Authors: B. D. Lamp, D. L. McCurdy, A. E. Moody, M. C. Nagan and J. M. McCormick
Last Update: September 08, 2010
|Formatting||Arrangement of Experiment in the Notebook||Discussion of Conclusions Outlines|
|General Formatting Rules||Statement of Purpose||Measurement Experiments|
|Attaching Output to the Notebook||Background||Synthesis Experiments|
|Treating Errors in the Notebook||Procedural Outline||Reporting on Physical Phenomena|
|Discussion of Conclusions|
|Summary of Results|
The laboratory notebook is perhaps the single most important piece of laboratory equipment. A scientist's notebook may be directly entered as evidence in court, and as such may be worth millions to a company in patent litigation. While you may never be in a situation where your notebook is worth a million dollars, good record keeping is essential in all scientific research. In an academic laboratory, the consequences of poor record keeping are wasted time as you repeat the experiment, or simply failing the exercise. In an industrial laboratory, inadequate lab records ultimately cost the company money, either in the cost of time and materials or as the result of legal action. In either case, the cost to the responsible employee is their job and all possible future employment. Thus, adequate record keeping will be stressed in all chemistry laboratories at Truman.
There are many different sets of rules for keeping a laboratory notebook,3 which range from the very elaborate rules followed by industrial chemists to the simplified rules listed below. Not all of the points given here will apply to all courses; your instructor will point out modifications to these procedures in his or her syllabus or in the laboratory. No matter what guidelines you use, the goal is to produce a record of a scientific endeavor that is understandable to a knowledgeable reader and which can be used to repeat the experiment and, presumably, get the same results.
Laboratory records are to be kept in a bound notebook (i. e., secured with glue), not a spiral notebook or a loose-leaf binder. The pages are to be consecutively numbered. No pages are ever to be removed (except for the copies produced by duplicating notebooks).
All entries are to be made directly in the notebook in black or blue ink. Everything related to the laboratory work must be recorded in the notebook in an organized and neat manner (if it cannot be easily read, it is not adequately recorded). It is critical that the material is intelligible and understandable to the notebook author and any trained chemist who reads the records, attempts to reproduce these results, or endeavors to finish an incomplete analysis. This concept is often known as "traceable" in the industrial world.
It is unacceptable under all circumstances to rewrite (or "copy over") an experiment in the notebook outside of lab. It is also unacceptable to type up portions of the laboratory notebook in a word processor and then attach the printout to your notebook. Plan your activities in the laboratory so that all information is properly entered into the notebook while you are in the laboratory.
Include in the notebook a complete description of the work performed, all reference materials consulted, and ideas that you have related to the work. There should be no loose scraps of paper in the notebook. Graphs, charts, spectra, or spreadsheet analyses should be affixed to the pages of the notebook with tape or glue (to both the original and duplicate pages of duplicating notebooks). Label the space where this material is to go with a description of the item and the results it contained. This way, if it is removed, there will be a record of it. Make no notes on the inserted material.
On the first page of your notebook are written the name of the class, your laboratory section and your name. It is also a good idea to put contact information (e. g., your phone number or email address) here, in case your notebook is lost. The next two pages are reserved for a table of contents (some notebooks come with a table of contents section on the inside front cover, or as a separate, removable sheet; these should not be used). The words "Table of Contents" are to be written at the top of these pages. The first entry is to be the table of contents itself. An entry is made in the Table of Contents for each experiment when it is begun. This entry includes the title of each experiment and the page number on which the experiment begins.
You may wish to dedicate one page to a "Preface" in which you describe yourself and the contents of the notebook. Another item that is sometimes included is a page titled "Abbreviations and Other Useful Information". These items must be completed before the first laboratory session.
If you are using a non-duplicating notebook, one usually uses only the right side pages. The left pages are reserved for minor calculations, notes of no consequence to the experiment and notes that refer to material found elsewhere in the notebook. In academic laboratories, especially in teaching laboratories, this rule is relaxed as a cost-saving measure for the student. Please check with your instructor on which protocol he/she wishes you to use.
If a page is skipped, a large "X" must be drawn across it. The page is then initialed and dated. While generally frowned upon, you may skip a line as needed to separate sections. There should be no unused empty space on a page, except for the printed margins. Treat large blocks of blank space like a blank page (this assures the reader that no information was added later).
At the top of each page write the title of the experiment that matches that in the table of contents. At the bottom of the page place the date that the last entry was made on that page, your printed name and signature (or initials).
If an error is made, draw a single bold horizontal line through the error so that it can still be read. Write the correct information to the right of the incorrect entry and have a short accompanying explanation of the reason for exclusion. Never use whiteout or completely obliterate the incorrect entry.
Do not copy any information from the notebooks of former or current students. The only exception is when working in a group, and only one member of the group recorded the data during the experiment. In this case, you must indicate in your notebook that the results were copied from the other person's notebook. Write the recorder's name and the page number from which the data were copied next to the copied data.
In general, the notebook should be arranged in chronological order, so that when one experiment ends the next one begins. In an undergraduate laboratory this is very easy to do, but as you progress in your study of chemistry, things are not always so well-ordered. If you must start a new experiment before another is finished, you simply note on the last page of the unfinished experiment the page on which it will be continued.
Each experiment's record includes the following sections: Title, Statement of Purpose, Background, Procedural Outline, Results, Calculations, Discussion of Conclusions and Error Analysis, and Summary of Results. Each section should be clearly labeled with the underlined words indicated below. Sign and date each page as it is completed. The Title, Statement of Purpose, Background and Procedural Outline sections must be prepared prior to the laboratory period (click here for a checklist of what to do before lab).
Title: This should include the experiment's title, your name, the name(s) of your lab partner(s), and the date the experiment was begun.
Statement of Purpose: Clearly and concisely (two or three complete sentences) describe the purpose of the experiment, including the general method that will be used and anticipated results. Do not begin a Statement of Purpose with the phrase "The purpose of this lab is to. .". Don't resort to stock phrases; be somewhat creative. The pedagogical purpose of an exercise is not the same as the Statement of Purpose. For the "Determination of Density" exercise, the pedagogical purpose is to learn about precision and accuracy, and the statistical treatment of data. But your statement of purpose might read "The density of a copper block will be determined by two methods: (1) from its dimensions and mass, adn (2) from its mass and volume, as measured by water displacement."
Background: This section contains more information on the goals of the experiment, the methods used and the procedure followed. The content of the Background section varies with the type of experiment being performed and the requirements of each laboratory course. Check with your instructor about what to include, but in general the Background section must include:
Procedural Outline: This section is a brief (this section should not be more than one or two pages long, at most), but complete, description of the steps taken to carry out the experiment. It is not a rewrite of the source material (e. g., laboratory manual, textbook or journal article); use your own words, You may use a bulleted list for the steps. At your instructor's discretion, you may not be allowed to bring the source material to the laboratory. So, be sure that your procedure is complete.
Before beginning the Procedural Outline, divide the pages that will contain the procedure into two parts by drawing a vertical line on the page, approximately 3/5 of the way across the page from the left-hand margin (many notebooks already have this line drawn for you). Record the procedure on the left-hand side, and any modifications or procedural notes on the right-hand side. You do not record your results on the right-hand side! Results are recorded in the Results section.
Read the experimental section for the exercise before recording any part of the procedural outline in your notebook. This will make writing the outline much easier and minimize errors. As you read, think through the manipulations that are required and re-read sections that indicate particularly hazardous or important steps (usually denoted by "CAUTION!"). Once you are sure of what you are going to do, go back and write out a step-by-step procedure in your notebook.
Results: This section does not need to be completed before you come to the lab, but you may want to prepare blank tables for recording data. Include in this section a listing of the reduced data (e. g., tables), all graphs, spreadsheet results, and spectra. Unlike the Procedural Outline, this and all following sections may use the entire right-hand page. A common error is to forget to leave space for the graphs (a hand-drawn graph should take up most, if not all, of the page so as to maximize the results' precision) and other items (e. g., spreadsheet output) that will be prepared as part of the exercise.
All data should be recorded in this section in chronological order. Include all measurements made (with proper units and correct number of significant figures) and any important observations noted when performing the work. When observations are recorded in the laboratory notebook, they are always written in the passive past tense. So instead of "I saw the solution turn green", one writes, "The solution turned green". In general, personal pronouns (e. g., "I," "we") are not used in scientific writing (the overuse of personal pronouns is taken as a sign of arrogance and the passive is thought to sound more objective). The observations are always written in complete sentences.
When possible, set up tables for repetitive data before coming to the lab. Thinking carefully about the data that will be taken should allow you to prepare a data table, which, although difficult to accomplish for the first few experiments, will save time and space in your lab notebook. The use of tables will make it much easier for the reader to assess your methods and results.
Information on the chemicals and instruments used in the experiment are also included in the Results. For a chemical, the name of its manufacturer, its purity, and the lot number of the chemical are recorded, if this information is available (look the bottle's label). It is easiest to record this information when a chemical is first mentioned. For example, "A saline solution was prepared by dissolving 5.00 g NaCl (99.999%, Aldrich, Lot # 56390-BX) in 500 mL of distilled water." The identity of all instruments used must be recorded, preferably including serial number, model, manufacturer, and any information on the calibration or settings used. Remember that you want to have enough information in your notebook so that you can easily repeat this measurement, if and when necessary (e. g., you find a mistake). If the instrumental data were saved on disk, include the filename(s) with the data (More Info).
Calculations: An example of each calculation performed to reach the final reported answers should be shown with the units clearly shown at each step. For most exercises in a teaching laboratory, only one example of each different calculation needs to be included. Be sure to label each calculation and parallel the order in which the calculations appear in the procedure. You may want to set up the calculations before coming to lab to maximize your laboratory efficiency.
It is sometimes acceptable to include calculations in the Results section as needed. This is usually done in research situations where you need to make a calculation that you did not anticipate at the start of the experiment, but is sometimes allowed in upper-level courses where the laboratory exercises are not "cookbook." Check your instructor's syllabus, or ask him/her, for the format that you are to follow in your course.
If you made more than one measurement on the same phenomenon, calculate the average and standard deviation. Perform other statistical analyses as instructed. When an accepted or theoretical value is available, calculate a percent error. Include the output from any programs used to perform these calculations, and the filename under which the data were saved.
Discussion of Conclusions and Error Analysis: Summarize your results paralleling what you set forth in the Statement of Purpose, compare them to the expected results and try to place them in context (either in the larger field of chemistry or what you have done in class). This is not a long section; it may only be two or three pages long in the notebook. The key to a good discussion section is to concisely cover the important points.
Do not write things like "I liked this lab", "This lab went well" or "This lab was successfully completed", and do not use personal pronouns. Take your time and put some thought into your conclusions.
The discussion should try to pinpoint various specific sources of error encountered from the standpoint of the most likely determinate and indeterminate errors in the procedure. Once you have identified a source of error in your measurement, evaluate how it affected the result, and then suggest how this error could be minimized or eliminated. Simply attributing everything to "human error" is insufficient, and will be graded accordingly. Some labs won't have numerical results to discuss, but you can still indicate sources of uncertainty and how they could be, or were, minimized. To help you learn how to organize your discussion, brief outlines for the three types of exercises usually encountered in undergraduate chemistry laboratory exercises are given below. The types are:
Many aspects of the discussion section are the same in all three, but there are subtle differences that you should appreciate. These outlines are meant only as guides; you will need to adapt them to each particular experiment. Some experiments may incorporate components of each of these three broad categories. In that case, you will need to write a conclusion that combines the three types of discussions.
Summary of Results: For measurement and synthetic exercises you will need to include a final table summarizing the results of your experiment. For a measurement exercise this table should include each individual value used in the establishment of the average (check with your instructor if you have more than three or four individual values), the standard deviation, and the confidence limit. For a synthetic exercise your summary table should include the percent yield and the measured physical properties of the new substance. Once the Summary of Results has been recorded, sign and date the experiment.
Labels for Products: If you prepared a substance in the exercise, you must place it in a properly labeled bottle and give it to your instructor. The bottle label must include:
Your Name, Instructor's Initials
CHEM xxx, Date Prepared
Name of Chemical
Formula of Compound (Structure is Optional)
Physical Properties used in Characterization
The other physical properties used in characterization may include: experimental melting point, boiling point, melting point, NMR chemical shifts, IR peaks, etc. Only one or two physical properties need to be listed (check with your instructor as to which one, or ones, to include). The corresponding literature value for each property should also be listed, if known.