POTATO CHALLENGE
Supplies needed (per lab team):
5 jars with lids
50 mL graduated cylinder
1 potato corer
1 marking pen
1 stirring rod
labeling tape
1 pair tweezers
scale to mass potato cores
1 scapel
1 potato
0.8 Molar sucrose solution (stock solution)
Procedure:
Label jars with the concentrations of sucrose solution noted below. Using
water and the 0.8 Molar sucrose stock solution, prepare 40 mL each of
the following solutions and pour into the appropriately labeled jar:
a. 0 M solution
b. 0.2 M solution
c. 0.4 M solution
d. 0.6 M solution
e. 0.8 M solution
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Place potato on a paper towel on the lab bench. Use a potato borer
to push a core of potato out crosswise through the potato.
Cut skins off core and cut core in half.
Immediately mass the core:
a. Tare the lid
b. Put potato in the lid
c. Record initial mass on data collection sheet (see attached data
collection sheet).
Place a potato core (after it is massed) in each of the labeled jars.
Soak potato cores overnight.
Remove each potato core from the jar, dab one end lightly on a
paper towel and immediately mass the core.
Record the mass on the data collection sheet.
Prepare a graph with the sucrose solution concentration on the Xaxis and the % delta mass on the Y-axis. Draw a “best-fit” line
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through the graphed points. (Note: some points of the graph will
fall below the X-axis so plan your graph accordingly).
Discuss the concepts of osmosis, diffusion, semi-permeable
membrane, isotonicity, hypertonicity, and hypotonicity in the
introduction portion of the lab report. In the results portion of
the report, discuss whether the potato was soaked in a hypotonic,
isotonic, or a hypertonic solution and why (for each point on the
graph).
Challenge Points: Determine the approximate tonicity of the
potato (units will be based on sucrose molarity).
[Concentration of
Sucrose
Solution]
Initial Mass
of potato
core
Final Mass % Delta Mass
of potato
core
0 Molar
0.2 Molar
0.4 Molar
0.6 Molar
0.8 Molar
CALCULATION OF % DELTA MASS:
(Final Mass – Initial Mass)/ Initial Mass * 100 = % Delta Mass
TO CALCULATE DILUTIONS OF SUCROSE, USE THIS
FORMULA:
Number of mLs of Stock Solution
Total Volume of Dilution
X
[Concentration
of Stock Solution]
=
[Final Concentration of
Sucrose]