Purpose: To estimate the osmolarity of potato tuber tissue by finding the molarity where the weight of the potato tuber tissue does not change.
Hypothesis: If
______________________________________________________________________________
______, and I set up
______________________________________________________________________________
_________, then the weight of the potato will not change in the ___________________ solution.
Procedure:
SETUP
1.
Obtain 100 ml of deionized water and 100 ml of .1 M, .2 M, .3 M, .4 M, .5 M, and .6
M sucrose solutions.
2.
Obtain 7 equal sized potato pieces about 5 cm long. Use a razor to cut them to equal size with no skin. Place them in a covered petri dish to prevent their drying out.
3.
One at a time, remove the potato from the petri dish. Blot it on a paper towel and record its mass to the nearest .01g.
4.
Immediately cut the potato lengthwise and transfer pieces to the beaker. Note the time.
5.
Repeat this process for each potato and place them into the appropriate solutions.
6.
Let the beakers sit for 24 hours.
AFTER 24 HOURS
1.
Record the time that the potato pieces are removed and determine the incubation period.
2.
Remove the first potato pieces from solution, blot the pieces on a paper towewls to remove excess solution only.
3.
Weigh the potato pieces together and record the final weight.
4.
Repeat this procedure until all the pieces are weighed. When finished, discard the potato pieces and clean out the beakers.
5.
Complete the data table by calculating the percent change in weight using this formula:
Data:
Percentage change in weight weight change initial weight
100
Final Weight (g)
Approximate time in solutions: _________________
Sucrose Molarity
0.0 0.1 0.2 0.3 0.4 0.5 0.6
Initial Weight (g)
Weight Change (g)
% Change in Weight
Plot percentage change in weight as a function of the sucrose molarity. Place 0 in the middle of the y-axis.
Weight increase should be above the axis and weight decrease should be below the axis.

Discussion:
At what sucrose molarity does the curve cross the zero change line on the graph?
Explain how this information can be used to determine the osmolarity of the potato tuber tissue. Explain why this information would be useful to a botanist.