DCP A1:
Raw Data
See Attachment
DCP A2:
Processed Data
A.
Distilled
Water
0.2 M
0.4 M
0.6 M
0.8 M
1.0 M
Percent Change in Mass of Potato Cores (%)
(Osmosis Part A)
Group 1 Group 2 Group 3 Group 4 Group 5
Class
(Period 4)
(Period 4)
(Period 4)
(Period 6)
(Period 6)
Average
18.9
13.8
20.0
7.2
15.0
5.7
6.3
-2.2
-25.9
-17.9
7.5
13.0
-21.6
-21.2
-27.4
-32.7%
11.1
-3.7
-30.9
-25.5
-30.2
9.9
0.0
-13.9
-25.6
-30.7
Expected
Values
21.4
8.5
3.9
-22.0
-24.0
-27.0
Sample Equation (Group 1: Distilled Water)
Percent Change in Mass = Final Mass – Initial Mass x 100
Initial Mass
Percent Change in Mass = 17.0 g –14.3g x 100
17.0g
Percent Change in Mass = .1888 x 100
Percent Change in Mass = 18. %
See graphs for Percent Change in Mass of Potato Cores on attachment
6.9
-4.5
-12.8
-23.0
-23.5
B. Onion Cell (Osmosis Part B)
Onion Cell Flushed with distilled water
Onion Cells Flushed with salt water
Percent change in Mass of Dialysis Bag (%)
(Osmosis Part C)
Group 1 Group 2 Group 3 Group 4 Group 5
C.
Distilled
Water
-4.2*
0.0
0.2 M
0.4 M
0.6 M
0.8 M
1.0 M
0.0
7.7
9.1
10.7
14.8
4.0
8
6.8
11.1
19.1
0.0
-1.2
Class
Average
-2.6*
4.4
8.6
11.3
16.0
8.2
8.2
*Possible error
1.53
11.1
16.0
20.0
3.3
8.9
9.2
13.5
14.8
-
Expected
Values
1.2
3.1
7.7
11.0
14.8
18.2
Sample Equation (Group 1: Distilled Water
Percent Change in Mass = Final Mass – Initial Mass x 100
Initial Mass
Percent Change in Mass = 24.0 g –25.0g x 100
25.0g
Percent Change in Mass = -0.0416 x 100
Percent Change in Mass = -4.2%
See Attachment for Percent change in Mass of Dialysis Bag graphs
D.
Initial
Contents
Bag
15% Glucose
& 1% starch
Beaker
H2O + IKI
Glucose and Starch Diffusion
(Diffusion Part D)
Solution Color
Initial
Final
Orange
Purple
Amber
Amber
Presence of Glucose
Initial
Final
Yes
Yes
No
Yes
DCP A3:
Presenting Processed Data
A. Percent Change in Mass of Potato Cores
The data acquired in the experiment showed a constant decrease in the mass of the potato
cores as the molarity of the solution in the beaker increased. In the distilled water the
potatoes showed an average mass change of 15% between the four groups; and in the 1M
solution, the potatoes showed a mass change of –27.0%. In the distilled water to the .4M
solution the potatoes were displaying a positive mass change, but in the .6M to the 1M
solution the potatoes had negative mass changes. As compared to the expected values
provided in class, our class averages we, in most cases, not close to those expected. Only
in the .8M solution did we have a value of –24.0 which was close to the given –23.0%,
and the .2M solution which showed 8.5% mass change when 6.9% change was expected.
Our class data showed a gain in mass for the distilled water, .2M, and .4M and a loss of
mass for the remaining three; when the expected values showed a gain in mass for the
distilled water and .2M only, and a loss in mass for the remaining four.
B. Osmosis in onion cell
Under our microscope we notices that the cells flushed with distilled water had a
membrane that fully expanded to the cell wall. But when flushed with salt water the cell
membrane shrank like a raisin to a grape, and did not fill up the entire shape the cell wall
provided.
C. Percent Change in Mass of Dialysis Bag
In the testing of the effect of the different molarity solutions on the passage of molecules
through the dialysis bag, we found that the higher the molarity of the solution the increase
in the change in mass. There was one error in the data, in the testing of the dialysis bag in
the distilled water there was a mass change of –4.2%, compared to the expected value of
1.2% and the other readings of 0%. This means that there was most likely a hole in the
bag allowing the loss off water from inside the bag. All of our class averages for this
potion of the experiment were very close to the expected values for the most part. The
.1M solution gained 3.3% compared to the expected value of 3.1%, the .2M solution
gained 8.9 compared to the expected value of 7.7%. The .8M solution was not very close
to the expected value of 18.2%; our data showed a gain of 14.8%.
D. Glucose and Starch Diffusion
In this potion of the experiment we our data shows that the selectively permeable
membrane of the dialysis bag only let the glucose diffuse into the beaker. The final
testing of the beaker showed no presence of starch as it did glucose. The final color of the
bag was purple which told us that the IKI had diffused from the beaker into the dialysis
bag.
CE A1:
Conclusion
A. Percent Change in Mass of Potato Cores
In testing the mass change of the potatoes left overnight in various solutions of different
molarities of sucrose, our data showed that as the molarity of the solution increased, the
mass of the potatoes decreased. Our values showed that the potatoes left in the distilled
water had an increase of mass by 15%, the potatoes n the 0.2M solution had an increase
of 8.5%, in the .4M solution a 3.9% change. After the .4M solution we began to see that
the potatoes we losing mass. The .6M lost 22%, the .8M lost 24%, and the 1.0M lost
27%. In the trials with distilled water, 0.2M and 0.4M showed an increase in mass
meaning the solution was diffusing into the potato in attempts to reach an isotonic state.
In our expected value the potatoes lost mass after more than a 0.2M concentration, but in
out class average began to lose mass after more than a .4 concentration. This told us that
the potato must have a 0.3M-0.5M concentration of sucrose.
B. Osmosis in onion cell
In the onion cell we saw the occurrence of plasmolysis as well osmosis. As we flushed
the cell with water, placing it in a hypotonic solution, the cells membranes each filled the
cell wall completely because the water moved into them. When we flushed the cells with
sate water creating a hypertonic environment, the water in the cells moved out in order to
balance out the higher and lower concentrations, thus demonstrating plasmolysis. When
the cell’s water was transferred into the solution the cell membranes appeared to
shrinking because of the absence of the extra water.
C. Percent Change in Mass of Dialysis Bag
In part C of this lab, we filled dialysis bags with various concentrations of sucrose, and
places them in distilled water. Our class data showed and increase as the expected values
showed. In testing the distilled water in distilled water we found that an error had
occurred due to the relatively high loss in mass, where in a solution of water placed in
water should have little to no diffusion. In the experiment we found that the increase of
mass in the bad was due to the fact that water was flowing into the bag to create an
isotonic solution. In the 0.2M solution, our class had an average mass gain of 3.3%, the
0.4M solution gained 8.9%, the 0.6M solution gained 9.2%, the 0.8M solution gained
13.5%, and finally the 1.0M solution gained 14.8%. With a higher concentration in the
bag, we saw a increase in the amount of water that flowed into the bag, therefore an
increase in the change in mass.
D. Glucose and Starch Diffusion
In part D, we placed a dialysis-tubing bag filled with 15% glucose and 1%starch into a
beaker containing water and iodine (IKI) for half an hour. As the bag sat in the solution
we began to see the bag was turning purple. This color change was due to diffusion. The
dialysis tubing did not let the starch pass through the bad to the beaker, but did allow the
IKI to flow into the bag. As the starch and the IKI combined the purple color was
displayed. As the IKI flowed into the bag, the glucose flowed out. We know this because
the initial testing for glucose I the beaker was negative and the final testing was positive.
CE A2:
Limitations & Weaknesses
In our experiments there were many factors that enabled us from having completely
accurate data. In class we only had time to do one trail, and we had to break up each part
into different groups. Therefore the was only one trail do by one group, so if a mistake
occurred we would have no real way of knowing and the entire class data would have
been effected. We also did not have access to measuring utensils that were accurate to
more than the tenths value, and had to share solutions, which could have lead to
unintentional cross contamination. Weaknesses in the experiment arose mainly from the
carelessness of measuring the proper amounts of solutions, when students “eyeballed” the
proper amount instead of using the graduated cylinders and beakers. Another weakness
could be seen in the tying of the dialysis tubing in order to create the bag, if the bag
wasn’t tied properly we could experience unknown leaking, and have outliers in the data
like the –4.2% mass change in part c of the lab.
CE 3:
Improving the Investigation
Improving these errors and limitations could include a dialysis tube that has already been
closed on one end to prevent a higher chance of leakage. With more time I think more
trials would have been able to be done by different groups; thus eliminating such a high
risk of mistake throwing off the entire set of data. To eliminate the sharing of solutions,
the bigger containers of solutions could have be divided up and placed in separate areas,
eliminating the chance of a new solution being measured with a utensil that had been
previously used with another solution. With more accurate scales and measurement tools,
the lab could have been more precise, and allowed room for more significant figures.