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Diffusion and Osmosis Lab

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Sarah Kohl

on 3 January 2013

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Transcript of Diffusion and Osmosis Lab

Diffusion is
da bomb Osmosis is a
kool cat Diffusion and Osmosis Lab By Katrina Wheelan, Sarah Kohl, and Katie Aman Conclusion Experiment One:
Our conclusion of Experiment One was that the medium agar block had the most rapid diffusion rate of the HCl. The small and large agar blocks had the same rate of diffusion. But the difference between all three of the blocks was minuscule and factoring in errors leads to a possibility that there was no cylinder block in particular that the solution diffused through the fastest. These results did not directly support our hypothesis. In all three experiments, we may have had both measurement and random error. In the first experiment, our measurement of the agar "cells" may have been off by about ±0.1 cm. The mass measurements in all three experiments could have been off by ±0.5 grams. The timing involved in the experiments likely had an uncertainty of roughly ±0.05 seconds and may have been set off even further by the fact we physically couldn't pull all the cells out of the solution at the exact second needed. The volumes of the solution probably had an uncertainty of ±0.5 ml. Diffusion and Osmosis Lab Conclusions and Discussion Mistakes and Experimental Errors Results By Katrina Wheelan, Katie Aman, and Sarah Kohl Introduction The objective of this project was to show how diffusion of solutions and osmosis affect living cells. Diffusion is the movement of solutes from an area of high concentration to low concentration and does not require energy input by cells. Osmosis is the movement of water through membranes. Water moves from areas of high potential (high free water concentration) to low solute concentration (low free water concentration). First Experiment Hypothesis Our hypothesis was that cells with a larger surface area to volume ratio are more efficient with diffusion because there is more surface area to absorb the solute with a smaller volume to diffuse into. More solutes enter the cell with a large surface area to volume ratio. Second Experiment Hypothesis We thought that the correlation between the amount of time spent in distilled water and diffusion of water and glucose through a cellular membrane was linear and negative. We thought that the longer the cell spends in a solution, the more the solution diffuses through the membrane. Third Experiment Hypothesis We thought that the potato cells in the hypertonic solutions would become limp and flaccid and the ones in hypotonic solutions would be rigid and turgid. We thought the one mole of sucrose was going to make the cells flaccid (lose mass) while the distilled water would make the cells turgid (gain mass). First Experiment Background In the first experiment, we tested how fast artificial cells made of agar diffused a solution based on the surface area to volume ratio. The agar was infused with phenolphthalein and NaOH. When phenolphthalein is mixed with a base, it turns pink. We then put it in a solution with HCl. As the acid diffused through the cell, the agar became clear. We tried to use the same amount of HCl with each solution and we used the same shape (cylinder) for each block. We timed how long it took for the acid to completely diffuse through the "cell". Lab question: If you put each of the blocks into a solution, into which block would that solution diffuse throughout the entire block fastest? Slowest? Second Experiment Background In this experiment, we wanted to determine the relationship between time and the amount of solution diffused (measuring change of mass). We used dialysis tubing to simulate a cell's selectively permeable membrane. We had 1 mole of glucose within the cell and then measured the mass. We then put 4 artificial cells in distilled water for periods of 0, 5, 10, 15, and 20 minutes. We then measured the mass again. We also used a glucose indicator to check the distilled water for glucose after each set amount of time. We used the same amount of glucose for the interior of each "cell" as well as the same amount of distilled water. We created this experiment to answer our question whether glucose moved out of the membrane and also to graph the diffusion process. Lab question: What is the correlation between time and the diffusion of the glucose solution? Third Experiment Background We wanted to determine the concentration of sucrose in various solutions by determining how much of the solution diffused in the potato cell by measuring the mass at the conclusion of the experiment and comparing it to the mass of the potato before it was put in the solutions. We kept the amount of time spent in the solution constant. We also kept the amount of each solution the same on the outside of the potato. Lab question: What changes do you expect to see when potatoes are exposed to different concentrations of sucrose? What is the concentration of sucrose within the potato? What are the molar concentrations of sucrose in the different solutions? Like a majestic dolphin! Materials Experiment 1 2% Agar containing NaOh and phenolphthalein
1% Phenolphthalein solution
0.1 M HCl
0.1 M NaOH
Plastic knife
Metric Rulers
Cup and test tubes Experiment 2 Distilled water
1 M sucrose
1 M NaCl
1 M glucose
5% ovalbumin
20 cm-long dialysis tubing
Scales Experiment 3 Potatoes
Cork borers
Metric rulers
Color-coded sucrose solutions of different, but unlabeled, concentrations prepared by teacher Along with uncontrollable factors of any experiment (temperature, location of each beaker, etc.), there was also more specific random error associated with each of the experiments. Random Error The first experiment specifically was affected by the cube from which the agar was cut. The "cell" with the medium surface area to volume ratio diffused the fastest, but also was cut from a different cube of agar. The cubes may have been poured at a different point or have contained a different phenolphthalein concentration, which would have affected the diffusion rate. The second experiment was greatly affected by how well the knots were tied on the dialysis tubing. Any of the artificial cells with poorly tied knots may have leaked and lost mass not due to diffusion or osmosis. The trial that we left in the distilled water for fifteen minutes had a "cell" that lost a great amount of mass due to leakage rather than the diffusion we were testing. It was also difficult to dry off the strings (which were not all the same lengths) and the dialysis tubing. The third and final experiment may have been affected by a variance in the potato pieces used. They may have varied in size, density, sucrose concentration, and in many other significant aspects. The added factors of the possible variance would have affected the diffusion rate of the sucrose and the mass of the potato pieces. Experiment Three Results Experiment One Results: Experiment Two Results Various Measures of Three Artificial Agar Cells Rate of Glucose Diffusion Through Artificial Cells Calculated Sucrose Concentrations Based on % Mass Change Conclusion Experiment Two:
Our conclusion to Experiment Two was that the glucose did diffuse through the artificial cell membrane. This does support our original hypothesis. At first the mass of the "cell" increased, perhaps due to immediate osmosis. But then the mass began to decrease because of the diffusion of the glucose through the membrane. At the 15 minute mark we got a very small mass due to a leaking "cell" but the other data were accurate enough to reach a conclusion. Conclusion Experiment Three:
Our conclusion to Experiment Three was that the cell with one mole of sucrose became flaccid (lost mass) and the cell with distilled water become turgid (gained mass). We also found the molar concentration for the substances that we wanted to find out:
Red: .98; Hypertonic Solution
Orange: .81; Hypertonic Solution
Yellow: .64; Hypertonic Solution
Green: .27; This was an isotonic solution (no diffusion) so we were able to conclude that the potato had a molar concentration of .27.
Blue: .17; Hypotonic Solution Thanks for WATCHING our PREZI!
We hope you enjoyed it. Questions? Comments? Just ask! Water is all around us!
If you are in water for long enough, like at a pool, your skin becomes wrinkled. This is due to osmosis; water enters your cells because you're in a hypotonic solution and this makes your cells swell. This appears to us as wrinkled and swollen skin. Volume= 3.14r^2*h Surface Area = 2(3.14)r^2 + 2(3.14r)*h Diffusion Efficiency = Volume (cm^3)/Time (seconds) % Change in mass (grams) = (final - initial)/initial * 100 Change in Mass = final-initial (grams) % Change in mass (grams) = (final - initial)/initial * 100 Change in Mass = final-initial (grams) Molar Concentration = (4/15) - (1/60)*(% change in mass)
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