WLHS / AP BIO / Monson Name
PRELAB for AP LABORATORY #1C/1D: Water Potential
**Read through the entire laboratory packet and answer the questions below. This will be stamped for completion and reviewed before we do the lab!
Background / Exercise 1C: Water Potential
1) How do botanists make use of water potential?
2) In which way will water always move?
3) What two factors affect water potential? Explain each below, including how a change (either increase or decrease) affects the overall water potential (& subsequent movement of water into or out of a cell).
See Procedure and Data Table 1.4 to answer the following questions:
4) What are the concentrations of the 6 solutions that will be tested in this experiment?
5) Assume your group was assigned to test the 0.6 M sucrose solution. In the space below, sketch your set up.
6) In general, what do you predict will happen to the change in mass of the potato cores as we move from distilled water to very concentrated sucrose solutions?
7) Once you graph your data (in graph 1.2), how will you use the graph to determine the molar concentration of the potato core?
Exercise 1D: Calculation of Water Potential from Experimental Data
1) In the space below, write the formula that allows us to calculate the solute potential of a solution. Define / explain each piece / component of the equation.
2) What is the solute potential for a solution that is 0.1 M? (assume i = 1 and a temperature of 22°C).
3) What is the solute potential for a solution that is 0.5 M? (assume i = 1 and a temperature of 0°C).
4) You measure the total water potential of a cell and find it to be -0.24 MPa. If the pressure potential of the same cell is 0.46 MPa, what is the solute potential of that cell?
5) If a cell having a solute potential of -0.35 MPa is placed in a solution of pure water, what will be its pressure potential at equilibrium?
6) What is the water potential of a cell with a solute potential of -0.67 MPa and a pressure potential of 0.43 MPa?