Guide to Writing a Lab Report

By Julia Benitez

This short guide is meant to help you write chemistry and physics laboratory reports in a fast and effective way. Besides the written explanation, it includes a Prezi presentation (that you can visit by clicking here) to help you visualize the information better. Before reading this guide, it is important for you to understand that the format of the report can vary depending on your professor and major, so remember to follow the rules of your particular assignment and use this as a reference

Why do you need to write a lab report?

The first step for conducting an experiment is to collect raw data, you can do this by weighing a sample, calculating the density of a substance, measuring the height of a certain object or by following the steps listed on your laboratory procedure. Because the data itself is just a collection of numbers and measurements, you must analyze and give some physical meaning to it. This is the reason why reports are so important; they are going to transform your raw data into something more than meaningless values. Laboratory reports help others understand the idea behind your experiments, its objectives, and the conclusions obtained after conducting it. Your report should be organized and very descriptive to help others understand the results you obtained and even guide them to execute the experiment themselves.

Title page

Now that you understand the purpose of a laboratory report it is time to move on to the title page. The title page should be the first page of your report, and it must include your name (or names, in case you are part of a group), laboratory section, instructor’s name, the date the experiment was conducted, and the number and title of the experiment. If you are unsure on how to organize this information, you should see the example included in the Prezi presentation. Remember that the design of your title page needs to be simple and professional, avoid using extravagant fonts and colors other than black.

Introduction

Once you have finished the title page, the next step is to write an introduction on a new page. For you to organize your ideas and have a better understanding of the experimental objective, it is highly recommended to complete the other sections of the report before writing this one. Going through the steps followed to execute the experiment and analyzing the results obtained, is key to completing this section effectively.

The introduction presents background information about the experiment, relating it to basic laws. Most of the time, the experiments are performed to support these laws, therefore, it is important to include information that validates all your statements and your procedure. The best way to accomplish this is by introducing relevant equations and defining variables.

Abstract

Some professors request including an abstract before the introduction. The abstract is a short summary of the entire experiment, where you should include the procedure followed, a statement on the experimental objective, and a comparison between your experimental results and literature values. Remember, if your professor does not ask for an abstract, the introduction should also include all the information you would normally have in the abstract section.  If you are still unsure about the difference between an abstract and an introduction, you should see the Prezi presentation where you will find some useful examples.

Procedure

You will now have to start writing the procedure. Although it might be tempting to include all the steps as they appear in your handout, be aware of using your own words. Summarize the techniques followed to perform the experiment, include all the important details and add sketches of the apparatus used. “Explicitly state any changes in the procedure that you are referencing”^[1]. Consider the procedure section as a cooking recipe that you are writing as a paragraph and not as a list. Avoid including observations and results, unless your professor says otherwise.

Results                                                     

Usually, students tend to confuse the results section with the discussion section. This common mistake can lead to an inefficient report, so it needs to be avoided. The result section should include observations and calculations made through the entire experiment. “Do not try to draw conclusions about the results, save them for the discussion section”^[2]. Omit including irrelevant information and focus on significant results that are going to lead to important conclusions. “Significant: colors, odors, physical state, viscosity, formation of precipitates, crystal type, etc” ^[1]. Include calculations that are relevant and represent an important part of your data and neglect basic algebraic calculations. “Calculations that are most commonly included are: Moles, limiting reactant, theoretical yield, actual yield, % yield” ^[1]. Be careful and consistent with your units because a number without units does not represent a quantity, it is just a meaningless value. Similarly, pay close attention to your significant figures and ask your professor about the right amount of significant figures your values should have.

Discussion

Now that you have finalized your results section you will use all the gathered data to start writing your discussion. Students tend to believe that the discussion should only be used as an error analysis section. However, the discussion should also refer to basic ideas and concepts, relating them to the results obtained. Explain how the reactions took place, analyze if the results were as expected and identify possible sources of error relating them to the procedure used. Some professors will ask you to compare your results to literature values. If this is your case, you must mention your percentage error and possible ways to decrease it.

Figures and Tables

Figures and tables play an important role when it comes to laboratory reports. Some professors will ask you to include them in the results section, others will request you adding them in a separate section known as the appendix, and some might even tell you to include them at the end of the report. Either way, you must have some rules in mind before including your figures and tables to your final draft:

• 1) Adding figures and tables to your document is going to move things around and your work will look messy and disorganized. Constantly trying to fix the problem is going to be a waste of your time. How to avoid this? Simply wait until all the other sections of the report are completed before including your figures and tables.
• 2) Add a number before the title of your figures and tables to identify and keep track of them.
• 3) When labeling figures remember that the title goes at the bottom of the figure (this can vary depending on your professor).
• 4) When labeling tables remember that the title goes on top of the tables (this can vary depending on your professor).
• 5) If you are going to include graphs, always label the X and Y axes appropriately, and add a descriptive title on top of the graph. Change the axes to fit the graph without wasting space, and add its trendline and R-squared value if you are requested to do so.
• 6) Always include references to your figures and tables throughout the different sections of the report. To do this simply add the references in parenthesis. For example: (See Table 1).

Reference

Finally, do not forget to include a reference section. Mention all the sources used, including your laboratory handout, and follow the format suggested by your professor (MLA, AMA…).

A final advice

As you can see writing laboratory reports is not that difficult. Ask your professor if you have any questions and make sure to understand the procedure that you will need to follow before performing the experiment. Relate the results you obtained with the concepts you learned during class, this will help you connect your ideas with the experimental objectives. And my last, but most important advice, is to enjoy the writing process because you will be writing very often!