Transcript Osmosis Lab - Boulder Valley School District

Whitney Dougherty, Divya Arcot, Kelly Christensen, Molly Horton
Period 4
What is Osmosis?
 Osmosis is the diffusion of water from areas of higher
concentration to areas of lower concentration.
 (From hypotonic solutions which contain less of the solute to hypertonic
solutions which contain less of solvent)
 This takes place in order to maintain homeostasis
within cells.
Purpose
 To determine how varying the type of food and
amount of salt concentration affects osmotic
regulation.
Procedure
1.
2.
3.
4.
5.
6.
Cut potato & apple
(approximately 1cm)
Weigh samples in grams
Place in variable salt
solutions*
Sit for 30 minutes
Removes samples, dab dry,
& re-weigh
Record data & analyze
results
*see next page
Salt
Procedure
(continued)
How to make a salt solution:
1. Measure 50 mL of distilled water
2. Measure the amount (in grams) of salt, which will be
the same number as the percentage of salt in the
solution (ex. 5 grams for a 5% salt solution)
3. Pour the salt into 50 mL of the solvent
4. Stir solution until the salt is visibly dissolved
5. Add 50 mL of the solution, so that you have a total of
100 mL of the solution.
Procedure
(continued)
Controls
 Size of samples
Variables
 Type of food
 Amount of solvent (H2O)
VS.
 Time
 Salt Concentration
Distilled
H20
1%
Salt
5%
Salt
10%
Salt
Hypothesis
 Because apples and potatoes are composed of different
materials, their chemical properties differ. These
characteristics will in turn cause variations in their
rates of osmosis. The rates of osmosis of the apple and
potato samples will also vary in different manners
when the samples are placed in salt solutions.
Prediction
 We think the potato will have a higher rate of osmosis
because they are more dense due to their starch
concentration. In comparison, apples are less dense
and have a higher concentration of water.
Data
Potato
Distilled H20
(g)
1% salt
(g)
5% salt
(g)
10% salt
(g)
2
2.1
1.9
2.2
1.2
1.3
1.5
1.5
1
1.1
1
1
.7
.6
.7
.8
INITIAL
FINAL
Apple
INITIAL
FINAL
Percent Change in Mass
EQUATION
MassInitial – MassFinal
_______________________________
MassInitial
X 100
Distilled H2O
(% grams)
1% Salt Solution
(% grams)
5% Salt Solution
(% grams)
10% Salt Solution
(% grams)
Potato
66.67
61.54
26.67
46.67
Apple
42.86
83.33
42.86
25
Percent Change in Mass
(Graphed)
Potato Percent Change
Apple Percent Change (g)
0
2
4
6
8
-0.2
Percent Change (g)
12
Potato percent
change (g)
-0.3
-0.4
-0.5
-0.6
-0.7
-0.8
-0.9
10
Molarity (mol/L)
0
Percent change (g)
-0.1 0
0
5
10
15
-0.1
-0.2
-0.3
Apple Percent
Change (g)
-0.4
-0.5
-0.6
Molarity (mol/ L)
Conclusion
The purpose and corresponding results:
 The purpose of this lab was to observe the effects of
food types on osmotic rates in various salt solutions.
 Our data showed that our prediction was correct. It
showed that the potato had a higher rate of osmosis
than the apple.
Conclusion
What could have gone wrong?
 Although our prediction was correct, the results of our
data were inconclusive, as they did not exactly follow
theory. We believe this was due to:
Potential contamination of the distilled water as the
data collected from the other solutions followed the
osmotic theory.
2. Denatured aquaporin pumps which facilitate the flow
of water into the cells of the food samples.
3. The fact that samples were taken from foods which
had been sitting out for a while.
1.
Conclusion
What We Learned:
 We learned how the cell membrane of different foods
respond in a similar fashion to variable salt
concentrations of a solvent.
 Since our results were inconclusive, the best method of
action is to re-do the experiment. In this way, we
would be able to test whether the distilled water was
actually distilled and verify the consistency of the rest
of our results which followed osmotic theory.