Download Egg and Osmosis Lab KEY

Name:
Fun with an Egg and Osmosis
Period:
Osmosis is a very important process for moving WATER through membranes in and out of cells.
We will immerse an egg in Acetic acid for a day. The acid will remove the shell, providing a natural
cell membrane around a giant cell with which to experiment. We can observe when water moves
inside and outside of the egg (cell), which is determined by the concentrations of water and solutes
in and out of the cell.
 The egg is 8% dissolved substances and 92% water.
 Vinegar is 5% solute and 95% water.
 The syrup is 60% solute and 40% water.
In your notebook, write the following two hypotheses:
Hypothesis 1: If the shell of an egg is missing, what will be the direction of osmosis (water
movement), into or out of an egg when placed in vinegar? Explain your reasoning.
Hypothesis 2: What will be the direction of osmosis, into or out of an egg when placed in corn
syrup? Explain your reasoning.
Materials:
Balance
Ruler
String
Graduated cylinder
Overflow can
Clear plastic cup (labeled: period # and
lab group name)
Vinegar
Corn syrup
Saran wrap
Egg
DAY 1:
1. Create a data table in your notebook (see below).
2. Measure the mass, volume, and circumference of an egg using the technique of
your choice. Describe your techniques. Record measurements in data table.
3. Set the egg in a plastic cup and pour vinegar over the egg until it is covered
with about 3 cm of liquid. Cover the cup with saran wrap.
4. Observe any evidence of chemical reactions taking place and record these in the
data table. Place the beaker and egg on the class tray for 24 hours.
DAY 2:
1. Observe any changes to the egg and record.
2. Carefully remove the egg, rinse and gently pat it dry. Measure the mass,
volume, and the circumference again. Record measurements and observations.
3. Pour out the vinegar and rinse the cup. Add 1 inch of corn syrup to your cup
then add the egg. Cover and leave on the class tray for 24 hours.
4. Answer Analysis/Interpretation questions 1-3 in notebook.
DAY 3:
1. Carefully remove the egg and measure the mass, volume, and circumference
again. Record measurements.
2. Observe any changes to the egg and record observations in the table.
Data Table
Treatment
(unit)
(actual data will vary)
Mass
(grams)
Circumference
( cm
)
Volume
(cm3)
Qualitative
Visual
Observations
61
14.5
53
Tiny bubbles form on the
egg and then float up
72
16
61
Transparent surface,
yellow yolk visible, plump
59
13
49
No color change,
dimpled/wrinkled surface
None
After Vinegar
for 24 hours
After Corn
Syrup for 24
hours
Describe how you measured:
Mass: Place the egg in a container on the electronic balance, subtract the mass of the
container
Circumference: Wrap a string around the widest portion of the side of the egg.
Measure the length of the string.
Volume: Fill the overflow can with water up to the spout. Hold a graduated cylinder
at the spout to catch water when you slowly lower the egg in the overflow can.
Measure the water in the graduated cylinder and convert to cm3
Analysis and Interpretation: Answer thoroughly in notebook. Be sure to include the
questions, or make the question very clear in your answer. You may type directly on
this page if you like, by accessing it on Mrs. B’s website.
1. Identify your manipulated and responding variables. Does this lab possess
reliability or validity measures? Explain.
MV=type of solution
RV=mass, circumference, volume
Validity/Reliability measures: Control group is no solution, calibrated
electronic balances, repeated by other groups, controlled variables including
time spent in solution, type of container, type of egg, etc.
2. After the shell was removed when immersed in vinegar, in which direction did
the water move, into or out of the cell?
Water moved into the cell from the vinegar.
3. Use tonicity terms to compare the egg and the vinegar when initially placed
together.
The vinegar is hypotonic to the egg because it has a lower concentration of
dissolved substances than the egg.
4. Explain the direction of the water’s movement in terms of the concentration of
water, both in the egg and in the vinegar.
Because it has a lower concentration of dissolved substances than the egg, the
vinegar has a higher concentration of water and water moves into the egg
(osmosis). This lowers the concentration of dissolved substances in the egg.
Osmosis continues until equilibrium is reached.
5. After immersion in the syrup in which direction did the water move, into or out
of the cell?
Water moved out of the egg into the corn syrup.
6. Use tonicity terms to compare the egg and the syrup when initially placed
together.
The corn syrup is hypertonic to the egg because it has a higher concentration
of dissolved substances than the egg.
7. Explain the direction of the water’s movement in terms of the concentration of
water both in the egg and in the syrup.
Because it has a higher concentration of dissolved substances than the egg, the
corn syrup has a lower concentration of water and water moves out of the egg
(osmosis). This raises the concentration of dissolved substances in the egg.
Osmosis continues until equilibrium is reached.
8. For centuries, salt and strong sugar solutions like corn syrup have been used to
preserve foods and protect them from being colonized by living bacteria and
fungi. This was long before refrigeration was invented. Why do these solutions
defend against spoilage so effectively? The egg was a model of all cells including
bacterial and fungal cells, which spoil food. What would happen to bacteria
and fungi which land on food treated by these substances?
These substances prevent bacteria and fungi from thriving by drying them out.
Because strong sugar and salt solutions are hypertonic to living cells, osmosis
draws water out of the bacteria/fungal cells. Because they don’t contain
enough water to ever achieve equilibrium, they dry up completely.