Osmosis Egg-Speriment Lab
Academic Biology
Name: ________________________________________ Period: ________________
Osmosis Egg-Speriment Lab
Introduction
Water molecules move across cell membranes. When there are more water molecules on one side of
the cell membrane, these molecules will tend to cross the cell membrane and move into the side where there
are less. This movement of water molecules will continue to occur until there are equal numbers of water
molecules on each side of the cell membrane. This process is called osmosis. Osmosis is the movement
(diffusion) of water across a cell membrane. In other words, osmosis is a type of diffusion that moves only
water.
Osmosis plays an important role when we think about cells because molecules of water surround cells.
Osmosis controls the distribution of water molecules inside and outside of the cell. The number of water
molecules both inside and outside of the cell need to be the same; this means they are at equilibrium.
When there are more water molecules outside of the cell than inside, you can say the concentration of
water molecules outside the cell is higher. In this situation, water will move into the cells. When there are
more water molecules inside of the cell than outside, you can say that the concentration of water molecules
outside of the cell is lower. In this situation, the water molecules will move out of the cells.
This experiment will look at how water will move in and out of an egg (a giant cell) when it is placed
into different solutions. You will be studying osmosis by using the mass of the egg to determine if water has
moved into or out of the cell.
Objective
Write the objective for this experiment (at least 3 complete sentences).
Hypothesis
Write a hypothesis for this experiment using if/than statements and indicate WHY you are making the
predictions that you do (complete sentences).
Diagrams
Using the information in the introduction, draw two diagrams below illustrating the direction of water
movement into or out of a cell when a cell is placed in an environment where there is a greater concentration
of water molecules outside of the cell AND when a cell is placed in an environment where there is a greater
concentration of water molecules inside of the cell.
Osmosis Egg-Speriment Lab
Academic Biology
Procedure Day 1
1. Label two eggs marking one A and the other B.
2. Label two cups, marking one A and the other B. Also mark the cups with your initials and class
period.
3. Place the eggs into the cups ensuring that egg A goes into cup A and egg B goes into cup B.
4. Fill the cups with 100mL vinegar. Observe for 2 minutes, and write observations below. Cover the
cups with aluminum foil and place where instructed. Leave the eggs in the vinegar for at least 24
hours, or until the eggshell has completely dissolved.
Observations Day 1 (write a 3 sentence summary)
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Procedure Day 2
5. Remove the aluminum foil and SAVE!
6. While keeping the eggs inside the cups, pour out the vinegar.
7. Remove egg A from the cup and GENTLY rinse the remaining vinegar from it. Rinse and dry the cup.
Gently place the egg back into the cup. Do NOT squeeze the egg or drop it back into the cup—
handle the egg gently.
8. Repeat step 7 for egg B.
9. Weigh the egg in cup A and record its weight in the appropriate column on Table 2. Put the egg back
into its cup. Repeat for egg B.
10. Measure out about 50mL of water and pour into cup A. The exact amount doesn’t matter, but it
does matter that you record the exact volume of the liquid you used in Table 1.
11. Measure out about 50mL of Karo syrup and pour into cup B. The exact amount doesn’t matter, but it
does matter that you record the exact volume of the liquid you used in Table 1.
12. Re-cover the cups with the aluminum foil from yesterday and place where instructed.
Observations Day 2 (write a 3 sentence summary)
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Procedure Day 3
13. Remove the foil from the cups.
14. Carefully remove egg A from the water. Allow any excess liquid to drip back into the beaker. Weigh
egg A and record the data in Table 2.
15. Repeat step 14 for egg B.
16. Carefully dispose of the eggs as directed by your instructor.
17. Using a graduated cylinder, measure the volume of the liquid in cup A. Repeat for cup B. Wash out
the cups and put them back on the counter to dry.
18. Wash the graduated cylinders you used in step 17 and clean up your desk.
Observations Day 3 (write a 2 sentence summary)
Egg A
Egg B
Osmosis Egg-Speriment Lab
Academic Biology
Data Tables/Results
Table 1—Liquid volumes of each cup
Beaker
Initial volume of liquid
A
(water)
B
(karo)
Table 2—Mass of eggs
Egg
Initial mass (day 2)
Final volume of liquid
Final mass (day 3)
Percent change in volume
Percent change in mass
A
B
Calculations (show your work)
1. Percent change in mass of egg A
2.
Percent change in mass of egg B
3.
Percent change in volume of water
4.
Percent change in volume of Karo
Post-Lab Questions (answer in complete sentences)
1. Which egg was heavier on day 3 than it was on day 2? Why did the weight increase?
2.
Which egg was lighter on day 3 than it was on day 2? Why did the weight decrease?
3.
Which solution had less liquid on day 3 than on day 2? Why did the volume change?
Osmosis Egg-Speriment Lab
Academic Biology
4.
Which solution had more liquid on day 3 than on day 2? Why did the volume change?
Identify whether each solution was hypertonic, hypotonic, or isotonic. Support your choice by explaining why
using your data.
a. Distilled water
b. Karo syrup
5.
Was your hypothesis supported or rejected? What data did you use to support or reject it?
6.
Explain why vinegar was used on day 1.
7. If a third egg had been placed in a 15% NaCl solution overnight on day 2…
(*note: Assume that the cell has a lower concentration of NaCl than the 15% solution.)
a. What type of solution (hypertonic, hypotonic, or isotonic) would the egg be in? How do you
know?
b. Would the mass of the egg increase or decrease? Explain your answer.
Conclusion
Write a summary of what you learned. The summary must be at least 7 sentences. You should use vocabulary
words in it like: osmosis, diffusion, equilibrium, isotonic, hypertonic, and hypotonic. (Attach lined paper if
you need more space.)