concentration inside cell crosses through x axis line of best fit
• Control variables - same potato, amount of time submerged in solution, same temp solution, same vol solution