Name: ______________________________ Date: _______________
Period: _____
Osmosis Lab
Background Information: Cells have an outer covering called the cell membrane. This membrane is
selectively permeable; it has tiny pores or holes that allow objects to move across it. The cell membrane
controls what moves in and out of the cell. Food and oxygen move into cells across the cell membrane through
the process of diffusion. Diffusion is movement of a substance from an area of high concentration to an area of
low concentration. Osmosis is a special type of diffusion; it is the diffusion of water across a selectively
permeable membrane. Osmosis occurs when water moves from an area where it is more concentrated to an
area where it is less concentrated.
In this lab you will have the choice of using eggs, gummy bears, or raisins. All of these materials will act as a
single cell, although each of them are made up of many many cells. The outside of each of these materials will
act as the cell membrane.
Safety notes if using eggs:
1. Raw eggs can carry salmonella (harmful bacteria). Be sure to wash your hands after handling the eggs.
2. Handle your egg very carefully so that it does not break.
Pre-lab Questions:
1. What do you think would happen to a shell-less egg/gummy bear/raisin if water passed into it through the
membrane?
2. What do you think would happen to a shell-less egg/gummy bear/raisin if water passed out of it through the
membrane?
3. What substance must pass through the placenta to a baby in a mother’s uterus?
4. What would happen to the developing baby if the placenta did not work correctly?
Purpose:
To soak an egg/gummy bear/raisin in various liquids and observe how the size of the egg/gummy bear/rainsin
changes as it gains or loses water through the membrane.
Materials:
Raw egg (4) OR gummy bears (4), OR raisins (4), vinegar, tap water, salt water, and corn syrup, metric tape,
balance, plastic cups, beaker, marker
Hypothesis:
Predict how the egg/gummy bear/raisin will respond when it is soaked in:
1. Vinegar:
2. Distilled Water:
3. Salt Water:
4. Corn Syrup:
Procedure:
1. Label your container with your section and initials.
2. In the data table, make a drawing and observation of the egg/gummy bear/raisin in the appropriate space
3. Weigh the egg in grams. Record mass.
4. Pour ________ mL of vinegar into the container. (other liquids used for set up of 3 other beakers)
5. Carefully place an egg/gummy bear/raisin into the container and allow it to soak overnight. Loosely place lid
on top.
6. Put your container in the designated space.
7. Clean up materials and wash your hands.
Name: ______________________________ Date: _______________
Period: _____
8. On day 2, day 3, and possibly day 4, take egg/gummy bear/raisin gently out of container, blot dry with paper
towel, and weigh on gram scale in a weigh boat. Record mass in data table.
Data:
Table 1: Daily Observations
Date
Substance
Mass
Observations
Table 2: Change in Mass of Egg/Gummy Bear/Raisin
Substance
Initial Mass
Final Mass
Observations of
Change