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. ©eScience Labs, LLC 2018 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. ©eScience Labs, LLC 2018 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!
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