You will be required to write a laboratory report for each lab performed. These are due at the beginning of the lab period the following week. Some of the reports, especially at the beginning of the semester, will be individual reports. For these, you may work with a partner collecting and analyzing the data. However, you must write up the data and any required components for the report on your own. As the semester progresses, you will be given the option of writing group reports. In these, you may work as a group both in collecting the data and in writing up all of the components of the lab report. You will also need to include a table showing the relative contributions of all members of the group for the lab (data collection and report writing). No matter what type of report is required for a laboratory, it is suggested that you exchange email addresses and phone numbers with your lab partners to facilitate completion of the lab. It is also recommended that data is backed up and given to all members of the group before leaving lab for the day.
Regardless of the type of lab report required, certain guidelines must be followed.
Components of the Lab Report
In a typical lab report submitted for publication in a scientific journal, there are a number of required components which are presented in a specific order: title, abstract, introduction, experimental procedure, results, discussion, conclusions, and references. Some reports also include appendices at the end. For a formal lab report (such as that required for the lab project), all of these components must be included. For the rest of the labs, only certain components will be required. These will be mentioned in the lab itself.
This component will be required for all labs. It can be at the top of the first page or on an additional sheet of paper (for a formal lab report). It should include the title of the experiment, the names of the people in the group, and the date on which the experiment was performed. If the report is an individual report, the name of the person submitting the report should be listed first and underlined.
An abstract is a short summary of the entire report. In scientific literature, it is often sited separately from the rest of the report and must therefore be able to convey the information contained in the report on its own. For this reason, even though it is the first component of the report to be read, it is usually the last component that is written. Most of the reports written for this class will not contain an abstract.
The abstract is about one paragraph in length and usually contains 80 to 200 words. It covers four major points: a statement of the problem addressed or the purpose of the experiment, what was the experimental plan used, a summary of the main results, and a summary of the major conclusions. Typically, no references are contained in an abstract.
An introduction is used to bring the reader up to speed on any required background to understand the work that was done in this report and why it was done or why it is important. In a scientific journal where the targeted audience is familiar with the background, the introduction is typically one or two paragraphs long. However, in this class where projects come from many different backgrounds, it may be necessary to make it a little longer to adequately prepare the reader.
The introduction needs to provide a clear statement of the problem or project being studied and why it is important to study. To do this, one needs to provide concise and appropriate background of the problem and its significance. This is done by essentially outlining what has been done before by summarizing and citing pertinent literature. This is not a general survey of lots of semirelevant literature.
Having provided background into the problem, one can then provide a basis for doing the current experiment. This is where a hypothesis is presented and elucidated to state how the current experiment differs from or is related to previous work that has been done. It is also appropriate at this point to indicate the significance, scope, and limits of your work.
Depending on the journal being used, this section may also be called “Experimental Methods,” “Experimental Section,” or “Materials and Methods.” This section is used to describe how the experiment was conducted so that other experienced workers can repeat the experiment and obtain comparable results. All of the lab reports will contain an experimental details section of some type.
For most of the labs, you will be following a standard method (the lab procedure). For these labs, it is sufficient to properly cite the appropriate literature (i.e.: the lab URL) and provide any additional details as needed for your particular completion of the lab.
For some of the labs, you will be designing your own procedure and need to provide this information in the experimental details section. It is important to remember that you are writing the experimental details section for a lab report and not the procedure for a lab manual. A lab manual gives a series of commands (sometimes numbered) for a student to complete. As such, it is not written in the third person, past tense form. A lab report provides a summary of what was done and how it was completed. Thus it is still written in the third person and past tense. It is in paragraph form and is not numbered.
When writing the experimental details, one describes what things were combined together, how they were worked up, and any unusual apparatus or equipment. If any standards or controls were used, these are described as well. It is not necessary to provide details on the procedures used if they are established and standard. For example, one would say that 15 g of NaCl was mixed with another chemical but would not describe how the NaCl was obtained. It is assumed that someone in a chemistry lab knows how to weigh out NaCl to obtain 15 g. It would also not be necessary to specify the type of container the NaCl was weighed in as someone doing the experiment should be able to identify an appropriately sized container.
In this section, it is important to identify all materials used as they are used. For chemicals, the correct chemical names of each compound should be used along with the amounts (both the measured amount and the corresponding moles). If a solution is used, the concentration should be noted. If a product for a reaction is isolated, it is appropriate to mention any tests to confirm its identity or purity and to give a percent yield. For an apparatus, one can either describe how different pieces of equipment are connected or provide a figure with the details.
The component of the lab report provides a summary of the data collected and any statistical treatment done on that data. It will be included in all of the lab reports for the semester. Often, this data is presented in tables or graphs. When providing the results, it is important to include only relevant data with sufficient detail to justify any conclusions made. It is up to you as the writer of the report to determine what is relevant, but bear in mind that you do not want to overwhelm the reader with the same material repeatedly. Often, a graph will be sufficient to show relationships in the results section while the table with hundreds of data points used to create it is redundant and therefore not included in the results section. It is important to make sure that all tables and graphs are clearly titled and labeled with correct units and that the information is presented in a way that makes it clear what was recorded and how that information was used. A sample of each type of calculation should be included in this section as well.
It is important to note that the results are not only the tables or graphs created while doing the lab. It is the job of the writer to guide the reader through the data by providing some sort of context. Thus, there will be at least a paragraph or two before and possibly between the various tables and figures which let the reader know what part of the experiment the data corresponds to, what the important number was in the table (like an average with significant figures), or what the observed trend was in the graph.
The purpose of this component is to interpret and compare the results of the experiment. You have just finished stating what the results of the experiment are, now you need to convey to the reader what they mean. As such, it is one of the most important parts of the lab report and is included in all of the lab reports. Sometimes the discussion will be combined with the results; sometimes it is kept separate. Either is fine although if they are kept separate it is important to avoid simply repeating the results in the discussion section.
It is critical to be objective when writing the discussion. You can point out successes of the experiment—what was the identity of the unknown, something new that was discovered, a tenant of chemistry which was verified. When doing this, you are making claims based on your observations in the results section. It is important to support these claims with evidence. Some of the evidence will be the data you recorded or calculations that were made. Other evidence will be based on previous work done in the literature. The key in this is to relate the current experiment to what is already known to determine whether or not you have resolved the problem you originally set out to solve. It is also possible at this point to extend the results further. Applications of the results to the real world may be suggested as well as new hypotheses or more studies.
It is also prudent to reflect on limitations of the work—was there anything which could not be done due to the apparatus available? Was there any mistake made which affected the results? Please note that when describing errors, things like “human error may have occurred” or “the balances might have been off” are not sufficient. Either they were or they were not. Not all labs have mistakes and if mistakes do occur, they should be evident either in the results of the experiment or in chemicals spilled all over the floor. Either way, they can be reasonably described and their effect on the results should be explained. If there was a better or different way to do the experiment, it should be noted. If the original hypothesis was incorrect, a new one should be proposed.
For some of the lab reports, there will be post-lab questions which must be answered during the course of the discussion. These can provide some guidance in formulating the discussion or in providing some type of application of the concept. For other reports, it will be helpful to reflect on questions that you had at the beginning of the lab. For all of the labs, it may be helpful to ask yourself, “What evidence do I have?” “How do I know?” “Why am I making these claims?”
This component of the lab report is sometimes included in the discussion and may not exist as a separate section, although it will be in each lab report in some format. Its purpose is to put the interpretation of the data into the context of the original problem based on the evidence presented in the report. If it is included as a separate section, discussion points should not be repeated and only relevant material should be included.
This section is provided at the end of the lab report to document sources of information. Typically, references are needed for material included in the introduction and the discussion. In ACS chemical literature, references in the document are often made using a superscripted number1 which is placed outside of the punctuation if it applies to a whole sentence or clause.2 The numbers begin with “1” at the beginning of the report and increase sequentially. If a reference is repeated, it uses the same number it had earlier.1
When citing the references in the reference section at the end of the report, there is again a certain format which is used. Each reference is preceded by its reference number in parentheses. The different components of the reference are then provided in a standard format. Please note that if you have a reference listed in this section, it must refer to a specific point which has been noted with the superscripted number in the body of the report.
(1) The ACS Style Guide, 2nd ed.; Dodd, J.S., Ed.;
American Chemical Society: Washington D.C., 1997.
(2) Author; author Journal, Year, Volume, Pages.
(3) Author; author Article title, Internet URL (date accessed).
There will often be times when a researcher has collected more data than what will reasonably fit in a lab report or has obtained interesting data which is only slightly related to the overall hypothesis being explored in the report. In these cases, the "extra" data is referred to at the end of the report in an appendix section which an interested reader can access if desired without taking up space in the main body of the journal itself. The appendix usually contains just the additional data collected without a lot of writing to describe what the data means.
Appendices will be used for lab reports in this class for both of theses scenarios as well. A graph included in the results section may not contain the corresponding data table in the results section because it is too large and it would be redundant to present both at that time. In this case, the data table would be included in Appendix at the end of the report, usually as an embedded Excel spreadsheet, and referred to in that manner. In this way, the instructor can check the data itself to make sure that all of the calculations were done correctly.
ie: A linear relationship was found between rate and time (Figure 2, Appendix 1).
In addition, some labs have questions to consider that were related to the concepts of the lab but were not a part of the main focus of the lab. The answers to these questions would be given in an appendix at the end of the lab report as well. If this is needed in a particular report, it will be mentioned in the lab itself.
Portions of this description were obtained from The ACS Style Guide, 2nd ed.; Dodd, J.S., Ed.; American Chemical Society: Washington D.C., 1997.