FORMAL WRITTEN LABORATORY REPORTS – Hershey High School

Introduction

An important part of the training of every young scientist is the ability to write a scientific report. Too often this skill is reserved for upper-level courses or even postponed until graduate school, often with abysmal results. It is therefore important to introduce students to “correct” scientific writing early in their careers. Of course, every journal and every instructor has its/his/her own rules for what this “correct” way of writing is. Thus, it is important in each case to read and understand the guidelines given by the instructor or by the scholarly journal to which one is submitting the report. The goal of this document is to present students with some of the rules for writing a scientific paper that will be consistent among ALL Hershey High School science courses.

Sections of a Lab Report

Almost every scientific paper contains the following sections in this order of coverage: title, abstract (not relevant for our labs), introduction, experimental method, results, discussion, and references. Some general guidelines for each of these sections follow:

1. Title: The title should reflect the report’s content. It should be brief, specific, and descriptive. Be sure to note the independent and dependent variables. If you are unsure about these terms, look them up or ask a teacher.

2. Introduction: The introduction should present a clear statement of the goals of the research and should answer the question of why the research is important. It might also include a brief description of the background of the problem, complete with relevant references to the literature to describe what others have accomplished in this area of research and how this project complements or improves upon their work. For purposes of our class, the Introduction section should also include a brief description of the theory behind the experimental technique which is employed in the project. It should also explain any equations used in the calculations and define their variables.

3. Experimental Method: The experimental section should describe the actual procedure used in the course of the experiment (it should not simply be a repetition of the directions in the laboratory manual) given in enough detail so that the experienced reader could reproduce your work using only the Experimental section of your paper as a guide. This entire section should be written in the third-person, past-tense, and passive-voice. For example, one would say that “Fifty-milliters of 0.20 M HCl were added to a 250-mL Erlenmeyer flask and titrated with 0.050 M NaOH until the phenolphthalein indicator changed from colorless to pink.” Calculations are typically not included in this section.

4. Results: Use the Results section to present only the relevant data. Record volumes, readings, etc. Present data for multiple samples in table form. Also include in this section any relevant graphs of the data or spectra. Be sure that graphs and figures are correctly labeled as described in a later section of this handout. Always refer to the data in figures and tables in the text by mentioning the figure or table number. Be careful not to draw any conclusions about the experimental data in this section. Reserve the actual analysis of the data for the Discussion section. For purposes of this course, a Sample Calculations section, showing one calculation of each type (including units), should be included immediately following the Results section, when requested by your instructor.

5. Discussion: State all conclusions as specifically and as objectively as possible. This is the section where the experimental results should be interpreted. Any references to particular sources of error should be specific in nature and should match It is also good practice to include a discussion of the limitations of the work in this section and suggestions as to how the work could be improved by further experimentation. Thus, for instance, if the calculated volume of H2O entering a dialysis bag is too high and you state that you might have made the bag hypotonic, you would lose points because the dialysis bag H2O volume would increase if the bag were hypertonic. Although many scientific journals allow the use of first-person in this section, try your best to avoid this temptation and to continue to write in third-person whenever possible.

6. References: Scientific journals have lengthy instructions for the format of references. Fortunately, very few references will actually be needed for lab reports in introductory courses. Most, if not all, of your high school course references will follow the MLA format. Our HHS library contains an extensive resource network. Therefore, your references should NOT contain a majority of random websites.

Some comments about grammar, style, and usage

1. The subject and its verb should be in agreement. For example, “the experimental data are given in Table 7,” not “the experimental data is given in Table 7.” The word data is plural. Likewise, “a series of compounds were tested,” not “was tested.” Units of measure are treated as collective nouns and are therefore singular. For instance, “5 mL of water was added,” not “5 mL of water were added.”

2. Capitalize only proper nouns. Do not capitalize the common names of element, chemicals, or equipment. Correct: “a Perkin-Elmer LS-5 spectrofluorometer was used to determine the emission spectrum of anthracene.” Do capitalize the elemental symbols (e.g. H, He, Li).

3. Numbers reported with units should be listed in numeral form, followed by a space and then the abbreviation for the unit. Always include a space between the number and its unit and use the correct abbreviations for units: e.g. g for grams, s for seconds, h for hours, min for minutes, s for seconds, mol for moles, mL for milliliters, K for degrees Kelvin, and °C for degrees Celsius. Numbers used as adjectives should be hyphenated: “3.45 g of sodium sulfate was added to a 100-mL Erlenmeyer flask.” Counting numbers (numbers without units) ten or smaller should be spelled out: “Eight test tubes were prepared and they were each mixed by inversion ten times.” Whenever a number begins a sentence, both the number and its units should be spelled out in their entirety. Try to avoid beginning sentences with numbers whenever possible. Ranges of numbers should be reported with dashes and the units following the latter numeral: e.g. “in each experiment, 0.20–0.45 g of FeCl3 was used.” A series of data with the same units should contain the units only after the final data point: e.g. “IR peaks were observed at 3200, 2894, 1730, 1450, 1260, 985, 750, and 450 cm-1.”

4. The third-person, past-tense, and passive-voice should be used for all experimental procedures. Do not use the words “I” or “we” in the Experimental section. “I” and “we” are permitted in the Introduction and Discussion sections, but their usage here should also be minimized whenever possible. Correct: “The 0.20 M KMnO4 solution was added to the 500-mL beaker which contained 0.20 M KI,” and “The results of this work indicated that the temperature dependence of the rate constant for the reaction of X with Y was exponential.”

5. Number the pages of your lab report using Arabic numerals in the upper right-hand corner. Do not, however, number the first page.

6. Figures should be numbered with Arabic numerals and referred to at the appropriate place in the text. Do not refer to a figure by writing “see Figure 2.” Instead, report that “the results of the pH titration are shown in Figure 2.” Each figure itself should be labeled with the figure number and a thorough description of the contents of the figure. The figure caption should be detailed enough that it could stand alone in describing to the reader exactly what data it contains and what experimental conditions were used in the collection of that data. The axes of graphs must be correctly labeled, including units. Graphs should be of an appropriate size such that the data are easily seen and that the points fill the entire section of the paper reserved for the graph.

7. Tables are also numbered sequentially using Arabic numerals (1, 2, 3, …). The same rules for referencing tables in the text and for labeling tables with descriptive captions apply to tables as they did to figures.

Printed with permission from Dr. Brian Pfennig, Ursinus College
Checklist Before Turning in the Lab Report

____ The project number, title, name, and date are included

____ The Introduction section presents an overview of the work and the reasons for doing it

____ The Experimental section is detailed enough so that a knowledgeable researcher could repeat it using only what you have written in this section

____ The Experimental section is written in the third-person, past-tense, passive-voice

____ All major results are included in the Results section

____ Multiple, related results are tabulated with appropriate table headings

____ The units for numbers in tables are given only in the column headings

____ The Results section refers in the text to any figures and tables by number and describes their contents, but it does not interpret the data

____ The Sample Calculations section contains only one set of the important calculations (including units)

____ The Discussion section explains the significance, trends, and limitations of the data

____ All pages after the first page are numbered in the upper, right-hand corner

____ There is a space between each number and its units

____ Subscripts and superscripts are typed, not hand-written

____ Each figure or table has a stand-alone, descriptive heading

____ The data in figures or tables are organized and have units

____ The paper was spell-checked and sounds fluent when read aloud

____ Any graph fills the entire page, the axes are labeled, units are included on the axis labels, & the range is such that the data fill the page

Formal Lab Report Assessment

Section / Components / Points Earned / Max Points
Title / Independent Variable
Dependent Variable
Object(s) being investigated / 1
1
1
Introduction / Background information
Goals of the research
The hypothesis
Explanation of any equations used / 2
1
1
1
Experimental Method
(Procedures) / Description of actual procedures
Not a reiteration of procedures from lab manual
List of materials required
No “I’s” or “We’s” / 3
1
1
1
Results / Present Tables and Figures that are:
-introduced in the text
-labeled and numbered properly
-meaningful
-organized
-clear
Sample calculations section / 2
2
2
2
2
2
Discussion / Interpret Data
Make a conclusion regarding hypothesis
Limitations of this work
Suggest additional experiments
Relate study to outside world / 1
2
2
2
2
References / Proper MLA format
Not exclusively Websites / 3
2
Total / 40


Example Lab Report

Project #52: Determination of the Empirical Formula of

Magnesium Oxide Formed by the Combustion of Magnesium Metal in Air

Zaccharias Ursinus

April 1, 2006

Introduction

When calcium carbonate, CaCO3, is decomposed by heating, it emits gaseous carbon dioxide and a white solid called lime, which glows brightly when heated. By measuring the volume of CO2 gas emitted in this process and then weighing the amount of the solid calcium oxide that remains, Watkins determined the empirical formula of lime to be CaO. Since magnesium contains the same number of valence electrons as Ca and lies directly beneath it in Mendeleev’s table of the elements, the purpose of this work was to ascertain the empirical formula of magnesium oxide. Magnesium oxide can be produced by the combustion of magnesium metal in air according to the procedure employed by Pfennig. The combustion of magnesium in air, however, also leads to the formation of magnesium nitrides, previously making gravimetric analysis of magnesium oxide impossible since the relative amounts of magnesium oxide and magnesium nitride formed in the combustion process are unknown. This work avoids that complication by converting the undesirable magnesium nitrides into magnesium hydroxide first and then quantitatively converting the magnesium hydroxide into magnesium oxide.

Experimental Method:

Three ceramic crucibles and their lids were heated with a Bunsen burner until they were red hot for at least 10 min. The crucibles and their lids were then removed from the flame by using a pair of tongs and carefully placed in a desiccator to cool. After the crucibles were cooled to room temperature (~25 °C), their masses were obtained to the nearest 0.0001 g using a Mettler analytical balance. This procedure ensured that any adsorbed water on the surface of the crucibles was completely driven off before the crucibles were weighed. Several pieces of freshly-sanded magnesium ribbon having masses of 0.24–0.32 g were carefully weighed to the nearest 0.0001 g on the analytical balance. The Mg pieces were placed inside the previously-weighed crucibles with the lid slightly ajar and heated to red heat using a Bunsen burner. After 10 min in the Bunsen burner flame, the crucibles were cooled to room temperature. A small portion of distilled water was added to each crucible in order to wet the solid contents of the crucibles. This procedure converted all of the magnesium nitrides formed by the combustion reaction into magnesium hydroxides. The crucibles were again heated in a Bunsen burner flame, at first slowly to drive off any excess water without splattering and then to red heat for at least 10 min. After cooling the crucibles to room temperature in a desiccator, their masses were again obtained to the nearest 0.0001 g using an analytical balance.