CHEM 143: How to write a laboratory report

CHEM 143: How to write a laboratory report 150 150 Affordable Capstone Projects Written from Scratch

A formal laboratory report typically contains the following sections in the order
listed:
1. Title
2. Abstract
3. Introduction
4. Procedure
5. Results and Discussion
6. Conclusion
7. References
8. Appendix (Supplemental/Supporting Materials: graphs, tables and
supporting calculations) The format for many undergraduate lab reports
places much of this material (supporting graphs and tables) within the
Results section, in which case an Appendix is not required.
For your first lab write-up, it would be overwhelming to construct a full formal
report with all these sections. We believe it’s better to develop confidence with
several key sections and then build towards a full write-up over time. To this
end, in CHEM 143 we will focus on developing skills in writing and formally
presenting the:
 Title
 Abstract
 Results and Discussion
 Appendix (Supplemental/Supporting Materials)
In other words, four of the eight sections typically seen in a formal write-up.
Future laboratory classes will address the other aspects of a formal laboratory
report. Why focus on the above four? To answer this, we should first give a
generalized description of the four sections:
 The Title should be specific and descriptive: identify what you were
investigating and the method employed to do so, being as specific as
possible while remaining extremely concise.
 The Abstract should provide a less-than-200-word summary of the entire
work: the purpose, procedure, key results, and their significance should all
be briefly addressed in this essential part of your report. The Abstract is
not the place to introduce the experiment or describe the underlying
principles in any detail. Most scientists write the Abstract after they have
written the rest of the paper, since it summarizes the work described.
Never present material in the Abstract that you have not also presented
somewhere in the main body of the report.
 The Results and Discussion section presents the key numerical results –
for example, the mean concentration and standard deviations of the
analytes in the sample. Briefly describe how these values were obtained
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directly referencing the calibration curves and calculations of the
Appendix. Discuss the apparent limitations and/or problems, the
potential sources of both random and systematic error, their likely
importance, and how they might be reduced.
 Appendix: Include your calibration curves, calculations and tables. You
may also include additional information that you feel useful to the reader,
but too detailed to be included in the main body.
Perhaps the two most important sections of any report are Results and
Discussion and Appendix. Obviously, without the material in the Appendix, you
won’t even have a report. But as you can glean from the description supra, the
Results and Discussion section presents the main outcomes, how they were
obtained from the raw and processed data, and discusses the limitations and/or
problems encountered – basically the core result and analysis of the
experimental work. Undeniably this is of central importance, for without it, we
just have data and no interpretation. Once the Results and Discussion section is
complete, it’s possible to construct an Abstract assuming you know something
about the procedure performed, the principles upon which it is based and can
summarize what you have accomplished in the experiment. As for the Title, well
you should be able to do this for any CHEM 143 experiment.
CHEM 143 Lab Report Requirements
The Lab 6 report is worth 50 points.
The report must be typed. Font size should be 11 or 12 point, and easy to read.
Your goal is to prepare a professional document. “Artistic” fonts are highly
discouraged.
You have a strict two page limit for the Title, Abstract and Results and
Discussion sections combined. Your TA has been instructed to stop
reading/grading after two pages, so there is no point to going beyond the two
page limit.
You also have a two page limit for the Appendix (graphs, calculations and
tables). Again, you want a professional appearance. Your TA has been instructed
to stop reading/grading after two pages.
The report is due at the very beginning of lab on week 8 (one week after Lab 6
concludes). This means you have a full week to complete the write-up. Please
don’t procrastinate. If you follow the guide presented infra, you should do well
– but this requires adequate time.
The quality of your data analysis, and the scientific and writing quality of your
report will combine to determine your report grade.
Assume your reader is someone practiced in the art, but who has not performed
this particular set of experiments. All writing should be in the third person (avoid
“I”, “me”, “we”) and the described experimental work should be written in the
past tense (not the present – because you already performed the work).
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Now let’s take the write-up process step-by-step.
It’s usually best to start with Appendix, that is, to work-up the data into its final
form. For all the graphs, calculations and tables, devise an unambiguous
numbering system – this will proved very useful when referring to a specific
graph, calculation or table in the Results and Discussion section.
1. Build your two A vs. C calibration curves in Excel as scatter plots with
linear trend-lines (one for FD&C Blue Dye #1 and another for glucose).
You should have much of this started already. Now your goal is to work
these into professional, publication quality plots. Be certain you have
appropriate, fully descriptive titles for each. Remember,
spectrophotometric analyses are wavelength dependent. This means
you must report the λmax – best practice dictates doing so in the title.
Don’t forget to properly label the axes. Grid-lines should be removed.
Significant figures and units count, so please be sure to control these.
You may need to adjust the scaling of the plots for a clear presentation.
Include the linear trend-line, the equation of the linear trend-line and
R
2
value – all from Excel. You will likely need to adjust the significant
figures (and possible the font size) displayed for the equation and R
2
value. There is a very detailed Excel graphing guide on D2L (within the
Lab 6 Materials) prepared by Instructional Laboratory Support
Specialist Sara Gallagher to assist you.
2. Present your calculations. This should be straightforward. You did
these calculations in your notebook (or should have). What’s different
here is the need for a clean, highly organized presentation. Be sure to
control the units and significant figures. You may find the equation
writer (in Word) very helpful. Click were you want an equation to
appear, click on the Insert tab, then click on Equation. After a few
minutes of exploring this tool, you should get the hang of it.
First present the glucose molar solution calculations.
Next, you want the give one example of each parallel dilution set
calculation performed for Lab 6. You should have three such
calculations:
 Equation (5.1) on pages 9 and 23 of the L5 manual – use the
examples on pages 9 and 23 as templates.
 Application of equations (5.3) and (5.4) and/or (5.11) to determine
Vdiluent and V0. There are several ways to approach/present the
calculations – just take care to ensure your presentation makes
sense mathematically and physically.
 Equation (6.7) on page 18 of the L6 manual – use the example given
as a template. To be complete, indicate the λmax at which each
analysis was carried out the writing Aλ, ελ and bλ; for example with
the glucose determination, we have A340, ε340 and b340. Since the
mean (𝐶̅) and standard deviations (s) were calculated in Excel, you
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can state 𝐶̅± sin the Results and Discussion section indicating they
are Excel derived so that presenting 𝐶̅and s calculations is NOT
required.
Finally, calculate the relative standard deviation (sr) for the FD&C Blue
Dye #1 concentration determination, and likewise for the glucose
concentration determination. See pages 12 – 15 (especially page 15) of
the L3 manual if you wish to accomplish this via Excel. Otherwise,
simply calculate (sr) by dividing s by 𝐶̅for each analyte (dye and
glucose). You can use the sr values to compare the methodexperimenter
precision in determining the analyte concentrations.
3. Present your parallel dilution tables, one for FD&C Blue Dye #1, the
other for glucose. Again this should be straightforward. You did this in
your notebook. What’s different is the requirement of a formal,
professional-appearing presentation. There are many table designs in
Word. Avoid gaudy, distracting designs – remember you want
something serious and formal. You will need an appropriate, fully
descriptive title for each table. Proper column headings, significant
figures and units count, so please be sure to control these.
With the Appendix done, writing the Results sub-section logically follows.
Present the mean concentration and standard deviation (𝐶̅± 𝑠) of FD&C Blue
Dye #1 for the three replicate runs of the sport drink. Do likewise for the glucose
determination on the same sports drink.
Describe in a few sentences how these values were obtained for the FD&C Blue
Dye #1, making direct reference to the λmax you determined, the A vs. C
calibration curve and the supporting calculations (at the λmax), all of which must
appear in the Appendix. See page 3 of the L6 manual – the paragraph under
FIRST WEEK more-or-less covers much of this – but keep in mind, you must write
in your own words citing your λmax value, A vs. C plot and calculations (in the
Appendix), and summarize down the information into a few sentences.
Now describe in a few sentences how these values were obtained for glucose,
making direct reference to the appropriate A vs. C calibration curve and
supporting calculations, which of course, must appear in the Appendix. See page
3 of the L6 manual under SECOND WEEK. Remember you need to write in your
own words pointing to your glucose A vs. C plot and calculations (in the
Appendix), and summarize the information into a few sentences.
Now we move the Discussion sub-section. Compare and contrast the analyses.
Use the R
2
values from the calibration curves to compare the calibration
precision of the two methods (See page 7 of the L4 manual). To compare the
method-experimenter precision in determining the analyte concentrations,
compare the relative standard deviations (sr). State the problems you
encountered and the apparent limitations of the quantitative analysis for the
dye and glucose. Was one less problematic? Remember, you performed two
rather different analyses – different scales, enzymatic vs. non-enzymatic,
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different temperatures, etc. Finish the section with a brief discussion of potential
sources of both random and systematic error (you might find pages 6- 7 of the
L3 manual helpful), their likely importance, and how they might be reduced.
At this point preparing the Title should be easy. But, if you need motivation, try
writing down four items:
 what you quantitated (the analytes)
 the sample name or type.
 in a few key words the method/approach.
 in a word or two the key instrumentation.
With this in front of you begin to shape a title. You should realize two different
instrument-based methods/approaches were used to quantify two very
different analytes in the same sample and be able to covey this in one succinct
title.
Finally, we come to the Abstract. For Lab 6 this should run 4-5 sentences. The
first sentence states the specific purpose. The second, the key quantitative
results for FD&C Blue Dye #1 and glucose. The third, the determination approach
for FD&C Blue Dye #1. Fourth, the methodology for glucose. Fifth, the utility
and/or apparent limitation of the quantitative analyses.
Don’t forget your name, section number and the date on the first page.


 

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