1
Chemistry L304 Laboratory
Instructor: Dr. Sally S. Hunnicutt
Textbook: D. P. Shoemaker, C. W. Garland, and J. W. Nibler Experiments in Physical Chemistry 6th Edition McGraw-Hill: New York, 1996.
Table of Contents
Table of Contents......
Introduction......
SAFETY!......
Table of Experiments......
Lab Schedule......
Lab Notebooks......
Formal Lab Report Format......
Grading......
Error and Uncertainty......
Propagation of Error......
Modeling Data Sets: A Basic Introduction to Linear Regression......
Least Squares Analysis in Microsoft Excel......
Introduction
Chemistry is an experimental science. It is impossible to learn chemistry without doing experiments. This is especially true for physical chemistry. You will complete 9 labs covering a wide range of topics including thermodynamics, statistical thermodynamics, transport phenomena, calorimetry, electrochemistry, kinetics, spectroscopy, and quantum mechanics. You will use a variety of techniques and apparatus. Due to equipment limitations, the experiments do not follow the lecture sequence. Use your textbook and the lab manual to prepare for the labs, especially those labs that are out of sequence with the lecture.
The goal of every good physical chemistry experiment is to collect data and model the data based on theory. No physical chemistry experiment is complete without both data collection and data modeling. In addition, I hope you achieve these additional objectives upon completion of the Physical Chemistry Laboratory class:
1. how to "investigate" in the physical chemistry laboratory;
2. how to keep a lab notebook;
3. how to write a formal lab report;
4. how to analyze data and evaluate error.
Chemistry 304 Laboratory is a full, two-semester course condensed to 10 weeks; it is also a writing intensive course. Formal lab reports and data analysis may take 20 hours to complete. If you are taking this lab class and the physical chemistry lecture course at the same time, I strongly urge you to do nothing else (no job or other classwork). Under no circumstances should you work a full time job while taking this class!
SAFETY!
1. Wear safety glasses or goggles at all times in the laboratory. No contact lenses in the lab.
2. Dispose of waste in appropriately marked waste containers.
3. Dispose of glass in broken glass boxes.
4. Thoroughly clean glassware, balances, and your lab station before leaving lab.
5. Wear appropriate clothes: long pants, shoes (not sandals), fitted, comfortable clothes.
6. Immediately report spills and accidents to the laboratory instructor.
7. Describe hazards specific to each experiment in your lab notebook.
8. Use common sense; work slowly; be prepared for lab; and THINK before acting.
Safety References:
1. H.A.J. Pieters and J.W. Creighton, Safety in the Chemical Laboratory, Butterworth, 1951;
2. G.D. Muir, Hazards in the Chemical Laboratory, 2nd Edition, The Chemical Society, London, 1977;
3. Prudent Practices for Handling Hazardous Chemicals in Laboratories, National Academy Press, Washington, D.C., 1981;
4. Prudent Practices for Handling Hazardous Chemicals in Laboratories, National Academy Press, Washington, D.C., 1983. 5. N.I. Sax, Handbook of Dangerous Materials, Reinhold, 1951;
5. Merck Index, 10th Edition, Merck and Co., In,., Rahway, M.J., 1983;
6.Aldrich Chemical Catalog.
Table of Experiments
Experiment Title / Source / Report / AuthorRubber Elasticity / handout / Y / class
Infrared Spectroscopy of HCl/DCl / SGN / Y / each partner
Heat Capacity Ratio for Gases / SGN / Y / each partner
Intrinsic Viscosity of a Polymer / SGN / N
Heats of Combustion / SGN / N / each partner
Iodine Clock Kinetics & Literature Search / SGN / Y
Laser Photooxidative Chemistry of Diphenylisobenzofuran / handout / N / each partner
ab initio Infrared Frequencies of Water / handout / N
NMR Spectroscopy and Determination of Keto-Enol Equilibrium Constants / handout, SGN / N
SGN: Shoemaker, Garland and Nibler, Experiments in Physical Chemistry, 6th edition.
See page 6 of this document for more information about the literature search.
Lab Schedule
In the table G1, G2, etc. refer to a pair of lab partners. You and your lab partner will be assigned a group number. Most labs are scheduled for three days. Most labs require one or two days; extra time is built into the schedule so that you can collect and analyze the data and write a rough draft before beginning a new lab. You may start a lab late (if both partners agree and you get my OK) in order to catch up on report writing. Seven different experiments run simultaneously. Be patient, especially early in the semester when you need the most help. Come to the lab prepared to do the experiment! Be aware of other experiments occurring nearby; observe how they work so you are better prepared to do each experiment.
start / end / HClDCl / Cp/Cv / polymer
visc. / bomb calorimetry / iodine clock kinetics / photo-
chemistry / calcs / NMR / rubber
band / due
6/9 / 6/10 / all / 6/16
6/14 / 6/24 / G7 / G8 / G2 / G6 / G3,G4 / G1 / G5,G9 / 6/30
6/17 / 6/24 / G8 / G7 / G9 / G5 / G1,G2 / G6 / G3,G4 / 6/30
6/28 / 7/1 / G3 / G4 / G6 / G7 / G5,G9 / G8 / G1,G2 / 7/8
7/7 / 7/12 / G1 / G2 / G7,G8 / G3 / G6 / G4,G9 / G5 / 7/19
7/14 / 7/19 / G9 / G1 / G2 / G7,G8 / G3,G5 / G4 / G6 / 7/24
7/21 / 7/26 / G4 / G6 / G5 / G9 / G1,G2 / G3 / G7,G8 / 8/2
7/28 / 8/2 / G5,G6 / G3 / G1,G4 / G8 / G7 / G2,G9 / 8/9
8/4 / 8/5 / G2 / G5,G9 / G3 / G1,G4 / G6,G8 / G7 / 8/11
Guidelines and Report Submission Policy
Everyone works with a partner; you keep the same partners for the semester. You prepare for and carry out the experiments as a pair; you work up the data and verbally discuss the results as a pair. However, you must write the lab reports individually. Each pair is assigned one lab schedule. Formal reports are due one week after the experiment was finished. Late labs will lose 2 points for one day late, 4 points for 2 days late, 8 points for three days late, 16 points for four days late, and 32 points for 5 days late. Lab reports that are 6 or more days late will not be accepted. Points lost due to lateness cannot be made up if rewritten and regraded.
Photocopies of lab notebook pages are due one week after the experiment was finished. Late notebook pages lose points the same way as formal reports. Lab notebook pages that are handed in 6 or more days late will not be accepted. There is no grace period. Photocopied lab notebook pages are assigned a numerical grade only for those labs that do not require a formal lab report. However, photocopied lab notebook pages must be handed in for every experiment. Formal lab reports are not complete unless the notebook pages are included (i.e., late or missing notebook pages make the report late).
Rewrites for graded labs are due 2 weeks after the graded lab has been returned. Turn in the original lab and the corrected lab. The section on grading below states which labs can be turned in for a regrade. The last lab, due August 11, cannot be rewritten due to time constraints.
Formal reports are required for four of the experiments (see the Table of Experiments). The report for the first lab will be written as a class. Photocopied notebook pages are required for every experiment.
Lab Notebooks
The laboratory notebook is an accurate daily journal of your laboratory activities. Use your notebooks to record your hypotheses, experimental plan, observations, measurements, calculations, and analyses. Always record your ideas, plans, data, observations, and results in real time.
Lab notebooks are legal documents. This is especially true for patent issues: patents are awarded to the scientist with the earliest properly recorded idea found in his or her lab notebook. The lab notebook is also the starting point for good, effective report writing. The report may be intended for your colleagues in industry, your thesis, or publication in a refereed journal.
EACH STUDENT MUST HAVE AN BRIEF INTRODUCTION AND DETAILED EXPERIMENTAL PLAN WRITTEN IN THEIR LAB NOTEBOOK PRIOR TO BEGINNING AN EXPERIMENT. I initial your notebooks before you begin the experiment.
A description of the notebook format follows.
a. Use a bound notebook with permanently attached pages. Leave the first pages blank - these will be your table of contents. Date each entry into the notebook. Use only black ink. Avoid complete cross-outs, and never use white-out. If a mistake is made, draw a single line through the erroneous entry, write in the correct entry, and initial it. When working on two or more problems simultaneously, clearly indicate using page numbers where each project in continued in the notebook. Blank pages should be avoided; if you have a blank page, cross it out with an X and sign and date the page.
b. The introduction must contain the statement of the problem (what question(s) will you answer? what is the hypothesis?); a survey of the literature (be careful not to plagiarize), including references; and the experimental technique(s) to be used. To avoid plagiarizing, you can write the literature survey in outline form. Also, you should you any literature till you understand the topic(s), put the literature away, and then start writing. In other words, the writing must come from your head.
c. The experimental plan must show how you will make solutions (be specific); a detailed list of measurements to be made, in order; and a sketch of the apparatus along with remarks on using the apparatus.
d. As you carry out the experiment, include observations in your notebook. What did you see, hear, smell as you did the lab? What quantitative measurements are made? What changes did you make in the procedure? What was the temperature in the lab? What was the humidity? Write it all down so you have a permanent record! Include sufficient detail that another pchem student could repeat your experiment without referring to the lab manual. Do not leave the data recording to one lab partner and then copy it later. Both partners must record the data as it is collected. Never record data on scratch paper and later copy the data into your notebook.
e. Results/Data Analysis: Use your notebooks to analyze the data and perform calculations. What equations are you using to model the data? Where do the equations come from? What graphs are required? Make tables of the data and the results. Tape graphs into your notebooks, or make sketches of the graphs in your notebooks. Include your error analysis here as part of the data analysis.
f. Discussion: Briefly list/highlight the main points of your discussion.
Formal Lab Report Format
No experiment is complete until the results have been reported. The purpose of the formal report (or journal article) is to tell the reader why you have done this research, what research you did, what the results are, and what the results mean. Good technical writing skills are imperative in order to tell your story convincingly. Write, read what you have written, then rewrite. Rewriting is key!
The discussion below briefly introduces the lab report format. In addition, Shoemaker et al. explain lab report writing and give an example; the ACS Style Guide is another good resource.
a. Title page: The experiment title, the date the lab was begun, the date the lab was handed in, the report author, the author's lab partner, and the abstract.
b. Abstract: A BRIEF, CONCISE statement of the experiment done summarizing the most important numerical results. The abstract starts with a sentence stating what was measured. The next sentence describes the experimental technique (how the experiment was done). Next, the actual results are stated along with a statement of the model used to analyze the data. Numerical results must always be reported with an uncertainty. Finally, the numerical results are placed in the context of previous work with the appropriate literature comparisons. Any symbols used in a sentence must be defined in that sentence. Sample abstract sentence: the density, , was 1.0 ± 0.5 g cm-3. Put the abstract on the title page. An abstract will average four to six sentences.
c. Introduction: a cleaned-up version of the introduction written in your lab notebook. Use at least three references. YOU MUST CITE ALL REFERENCES. All equations must be part of a sentence. Again, symbols are defined in sentence form the first time they are used. To write a good introduction, try the following. Read all the background material until you have formed a clear picture of the experiment and theory in your mind. Take brief, sketchy notes. Work out the derivations. Write an outline (not necessarily a linear, I. A. 1. a. b. 2. B. etc. outline). Once your mental picture is clear and organized, begin writing.
Write short sentences and paragraphs if possible. Use first person if necessary for clarity. Keep the subject and verb close together in your sentences. Most importantly, review and revise what is written. Read it after some time (even half an hour will work), and see if it makes sense. If it does not, revise! The key to good writing is revision. Few writers can craft a perfect sentence in their first draft.
A more extensive literature search is required for the Iodine Clock Kinetics report. Start by reviewing kinetics in your general chemistry textbook. What are the methods used to determine mechanisms? Next, look up mechanisms for clock reactions in a physical chemistry textbook such as Atkins. What are the important features of a clock, or oscillating reaction? How do these reactions differ from other reactions we are more familiar with? Finally, look up at least three journal articles referenced in Shoemaker et al. Attach photocopies of the articles to your report. In your report introduction, summarize the articles. Focus first on the authors' experimental sections (what methods did they use to understand the kinetics?). Second, determine the authors' reasons for doing the experiment - why they chose this particular chemical system and the experimental technique. Last, briefly relate the authors' conclusions about the mechanism for this reaction. Be sure to include the correct references.
d. Experimental: A summary of the experiment, but not a list of instructions. What instrument(s) did you use? What solutions? What procedure did you follow? Again, use first person if necessary for clarity. Refer to your notebook.
e. Results and Discussion: This is the BIGGIE. First state your results; make a table, title it, and discuss it in the text. All results must be reported with errors (i.e., uncertainties) and a statement of how the errors were calculated. Explain how results were calculated, and, if necessary, refer to and discuss specific, titled figures[1] (graphs) to explain your calculations. All figures and tables must be numbered, titled, and include a one sentence caption. Compare your results to the appropriate literature values (include references) and discuss discrepancies. Be specific; statements like "the values are close" or "the values are bad because of poor experimental technique" are NOT acceptable. If no exact comparison can be made between your results and the literature, consider whether the results fall within the expected range of values for similar systems.
Next, discuss the meaning of your results. Can you connect your results to topics discussed in class? How do your results fit with your statement of the problem in the introduction? How does the molecular structure of the compound you investigated affect whatever properties you observed? What further experiments would help to unravel the problem?
DO NOT include sample calculations in your lab reports. DO include all your calculations in your lab notebook. If the same calculation is done repetitively, include at least one worked out example in your notebook
For the iodine clock kinetics lab, relate your results to the mechanisms proposed in each of your references. Compare their experimental method to yours. If possible, make a table comparing rate constants for specific reactions, including constants you have determined. Discuss differences between your experiment and theirs: what properties or values did they measure which you did not measure?
Grading
formal lab reports, 50 points each except for the iodine clock reaction lab, worth 100 points
lab notebook pages for labs without formal reports, 50 points each
lab notebook pages for labs with formal reports, comments only (no numerical grade)
subjective observations by the instructor in lab, 50 points
Lab notebook grades are based on adherence to the format and on the level of detail. For labs that do not require a formal report, it is critical that the data are analyzed fully and the results are presented completely in the lab notebook. Grading is lenient the first few times lab notebook pages are turned in. Be sure to follow the suggestions for improvement.
Grade assignments for photocopied lab notebook pages are made according to:
46-50 points: a superb notebook. Contains all sections, follows the format, includes explanations, observations, diagrams, calculations, tables, and figures.
41-45 points: a good notebook. Follows the format.
36-40 points: an acceptable notebook. May not follow the format exactly, have sufficient detail, or contain calculation errors.