Name:_______________________________
Date:___________________
Laboratory:
Observing Osmosis in Gummy Bears
Purpose: To investigate the movement of water into and out of a Gummy Bear (a gelatin
polymer).
Problem: Where is the concentration of H2O molecules highest? In tap water, salt
water or gummy bears?
Background Information:
Gummy Bears are made of gelatin, starch, and sugar. Gelatin is a polymer (huge
molecule made of many repeating units) that forms large three-dimensional matrices which
give structural support to jellies and jams, and lots of other things that you use every day. (A
matrix is like a complex cage)
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.
Hypotheses: Create a hypothesis for the following solutions. Remember to use the "If...then"
format.
Hypothesis for water:
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Hypothesis for salt water:
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Hypothesis for mystery solution:
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Materials:
Three 100 ml. beakers
Masking tape
Permanent marker
Tweezers
Paper towel
Gummy Bears
Tap water
Salt
Mystery Solution
Ruler
Scale
Graduated Cylinder
Weight Boat
Glass stirring rod
pH indicator strips
Procedure:
PARTA:
1.
2.
3.
Obtain three beakers, three colored Gummy Bears and a ruler.
Label your beaker with a piece of masking tape (folded over)
4.
5.
6.
Label one Beaker "TAP WATER", one "SALT WATER", and the other "MYSTERY SOLUTION"
Write your name and class period using a permanent marker.
Record the color, and texture of the gummy bears and record in the data table 1.
Measure your bear (in cm) from top to bottom (length) and from side to side (width) and from
front to back (height).
7.
8.
9.
10.
Record the dimensions in centimeters in the data table 2. Use decimals.
Find the mass of each bear. Record the mass in the data table 3 in grams. Again, use decimals.
Place the gummy bears in the beakers.
Using a graduated cylinder, measure out 50mL of water and pour into beaker marked for "TAP
WATER". The gummy bear should be covered completely.
11. Next, weight out 10g of salt, and pour into a clean beaker.
12. Using a graduated cylinder, measure out 50mL of water and pour into the beaker with the salt. Mix
together until the salt dissolves.
13. Pour your salt mixture into the beaker marked "SALT WATER". The gummy bear should be
completely covered.
14. Next, measure out 50mL of the mystery solution with a graduated cylinder and pour into the beaker
marked "MYSTERY SOLUTION". The gummy bear should be completely covered.
15. Take a glass stirring rod, and dip the end into the beaker with the mystery solution. Test the solution
with a pH indicator strip. Record pH here:________________.
16. Place the beakers on the counter away from direct sunlight.
17. Let them sit overnight.
PART B:
18. On the next lab day, gently pour the water over a screen into a sink.
19. Catch each gummy bear using your hand, and place the gummy bear on paper towel or waxed
paper. BE CAREFUL not to break the bears, they are very fragile.
20.
21.
22.
23.
Blot dry by placing bear on a paper towel.
Record the color, and texture of each gummy bear in the data table 1.
Measure the length, width, and height of each gummy bear and record in data table 2.
Carefully place gummy bear on weight boat, and measure it's mass. Record the mass in the data
table 3.
24. Place gummy bears back onto paper towel.
25. Calculate the volumes (L × W × H).
Data Table 1
Gummy Bear 1
Gummy Bear 2
Gummy Bear 3
Initial
Color
Initial
Texture
Initial Color
Initial Texture
Initial Color
Initial Texture
Color
After
Texture
After
Color After
Texture After
Color After
Texture After
Day 1
Day 2
Data Table 2
Gummy Bear 1
Length (cm)
Width (cm)
Height (cm)
Volume (cm3)
LxWxH= cm3
Gummy Bear 2
Gummy Bear 3
Initial
Final
Initial
Final
Initial
Final
Before Soaking
(Day 1)
After
Water
(Day 2)
Before soaking
(Day 1)
After Salt
(Day 2)
Before Soaking
(Day 1)
After Mystery
Solution
(Day 2)
Data Table 3
Gummy Bear 1
Gummy Bear 2
Gummy Bear 3
Initial
Final
Initial
Final
Initial
Final
Before Soaking
(Day 1)
After Water
(Day 2)
Before soaking
(Day 1)
After Salt
(Day 2)
Before Soaking
(Day 1)
After Mystery
Solution
(Day 2)
Mass (grams)
Analysis:
Calculate the percent changes in volume after each step of the experiment.
Our scales are accurate to 0.1 gram, therefore your calculations using mass should be rounded to
the nearest tenth or 0.1 gram
% Change in mass =
(Final mass - Initial mass)/ Initial mass × 100 = _________ %
Place the percentages in the table below:
Data Table 4
Gummy Bears
1
2
3
% Change in water
% Change in Salt
Water
% Change in
Mystery Solution
Analysis questions: Answer the following using complete sentences. Be sure to
restate the question in your answer!
1. Were your hypotheses correct? Why or why not?
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2. What happened to the bears when placed in water? Why?
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3. What happened to the bears when placed in saltwater? Why?
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4. What was the pH of the mystery solution? What did this indicate?
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5. What happened to the bears when placed in the mystery solution? Why?
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Conclusions:
Write a paragraph which explains the results of this experiment using the concept
of osmosis. Think about how much swelling can occur (equilibrium). Include your specific
data to explain your results and to support your conclusions.
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