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  • Osmosis
    • Diffusion of water molecules
      • Across partially permeable membrane from area of high water pot to low water pot
      • Water potential: potential of water molecules to diffuse out of/into a solution
      • Pure water has highest water potential- all solutions have lower water pot. than water
      • Two solutions with same water potential are isotonic
    • Rate of osmosis
      • Water potential gradient: higher= faster. Over time, difference in water pot on either side of membrane decreases, rate levels off.
      • Thickness of exchange surface: thinner=faster
      • Surface area of exchange surface: larger=faster
    • Making up solutions
      • 1) Start with solution of known concentration e.g. 1M
      • 2) Divide concentration of this solution by concentration you want e.g. 1\0.4=2.5
      • 3) Make solution 2.5 times weaker: 15\2.5=6cm3
      • 4) Top up test tube with distilled water to reach desired volume i.e 9cm water
    • Potato Practical
      • 1: Use a cork borer to cut potatoes into identically sized chips
      • 2: Divide chips into groups of three and measure mass of each group
      • 3: Place one group into each of your sucrose solutions
      • 4: Leave chips for 20 mins
      • 5: Remove chips and dry with paper towel
      • 6: Weigh each group again, record results
      • 7: Calculate % change in mass for each group, use results to make a calibration curve


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