EGG OSMOSIS LAB INSTRUCTIONS

READ THE INSTRUCTIONS COMPLETELY BEFORE YOU START! The data you record in this lab will be used
to create your lab report that is worth 20 points of your lab grade!
Purpose
Determine (by calculation) the isotonic point and concentration of an unknown sucrose solution based
on graphed data.
Objectives
Demonstrate an understanding of homeostasis and its importance in the functioning of the human
body systems (chapter 1)
Explain how the properties of water make it vital to homeostasis (chapter 2)
Compare the mechanisms by which substances enter and exit the cell (chapter 3)
Collect data and analyze the results of physiological experiments, using the Scientific Method
Materials
2 de-shelled eggs
2 beakers, each containing the same concentration of sucrose
Scale
Weigh Boat
Paper Towels
Timer (Set to 15 minutes)
Recorder (one person will write down the weights in a journal and then enters them into the group
record)
Methods
First, you should prepare a chart like so (although you will also be adding your data to an Excel
spreadsheet that will be shared with the entire class that you can record in Table1):

2
1. Gently dry your de-shelled eggs.
2. Place the weigh boat on the scale and tare (0) the scale. Place egg #1 on the scale and record its
weight. Repeat this procedure for egg #2.
3. Place ONE egg into EACH beaker of sucrose solution and start your timer.
4. After 15 minutes, remove egg #1 from its beaker, dry it gently, and weigh it. Repeat this step for
egg #2. (Don’t mix up your eggs!)
5. Place your eggs back into their beakers and set your timer for another 15 minutes, then repeat
step 4.
6. Repeat steps 4&5 until you reach 75 minutes total. You should have six weights recorded for
each egg.
7. Record your data in the group data table on your instructor’s computer, in the appropriate
section for your sucrose concentration. This data will be shared with the class.
NOTE: The whole experiment consists of performing this procedure for various concentrations
of sucrose. Your lab group is just one ‘treatment’ group (or you may be the control). There is
also one group working with an ‘unknown’ concentration. We will perform the experiment with
2 beakers of the same concentration (replicates) in order to ensure reliability and account for
error.

Lab Report Instructions (This is an individual effort)

FORMATTING:
1. Single-spaced, 1” margins on all sides, page numbers
2. Size 12 point font in Time New Roman or Arial
3. Use bold, numbered headings for each section
4. Use complete sentences in paragraph form
5. You are not graded on the ‘right’ result—the data is what it is. You are graded on your analysis of
the result in relation to your hypothesis.
6. Submit to Assignments folder on D2L by due date
LAYOUT:
1. Introduction
a. Define osmosis in your own words
b. Explain how osmosis is being demonstrated in this experiment in your own words; state this in
the form of the ‘purpose’ of the experiment
2. Hypothesis
a. State hypothesis for experiment (what will happen and why, based on the intro)
b. Present a logical argument to support your hypothesis based on information from your
introduction
3. Methods
a. State specific methods used during experiment, including (be thorough)…
b. How were eggs prepared (vinegar w/ 3% acetic acid)
c. What were the %’s of sucrose used
d. How long were eggs in sucrose and when were they weighed
e. How was data collected
3
4. Results
a. What was the concentration of the unknown?
i. Explain how you determined this
b. What was the isotonic concentration?
i. Explain how you determined this
c. Write up what you found in Tables 1-3 & Graphs 1-2 in sentences
d. Insert Tables #1-3
i. Weights vs. Time
ii. Change in Weight vs. Time
iii. Change in Weight vs. Sucrose %
e. Insert Graphs #1-2
i. #1 Weight CHANGE vs. Time for EACH sucrose concentration
ii. #2 Total Weight Change vs. Sucrose
a. INCLUDE LINEAR TRENDLINE and generate equation from trendline
b. Calculate isotonic point & concentration of unknown from equation
5. Discussion
a. Discuss findings in terms of osmosis definition from introduction
b. Did your findings support your hypothesis? Discuss.
c. Answer the following questions within your discussion (do not just answer them under the
questions – use sentences & paragraphs)
i. What conclusion can you draw from the data in graph 1
ii. Which solutions were hypotonic? Hypertonic? Isotonic?
iii. What would you expect to happen if an egg was put into a sixth beaker containing a 50%
sucrose solution? Why?
d. Discuss sources of error that may have caused problems with the results
4
Table 1: This table contains the raw data from each group. You can use Excel to make Tables 1-3 to
automatically calculate these tables.

Mass of Egg (g) Vs. Time (min) X Concentration

Table 2: This table is used to average the mass of Egg 1 and Egg 2 for each sucrose concentration and
the unknown at each time. Use the data from Table1. (Calculation: (Mass of Egg 1 + Mass of Egg 2)/
2= Average Mass)

Average Mass of 2 Eggs (g) Vs. Time (min) X Concentration

5
Table 3: From Table 2 you will calculate the average change in mass at each time point for each
sucrose concentration and for the unknown solution. You will use all rows of data to create Graph 1
and only the data at t=75 minutes for Graph 2. From Graph 2 you will determine the isotonic point
and concentration of the unknown solution. (Calculation: (Average mass at t=x)-(Average mass at
t=0) =Average change in mass) If the number is +positive that means the egg gained mass and if the
number is negative the egg lost mass.

Average Change in Mass (g) Vs. Time (min) X Concentration

Example of Graph 1: Average Change in Mass of Egg vs. Time. For this graph you will use the data
calculated in Table 3 to show the average mass change of the eggs at each time point for each sucrose
concentration and the unknown solution
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
0 15 30 45 60 75
Average Change in Mass (g)
Time (min)
Average Change in Mass of Eggs vs. Time
0% 10% 20% 30% Unknown
6
Example of Graph 2: Average Change in Mass vs. Sucrose Concentration. For this graph you will use
the data calculated in Table 3 at time= 75 minutes for each sucrose concentration. You will not
include the unknown since you do not know its concentration. From this graph can be used to
determine the sucrose solution of the unknown and the isotonic point by including a linear trendline
and equation.

-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
0 5 10 15 20 25 30 35
Average Change in Mass (g)
Sucrose Concentration %
AVERAGE CHANGE IN MASS (G) AT T=75 MIN
VS. SUCROSE CONCENTRATION (%)

Last Updated on January 27, 2018