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AP Biology pd.3/6
7 October 2011
Effect of Solute Concentration on Water Potential
Research Question: Investigate the concept of water potential in relation to the movement of water into or out of a plant cell (potato). This will be researched by immersing potato cores in sucrose solutions (0.0M, 0.2M, 0.4M, 0.6M, 0.8M, 1.0M) and determining the change in mass (in percent) of the cores.
Hypothesis: If the solute concentration is increased, then the water potential of solution will have increasingly more negative values. In other words as the concentration of the sucrose solutions becomes more hypertonic than the potato core (the solution has greater solute concentration and lower water potential) the potato will begin to loose mass since water will leave the hypotonic potato core (the core has less solute concentration hence higher water potential) to the hypertonic solution in order to dissolve the sucrose solution. Water potential is the concept used to combine the differences in solute concentration and pressure to predict the direction in which water will diffuse through the living plant tissue and states that the net movement of water will always be from an area of higher water potential to and area of lower water potential. Water potential can be confirmed by taking the graph of the data. This data can be used to experimentally determine the value for C (molar concentration of sucrose at equilibrium) in order to determine a value for Ψs (Ψs =solute potential).
Variable | Unit | How to Control |
Independent- Sucrose Concentration | 100mL with varying Molarities (0.0M, 0.2M, 0.4M, 0.6M, 0.8M, 1.0M) | Premade solutions by lab tech so should be correct. However, will label test tubes with correct Molarities so no confusion occurs. |
Dependent- % change in mass | % | Will not control since want to see the effects of the independent variable on this variable |
Control- only use pure, distilled...