Writing the Experimental Section of a Lab Report
The standard lab report will typically have 8 sections:
4. Experimental - Link to PDF form
I. General Idea:
This worksheet is intended to help you write the experimental section. The experimental section is the part of a lab report that tells the reader how to reproduce what you did in lab. If another person follows the directions written in the experimental section, he or she should achieve the same results you achieved.
In scholarly research, this section is very important because it prevents people from publishing fake results and helps other researchers duplicate, verify, and expand on your findings.
In Chemistry 1210, all of the experimental procedures are described in detail in the laboratory manual. When writing your Experimental section, do not re-write or copy the lab manual. This is completely unacceptable. Instead, your experimental section should have three parts:
1) Cite the procedure in the manual. Your first sentence should then be something like, ̉The procedure for this lab has been described in detail in the lab manual. [Insert citation number here]" Make sure you remember to include the full citation at the end of the report.
2) Brief description of what you did. Simply write a few sentences describing what you did in the lab. There is no need for a detailed description, this can be found in the lab manual, which you previously cited.
3) Note any changes. If you deviated in any significant way from the procedures described in the lab manual, you need to describe those significant deviations. These should be described briefly (preferably, no longer than a paragraph). Link to examples of significant/insignificant changes.
II. Step by step example of writing an experimental section
This example is written based on Experiment 5, ̉Using conductivity to determine the end point of a titrationÓ
Step 1: Answer the following three questions:
Is there any manual or text book in which a detailed lab procedure is written? If so, what is it?
This procedure is based on Experiment #5 detailed in our manual, General Chemistry II Laboratory Experiments .
If I ran into a friend in the hall and only had 1 minute to tell him or her how the lab was done, what would I say? Be sure to include enough information to enable your friend to reproduce your work, but remember that you only have one minute to talk.
I took a 250 mL Erlenmeyer flask and filled it with 50 mL of sulfuric acid (H2SO4) of unknown concentration. I then diluted this solution with approximately 100 mL of distilled water. Using a computer-interfaced conductivity probe, I monitored the conductivity of the H2SO4 solution as I added 0.2 M barium hydroxide (Ba(OH)2) in 1 mL increments. I continued to add Ba(OH)2 and monitor the conductivity until my curve of conductivity versus volume of Ba(OH)2 formed a v-shape.
Did I do anything differently from what was described in the lab manual? If so, what was it?
The lab manual tells us to remove the conductivity probe after each measurement and clean it in distilled water. However, we left the probe immersed in the solution throughout the titration.
Step 2: Put all of the above answers together in the form of a paragraph written in the passive voice (when possible), citing all sources. [The passive voice is described in the Abstract section.]
The procedure for this experiment has been described in detail elsewhere . Briefly, 50 mL of H2SO4 of unknown concentration was placed in a 250 mL Erlenmeyer flask and diluted with 100 mL of distilled water. The conductivity of this solution was monitored with a computer-interfaced probe while 0.2 M Ba(OH)2 was added in 1 mL increments. The addition of the Ba(OH)2 solution was continued until the graph of conductivity versus volume of Ba(OH)2 formed a v-shape. In contrast to the published procedure , the conductivity probe remained immersed in the solution throughout the titration. It was not cleaned in distilled water in between 1 mL additions of Ba(OH)2.
Step 3: Remember to include the references to your citations at the end under the heading, References.
 Brown, P., General Chemistry II Laboratory Experiments, McGraw Hill, NY, 2000.