Egg Osmosis experiment for Science Bowl 2016—Egg each other on to Egg-cellence!
OVERVIEW:
The Standard that is particularly addressed in this activity is Life Science Standard Three for 7th grade:
Understand the cellular structure of single-celled and multicellular organisms.
In particular 7.3.1, 7.3.2 and 7.3.7.
Abstract:
Students will explore how the concentration of sugar solutions in which shell-less eggs are soaked
affects the mass of the egg after a 24 hour immersion in the solution. After the shell is removed from
the egg, the egg is placed in various concentrations of aqueous sugar solutions to determine the
change in mass of the egg. Discussion should focus on how materials move into and out of the cell
across a cell membrane. Terms that students should be familiar with are diffusion, osmosis,
hypertonic, hypotonic and isotonic.
This experiment will involve three parts.



One is preparing solutions of various concentrations;
the second is removing the shell on a raw egg by soaking in vinegar, and
the last is soaking the eggs overnight in sugar solutions of various concentrations. Students will
perform calculations with their collected data to determine the percentage change in mass of
their eggs in each solution and then plot the data points and interpret their results to determine
the effect of sugar concentration on the mass of the egg.
Part I: The solutions can be made any time prior to beginning the experiment, but after being prepared,
they need to be stored covered at room temperature so no water evaporates.
Part II: The eggshells should be removed by an overnight soaking in vinegar. Up to 24 hours is okay—
from one after school session to the next day’s session is fine. The shells do not have to be totally
removed for the experiment to work, but students should make note of eggs which do not have shells
entirely removed. This part should not be done over a weekend—or vacation day.
Part III: When the weighed eggs are placed in the various sugar solutions, students MUST be able to
determine their masses the next day—and again, all at the same time. You don’t want some weighed in
the morning, and others in the afternoon if they are in the same set of data. If you have time to let the
eggs sit one more day after the initial weighing, that is fine—this data should be graphed as 48 hour
data rather than 24 hour data and compared to the previously obtained data.
Supplies:
Laboratory balance, (it is preferable to have an electronic balance if at all possible. Beg the high school
or junior high teacher to borrow one of theirs.)
Sucrose (sugar from home—5 pound bag should be plenty. That is over 2000 grams of sugar. Each set of
solutions will require around 220 grams of sugar. You can judge how much you will need. ),
Plastic cups big enough to hold an egg and 125 mL of solution,( see pictures),
Containers in which to store sugar solutions (beakers, flasks, 1 pt canning jars)
Saran wrap,
Tap water and a way to heat some of it—use a microwave and bring the warm water to the classroom
or put it in a thermos—the sugar will dissolve easier in warm water for some of the more concentration
solutions,
Plastic spoons,
Cups to weigh the sugar in on the balance,
Paper for recording data.
Empty two liter soda bottles, with the tops cut off, mid-way. These will be used to place the vinegar
and eggs in to remove the shells. Do not put more than 4 eggs in a container.
Household vinegar (cheapest brand),
One dozen raw eggs. (medium size is fine) You can do more depending on the number of trials and
student groups. (Sorry eggs are so expensive now—how was I to know about the avian flu?) One dozen
eggs will allow for 6 duplicate trials, assuming no eggs are broken or rupture
Roll of kitchen paper towels.
Golf balls, as many as you have eggs. They don’t have to be new—or marbles can work—these will be
used to keep the egg submerged in the sugar solutions. They will be placed on the saran wrap which is
placed over the cup containing sugar solution and egg. You will need as many golf balls as you have eggs
in solutions.
Procedure:
Part I:
Sugar solutions with concentrations varying from about 40% to 0% (pure water) will be made. Making
250 g of solution will allow for duplicate trials at each concentration. If you want to have more trials, you
can increase the amounts of sugar and water. (For example, for 4 trials, you would double both the
amounts of sugar and water.) Students should be familiar with how to calculate a percentage by mass.
They do this by taking the mass of the sugar used and dividing it by the sum of the masses of both sugar
and water used. The following table shows some masses which can be used, but you can use what you
want. Please note that the higher concentrations might need to have some slightly warmer water to
dissolve.
To make a total mass of 250 g of sugar solutions
Concentration
Amount of sugar in grams
36%
90.0g
20%
50.0g
15%
37.5 g
10%
25.0 g
5%
12.5g
0%
0
Amount of water in grams (d=1 g/mL)
160 g = 160 mL
200 g
212.5 g
225 g
237.5 g
250 g
After sugar solutions are prepared, store them in covered containers until ready to use. They should be
labeled accordingly.
Part II:
Prepare the 2-Liter beverage containers by cutting off approximately the top half. The part that is left
should hold approximately 4 eggs.
Check eggs for cracks in shells. Place 4 eggs in each container. Do not put more than 4 eggs in each
container. Pour in vinegar to cover the eggs—have approximately 1 inch of liquid above the level of the
eggs. Have students write their observations of what is happening in the container when vinegar is
added.
Allow eggs to remain in the vinegar for around 24 hours. Have students write their observations of the
eggs/vinegar after the soaking.
Part III:
Students need to carefully remove each egg from its soaking solution and observe it. They will be very
fragile so must be handled gently. Carefully rinse with room temperature water, and place on a paper
towel so as to remove any excess water.
Each egg needs to be weighed on a balance to determine its initial mass. It really makes things go much
faster if you can borrow an electronic balance from the junior high or high school science teacher. The
balance pan should be protected from dampness, by keeping a piece of paper on the balance pan, or
using a weighing cup. The mass of the cup or paper needs to be accounted for.
Each egg should be then placed in a labeled cup for a different concentration of sugar solution. The cup
should be covered with a small piece of pre-cut saran wrap. A golf ball or large marble should be placed
on the saran wrap to keep the egg submersed in the solution as some will be floating. (Why?)
After 24 hours, carefully removed the egg from the solution, roll it on a paper towel to remove any
remaining liquid and re-weigh it. Save the solution so the egg can be replaced in it if a 48 hour weighing
is planned. Repeat procedure after 48 hours if desired.
Possible table might look like this:
Solution
concentration,
label
0%, 0-A
0%, 0-B
36%, 1-A
36%, 1-B
30%, 2-A
30%, 2-B
15%, 3-A
15%, 3-B
10%, 4-A
10%, 4-B
5%, 5-A
5%, 5-B
Initial mass
of egg in
grams
59.49
56.02
Mass of egg after
24 hours in grams
Difference in
Mass of egg
72.01
68.32
12.52
12.32
Percentage
change in
mass of egg
21.05%
22.00%
Average of
percentage
change
21.52%
Students need to discuss why the percentage change in mass of the egg is necessary to use rather than
just the change in mass.
Analysis of data:
The students should graph the Percentage Change in Mass versus the % Concentration of Sugar
Solution. They should note the trend and draw a smooth trend line through the data. If a 48 hour trial
is done, they can add the data to the same graph using a different color for the data points and line.
Students should be able to explain what is happening by looking at the trend line on the graph.
Cleanup and Disposal:
The vinegar solution can be safely poured down the drain as can the sugar solutions. The containers can
be rinsed and recycled or placed in the trash.
The eggs should be placed in a plastic bag, closed and placed in the trash.