1. Diffusion and Osmosis

2. Diffusion and Osmosis Overview
You will investigate diffusion and osmosis in a model membrane system
You will investigate the effect of solute concentration on water potential as it relates to living plants.

3. Concentration Effect

4. Molarity C6H12O6 = glucose Sucrose = 2 glucose C6H12O6 + C6H12O6 =
C6H12O6 - H2O = C12H22O11 so
Using the periodic table, you can calculate GFM of sucrose (342g)

5. So to make 500 ml of solution…….
0.0 Molar = 342g x 0 x .5
0.2 M = 342 x .2 x .5
etc

6. Prepare dialysis bags……
Add sucrose solutions to bags
Mass carefully
Place in distilled water for 30 minutes
Re-mass
Calculate the % change in mass

7. Final Mass-Initial Mass Initial Mass
To Calculate the % change in mass:
Final Mass-Initial Mass Initial Mass
X 100

8. Period 4 Lab 1B Data
% Change In Mass Period 6 M A B C D E
Class av.
1.0
0.8
0.6
0.4
0.2
0.0

9. Period 5 Lab 1B Data
% Change In Mass Period 6 M A B C D E
Class av.
1.0
0.8
0.6
0.4
0.2
0.0

10. Period 4 Lab 1C Data

11. Period 5 Lab 1C Data

12. Lab 1C: Ideal Class Data Contents in Beaker % Change in Mass
Distilled Water
21.4
0.2 M Sucrose
6.9
0.4 M Sucrose
- 4.5
0.6 M Sucrose
- 12.8
0.8 M Sucrose
- 23.0
1.0 M Sucrose
- 23.5

13. LinearFit for: Data Set
Percent Change in Mass

14. Water Potential In Potato Cells
Osmosis is a special type of diffusion. It is the movement of water molecules through a selectively permeable membrane from a region of higher water potential to an area of lower water potential
Water potential is the measure of free energy of water in a solution
Water always moves to a more negative water potential.

15. Water Potential = Yp + Ys
Where there is no % change in mass, the solution in the beaker has the same water potential as the potato cells.
(Y = Yp + Ys) = (Y = Yp + Ys)
Beaker Potato
Yp = 0 (open beaker) so Y = Ys

16. To Calculate Ys See page 13 of the lab Ys = -iCRT
i = Ionization constant (sucrose is 1.0 because it does not ionize).
C = Molar Concentration (from line of best fit where the line crosses the x axis)
R = Pressure Constant ( liter bars/mole °K
T = Temperature °K (273 + °C)

17. So lets say the line of best fit crosses the x axis at 0.36……..
Ys = -iCRT
Ys = -(1.0)(0.36 mole/liter)( liter bar/mole ° K)(295 ° K)
-8.83 bars
This equals the entire Y of the cell