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.

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.

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.

Investigating water potential Tube A - 0.05 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 -0.50 MPa Draw up a table for your results A B

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.

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

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.

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.