Experiment 1: Tonicity
and the Animal Cell
In this experiment you will explore the
effects of osmosis on eggs. An egg is surrounded by a permeable membrane and a
hard shell. To observe the effects of osmosis the shell will first need to be
Acetic Acid (Vinegar)
100 mL Graduated Cylinder
*You Must Provide
Note: This lab
requires at least one day to prep and at least one day for observations. For
best results, please use a medium or large sized egg. Jumbo or extra large eggs
are too large for the experimental set-up.
- Set out four beakers with one egg in each beaker.
wear gloves when handling raw eggs.
- Cover each egg with acetic acid (vinegar).
- Cover each beaker with a piece
of foil and allow the eggs to sit for 24 hours. Keep foil for entire
experiment. You will need it later in the experiment.
Figure 2:An egg that h as been soaked in vinegar and rinsed with
- You will be placing eggs (cells) in different tonicities and
observing the results. Develop a hypothesis and record it in the data
section for this experiment.
- After 24 hours, check to see if the egg shell is dissolved by gently
taking out each egg and rinsing with a small amount of water. The eggs
should have a yellow tint to them and you should be able to lightly squish
the egg between your fingers (Figure 2). BE CAREFUL TO NOT BREAK THE EGG.
- If any of the eggs still have a hard shell after 24 hours allow the
eggs to sit for another 12 – 24 hours.
- Once the egg shells have been dissolved remove them from the vinegar.
HANDLE EGGS CAREFULLY. THEY CAN EASILY BREAK.
- Rinse out and dry all four beakers.
- Label one beaker “100 % distilled water”, one “100% corn syrup
solution”, one “10% corn syrup/90% water solution” and one “control”.
- In the beaker labeled “10% corn syrup/90% water solution”, prepare a
10% sugar solution by mixing 45 mL of distilled water with 5 mL of corn
syrup. Mix well with a stirring rod. Record the initial volume in Table 1.
- In the beaker labeled “distilled water”, measure and pour 50 mL of
distilled water. Record the volume in Table 1. The egg should be covered.
Add or reduce the amount of water if necessary. Record the initial volume
in Table 1.
- In the beaker labeled “100% corn syrup solution”, measure and pour 50
mL of corn syrup (100% sugar solution). The egg should be covered. Add
more corn syrup if necessary. Record the initial volume of the solution in
- In the beaker labeled “control”, do not add any solution. Record the
volume in Table 1.
- Add one egg to each beaker and cover with foil.
- Let the eggs sit for 24 hours. In the meantime, develop a hypothesis
stating how you believe each egg will be affected by the solution in the
beaker over the 24 hour period. Record your hypothesis in the Post-Lab
- After 24 hours have passed, observe the eggs. If you do not see any
noticeable difference let the eggs sit for another 12 – 24 hours.
- After the eggs have rested for 24-48 hours in the solutions carefully
remove them from the beakers. Make sure to note which eggs came from each
beaker. Be careful to not spill the solutions.
- Record the final volume of each solution using a graduated cylinder
and record your results in Table 1.
- Observe the eggs. Draw your observations in the in Table 2 of data
Table 1: Osmosis Results
Volume (mL) Before Osmosis
Volume (mL) After Osmosis
100% distilled water
100% corn syrup
10% corn syrup/ 90% distilled water
Table 2: Observations of
100% Distilled Water
100% Corn Syrup
10% Corn syrup/ 90%
- Record your hypothesis from Step
15 here. Be sure to include scientific reasoning to support your
- How do each of the three eggs
placed in solution compare to the control egg?
- For each beaker, identify whether the
solution inside was hypotonic, hypertonic, or isotonic in comparison to
the control beaker.
- What was the direction of osmosis
in the beaker labeled “100% distilled water”? Did the egg in this beaker
- Was there a volume in the
“control” beaker after 24-48 hours? If so, why do you think this is? If
not, why do you think this is?
- Which solution contained a
dehydrated cell? Think about someone having a high sugar diet. Hypothesize
how their cells might be affected by osmosis?
- Osmosis is how excess salts that
accumulate in cells are transferred to the blood stream so they can be removed
from the body. Explain how this process works in terms of tonicity.