Osmosis
- Created by: jessicawarren
- Created on: 11-04-16 14:03
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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
- Diffusion of water molecules
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