HOW CONCENTRATION OF
SOLUTE AND TEMPERATURE
AFFECTS OSMOSIS THROUGH
THE SEMI-PERMEABLE
MEMBRANE
Mikayla Heiss
Abstract
The effect of temperature and concentration on diffusion was investigated in this lab. Dialysis
tubing was used to represent the cell with different concentrations of sucrose in each tube. The
results indicate that as temperature increases the rate of diffusion also increases, and as
concentration increases the rate of diffusion also increases.
Student Mikayla Heiss
Mrs. Costa
November 11, 2014
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Introduction:
The semi-permeable membrane is a complicated part of the cell that was researched.
Made up of phospholipids, the membrane has a hydrophilic and hydrophobic layer. The
hydrophobic layer is the “inside” layer and is made up of the tails of phospholipids. The outside
of the membrane is made up of the heads of the phospholipids and helps block any unwanted
molecules. Small hydrophobic molecules can pass though this membrane easily (CO2, O2).
Bigger molecules have to find a different way to pass into the cell. They do this through passive,
(requiring no ATP) or active transport, which requires energy (Passive). Molecules will often
pass through protein channels to reach equilibrium in the cell. Sucrose, however, can’t pass
through the membrane and so water is diffused across the membrane to balance the
concentration. This is called osmosis. If a cell is hypertonic, water will enter the cell, making the
cell gain mass. If the cell is hypotonic, the cell will lose water, thus losing mass (UNM). This
concept can be seen throughout the lab.
Materials and Procedure:
In the first experiment, six pieces of dialysis tubing were put in cold water (to help active
the tubing). Next, one end of the tubing was tied off. We then obtained fifteen milliliters of
distilled water, 0.2M, 0.4M, 0.6M, 0.8M, and 1M of sucrose. In each tube, pour in fifteen
milliliter of each concentration then tie off the other end. Record the weight of each bag on the
data table. These tubes will serve as a model of a cell with the tubing being a semi-permeable
membrane. Next fill a 250mL beaker with 150mL of distilled water. Then place each bag in a
different beaker and wait for thirty minutes. Take bags out at the same time and record the
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new weight of each bag. Last, calculate the percent change in mass of each bag and record this
on the data table.
For experiment number two begin by putting one beaker of 300mL of water in a fridge.
Put another beaker of 300mL of water on a heating pad, not letting the water get to a boil. The
last beaker of water should remain out in room temperature. Next obtain six dialysis tubing and
put them in cold water for ten minutes. Take them out and tie off one end. Pour in 15mL of a
sucrose solution of 0.4 molarity into the other end of the tube, tie off the other end. Measure
and record the weight of each tube. Take out the water beakers and measure out 100mL of the
heated water in one beaker, 100mL of the room temperature water in another beaker, and
100mL of the cold water in the last beaker. Measure and record the temperature of each
beaker. Put in one dialysis tube for each beaker and wait 30 minutes. After waiting, take out the
tubes and measure and record the mass of each tube. Last, calculate the percent change in
mass. Repeat this entire experiment once more.
Data:
Mass Increases As Concentration Increases
Concentration of Sucrose (M)
0
0.2
0.4
0.6
0.8
1
% Change in Mass
1.5
6.4
8.5
16.6
17
20.5
This was the data table for experiment one showing
an increase in the change in mass as molarity
increases.
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Percent Change in Mass As Temperature Changes
Trial
Temperature (in
Mass
Mass After
Percent
degrees Celsius)
Before
(grams)
Change in
(grams)
Number 1
Number 2
Mass
10
15.62
17.92
14.7
18
15.25
18.12
18.8
65
14.92
17.67
18.4
8
15.23
17.46
14.6
20
15.35
18.07
17.7
90
15.42
18.6
20.6
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This is the data collected in experiment two. The top three temperatures were trial number one and
the bottom three were trial number two. In both trials, the percent change in mass was very different
in the cold beaker than in the other two. In Trial two, the change in mass increased as temperature
increased unlike the data in trial number one. In trial one, the probability of an outlier is high at a
temperature of 18 degrees Celsius because, in the other trial, temperature did have an effect on
change in mass.
Change in Mass (%)
25
Change in Mass Due to Osmosis as Temperature
Increases
20
15
10
5
0
0
20
40
60
80
100
Temperature of the Beaker (Celcius)
Graph 1: A graph of the results of the second experiment, this shows that there is a small
increase in the percent change in mass as temperature increases.
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Graph 2: This is a graph of the first experiment showing that, as molarity increases, the change in
mass increase.
As Molarity Increases Change in Mass Increases
Change in Mass (%)
25
20
15
10
5
0
0
0.2
0.4 Molarity
0.6
0.8
1
Results:
In experiment one, as the concentration of sucrose increased, the change in mass
increased as well. The distilled water showed the smallest change in mass at 1.5 percent
increase. At 1.0 molarity, there was a 20.5 percent increase in the percent change in mass.
When the solution in the bag had a 0.6 molarity, the change in mass was 16.6 percent. This
shows that as concentration in the cell increases, the more water will diffuse across the
membrane. In experiment two, trial one, the cold beaker showed a 14.7 percent change in
mass, and the warm water beaker showed an 18.4 percent change in mass. The room water
beaker showed an 18.4 percent change in mass making the results show no real trend.
However, trial two showed a positive correlation so there is a possibility that the data collected
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when the temperature was 18 degrees Celsius is an outlier and more repeats of this experiment
should be done. In trial two, the cold water showed a 14.6 percent change in mass. The warm
water beaker showed a 20.6 percent change in mass, and the room temperature water showed
a 17.7 percent change in mass. This trial showed that as temperature increased, the rate of
osmosis increased as well.
Discussion:
Through these experiments, we learned a lot about the permeability of the membrane.
As seen in the first experiment, the molarity of the solution will impact the rate of diffusion. As
the molarity increases the rate of osmosis (the diffusion of water) increases as well. This is
because if the concentration is higher inside the cell, water will come into the cell to dilute the
solution in an attempt to reach equilibrium, a point during which the concentration inside the
cell equals the concentration outside of the cell. In the second experiment, temperature was
seen to have no statistically significant effect on the rate of diffusion. After doing the Chi
squared test, the sum of the two temperatures compared to the room temperature was
0.90266 which was less than 3.84 (relative standard) meaning the null hypothesis is accepted.
In the second trial, there was a smaller difference of about 2.83 between chi squared and the
relative standard, however, chi squared was still less than the standard of 3.84 so the null
hypothesis was still accepted. The two trials showed different results. In trial one, the room
temperature water made the membrane less permeable than at warm water temperature. In
trial two, the warm water molecules seemed to be able to pass through the membrane easier
than the room temperature molecules. This is what was expected because, at warmer
temperatures, molecules move faster, and the faster the molecules move, the faster the rate of
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diffusion. In cold temperatures, molecules moved very slowly and therefore, couldn’t diffuse as
fast. However, when doing the chi square test, the null hypothesis was accepted, indicating that
temperature had no statistical significance on the rate of diffusion. Trial one clearly
demonstrated the null hypothesis, and even in trial two which indicated a positive correlation,
the null hypothesis still applied. According to chi squared test, the effect of temperature on the
rate of diffusion was not statistically significant.
Error Analysis:
In experiment one, the size of the tube may have influenced the rate of diffusion. At the
end of this experiment, tubes with a molarity of 0.8 or 1.0 looked about ready to burst, so
giving more space for the cell to grow may have solved the problem. The lack of space would
have led to the percent change in mass to be lower than it should have been. This problem can
be solved by using a longer dialysis tube. In experiment two, the mass of the tubes at the end
might be wrong due to the water that was on the scale. This could lead the final percent change
in mass to be higher than it should have been. To solve this, simply add a step to wipe the
water off the scale before use at the end of each weighing. We also may have mixed up the
temperature in trial one so the data may actually have shown an increase in the percent change
in mass as temperature increased. More trials should be done to determine if there is an actual
correlation.
Conclusion:
These experiments supported the hypothesis that concentration of the solution in the
cell will influence the rate of diffusion. The results show that the higher the concentration in a
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cell, the more water will diffuse across the membrane to reach equilibrium. This also shows
that water will be drawn to a hypertonic cell or out of a hypotonic cell. Temperature was
determined to have no statistical significance on the rate of diffusion. To further test the effects
of temperature on the rate of diffusion, repeat the experiment, but make change both the cell
and the outside temperature. This should better illustrate the effects of temperature on the
rate of diffusion. To better explain osmosis one could change the pressure applied to the cell,
repeating the experiment, keeping temperature constant throughout.
Chi Squared For Trial Number One:
Temperature Observed Expected (0-e)^2/ e
Cold water
14.7
18.8
0.8941
Warm Water
18.4
18.8
0.008511
0.90266˂3.84 (Null hyp.
Accepted when compared to
room temperature)
Chi Squared For Trial Number two:
Temperature Observed Expected (o-e)^2/e
Cold water
14.6
17.7 0.542938
Warm water
20.6
17.7 0.475141
1.01801˂3.84 Null Hypothesis Accepted
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Citations:
"Passive Transport - Taking the Easy Road." Biology4Kids.com: Cell Function: Passive Transport. N.p., n.d.
Web. 09 Dec. 2014.
"UNM Biology Undergraduate Labs." Untitled 1. N.p., n.d. Web. 09 Dec. 2014.