1. Osmosis Why cant lost blood be replaced by water?
Objective
Know osmosis is a special case of diffusion in which water moves from a solution of higher water potential to a solution of lower water potential through a partially permeable membrane.

2. Investigating water potential
Objectives
Today we are learning to
Understand osmosis is a special case of diffusion in which water moves from a solution of higher water potential to a solution of lower water potential through a partially permeable membrane.
Produce an appropriate dilution series when provided with stock solutions of reagents.
Carry out an investigation in a methodical and organised way, demonstrating competence in the required manipulative skills and efficiency in managing time.

3. Investigating water potential
Describe concisely, but fully, the trends and patterns in data collected,relating these to specific values, quantities and units.
Draw valid conclusions, relating explanations to specific aspects of the data collected and applying biological knowledge and understanding from the AS specification
Identify the limitations of the materials, apparatus and techniques used, discuss their effect on the conclusions that may be drawn, resolving conflicting evidence.
Suggest realistic ways in which the effect of these limitations may be reduced.

4. Investigating water potential
Tube A mol dm -3 sucrose solution
Lettuce for 30 minutes
Water diffuses into the lettuce.
The surrounding solution becomes more concentrated
This increases the density
Add a drop from tube B
-0.05 mol dm -3 sucrose solution
The blue drop will float as it is less dense.
As you set up the apparatus make predictions for the other tubes.
The expected water potential is MPa
Draw up a table for your results A B

5. Interpreting the results
If the test tubes are not clean, any solutes will increase the density.
If they are not dry, excess water will decrease the density.
If the solution is not thoroughly mixed, the two test tubes of a pair will not have the same density.
These will all make your results inaccurate.

6. Table to show the effect of concentration on density of solution
Concentration of sucrose
/mol dm -3
Group
Average
0.05
0.1
0.2
0.3
0.4
0.5
0.6
0.7

7. Investigating water potential
Objectives
Today we are learning to
Understand osmosis is a special case of diffusion in which water moves from a solution of higher water potential to a solution of lower water potential through a partially permeable membrane.
Produce an appropriate dilution series when provided with stock solutions of reagents.
Carry out an investigation in a methodical and organised way, demonstrating competence in the required manipulative skills and efficiency in managing time.

8. Investigating water potential
Describe concisely, but fully, the trends and patterns in data collected,relating these to specific values, quantities and units.
Draw valid conclusions, relating explanations to specific aspects of the data collected and applying biological knowledge and understanding from the AS specification
Identify the limitations of the materials, apparatus and techniques used, discuss their effect on the conclusions that may be drawn, resolving conflicting evidence.
Suggest realistic ways in which the effect of these limitations may be reduced.