Biology
Unit 2. C. 7
Rubber Eggs!
Name ________________________________
Purpose. The purpose of this investigation is to study the phenomena of diffusion and osmosis using an
egg as our example cell.
Background. All living things must take in certain substances and give off others. Since all living things
are made of cells, these substances must move into and out of each cell through the cell membrane. In this
experiment you will observe how some substances can move into and out of cells.
An egg can be thought of as one of the world’s largest cells. In this experiment you will remove the shell
from a chicken egg and the egg and its membrane will serve as a giant model of a cell and its membrane.
Experiment: Using an Egg as a Model of a Cell.
Procedure.
Day 1. Removal of Shell.
a. Place your egg in a vinegar solution and observe. Leave it overnight or over the weekend.
Day 1 observations. What happens when the egg is placed in the vinegar solution? (5% acidity) (try to
have at least 3 good observations)
Day2. Into the Syrup!
Question. What is the effect of corn syrup on the mass, volume and density of an egg?
Hypothesis.
Procedure
a. Carefully remove your egg from the vinegar solution. You may need to wash it in water and rub
it lightly to remove any remaining eggshell material. Be very careful not to break the egg or
you will have to start over. Be Gentle!
b. Observe the egg. Draw a picture of your egg in the space below.
c. Measure the egg’s mass and volume (use displacement) and record these values.
d. Calculate the density of the egg and record this value. (Density = mass/volume)
e. Measure 100 mL of corn syrup using a graduated cylinder. Pour the corn syrup into a small
beaker or cup. Observe the corn syrup carefully so that you can compare these observations
to ones you will make tomorrow. Write your observations in the space below.
f.
Place your egg in the corn syrup, cover the cup with Saran wrap, label your cup and leave it
undisturbed overnight.
Day 3. From corn syrup to distilled water.
Question. What is the effect of distilled water on the mass, volume and density of an egg?
Hypothesis.
Procedure and observations.
a. Carefully remove your egg from the corn syrup allowing excess syrup to flow back into the
beaker. Do not dispose of the corn syrup!
b. Record your observations of the egg. Draw a picture of the egg in the space below. Note any
changes!
c. Determine the egg’s mass and volume (by displacement) and record these values. Calculate
the density of the egg. Density = mass/volume.
d. Carefully observe the corn syrup and record your observations. Find the volume of the corn
syrup.
Corn syrup observations
volume of corn syrup ___________
e. Discuss any changes in the egg and corn syrup with your group. Try to explain all of the
observed changes. Record these explanations.
f. Place your egg into 80 mL of distilled water, cover the cup and leave it overnight.
Day 4. The Egg in the distilled water
Procedure and Observations.
a. Carefully remove your egg from the water and record your observations. Record its mass and
volume. Calculate the density (d = m/v) of the egg.
b. Record the volume of the water remaining in the beaker and compare it to the original volume.
Volume of water in beaker. ________________ Original volume = __________________
c. Discuss any changes in the egg and water with your partner. Try to explain all of the observed
changes.
Data Table
Day
Mass (g)
Volume (mL)
Density
(g/mL)
Length of egg
Width of egg
2
3
4.
Conclusion.
a. How did the egg respond when placed in the corn syrup and then the distilled water?
b. What material was moving into and out of the egg? How do you know?
c. Explain the changes in your egg each day by drawing diagrams. Use X’s for water and O’s for
sugar (use a key). Add arrows to your diagram to show movements of the water and the corn
syrup. Indicate where solutions are hypertonic, hypotonic, isotonic.
d. How do single celled organisms (i.e. paramecium bursaria) deal with this situation as they live
their lives in fresh water (they would have a lower concentration of water (hypotonic) when
compared to the pond water that surrounds them).
e. Why is it a terrible idea for a person to drink sea water (2.5% salty)?