CHEM 461 - HOW TO WRITE LAB REPORTS
by C. T. Campbell
Notes on Form
1. Double space, even if hand written, to leave room for grader's comments.
2. Pencils allowed, but remember that pencils tend to smear, and ...
3. Any sections that are difficult to read due to smears, poor penmanship, or poor grammar will not be given credit.
4. Write on one side of page only.
5. Staple or otherwise bind entire report together, except perhaps large sheets of recorder paper, which should be labelled with your name and experiment number.
FORMAT
Title Page - Include title of experiment, experiment number, your name.
I. Introduction (11 points,
Should contain a brief description of the experiment that will be done, naming the compounds or reactions that will be studied and the techniques that will be used to study them, and the phenomena that will be studied. Avoid long theoretical developments that already appear in the handout. However, all equations that will be used in calculating/analyzing data should be properly introduced here, defining all terms. Give the equation an equation number. The equation should be a natural part of a sentence, and it should be properly referenced. Example:
"In this experiment, temperatures were monitored with a thermistor, whose resistance (R) changes sensitivity with temperature (T). According to Mermin [5], over a limited temperature range most resistors behave:
R = aT + b , (3)
where a and b are constants ...."
If this equation is needed later, it can simply be referred to as "Eq. (3)."
Any constants, values or relationships that are supposed to be determined by the experiment should be clearly stated as objectives.
II. Experimental (3 points, 1 page).
Refer to the lab handout procedure here. Don't copy it. Point out any exceptions to this procedure only. Also, use this section to include details of don't wish to keep repeating in the Results section, or details which would interrupt the smooth flow of the Results section.
III. Results and Discussion (60 points,
~10 pages)Should present raw data, then manipulated data, then manipulated data plotted against theoretical relationships, then conclusions based on fits to theory. Include tables, figures, spectra, etc. directly in this section as they occur, or at end of report in an Appendix. Error analysis should also in this section, with comparison to literature values and speculation of reasons for discrepancies.
IV. Conclusions (5 points,
~ 1 page)Contains a brief summary of the experiment and its objectives, and most importantly a review of all of the major values determined (include error bars) compared to literature values. Review any other major conclusions (e.g., identity of unknowns).
V. Literature References (1 point,
~ l page)VI. Appendices:
Can include spectra, graphs, tables, figures here or in Section III. Note: points off if units and units analysis not clear. Can include sample calculations here if you think them necessary.
HOW TO WRITE A QUALITY LAB REPORT (Pirsig - p. 185)
HINTS, DEVICES AND TECHNIQUES
ORDER OF WRITING: Not the same as above.
1. Experimental - details you don't want to have to repeat in results because they would interrupt flow and logical development: general procedures, apparatus, starting materials. Highlight changes from procedure of lab manual. (Example - room temperature, barometric pressure, etc.)
2. Read handout from Sime, "P. Chem.," Chapter 8 for preparing Tables, Figures, Graphs (p. 161-165). Get all "Figures" and "Tables" of raw data in good form first. Then make up any Figs. or Tables which show data after mathematical treatment to fit theoretical behavior, predicted curves. Finally, order all of these such that they can be presented most logically. Use this ordering as your outline for (3).
3. Results and Discussion - longest section. Where to start? Pirsig - p. 170. Read handout from Sime, "P. Chem.," Chapter 8, p. 165-168, and #7 below, for hints on writing style.
… Now qualitatively describe the data, then quantitatively describe any important features: "As can be seen, the retention time decreases smoothly with increasing column temperature. The retention time decreased from 3 minutes to 0.1 minutes in this temperature range."
… Now remind the reader of any theoretical relationship which might be useful to explain the data. Refer to this with a title if possible, and an equation number from Introduction. EXAMPLE: "The Mickey Mouse relationship (Eq. l) predicts that ln (retention time) should vary inversely with the column temperature (Tc)." NOTE: As you write the Results and Discussion keep two pieces of paper at hand, labelled "Intro." and "Conclusions." As you come across theoretical relationships required, jot these down in order on the "intro." list. Do the same with major "Conclusions" on their list. Use lists as outlines later for writing "Introduction" and "Conclusions." (You may want to make a list of "Experimental Details" to add to "Experimental" section also.)
… Now introduce a plot of your data against the theoretical curve, using axes appropriate to theory. EXAMPLE: "Fig. 2 shows the data of Fig. 1 replotted as ln (tr'/min.) versus 1/Tc, together with the best least squares straight-line fit to the data predicted by Eq. 1. The slope of this line is (20 ± 2ƒC) and the y-intercept is -(121 ± 12)."
… Now qualitatively and then quantitatively describe the quality of fit, and explain any major discrepancies. "The fit to the data is rather good, with a correlation coefficient of 0.95. The major deviations are at very short retention times, where the relative error in measuring retention time was largest due to small (~3 sec.) errors in assigning tD and tr." (Show error bars here.)
… Now draw any major conclusions from theoretical fit. EXAMPLE: "From the slope of Fig. 2 we can determine the Mickey Mouse Factor (Fm) for our column, which is given by the slope divided by the column length: Fm = (20 ± 2ƒC)/3m = 6.7 ± 0.7ƒC/m."
… Now go to the next Figure or Table of raw data, and repeat all the last six steps. Continue until you are finished with the Figures and Tables.
4. Conclusions - Use your outline list from above. Try to summarize objective and experiment in as few words as possible. Then emphasize all the major conclusions on your list, plus any other conclusions that result from correlating these conclusions.
5. Introduction - Use your outline list from above. First introduce the experiment and the technique, briefly describing the objectives of the experiment. Introduce in order any theoretical relationships you need for your list. Try to define all terms and reference the source literature for the relationship. I find brackets with numbers good for references. EXAMPLE: "[7]."
6. Literature References - This is a list of all sources quoted or referred to in text, preferably in the order in which they appear in text. To help keep these in order, I usually leave blank bracks [ ] for reference numbers in text, and then go back and fill these in and make the reference list after the text is complete.
7. Notes on Sentence Structure - Pirsig - p. 145.
… Re-read paper. Avoid long sentences. Always make two sentences out of one when it requires fewer or equal words.
… Avoid indefinite reference words such as "this," "these," "it," "which," etc., where it is ambiguous to which noun these refer. EXAMPLE: "The fur of a mink can be several shades of brown, depending upon its age." Does "it" refer to the fur itself or the mink? Reread to hunt for such usage.
… Avoid any potential for ambiguity. A good example would be a new paragraph which starts: "These results show that ... ." Is the writer referring to the results of Fig. 1, 2, 3, or 4? Be specific. "The results of Fig. 4 show that ... ." Not necessary if this sentence is part of a paragraph where only Fig. 4 has been presented previously. Re-read to make sure reader doesn't have to read your mind or guess about your meaning. Be as specific as possible: EXAMPLE: "The experimental results deviate from the Mickey Mouse Equation.". BETTER: "The curve for the experimental results is non-linear and is much steeper at large 1/tr' than predicted by Eq. 1."