POTATO CHALLENGE

Supplies needed (per lab team):

5 jars with lids50 mL graduated cylinder

1 potato corer1 marking pen

1 stirring rodlabeling tape

1 pair tweezersscale to mass potato cores

1 scapel1 potato

0.8 Molar sucrose solution (stock solution)

Procedure:

Label jars with the concentrations of sucrose solution noted below. Usingwater and the 0.8 Molar sucrose stock solution, prepare 40 mL each of the following solutions and pour into the appropriately labeled jar:

  1. 0 M solution
  2. 0.2 M solution
  3. 0.4 M solution
  4. 0.6 M solution
  5. 0.8 M solution
  1. Place potato on a paper towel on the lab bench. Use a potato borer to push a core of potato outcrosswise through the potato.
  2. Cut skins off core and cut core in half.
  3. Immediately mass the core:
  4. Tare the lid
  5. Put potato in the lid
  6. Record initial mass on data collection sheet (see attached data collection sheet).
  7. Place a potato core (after it is massed) ineach of the labeled jars.
  8. Soak potato cores overnight.
  9. Remove each potato core from the jar, dab one end lightly on a paper towel and immediately mass the core.
  10. Record the mass on the data collection sheet.
  1. Prepare a graph with the sucrose solution concentration on the X-axis and the % delta mass on the Y-axis. Draw a “best-fit” line through the graphed points.(Note: some points of the graph will fall below the X-axis so plan your graph accordingly).
  2. 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).
  3. 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
of potato core / % Delta Mass

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 [Concentration [Final Concentration of

Total Volume of Dilution X of Stock Solution] = Sucrose]