Chemistry 251 Laboratory -- Spring 2009
Writing Laboratory Reports

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Specific Comments for the Unknowns Lab Report


Being a clear writer is as important to a scientist as being proficient in the laboratory. A discovery made in the laboratory does not contribute to scientific knowledge until it is communicated to the rest of the scientific community, normally through publication as a journal article. It is through your writing that you (and your results) are judged. A poorly written paper will be rejected by referees and editors and will not be published. In addition, a scientist needs to convince others of the importance and feasibility of his or her work in order to secure funding; in this regard good grant writing is also essential. Even if you do not intend to be a scientist, writing will almost certainly be an important part of your career. A major portion of your laboratory grade in this course will depend on your ability to write lucid reports in correct scientific style.

The best way to learn how to write scientific papers is to read a few of them! Don't be afraid to wander over to the magazine racks of the library and pick up an issue of the Journal of the American Chemical Society. Although the overall structure and style of all scientific papers are similar, each subdiscipline has its own conventions for certain aspects of the paper. Thus, if you are writing for a specific subdiscipline, look at one of the important journals in that field: for example, Journal of Organic Chemistry, Inorganic Chemistry, Journal of Chemical Physics. For additional information you should consult The ACS Style Guide. Other books on writing scientific papers may also be helpful. (For example, Robert Day's How to Write and Publish a Scientific Paper). Many of the ideas outlined below were obtained from these sources.

Your reader has certain expectations for the style and format of the scientific paper. You must accommodate your reader or your ideas will lose their impact since the reader will spend his or her time thinking about the structure of the paper, not the content. Our goal is for you to complete this course with the ability to write a complete paper in a standard format used by the Journal of the American Chemical Society: Title, Abstract, Introduction, Results, Discussion, Conclusion, Experimental Section. To accomplish this goal we will begin, in the first reports, by focusing on individual parts of the scientific paper. Later in the year you will be required to combine all these elements into a complete report.

A well written scientific report is the culmination of a great deal of work. It depends on a well performed experiment that is carefully documented, a well-kept lab notebook is essential. The results of the experiment must then be objectively analyzed to assess the implications of the work. It is during the writing of a report that much of the critical thinking about an experiment takes place. Give yourself time to revise your initial drafts; it may only be at the end of the first draft of your report that you fully realize what your results mean. It is then necessary to go back and revise your report with this information in mind. Have other students in the class read your draft and provide feedback on parts that are unclear.

Clarity is the most important feature of a good scientific report. This requires clear writing and careful organization. If you want help or advice in writing a report, the Writing and Learning Center is a good place to visit. A published novelist, and professor at UPS, once took her own writing to the writing center and remarked to me that she was impressed by the suggestions they made. The Writing Center has several upper level science students who serve as writing consultants.

Getting Started Writing

Many students make the mistake of trying to write the report in the same order in which it appears. One approach for writing a scientific paper which works well is given below:

A. Organize your thoughts and your data

B. Write the Experimental Section

C. Prepare the important illustrations (i.e., Tables, Figures, and Schemes)

D. Write the Results section (using the illustrations as a guide)

E. Draft an outline of the Discussion section

F. Write the Introduction

G. Complete the Discussion Section

H. Write the Conclusions

I. Add References

J. Write the Title & Abstract

I have included some examples of Title, Byline, Abstracts, Introductions, and Conclusions from recent papers in the Journal of the American Chemical Society. Inspect them to understand the format that you should follow.

Writing Style in Scientific Reports

[Much of this section is taken from a copy from a book or article to which I don't have the reference. If you know the source, please let me know so I can supply attribution.]

Don't worry too much about your style during the first draft (so that you avoid writer's block). Listed below are some things to work on during your revision(s).

Since clarity is your main goal, avoid long, run-on sentences. To create a sense of flow you can use connective words at the beginning of your sentences:

 above    accordingly   and so   again

besides consequently alternatively for instance

furthermore however in addition indeed

in particular instead likewise moreover

nonetheless rather similarly still

then therefore though thus

Avoid Redundancies

Do not use unnecessary words. If a word can be removed without distorting the meaning of the sentence, then remove it. Try removing unnecessary words from the sentences below. For example, in the first sentence the phrase "...a period of..." repeats the meaning conveyed by "...eight weeks...", and can be removed.

1. The civil-engineering survey will last a period of eight weeks.

2. Physically it is smaller than either of the others.

3. The temperature ranged from a minimum of 100 °C to a maximum of 120 °C.

4. The new switch is smaller in size.

Use Strong, Active Verbs

Many scientific articles are written in the passive voice; the action is directed away from the actor. Although less flexible, the active voice is more direct. For example, "The reaction mixture is refluxed in a 220 mL flask.", can be changed to "Reflux the reaction....". Do not use the active voice exclusively, but look for sentences where changing from a passive to an active voice provides power to the sentence. Suggest an active form for the following sentences.

1. This can result in a further reduction in the number of gaps.

2. A protective series resistance is included in the circuit.

3. The purpose of this equipment is to accept, analyze, and report system failures.

Use Simple Words

Use simple rather than complex words. This is similar to removing redundancies in that you decrease verbiage. Some simpler words to use are: so, as, and, or, to, by, with, and if. For example, in the first sentence replace " such a manner..." with "".

1. This application affects the porous material in such a manner leakage does not occur.

2. In order that the compatibility of the system could be maintained, we rejected the device.

Emphasize the Action

Focus on changing the stress from the subject to the verb or action which takes place. This is done by eliminating unneeded connecting words. An example is to delete the words "It is..." and "...that..." in the first sentence.

1. It is this necessity that adds to the complexity of the simulator.

2. There are many application that make this device useful for speech analysis.

3. The valves were found to contain metal chips. (Keep the past tense.)

4. With reference to the instructions they must be followed exactly.

General Guidelines for Preparing Various Sections


The title is a label for the contents of the paper. The title should be as specific as possible. If you were looking for canned peaches at the supermarket you would be dismayed to see all the canned fruits labeled "Fruit". In fact, you might even be annoyed to find cans simply labeled "Peaches" -- are they peach halves or peach slices? Packed in water or syrup?

Words in the title are used to generate both written and computer-based indexes. Thus the title should contain specific keywords that will allow potential readers to find your article using these indexes. The title is not normally a sentence and should be as brief as possible. Any unnecessary words should be ruthlessly removed. Avoid phrases like "a study of" or "a report on". In most cases, omit "the" at the beginning of a title. The title should be in bold face and in a slightly larger font than the text. Center the title at the top of the page and capitalize the first letter in all important words.


A Study of Bond Lengths

[This title is so general that it is nearly worthless.]

A Study of Bond Lengths in Cyanine Dyes

[This title is better, since we now know what type of bond lengths were studied, but the phrase "A Study of" is vague. This title would be improved just by removing the words "A Study of", or better yet describe what was done.]

Calculation of the Average Bond Length in Cyanine Dyes
Using the "Particle in a Box" Model

[While a bit on the long side, this title clearly indicates the emphasis of the article.]

Action of Antibiotics on Bacteria

(This title is too vague, it is more like the title for a book. We don't know which antibiotics or which bacteria were studied.)

Action of Streptomycin on Mycobacterium tuberculosis.

(This title is much better, but "Action of" is vague.)

Inhibition of Growth of Mycobacterium tuberculosis by Streptomycin

(Now we know exactly what this paper is about.)

Some titles from recent issues of the Journal of the American Chemical Society:

Mechanism-Based Inactivation of Pyruvate Formate-Lyase by Fluoropyruvate:
Direct Observation of an a-Keto Carbon Radical

Total Synthesis of the Unusual Marine Alkaloid (-)-Papuamine
Utilizing a Novel Imino Ene Reaction


The Byline follows the title and should be centered and in bold using the normal font size. Your name, date, course name and number. Others who worked with you on the research may be listed as coauthors.


The abstract is a brief (typically < 250 words) description of the contents of the paper. Its primary purpose is to permit readers to determine whether they should read the paper. Researchers searching for information in Chemical Abstracts or other indexes will use the abstract to decide whether to go to the trouble of getting a copy of the paper.

The abstract could be written by an editor (or another chemist) since it contains only information present in the rest of the paper. Since it reflects the contents of the paper, write the abstract last. Center it on the page, indented one-half inch from both margins. The abstract must stand alone; therefore you may not cite any tables or figures.

There are currently two types of abstract in general use: informational and indicative. Most organic chemistry articles use an information abstract, but in some cases these two types are mixed.

Informational Abstract

As described in the ACS Style Guide, "in the abstract you should briefly state the problem or the purpose of the research when that information is not adequately contained in the title, indicate the theoretical or experimental plan used, accurately summarize the principal findings, and point out major conclusions." The informational abstract often uses the past tense to describe what was done, and may switch to the present tense to describe results (that are now known). The passive voice has traditionally been used since scientific results should not depend on the person doing the study.

Indicative Abstract

In contrast to the informational abstract, the indicative abstract is written in the present tense and describes the paper itself, including the major findings. It is in the present tense since it is describing the paper which exists now. The indicative abstract is like a table of contents for the paper and may also be written in the passive voice.


The introduction shows why the research described in the paper is interesting and important to a chemist. What is the motivation for doing the research? The answer to this question will often require a historical account describing previous research along with appropriate references. It is the author's responsibility to convince other chemists of the value of this work. The introduction provides a clear statement of the problem or project. It sets the stage for the research and puts it in a chemical context. In some cases this will require a discussion of the theoretical background for the work. Present and past tenses are correct in the introduction: "Absolute rate constants for a wide variety of reactions are available. Jones reviewed the literature and gathered much of this information."

Results and Discussion

In all writing it is important to consider your audience and your relation to them. In a scientific paper your audience may change from section to section. When writing the Results section you should think of yourself as an impartial observer reporting data to someone knowledgeable in your field, while in the Discussion section you are writing as an expert to all chemists interested in your study (even if they aren't as knowledgeable as you).

The Results section summarizes the data you have collected (along with statistical treatment of them) and consists chiefly of elaborations of information in Tables, Figures, and Schemes (including uncertainties if appropriate). The Results may also present an overview of the experiments, but without the detail provided in the Experimental Section. (Most readers will NOT read the Experimental Section so don't assume that they have.) The Results section is predominantly in the past tense, but references to data in tables may be in the present tense.

The purpose of the Discussion is to analyze the observed facts. What are the "principles, relationships, and generalizations shown by the Results." The Discussion section compares your results to literature values or to the results that might be expected from various theoretical models. (This may require the use of error analysis.) The logical implications of your results are described. Any exceptions should be noted and, if possible, explained. You are building an argument, making a case. It is your responsibility to convince other interested chemists that the conclusions you draw are valid and make sense based on the data presented in the paper. The Discussion is usually in the present tense.

The Results and Discussion sections are often combined so that the each result can be discussed in turn. Feel free to separate the two whenever you feel it is appropriate.


This section usually contains a brief summary of the major results along with their significance. The object is not to merely restate the results, but to give the reader a feeling for the broader significance of the results. In this sense, whereas the introduction provided the context for the results and discussion, the conclusions state the relevance, importance, and significance of the results to a better understanding of a phenomenon.

The conclusions may corroborate previous experiment or theories, validate previous models or observations, or suggest possible improvements in experiment or theory. Future applications of your findings may also be noted in this section, or you may simply state the direction of future work.

Many readers will read only the Abstract, Introduction, and Conclusions, so make sure they get the proper message and the bottom line. The relative importance of your work should come across clearly in these three sections.

Experimental Section

Here the details of the actual procedure are described. This is what you actually did, not a copy of the lab handout, nor a recipe for someone else to follow. The level of detail necessary depends to some extent on the audience, but in general the experimental section should give all the information necessary for someone to actually repeat your experiments successfully.

The experimental section is always in the past tense with the passive voice.

An experimental section normally begins with a General section that provides information on materials and methods that are common to several experiments. The type of instruments used (including make and model) and important instrumental parameters are noted. Sources of chemicals are listed. Following the General section, each experiment is described in a separate paragraph that has a brief, descriptive title in bold. (For organic reactions this title is often the name of the compound synthesized.)

The Experimental Section has a well-defined, formal, almost cryptic, style that varies depending upon the exact type of experiment performed. Thus, it is essential to look at examples in the literature to get a feel for the accepted format. You may assume that your reader has had an organic chemistry course and is familiar with standard laboratory procedures.

A few examples from Experimental Sections are shown below to serve as models for preparing your own. You might wish to look at additional examples in the Journal of the American Chemical Society or the Journal of Organic Chemistry .

Footnotes -- End Notes -- References

Any reference to previous work or literature values should be cited. References should be collected at the end of the paper in the numerical order in which they appear in the body of the paper. Different journals use different formats for their references. We will use the Journal of the American Chemical Society format. Do not use "ibid." There should be only one citation in your footnotes for each book or journal article, no matter how many times you refer to it.


(52) Boyer, J.H; Mack, G.H.; Goebel, W.; Morgan, L.R. J. Org. Chem. 1959, 24, 1051.

(53) Martin, S.F.; Oalmann, C.J., unpublished results. (or personal communication)

(54) Lin, H.W.; Walsh, C.T. Biochemistry of the Cyclopropyl Group. In The Chemistry of the Cyclopropyl Group; Patai, S., Rappoport, Z., Eds.; Wiley: New York, 1987; Chapter 16.

(55) Bindraa, J.S.; Bindra, R. Prostaglandin Synthesis; Academic Press; New York, 1977.

Illustrations: Tables, Structures, Schemes, Equations, & Figures

For most papers the narrative is only half of the story. If most papers were written without the use of illustrations, they would be at least twice as long, and probably completely unintelligible. In the same way that there are conventions about how to structure a scientific paper, there are conventions about the use and format of illustrations. We will follow the format used in the Journal of the American Chemical Society. A few comments on each illustration type are given, but look at examples from the journal to see the proper format.


Tables are numbered sequentially and labeled Table 1, Table 2, etc. in bold face above the table and left justified. Unlike Schemes, tables have an informative title that immediately follows the label. Footnotes (a,b,c...) describing aspects of the table may be place directly below the table.


Chemical structures are set off from the text, centered, and numbered with bold face Arabic numerals. The numbers are centered below the structure and may also include names.


A scheme is an illustration that links together several steps in a procedure. The Scheme is commonly used to illustrate a series of steps in an organic synthesis. (Although it could also be used to show a series of steps in a complex purification procedure.) Schemes are numbered sequentially and labeled Scheme 1, Scheme 2, etc. in bold face above the Scheme and left justified. Schemes do not normally use informative titles. Footnotes (a,b,c...) describing steps in the scheme may be place directly below the Scheme.


Most equations, unless they are very simple, are set off from the text, centered, and numbered consecutively by using Arabic numerals in parentheses along the right hand margin. Long derivations are usually relegated to appendices unless vital to the main thrust of the paper.


All other illustrations are figures. Notice that graphs are called figures in scientific papers. Figures are numbered sequentially and labeled Figure 1, Figure 2, etc. in bold face below the table and left justified. The figure normally contains a legend that describes what it is showing. The figure legend immediately follows the label, but is not in bold.

Referring to illustrations in the text

Any illustration in your paper must be referred to somewhere in the text. You may refer to the table or illustration directly: "The optical, thermal, and thermodynamic data of these compounds are given in Table 2." Alternatively, it is often preferable to refer to the illustration parenthetically at the appropriate point in the text: "Retrosynthetic analysis of 6 using this idea gives the pyrone 26 as the key intermediate (Scheme 8)."


When I write a paper, I usually model it off of a similar paper already published. I recommend you do the same. Look in the the Journal of the American Chemical Society or Journal of Organic Chemistry to see examples of Tables, Schemes, Structures, and Figures. When reading the Results and Discussion sections don't worry too much about what is said (i.e., the content), focus on how it is said. What tense is used? Is it always the same? How are illustrations referred to? Notice that using the first person is acceptable. But don't overdo it. Look at experimental sections to get a feel for the concise format and the type of information provided.

Specific Comments for the Unknowns Lab

For this report you only need to prepare a Results and Discussion Section. I recommend combining your Results and Discussion sections for this report. This section should be divided into two parts, one that focuses on the liquid unknown and the other on the solid unknown. Assume that your reader is a chemistry major who has already had organic (but they may have forgotten some of the details).

Your report should summarize all the data from the various aspects of your lab. For each unknown include a table that summarizes the data you collected for that unknown. (In the table IR, NMR, and ms data should be presented in the standard form used in experimental sections.) Tables should be clearly labeled, mentioned in the text, and follow the correct format. Your spectra should be annotated and included as figures (complete with figure legends) and important absorptions should be identified. Show how your results allow you to identify your unknown -- be organized and logical in your argument, it is your job to convince the reader. Although you should compare your data to that reported in the literature, it is not sufficient to identify your unknown by simply stating that your data is identical to the literature data -- you should describe the information you obtained from each piece of spectral and solubility data and how this is consistent with your unknown. If you are uncertain about the actual identity of your unknown this should be noted and explained. Compare your data to literature values and include references to these literature values.

You do not need to include any detailed information about the procedure you used for obtaining the melting point, index of refraction, etc., unless there is something unusual. This type of detailed procedural information would be presented in the Experimental Methods section. You also don't need an Abstract or Introduction.