Pre-AP Biology Investigation: Diffusion and Osmosis
7. Cover each cup with plastic wrap (or similar) to prevent evaporation and
allow too sit overnight.
Student Group/Name: _________________________________
Next Day Directions:
Materials Needed per Group
1. The following day, remove the cylinders from the cup containing solution #1.
Place the cylinders on a paper towel and gently blot them dry. Determine the
mass of the four cylinders and record the mass in the Data Analysis section.
6 Plastic Cups, 7oz
Shared Materials
Potatoes
Cork borer
Solution #1 --- Green
Solution #2 --- Clear
Solution #3 --- Orange
Solution #4 --- Blue
Solution #5 --- Yellow
Solution #6 --- Red
Electronic balance
Safety
Safety goggles
Gloves
Lab Apron
Directions:
1. Fill each of your 6 cups about hallway with solutions #1-6. You do not need to
label the cups because the solutions are color-coded.
2. Slice a potato, or potatoes, into several disks of approximately 3cm in width.
3. Using a cork borer cut several “cylinders” of potato out of the middle of the
disks. Do no include any skin on the cylinders. You will need four cylinders per
cup for a total of 24 cylinders.
4. Using an electronic balance, determine the mass of four potato cylinders and
record the mass, to the resolution of the balance, in the Data Analysis section of
the lab.
5. Place the four cylinders in the cup containing solution #1 (the green solution)
6. Repeat step 4 for the remaining cylinders/solutions. Remember to record the
mass for each group of four cylinders before adding it to the appropriate cup.
2. Repeat step 8 for the remaining cylinders/solutions. Be sure to record the
mass for each group of cylinders.
3. Calculate the percent change in weight for each group of cylinders and record
it in the Data Analysis section.
4. Clean up and dispose of all materials according to your instructor. Be sure to
wash your hands before leaving the lab.
DATA ANALYSIS
Solution #
Initial Mass
Final Mass
DATA ANAYLSIS
% Change in Mass
(Final Mass- Initial
Mass/Initial Mass x
100)
Graph your results for each of the solutions on the graph below in order of
largest percent decrease in mass to the largest percent increase in mass. After
all of the data points are entered, draw a line of best fit on the graph.
1
2
3
4
5
6
Wrap-Up Questions:
1. Can you place the solutions in order of higher concentration of sucrose to
lowest?
2. What part of the data did you use to order the solutions?
3. What would your results be if the potato were placed in a dry area for several
days before your experiment?
4. When potatoes are in the ground, do they swell with water when it rains? If
not, how do you explain that, and if so, what would be the advantage or
disadvantage?
Wrap-Up Questions:
5. Why are most cells small, and why do they have cell membranes with may
convolutions (folds or twist)?
6. What organelles inside the cell have membranes with many convolutions?
Why?
7. Do you think osmosis occurs when a cell is in an isotonic solution? Explain
your reasoning.