Gummy Bear Osmosis and Diffusion
Purpose: To investigate the movement of water into and out of a polymer. Gummy Bears are
made of gelatin and sugar. Gelatin is a polymer that forms large three-dimensional matrices
which give structural support to jellies and jams, and lots of other things that you use every
day.
Hypothesis:
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Materials: for pairs of students
2 - plastic cups (8oz)
permanent marker
1 - plastic screen
2 - Gummy Bears (different colors)
Distilled water
tap water
saturated salt solution
1 - centimeter rulers
Safety Considerations: There are not any safety hazards with materials used in this experiment.
The filters may become moldy after storage for several days or more. If that occurs, they
should be disposed of in the trash.
Procedure
1. Obtain two plastic cups, two different colored Gummy Bears and one ruler.
2. On the side of each cup, write your name and class period using a permanent marker.
3. Label one cup "TAP WATER" and the other "DISTILLED WATER".
4. Measure your bear (in cm) from top to bottom (length) and from side to side (width)
and from front to back (height). Record the centimeters in the data table.
5. Find the mass, in grams, of each gummy bear prior to being placed in water.
6. Place the bears in the cups and cover one with distilled and one with tap water.
7. Place the cups on the counter away from direct sunlight. Let them sit overnight.
8. On the next lab day, gently pour the water over a screen into a sink. Catch each bear on
a separate screen.
9. Find the mass, in grams, of each gummy bear after being placed in water.
10. While on the screen, measure the length, width, and height. Record. Blot the screen dry
by placing it on a paper towel. BE CAREFUL not to break the bears, they are very fragile.
11. Place the bears back into their correct cups. Cover the bears with saturated salt
solution. Let them sit overnight.
12. Find the dimensions of the bears and record. Calculate the volumes (l x w x h).
13. Find the mass, in grams, of the gummy bears after being soaked in the salt water.
Data Table for Dimensions in centimeters: (Use decimal numbers.) ALL measurements should
reflect the SAME precision (same number of decimal places).
Gummy Bear in Tap Water Mass (g) Length Width Height Volume
Before Water
After Water
After Salt Water
Gummy Bear in Distilled Water Mass (g) Length Width Height Volume
Before Water
After Water
After Salt Water
Conclusions:
1. What happened to the bears when placed in distilled water? Why?
2. What happened to the bears when placed in tap water? Why?
3. What happened to the bears when placed in salt water? Why?
4. What do you think would have happened to the bears if, after the last day, they were
again placed in distilled water?
5. Calculate the percent change in volume after each step of the experiment.
% change in volume = (final volume - initial volume)/ initial volume x 100
6. Place the percentages in the table below:
% Change in % Change in Salt
Bears
Water Water
Tap Water Bear
Distilled Water
Bear
7. Make a bar graph of the percent changes. Label axes. Place a scale on the vertical axis
for percent change and give a title for the graph. Place the data for both bears on the
same graph. USE GRAPH PAPER. If you have a negative value for a percent change,
start the vertical axis at a negative number. (For example: -50, -25, 0, 25, 50, 75, 100,
etc.) An example of the horizontal axis is below:
Tap Salt Distilled Salt
Water Water Water Water
8. Write a conclusion which explains the results of this experiment using the concepts of
diffusion and osmosis. Think about how fast changes like these take place (kinetics and
rates of diffusion) and how much swelling can occur (equilibrium and limiting swelling
volume). Include your data where appropriate to explain your results and conclusions.
Use your “How to Write a Lab Report” handout paying particular attention to the
criteria listed here.
