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Lab report instructions for General Chemistry a
Why a Journal article report (JAR)? A primary goal of this course is to see if you can think like a scientist, interpret data, and communicate that knowledge to your peers. Journal article reports allow you to develop your understanding of the experiment and the critical thinking necessary for clear, concise communication of those ideas. This is also a chance to improve good writing, communication, and computing skills.
These instructions are meant to be general instructions for JAR type reports. Specific supplemental instructions may be given for some experiments.
Academic Honesty: A reminder that all data analysis and calculations that are not done in the laboratory, as well as all writing, is to be your own work and not shared with others. If you need assistance please see the TA’s, the writing center, or me. Also, Failure to provide in-‐ text citations and references at the end of any work that provided you with information is also a form of plagiarism.
“In-‐text citations”. After each statement that either quotes or paraphrases an idea or statement from another source there must be an in-‐text citation and corresponding reference at the end of the report. You may use either the MLA or the American Chemical Society (ACS)1 method of citation and reference. In-‐text citations are usually of the form of superscripts, (number) or author -‐ date: “The measurement of the ∆Hrxn was conducted using the standard calorimetry procedure presented in the lab manual.”2 or “…manual (1).” , or “…manual (Grossie and Underwood, 2014).” all of which refer the reader to the reference at the end of the report in this case the lab manual.
Resources for writing lab reports are available here and through Pilot:
1. The outline below is a convenient reference for the main points for each section 2. The following description details the expectations for each section. 3. “Writing Laboratory Reports” Chapter 7 3 This is available through Course Electronic
Reserves. The instructions for using the reserves are on pilot as is the reference for this book should you need to reference in your report. In particular it compares good and poor ways of doing things. The whole book is available in Dunbar Library.
4. “How to write a lab report” Reed College. The link is on pilot. In particular compare the example of “well-‐written lab report” and “poorly written lab report” to see how yours might be improved.
5. Lab manual preface. 6. Get assistance from the University Writing Center, http://www.wright.edu/university-‐
college/academic-‐help/writing-‐center/overview, 031 University Library, 937-‐775-‐4186 (see link for hours).
7. Get assistance from the TA’s
a Spring 2014. Adapted from Dave Dolson summer 2013 and spring 2011 by Lary Sanders.
Outline of sections of a lab report (provided for quick reference)
1. Title (meaningful but not the same as manual), author date, lab partner, TA and section. Significant points may be deducted if the TA name or section is missing.
2. Purpose: (1210L Only) hypothesis to be tested, or Claim. We are substituting this for the abstract as a way to focus on the primary scientific objective.
a. This section replaces the abstract suggested in “Guidelines…” b. State the purpose of this work?
i. Is it to test a scientific hypothesis such as verifying gas laws in the upcoming gas behavior lab or is to answer a scientific question such as, what is the vitamin C content in a particular sample?
c. Another way to look for the purpose is to identify the scientific hypothesis to be tested or the claim that the report is making
d. The purpose or hypotheses is the main point of the introduction. The claim or result is the main point of the discussion/conclusion section
3. Abstract (1220L Only) (typically 150-‐250 words) – Present tense a. Statement of the purpose or problem (approximately 1 sentence) b. Experimental method & theoretical support used – brief c. Summary of data, results, or findings d. Stands alone – may be only thing a reader sees. e. Concise, organized, accurate representation of article f. Write last – similar to conclusion section but not copied.
4. Introduction a. State the objective b. Background theory – will include relevant citations c. Methods: state briefly the methods by which the objective will be pursued
i. Are you using a titrimetric method, spectroscopic method, etc.? ii. For what purpose will you employ these methods? iii. Leave the details for the Experimental section
d. Finish with Purpose/hypothesis/point. 5. Experimental method.
a. In General Chemistry, always begin with an in-‐text citation reference to the experimental procedures in the laboratory textbook. ACS allows a superscript number outside the punctuation if referring to the whole sentence.1 Also italic (1). Inside punctuation, or author year method such as (Grossie and Underwood, 2014). Use the same number if a reference is repeated.b
b. Reference 1 in the “References” section should resemble the following but with the appropriate lab cited:
i. Grossie, D. A. and Underwood, K. A. , Laboratory Guide for Chemistry, 7th ed., “Analysis of Hydrated Copper Sulfate”, Wright State University, Dayton, 2014, Exp’t 5, pp. 25-‐28.
b In Word this can be done with insert> cross-‐reference.
c. A brief statement of experimental method so that the reader need not have a copy of the text to know the general methods used. There should be enough information that the reader can understand the experiment.
d. Details of any changes (omissions/additions) e. “Materials used” (p xx) not so important for CHM 1210L or 1220L reports.
6. Data and Results a. Primarily narrative text, supported with tables, graphs, figures as is appropriate to
each experiment b. Organize presentation in logical order
For example, wt. % composition of Cu, sulfate, water before empirical formula determination
c. Report “Significant Outcomes” – present the relevant results, those used to address the purpose of the experiment.
d. Omit small details. e.g., mass of filter paper e. Tables, Graphs, Figures presented within the report in an appropriate order. f. Properly labeled (see p.xx) g. Tables numbered and titled above h. Graphs & Figures numbered below with caption i. Presented with narrative text for the reader. Table and Figures “don’t exist” if they
are not discussed in the text. Don’t assume the reader will find her/his way. j. “Sample calculations” if required are put in an appendix rather than in results. It is
assumed the reader knows how to do the calculations. 7. Discussion and Conclusion.
a. Most important. b. Interpret/Explain results c. Do results answer your question or support your hypothesis (was experiment
purpose satisfied)? Do the results support your claim? If not that’s ok but you need to explain why.
d. How strong is your evidence – what are the limits of your knowledge or measurements?
i. Compare your experimental measurements to literature (known or accepted) values when available
ii. Address sources and magnitudes of errors or uncertainties in measurements – random vs. systematic
iii. Is the direction & magnitude of possible errors in agreement with your results compared to literature values?
8. References a. State literature references
i. For references to theory ii. For experimental method iii. For literature values compared to your results iv. Any other sources of information.
Detailed descriptions of Laboratory Report sections.c
Purpose (1210L only):
This is not normally a separate part of a journal article. We are using it here in place of an abstract to help you isolate main ideas of the experiment. What is the hypothesis to be tested? Frankly – why do the experiment and why should anyone care? In other words, what scientific questions are we attempting to answer? What claim will the report make?
Avoid starting with “The purpose is……”
Abstract (1220L only) (150-‐250 words)
The abstract stands alone. A reader should be able to read only your abstract and understand the report. Therefor it must contain the purpose and the important results. Avoid judgments or interpretations. These are for the discussion section.
Avoid starting with “The purpose is……”
This section summarizes what was measured and the overall quality of the measurements. It is sometimes the only section a causal reader will look at or that may be available without buying the paper and therefore must stand-‐alone. It will determine if they want to read further.
The abstract should be written last – it is the summary of the paper. The beginning of the abstract pulls from the introduction – background and theory, the middle refers to the results, and the ending sentence(s) from the end of the conclusion. Note the inclusion of final numbers where appropriate. Be specific – name compounds and instruments used (not model type). Specific amounts can be used if relevant to the scientific understanding.
Because the abstract stands alone, avoid statements that would require references. Refer to your own work.
Of course it is best to rephrase statements used in the body of the report rather than copy them.
Introduction:
The lab text tells you that this “should be a concise statement of the theory/reason behind the experiment, . . . “ Please don’t interpret “concise statement” to mean a single sentence. This section should introduce the experiment to your reader, generally in a paragraph or two, but some experiments may require more. Your introduction for the reader should explain important concepts and introduce equations that will be used to evaluate the data that will be presented later. Variables in equations should be defined. The audience for this section, as for the entire report, should be for your peers – other students who have not yet performed this experiment. Don’t assume that the reader has more advanced knowledge so that you omit information that should be conveyed to a peer reader.
c Spring 2014. Adapted from David Dolson CHM 127.
Notice the topics that make up the introduction section in the lab text. In some cases additional reading in other sources may be necessary for a more complete treatment of background information and concepts pertaining to particular experiments. Usually the concepts and equations developed in this section should be conveyed to your readers also – but they should be understood by you, the writer, and then presented to your reader in your own way. Don’t simply take sentences from the lab text or other reference and write it as your own work – that is plagiarism. And don’t simply read through the lab text introduction or other reference and rewrite the sentences in a slightly different way – this also is plagiarism. Write from your own understanding of the topics, which requires that you do some reading in the lab text and perhaps read in other resources and that you have an understanding from which you can write an introduction of this experiment for a peer reader. The writing in this section and throughout the report should be grammatically correct.
Take the “Heat of Reaction and Solution” experiment in the lab text as an example. Based upon the written introduction presented in the laboratory text, it would seem reasonable to include the following items in your laboratory report introduction section:
• Statement(s) that this experiment concerns calorimetric measurements to determine the heat of reaction for several acid-‐base reactions and for a solution reaction.
• Further statements of which reactions were studied • Concepts of endothermic and exothermic processes, heat and heat capacity should be
explained and that because heat is transferred between the reaction and the calorimeter, qrxn = -‐qcal. The heat calculated from the calorimeter’s point of view is of the same magnitude as that produced by or taken in by the reaction but has opposite sign.
• Equations for calorimeter heat (qcal = C ΔT or qcal = mc ΔT) and to define reaction enthalpy change (ΔH = qrxn/moles of reactant) should be developed with an explanation of the symbols provided for your reader.
• Equations should be numbered for easy reference in the text.
Experimental Methods:
The American Chemical Society (ACS) Style Guide indicates when using a standard method, as we do in most of our labs, to “cite the appropriate literature and give only the details needed”Error! Bookmark not defined.. For nonstandard procedures enough information needs to be given to replicate the work.
Can the reader understand what was done without having the manual at hand?
The laboratory text should be referenced as the source for the experimental procedures unless a handout is involved. A simple reference citation is insufficient information in a laboratory report, which might well be read without the simultaneous availability of the cited reference for procedure. Accordingly, your report should present a concise description of the experiment even though it may omit many small details of the work.
Deviations of actual experimental procedures from the method described in the laboratory text must be stated.
Data & Results:
Here a full analysis of the results is presented. First show the raw data and the equations used to analyze the data. This is objective date without interpretation. Sample calculations, if required, would be presented in an appendix. The results should flow logically through the data from beginning to end.
The lab text calls for students to state all results and numerical calculations, present graphs where appropriate and to compare results to literature values with stated uncertainties where possible. We would remind students to remember that this is a written document that must use written text to explain the results to your reader. A data table cannot simply appear without a written explanation given for its contents. The table should be introduced and presented with text. Too often, student writers believe that because someone with knowledge of the experiment will grade their report there is no need to describe the results – the grader will know how they were obtained. The report should be written for a reader from your peer group but one who may not have had this same laboratory experience. The report must describe the experiment, its results and their meaning for one who has not performed it.
If there is a table it should have a title and labeled headings, and measurement units must be stated in some manner. All measurements have uncertainties associated with them, and these should be stated in some manner. An example, from the CHM 1210 Paper Chromatography experiment, might appear as follows:
Table 1. Chromatogram Measurements for Determination of Retention Factorsa
Amino Acid Solvent Distance Spot Distance Rfb 1 = arginine 71 ± 1 mm 17 ± 1 mm 0.24 ± 0.01 2 = glycine 71 ± 1 mm 21 ± 1 mm 0.30 ± 0.01 3 = alanine 71 ± 1 mm 29 ± 1 mm 0.41 ± 0.02 4 = leucine 71 ± 1 mm 54 ± 1 mm 0.76 ± 0.02 5 = Cystine 71 ± 1 mm 11 ± 1 mm 0.15 ± 0.01
6 = Unknown# . 71 ± 1 mm 55 ± 1 mm 0.77 ± 0.02 7 = Unknown# . 71 ± 1 mm 22.5 ± 1 mm 0.32 ± 0.01 a. Adapted from reference 2.
b. An example uncertainty calculation appears at the end of this document for the leucine measurements – this actual footnote is specifically supplied for this document. Footnotes are not necessary for all tables.
Note that the table is “self contained”. It has its own footnotes (b) explaining the calculation. It also has a footnote (a) under the table indicating a reference in the text as in “adapted from”. In MS word these need to be done manually rather than try to use the “footnote”/”endnote” tracking.
If there is a plot or graph, it should be computer created, it should have a title, and the axes should be labeled. Best-‐fit lines (or curves) through the data points should be fit using the programs least squares fitting algorithm such as Excel’s trendline function if the equation is necessary for calculating subsequent data. Understand that neatness does count -‐ if you wouldn’t want a prospective employer seeing your lab report for a job interview don’t submit it in this class without improvements. Also note that figures have the caption listed underneath rather than on top as is Tables. Figures must be discussed in the text. Avoid captions the equivalent of “x” vs “y” as in this case “Fluorescence vs time” would tell the reader nothing that they can’t see in the plot.
Figure 9. Time-‐resolved SO2(ν3) IR fluorescence emission observed through a spectral bandpass filter.4
Discussion and conclusion:
Often our experiments are done to illustrate a known chemical principle. In this section the results should be compared to the expectations arising from a theory or from earlier work by other scientists. Numerical data previously reported in the scientific literature often serves as an accepted or literature value with which your work may be compared. This comparison must be made within the expected uncertainty of your experimental value(s), and this requires that you consider the possible sources of error that may affect your reported experimental value(s) including the direction and magnitude of each effect. If, within twice the expected uncertainty of a measurement, your value is in agreement with a literature value you may make this claim with 95% confidence. (This statement arises from a consideration that for random errors 68% of the population is expected to fall within ±1 standard deviation and 95% within ±2 standard deviations.) If your observations agree with a chemical law that is to be tested you may claim
experimental support for this law (for example the observation of a linear arrangement of gas pressure plotted against inverse volume supports Boyle’s law, as does a constant P⋅V product for a fixed mole quantity of gas). If the values do not agree within the expected uncertainty of your measurements or do not support an expected chemical law, it is necessary to address the possible reasons for the disagreement. Perhaps the magnitude of one of the errors is larger than you may have estimated or perhaps there may be the possibility of some specific systematic error. The method by which the measurement uncertainties were determined should be stated in the text of this section. And you should communicate support of or disagreement with literature values or chemical laws provided from your experiment with possible explanations given when there is disagreement. “Human error” is not an acceptable explanation.
If a literature value for a numerical measurement is not explicitly stated in the lab text, it still may be found in your lecture textbook or from another source. Ask the course instructor or your GTA and be sure to cite and reference the source.
References:
These will generally be the lab manual and the textbook. Some reports, especially in 1220L, may require additional references.
We are accepting either the MLA or the ACS method of citing references. A brief ACS method (Style guide) is available on Pilot. If using Internet sources make sure they are reliable. Wikipedia is not an acceptable source as anyone can add content. However you may be able to find reliable source within the references of a Wikipedia article.
1 Brief ACS style guides are available on Pilot. 2 Grossie, D. A. and Underwood, K. A. , Laboratory Guide for Chemistry, 7th ed., Wright State University, Dayton, 2014. 3 A short guide to writing about chemistry / Holly B. Davis, Julian F. Tyson, Jan A. Pechenik Boston : Longman, c2010 Ch 7; pp111-‐132 4 Adapted from Brumfield, B.R., M.S. Thesis WSU, 2005.
