Lipid Written Signature Assignment v5.8

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University Of Arizona *

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Feb 20, 2024

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Chemical Thinking Lipid Written Signature Assignment v5.8| 1 CHEM 151 LWSA v5.8 6-3-23 Lipid Written Signature Assignment Your name: Your email: Your lab partner’s name (s): Your lab partner’s email (s): Your lab instructor’s name: Your lab section: 1. Overall Project Goal (1 pt) . In complete, well-written sentence(s), summarize in your own words the overall goal(s) for the Lipid Project . The overall goals of the lipid project are to explore the solubility of major food components and then use the results to isolate a practice snack food, as well as to learn how to use the iodine test to ensure that the isolated fat is free from starch. Then, write a plan to separate the fat of an unknown snack food while running a control to calculate a isolation control factor. Re-run the iodine test and with the results calculate a fat percentage weight for the unknown snack food. Then write a new plan to run 2 concurrent runs of the same values at the same time with a single control and include how you would calculate the average percent fat weight of the 2 runs. Finally, carry out the plan, determine a new isolation correction factor, calculate the percentage fat weight of both runs, and calculate an average percentage fat weight for both. 2. Implementing Group Proposal 2: Raw Data, Observations and Results (5 pts). Complete Table 8 , which gathers the supporting raw data for your two (2) replicate assigned snack food runs and the concurrent oil control run. Then finish Table 9 . Table 8. Assigned Snack Food (QF6) Replicate Lipid Quantitation Raw Data Assigned Snack Food (Unknown) Mass (finely ground) Volume of Cyclohexane Volume of NaCl Beaker “ 1 ” Mass (m beaker 1 ) Unknown Isolate + Beaker “1” Mass (m 1 ) 0.75 g 2.5ml 2.5 ml 77.238 g 77.988 g 0.75 g 2.5ml 2.5 ml 71.333 g 72.083 g Vegetable Oil (Control) Mass Volume of Cyclohexane Volume of NaCl Beaker 2 Mass (m beaker 2 ) Control Isolate + Beaker 2 Mass (m 2 ) 0.251 g 2.5 ml 2.5 ml 108.338 g 108.589 g Table 9. Assigned Snack Food (QF6) Replicate Lipid Quantitation Results and Observations Assigned Snack Food (Unknown) Unknown Isolate Mass (m ULI ) Observations 0.317 g This value is significantly smaller than the second run 0.390 g This value is significantly bigger than the first run All work must be very neat and organized . If you need to collect your thoughts, please use a separate sheet of paper. Written Signature Assignments are an individual effort for sections 4 - 8 of the present document (while sections 1 - 3 are a group effort). Please individually submit your completed document to the lab Lipid Written Signature Assignment D2L DropBox folder before the scheduled end of lab. Always check to confirm the correct document/file has imported to the correct lab D2L Dropbox folder – no excuses. Submission to an incorrect Dropbox folder will be subject to a 1-point penalty. If you submit an unintended document, or need to update a submission, you can always resubmit so long as you are not past the deadline . If you submit the wrong document and fail to realize this until after the deadline, a resubmission cannot be accepted. So please be careful and always double check!

Chemical Thinking Lipid Written Signature Assignment v5.8| 2 CHEM 151 LWSA v5.8 6-3-23 Vegetable Oil (Control) Control Isolate Mass (m CLI ) Observations 0.174 g This is a smaller value than we got during the second session meaning the experiment was most likely run better last session

Chemical Thinking Lipid Written Signature Assignment v5.8| 3 CHEM 151 LWSA v5.8 6-3-23 3. Implementing Group Proposal 2: Starch Test Results (3 pts) . In the space below, clearly report in complete well-written sentences the iodine-potassium iodide (I 2 -KI) test observations and results for the isolated lipids (of Table 8 ) and the positive and negative test controls concurrently run . The first run of the two concurrent unknown snack runs had a negative test for starch when we put a drop of iodine in the lipid. The drop of iodine turned a reddish orange with no black meaning that there was no starch in the lipid. The second run had the same result, but the drop of iodide stayed more orange than it did in the first run, but because no starch was present the drop of iodine did not turn black. Parts 4 - 8 (the sections below) are strictly an independent (individual) effort. Sorry, no group work! 4. Assigned Snack Food Isolation Correction Factor (3 pts) . Present in a well-organized manner and in complete detail the isolation correction factor for your assigned snack food based only on Tables 8 and 9 . Clearly state symbolically the equation(s) being used, then substitute in actual values, and finally give the results . Mass oil control (original) = 0.251 g Control lipid Isolate Mass = 0.174 g Fc = Mass oil control (original) / Control Lipid Isolate Mass Fc = 0.25 g / 0.174 g = 1.4368 5. Replicate Runs: Assigned Snack Food Percent Fat by Weight (4 pts) . Show the percent fat by weight calculations for your assigned snack food replicate (repeat) runs in a highly organized manner and in complete detail based only on the values from Tables 8 and 9 . Clearly state symbolically, at least once, the equation(s) being used, then present separate calculations for each replicate run . Mass of lipid = Fc * Unknown lipid Isolate mass Mass of lipid (run 1) = 1.4368 * 0.317 g = 0.455 g Mass of lipid (run 2) = 1.4368 * 0.390 g = 0.560 g Percentage fat by weight = Mass of lipid/ Mass of Snack food * 100% Percentage fat by weight (run 1) = 0.455 g / 0.75 g * 100% = 60.667 % Percentage fat by weight (run 2) = 0.560 g / 0.75 g * 100% = 74.667%

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Chemical Thinking Lipid Written Signature Assignment v5.8| 4 CHEM 151 LWSA v5.8 6-3-23 6. Assigned Snack Food Average Percent Fat by Weight (3 pts) . Present your calculation to determine the average percent fat by weight for the assigned snack food based solely on the above Group Proposal 2 results. Again, to receive credit, the presentation must be very well-organized, highly legible and in complete detail – sloppy work will receive a “zero . ” First write an appropriate equation symbolically, then substitute in values and show the results . Percentage fat by weight (run 1) = 60.667 % Percentage fat by weight (run 2) = 74.667% Average percent fat by weight = (Percentage fat by weight (run 1) + Percentage fat weight (run 2)) / 2 Average percent fat by weight = 60.667 % + 74.667% / 2 = 67.667 % 7. Reflection 1 (3 pts) . In complete, well-written sentences, discuss your confidence in the results, and methods by which the reliability of the experiment/analysis could be improved (further procedural modifications that could be taken to improve the confidence in the resulting data ). I am not totally confident in the end results of the experiment/analysis due to our isolation control factor value. I can be confident that both of our lipids were isolated and free of starch, but we seemed to have lost a lot of our control lipid from either burning it off or not isolating the lipid good enough which could have affected our results.. This could have been human error through pipetting off the top layer of cyclohexane and lipid after going through the centrifuge or adding to much or to little of either cyclohexane or aqueous solution (NaCl). Or it may be because our chosen aqueous solution doesn’t separate our lipid as good as we would like it to. To better improve the reliability of the experiment and improve the confidence of the results, we could retest all the aqueous solutions and redo the experiment with a different aqueous solution to see whether our results turn out better. To try to reduce human error, we can try to pipette off more of the cyclohexane/lipid layer than we did to try to make our Fc closer to one. When preparing the experiment, we can use a more accurate measurement tool than the micropipette to prepare our centrifuge tubes to get a more accurate measurement.

Chemical Thinking Lipid Written Signature Assignment v5.8| 5 CHEM 151 LWSA v5.8 6-3-23 8. Reflection 2 (3 pts) . In complete, well-written sentences, indicate the important experimental design concepts you experienced/learned through this Project . The important experimental design concepts I learned/experienced while doing this project, were how to use lipid isolation techniques through using the centrifuge and the hotplates to determine the fat percentage of a unknown snack. I learned the importance of analyzing the isolating capabilities of different aqueous solutions, and choosing which aqueous solution isolates the best. I learned experimental uses of a hot plate, as well as the experimental uses and how to use a centrifuge. I also learned the uses of running a control with your experiments to determine the error of your results to try to cancel the error using a control factor on your results. Lastly, I learned how to use an iodine test, and its practical uses of determining whether a mixture contains starch.