Writing a Lab Report

The main focus of this section should be to help the reader understand the purpose and methods, and to identify the reasons these particular methods are being used.

• Brief overview of experiment's purpose and strategy/techniques used.  Explain key concepts.
• Background information. Example for titration lab:  What is acetyl salicylic acid and why is it used? Cite sources.
• What was the purpose of the experiment?
• What types of reaction(s) and/or technique(s) were being used?
• Why were these techniques selected?
• What was the equation for the specific reaction that took place?
• What kinds of calculations did you use as part of the experiment?
• What will the final results tell you (i.e. why is the final result important)? Do not report the final results yet.

Simple bullet-point listing of all equipment used.  Provide enough detail so that your reader could replicate the experiment.

• Correct:
  • 50 mL burette with stand and clamp
  • 500 mL volumetric flask with stopper
  • Graduated cylinder
  • Distilled water
  • NaOH solution
• Incorrect:
  • Burette
  • Flask
  • Graduated cylinder
  • Water
  • NaOH
• Incorrect: For this experiment, we used a 50 mL burette with stand and clamp, 500 mL volumetric flask with stopper, a graduated cylinder, distilled water and a NaOH solution.
• Graphics of complex setups may be included.  If you use someone else’s graphics, you MUST cite it.

Write a narrative of what you did, describing the steps of your procedure.  Do not write a numbered list or copy procedures from the lab manual.  Since you are reporting what you did in the past, you should describe the steps in past tense. 

• Write about what really happened, not what “should” have happened.
• Report observations (e.g., color changes, gas production, precipitation) that would tell someone repeating your experiment that they are successfully replicating your efforts.
• Do not report any numbers in this section that would be considered final results.
  • Correct:  The final buret reading was recorded to two decimal places.
  • Incorrect:  The final buret reading was 21.50 mL.

Correct: About 500 mL of water free from carbon dioxide (CO2) were prepared by boiling the distilled water for five minutes.  Three triplicate samples of KHP with a mass of 0.4-0.5 grams in each sample were first weighed and were then poured into three 250 mL Erlenmeyer flasks. The masses of these samples were rounded up to three decimal places.

Incorrect: (Numbered list)

1. 500 mL water (free of CO2) prepared by boiling distilled water for five minutes.

2. Three samples of KHP (0.4-0.5 grams each) weighed, then poured into three 250 mL Erlenmeyer flasks.

3. Masses of samples rounded up to three decimal places.

Incorrect: (Not past tense): About 500 mL of water free from carbon dioxide (CO2) should be prepared by boiling the distilled water for five minutes.  Three triplicate samples of KHP with a mass of 0.4-0.5 grams in each sample are first weighed and are then poured into three 250 mL Erlenmeyer flasks. The masses of these samples will be rounded up to three decimal places.

What were the results of the experiment?

• Raw data (graphs or tables). Label and title visual data properly.
• Report yields, statistical analysis, and description of the final product.
• Provide statistical analysis of the collected data (example, for multiple titrations, perform a Q-test to determine whether the experiment yielded viable data.  Calculate the mean, standard deviation and relative standard deviation to determine the standardized molarity.)
• Show formulas for all calculations but not the full calculations themselves.
• Do not report conclusions – only state results (numbers, colors, etc.).

This section is the most important part of the report. This is the section where the results are explained, and a student can show the instructor that he or she has a thorough understanding of the concept of the experiment and the results obtained. The main question to be addressed in this section is “What is the significance of the results?”

• Explain results in terms of purpose. Do not recap the procedure. If the original purpose of the experiment was achieved, explain how the results show that the purpose was accomplished. For example, if the purpose was to determine the percentage of hydrogen peroxide in a commercial antiseptic, you can compare real percentage to the calculated result from the experiment.
• Analyze experimental error: There is a degree of error in every experiment, so every lab report should mention potential causes of error (usually 2-3 errors). Be specific about what caused the error. Was it due to the equipment? Impurity of the sample? Do not include mistakes done by you due to not reading the procedure or calculation error. Include the results of your Q-test in your discussion.
• Explain how the methods could be improved. Once you have decided what might have caused the error, you should explain how the error might have been avoided. How could the setup be made more effective? Should you have been more careful with measurements? How could contamination have been prevented more effectively? Should more precise equipment be used?

Only a few sentences.

• Introductory sentence restating purpose of experiment.
• The most important conclusion of your experiment supported by numbers from results section (2‒3 sentences). I should not have to look back at any sections to find data.
• Evaluation of whether the experiment effectively achieved the goal or purpose outlined in the Introduction section along with evidence to back that evaluation.

This section simply lists, in standard bibliographic format (APA Style), the resource materials that you used in doing the experiment and preparing the report. Internet sources are not acceptable, unless they are peer-reviewed journal articles. Don’t forget about the procedure handout provided by the instructor and any graphics or other sources that you use.