Section 1
Understanding Life Systems
Egg Osmosis
Observe osmosis through eggs.
When we exercise, our body sweats and we feel thirsty. To
replace the water we lose when we sweat, we need to drink
water. Have you ever wondered how our body absorbs the
water that we drink? Our body absorbs it through osmosis.
Osmosis helps our body get the water and nutrients from food
into our blood. It also transfers waste products out of our
blood.
So, what is osmosis? Osmosis is the natural movement of
water through a semipermeable membrane (a membrane
that has tiny pores, allowing small molecules to move through
it). During osmosis, water moves through a semipermeable
membrane from the side that has a high concentration of
water to the side that has a low concentration of water. The
semipermeable membrane surrounding the cells in our body
allows water and small molecules to move in and out of the
cells. So, moving water from cell to cell is what allows us to
keep the levels of water and nutrients in our body in balance.
Try the experiment below to learn
how osmosis occurs.
Let’s get some water to drink.
Popular Book Company (Canada) Ltd. Complete ScienceSmart • Grade 8 1
Section 1
Understanding Life Systems
Egg Osmosis Level of
Difficulty:
advanced
In this experiment, you will examine the
direction of water movement during Time
osmosis. Needed:
1 week
Before doing the experiment, we need to prepare
two eggs with no shells in advance. Each shell-less egg
represents a cell and its semipermeable membrane.
Eggs with No Shells
Leave the eggs in vinegar for 24 hours. The
egg shells will dissolve in the vinegar. During this
process, carbon dioxide is released, which can
be seen as bubbles on the surface of the shells.
vinegar
carbon dioxide
After the shell dissolves, the membrane is semipermeable and
rubbery in texture. Pour all the vinegar down the drain and
gently rinse the eggs off under running water to get them ready
for the experiments.
Popular Book Company (Canada) Ltd. Complete ScienceSmart • Grade 8 2
Section 1
Understanding Life Systems
Egg Osmosis
Materials:
Hypothesis: • 2 shell-less eggs • 2 jars
For each experiment, write • a scale • paper towel
the correct word to show • water • corn syrup
your hypothesis.
Experiment 1
If a shell-less egg is added to a jar of water, I predict that the egg will
.
shrink/expand
Steps:
1. Measure and record the weight of the shell-less egg in the chart on the
next page.
2. Place the egg in a jar and add enough water to cover the egg.
3. Observe the egg after one week.
4. Measure and record the weight of the egg.
5. Record your observations.
Experiment 2
If a shell-less egg is added
Experiment 1 Experiment 2
to a jar of corn syrup, I
predict that the egg will
. water corn syrup
shrink/expand
Steps:
Follow the same procedure as
in Experiment 1, but add corn
syrup into the jar instead of
water.
Popular Book Company (Canada) Ltd. Complete ScienceSmart • Grade 8 3
Section 1
Understanding Life Systems
Egg Osmosis
Experiment 1 Experiment 2
Initial Weight
Final Weight
Difference in Weight
(gain/loss)
Observation
Conclusion:
Circle the correct words after conducting the experiments.
The egg in water shrinks / expands and the egg in corn syrup
shrinks / expands .
Experiment 1: My hypothesis was correct / incorrect .
Experiment 2: My hypothesis was correct / incorrect .
Explanation:
higher
In Experiment 1, the water molecules concentration
moved into the egg through the of water
water
semipermeable membrane until it
reached equilibrium (the state in movement
of water
which the concentration of water on lower
both sides is equal). You may have concentration
of water
noticed that the egg expanded.
In Experiment 2, the corn syrup is lower
concentration
mostly sugar and has a lower
corn syrup of water
concentration of water than the egg.
Hence, the water moved out of the movement
of water
egg to the corn syrup until it reached higher
equilibrium. This outward movement concentration
of water
of water caused the egg to shrink.
Popular Book Company (Canada) Ltd. Complete ScienceSmart • Grade 8 4
