Because the methylene blue on the gelatin with the

because the methylene blue on the gelatin with the higher weight diffused
faster and further down and by doing this experiment. Another important
thing that I learned what is the correlation of cell size with diffusion rate And
how the surface area to volume ratio directly affects diffusion time.
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Diffusion and Osmosis

EXPERIMENT 2: DIFFUSION CONCENTRATION GRADIENTS
AND MEMBRANE PERMEABILITY
Data Tables
Table 2: Indicator Reagent Data
Indicator Starch Positive
Starch
Negative
Glucose
Positive
Glucose
Negative
Glucose Test
Strip
n/a n/a Lime green
Yellow/didn’t
change color
IKI Solution Greenish black Orange brown n/a n/a
Table 3: Diffusion of Starch and Glucose Over Time
Indicator
Dialysis Bag After 60
Minutes
Beaker Water After 60
Minutes
Glucose Test Strip
Lime green Yellow/didn’t change color
IKI
Greenish black
Orange brown
Post-Lab Questions
1. State your hypothesis.
I hypothesize that when starch is exposed to iodine potassium iodide the solution will
change to a dark green color.
13. Why is it necessary to have positive and negative controls in this experiment?
It is very important to have positive and negative controls in this experiment to have
them as a baseline for comparison and contrasting the results of the experiment.
14. Draw a diagram of the experimental set-up. Use arrows to depict the movement of each
substance in the dialysis bag and the beaker.
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Diffusion and Osmosis

15. Which substance(s) crossed the dialysis membrane? Support your response with data-
based evidence.
None of the substances crossed through the dialysis tubing. Because the water in the
beaker tested negative for both glucose and starch
16. Which molecules remained inside of the dialysis bag?
Both the glucose and starch solution
17.
Did all of the molecules diffuse out of the bag into the beaker? Why or why not?
None of the molecules diffused out of the bag, it’s because of the cell size of starch that
it did not diffuse.
Reflection (Discuss what you have learned by doing this experiment. How have your ideas
changed? Do you have any new questions? What connections did you make between the lab
and lecture?):
I learned about diffusion and I learned about the functions of a dialysis tubing. I also learned
about using different solutions to test for the presence of certain other substances such as
using glucose test strips to detect the presence of glucose and to use iodine potassium
iodide to test for the presence of starch. I learned about diffusion through dialysis Tubing.
However, I must mention that upon researching online, im not sure if my glucose was
supposed to stay in the dialysis tubing or not, but upon giving it over an hour and testing
multiple time the beaker water still did not test positive for glucose. If you could please
explain this for me professor, I would highly appreciate it thank you!