Lab Report
Diffusion and Osmosis
Abstract
The process of diffusion and osmosis was examined by studying various topics: water
potential, pressure potential, and osmotic potential. Dialysis tubing was used to represent a cell
model. The data that was collected concluded that at all molar concentrations, the mass in the
dialysis tubing increased. For part 2 of the lab, a real cell system, the potato core, was used to
observe water potential. By submerging potato cores into different molar concentrations of
sucrose, the mass difference was observed. As the molar concentration in sucrose increase, the
mass of the potato cores decreased.
Introduction
The objective of this experiment is to calculate the difference in mass when a potato
cylinder is submerged in sucrose distilled-water. We predict the cylinders will lose about 10% of
it initial mass over the course of day when submerge in the sucrose distilled-water.
Methods
This study was conducted in room 403 of New Tech High @ Coppell through the weeks
of September 4th and September 11th. The work and experimentation was divided evenly
between six, four person groups, and consisted of two parts.
In part one, we filled dialysis tubing with different sucrose solutions, weighed them, and
then placed them in a beaker of tap water. We waited twenty minutes, took out the tubes, and
weighed them again. We then found the percent change in mass of the different sucrose
solutions. In part two, we weighed cylinders of potatoes, and then placed them in different
sucrose solutions. We waited one day, then removed the cylinders. In part two we not only
found the percent change in mass, but also measured the temperature.
Results
Dialysis Bags
Contents of
Beaker
Initial
Mass
Final
Mass
Mass
Difference
% Change
in Mass
0.0M Surcose
10.08
10.88
0.80
7.94%
0.2M Surcose
17.07
18.16
1.09
6.39%
0.4M Surcose
14.03
15.68
1.65
11.76%
0.6M Surcose
16.41
20.11
3.70
22.55%
0.8M Surcose
13.55
16.88
1.33
9.82%
1.0M Surcose
15.86
20.21
4.35
Group Dialysis Bag
Contents of Beaker
% Change in Mass
0.0M Surcose
15.89%
0.2M Surcose
14.03%
0.4M Surcose
3.38%
0.6M Surcose
40.26%
0.8M Surcose
10.72%
1.0M Surcose
27.72%
27.43%
Potato Core Individual/Group
Contents of
Beaker
Temperature
Initial Mass
Final Mass
Mass
Difference
0.0M Surcose
0.2M Surcose 25 degrees
celsius
% Change in
Mass
19.06%
7.04
6.99
-0.05
-0.71%
0.4M Surcose
-25%
0.6M Surcose
-25.7%
0.8M Surcose
-46.7%
1.0M Surcose
-52.68%
Calculations:
= -iCRT
= -(1)(-0.71)(0.0831)(25+273)
= (0.71)(0.0831)(298)
= (0.059)(298)
= 17.582
Discussion
We can conclude there was more of an increase in mass the more sucrose there was in
the solution in the dialysis bag. We can come to this conclusion because from the results the
more sucrose that was in the solution in the dialysis bag the more the mass increased.
If a potato was allowed to dehydrate in open air the water potential would decrease. It
would decrease because both pressure potential and osmotic potential both would decrease.
The water is slowly coming out of the potato, that is hypertonic, and into the surrounding area
that is hypotonic. Water always moves from hypertoinc to hypotonic. The potato has less water
potential.
The cell must be hypotonic. If the water potential is more in the surrounding area of the
cell it means that the surrounding area is hypertonic making the cell hypotonic. In order for it to
be isotonic the surrounding area must have the same water potential. If water potential is not
the same pressure must be applied in order to create an isotonic environment.
We could use a lab to find out how much sugar is in the apple. We could say this apple
should have a certain amount per volumes of water. Like the potato if the apple loses mass is
means it had more sugar than we though. If the apple gains mass it means it took more sugar in
and had less than we had previously thought.
Conclusion
The potato cylinders submerged in the 0.2 Sucrose Water lost 6.39% of its initial mass
during the experiment. We predicted the cylinders would lost 10% of its initial mass. We had a
close but not correct hypothesis. Better and more accurate measurements (mass) could be
used in future experiments.