CHEM 331L

Physical Chemistry Laboratory

Revision 1.1

Lab Reports

Each laboratory report should follow the suggested format below. Please type all the text

sections of the report. If you wish, you may insert equations by hand. However, using an

equation editor would be good practice and so you might want to start practicing now.

It is important to remember that laboratory work is not complete unless that work is fully

analyzed and reported to a wider audience. And, always keep your audience in mind when

writing your report. As pointed out by Sime; “Because formal scientific writing is not literature,

it should not be written with flair, humor or emotion. Instead, you should strive for brevity and

clarity.”

The report should contain the following sections organized as listed:

Title

Abstract

Introduction

Experimental

Results and Discussion

Conclusions

Appendices

References

Do not be “creative” with your report. Galileo’s Dialogue Concerning the Two Chief World

Systems used a character named Simplicius to present the geocentric view of the Universe. And,

he wound up on trial before the Inquisition.

Although not literature, keep in mind you are trying to tell a coherent story. Do not simply string

together a series of equations with occasional graphs or tables inserted to break the monotony.

Your story should also be presented using the correct tense.

The proper choice of tense invariably causes great difficulty to inexperienced writers of scientific

reports and articles. Don’t worry, however, for it’s really quite simple. About 95% of the time,

just two tenses satisfy the requirements of good style: the simple past and the present. The rules

are quite simple. You must report your work in the past tense and the work of other scientists in

the present tense. Further generalizations follow from these rules. Since the introduction is

essentially a summary of other scientists’ work, it is written in the present tense. On the other

hand, the experimental section, a presentation of your work, is written in the past tense and is

usually chronologically ordered. Take care to avoid the future tense; it is almost never appropriate

in scientific reporting.

Physical Chemistry: Methods, Techniques, and Experiments

Rodney J. Sime

Because you are telling a story, do not interrupt the flow of the narrative with lengthy Tables or

Graphs. Shorter tables and graphs can be inserted into the text of the report. Those that are more

involved should be included in appropriate Appendices. Even though they are presented in an

Appendix, the report’s narration should refer to these graphs and tables as well as their purpose.

Tables should include a descriptive and informative title, with each column also titled, and each

should be provided with a number. Each column title should include appropriate units of

measurement. Any variables used in titles should be fully defined within the body of the lab

report. Tabulated numerical data should also include error estimates.

Graphs should also be titled descriptively and be numbered. A title such as Density vs.

Concentration is not descriptive. Something more appropriate might be Density of Aqueous

Ethanol Solutions at 25oC. Each of the graph’s axes should be labeled along with units of

measurement. Each data point should be distinctively marked and should include an error bar. If

multiple data sets are included on a single graph, each set should have a different marking and a

legend of the markings should be provided. Graphs should be scaled so the bulk of the area is

used for presenting data. Appropriate trendlines should be included along with a least squares

analysis of the trendline equation parameters.

What follows are some details concerning each of the above mentioned report sections. I present

an example drawn from the literature for most of these sections. Pay attention to not only what

is said in each example, but how it is said. Different Journals require different styles of

presentation. All of the examples presented below are drawn from the Journal of Physical

Chemistry.

Title

Appropriately title the lab report. The title should be fully descriptive of the presentation you

will be making. Don’t simply title a report Surface Tension Measurements. This begs the

question; surface tension measurements of what? Something more appropriate might be The

Surface Tension of Aqueous n-Butanol.

Abstract

This is a very, very short description of the experiment completed. It should not exceed three

sentences in length. It should answer the following three questions:

i) What was measured or determined?

ii) How was the measurement performed?

iii) What were the results?

Only one or two key numeric results should be presented at this point. Any numeric results

presented, however, should also include an error estimate.

The following example is fairly well written.

What was determined: second hyperpolarizabilities. How were they determined: they were “calculated”.

(A modeling program was used.) Some verbiage is also presented concerning the general results.

Introduction

Begin with a short description of the purpose of the experiment and the relevant theory involved.

Key equations to be used in the analysis should be presented in this section. Define all symbols

used in these equations; unless they are defined in the lab handout. This section should provide

an overview of the experiment and the key results to be determined.

Notice how, in the following example, the author proceeds from generally applicable theory to

specifics concerning what will be presented in subsequent sections of the report.

.....

Experimental

Provide a descriptive narration of the experimental procedure. This should be given in the past

tense as it is a description of things already done. It should follow the logical order in which the

experiment was carried out.

Include relevant information concerning any specialized apparati, the chemicals used and how

experimental variables were controlled. Do not simply regurgitate the published procedure.

This should be a description of the procedural steps you actually performed. Although it should

also be short, it should contain all the specifics needed for an independent experimenter to repeat

the experiment. Include error estimates for all experimental data. Do not include details of

procedures that are considered common place in the chemical laboratory. Be as concise as

possible.

Again, the example should be studied carefully.

Results and Discussion

Here is the point at which you will include important experimental observations, key

experimental results along with their error estimates and any deviations from the published

procedure. Include tables of data, where relevant, and all calibration curves generated.

Then, present and discuss the results of your data analysis. This should be presented in a logical

order; starting with your first calculated results and proceeding to those calculations that build on

these results. Provide sufficient narration that the reader can follow the flow of the arguments.

Do not simply provide a string of data calculations without any rationale for why they are being

performed. However, do not become chatty and verbose.

If graphs or tables are used, refer to them in your narration. Include some verbiage as to what is

learned from their presentation.

All calculations should include:

i) One relevant sample calculation; all subsequent repetitive calculations should be

omitted. Results of repetitive calculations should simply be tabulated.

ii) Equations used should be presented in their general form, followed by a single case

into which data, along with units, are inserted.

iii) All results should include corresponding units.

iv) Each calculation should be followed by an appropriate error analysis. The format for

presenting error analysis calculations is the same as that described for other

calculations.

If computer programs are used for data reduction, a sample calculation, with error analysis,

should be presented here. A program listing for any specialty software used in the data reduction

should be included in an Appendix. Complete software output should also be included in an

Appendix.

Note the narrative style of the example.

Because this is a laboratory report, and not a paper to be submitted for publication, some detail

concerning calculations should be provided. For example, a calculation of the acceleration due

to gravity from pendulum measurements might be presented as:

g = 4π2l / T

2 = 4 π

2 (1.00 m) / (2.00 sec)

2 = 9.9 m/sec

2

Errors in the measurement of l and T were estimated based on repeated observations of the

same system. A maximum error estimate of g is thus:

∆g = (4π2/T

2) ∆l + (8π

2l/T

3) ∆T

= (4 π2 / (2.00 sec)

2) (0.01 m) + (8 π

2 (1.00 m) / (2.00 sec)

2) (0.02 sec)

= 0.3 m/sec2

The error estimate should never be reported with more than one or two digits. Also, the precision of the

calculated result should match the precision of the error estimate.

Conclusion

Sum up your experiment and the derived experimental results. Compare your results with those

of the literature. Consider experimental sources of error. Discuss how these errors might be

reduced or how the experiment might be improved upon.

In general, the conclusion should reverse the point of view of the introduction. Start with

specifics concerning your experiment and proceed to a more general discussion.

......

References

Sources cited or used, other than the experimental procedure provided in class, should be

appropriately referenced.