Lab # Egg Osmosis Date
I. Purpose: How does solute concentration affect the movement of water across a living membrane?
CA Standard: (1a) Students know how cells are enclosed within semipermeable membranes that regulate
their interaction with their surroundings.
Background: Osmosis is the diffusion of water across a semipermeable membrane from an area of high
water concentration to an area of low water concentration. Osmosis also occurs in response to
changing concentrations of water-soluble solutes. Water moves toward the highest solute
concentration. Osmosis can be observed in individual cells or in collections of cells, as in
multicellular organisms or their structures. After an egg’s shell is removed, the egg’s external
membrane can be used to demonstrate how osmosis can occur in solutions where there are changes
in the concentrations of solutes.
II. Materials: 1 egg cup paper towels vinegar string
syrup water electronic balance
1. Obtain an egg and determine the mass using a balance to 0.1g.
2. Using a string determine the circumference of the egg to 0.1cm.
3. Place the egg in a cup and add enough vinegar to cover egg. Set aside for 24 – 48 hours.
4. Remove egg gently, blot dry with paper towel and obtain the mass.
5. Using the string obtain the circumference.
6. Rinse the cup & place the egg in the cup. Pour syrup into the cup just covering the egg. Set aside 24 hours.
7. Repeat #4 and #5.
8. Rinse the cup & place the egg in the cup. Pour water into the cup just covering the egg. Set aside 24 hours.
9. Repeat #4 and #5, once again.
Note: Record your data in Table 1.
Egg Raw Egg Without Shell After Syrup After Water
Day 1 Day 2 Day 3 Day 4
Graph the data collected for the four days of lab. Using only one graph, place the # of days and condition of
the egg on the X-axis and the mass and circumference on the Y-axis. Label each line, title your graph.
(SAMPLE graph shown)
TITLE of graph
Day 1 Day 2 Day 3 Day 4
Raw Egg No Shell After Syrup After Water
VI. Questions (Re-state the questions and answer in a complete sentence.)
1. What happens in a hypertonic solution?
2. What was the egg placed in when it was in a hypertonic solution?
3. What happens in a hypotonic solution?
4. What was the egg placed in when it was in a hypotonic solution?
5. If you were to place the egg in distilled water do you think it would gain more or less mass vs. being
placed in tap water? WHY? (Distilled water is pure water, it has no dissolved solute. Read the
background again before answering this question.
6. What was the consistency (how thick or thin) of the syrup after the egg was removed compared to
when it was first poured into the container? Why?
7. Looking at your graph, do you think there is a direct or inverse relationship between the mass and
circumference of an egg going through the osmosis experiment? Why? (Direct will mean the two graph
lines move in the same direction,, inverse will mean the two graph lines move in opposite directions.)
Answer the purpose. Re-state and answer in a complete sentence.