Name: _________________________
Facilitator: ______________________
Date: __________
Investigation: Osmosis with Gummi Bears
Purpose
To investigate the movement of water into and out of a polymer
Background
Gummi 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.
Molecules are in constant motion, and tend to move from areas of higher
concentrations to lesser concentrations. Diffusion is defined as the
movement of molecules from an area of high concentration to an area of low
concentration.
The diffusion of water molecules through a selectively permeable membrane
is known as OSMOSIS. Selectively permeable means that some molecules
can move through a membrane while others cannot.
Movement through membranes is called transport. Diffusion and osmosis are
forms of PASSIVE TRANSPORT; this means that they do not need energy
to move from areas of high concentration to areas of low concentration.
ACTIVE TRANSPORT requires energy to transport molecules from low
concentration to high concentration.
OSMOSIS is the movement (transport) of water (small dots) through a
selectively permeable membrane from an area of high concentration to an
area of low concentration.
Research Question
Will soaking Gummi Bears in tap water, distilled water, and then salt water
affect the size and/or mass of a gummi bear?
Hypothesis: _______________________________________________
_________________________________________________________
Materials
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(2) Gummi Bears
(3) clear plastic cups (8oz)
Distilled water
Tap water
Small squares of foil
Centimeter ruler
Saturated salt solution (water and carton of salt)
Paper towels
Permanent marker
Procedure
Day 1
1. Obtain two clear plastic cups and two different color gummi bears.
2. Label one cup tap water and the other distilled water with your
marker.
3. Measure your bears from top to bottom (length), from side to side
(width) and from front to back (height). Use your measurements to
calculate the volume. Record your data in the data table.
4. Place the bears in the cups.
5. Pour distilled water in the cup marked distilled. Pour enough water in
the cup to fully cover the bear (1/2 cup full).
6. Pour tap water in the cup marked tap. Pour enough water in the cup to
fully cover the bear (1/2 cup full).
7. Set the cups aside and let them soak overnight.
8. Now make your saturated salt solution. To make the saturated salt
solution measure out one (1) cup of warm tap water. Add salt to the
water one tablespoon at a time, stirring after each addition. Keep
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count of the number of tablespoons you are adding to the water. You
will not need to add the entire carton of salt to the water. When
adding the salt to the water, stir after each addition of salt, until all
the salt is dissolved. Keep adding salt, one (1) tablespoon at a time,
making sure that the salt dissolves completely with each addition until
the salt stops dissolving. When this happens salt crystals will be
visible at the bottom of your cup. Set your saturated salt solution
aside until the next day. Check out this YouTube video for
clarification: https://www.youtube.com/watch?v=95ChO2oEJPA
How many tablespoons of salt did you add to the water? ____
Day 2
9. On the next lab day, pour all the water from each cup. Then gently
place the gummy bear on a small sheet of foil. Use a paper towel to
gently blot the water from the foil.
10. How do your gummi bears look? __________________________
__________________________________________________
11. While on the foil, measure the height, width, and depth. Calculate the
volume (length x width x height = volume). Record your data.
12. Place the gummy bears back into their respective cups. Cover the
bears with the saturated salt solution you made the day before. Let
this sit overnight.
13. Make a new hypothesis. What will happen to the gummi bears in the
salt water? ___________________________________________
____________________________________________________
Day 3
14. On the third lab day find the length, width, and height of the bears
using the same procedure as the previous day. Don’t forget to record
your data and calculate the volume.
Data Table for Volume:
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Dimensions
Gummi Bear 1 (color: _______)
Before
After tap After
Soaking
water
salt
(day 1)
(day 2)
water
(day 3)
Gummi Bear 2 (color:________)
Before
After
After
soaking distilled
salt
(day 1)
water
water
(day 2)
(day3)
Length (cm)
Width (cm)
Height (cm)
Volume (cm3)
Conclusion
Answer questions 1 through 5 on a separate piece of paper and attach to this
sheet.
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. Was there a difference in your results using tap water compared to
distilled water? If so, why?
4. What happened to the bears when placed in salt water? Why?
5. What do you think would have happened to the bears if, after the last
day, they were again placed in distilled water?
6. Calculate the percent change in volume after each step of the
experiment.
a. % change in volume = (final volume - initial volume)/ initial
volume x 100
b. Place the percentages in the table below:
Bears
% Change in Water
% Change in Salt
Water
Tap Water Bear
Distilled Water Bear
7. Make a bar graph of the percent changes.
a. Label axes
b. Place a scale on the vertical axis and give the graph a title.
Place the data for both bears on the same graph. USE GRAPH
PAPER or Create a Graph.
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c. 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.)
8. On a separate piece of paper, write a paragraph that explains the
results of this experiment using the concept of diffusion. Include
your data where appropriate to explain your results.
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