How to Effectively Use a Lab Notebook

Why is it Important to Keep a Good Laboratory Notebook? [MIT]

Keeping a complete and accurate record of experimental methods and data is a valid part of science and engineering. Your laboratory notebook is a permanent record of what you did and what you observed in the laboratory. Learning to keep a good notebook now will establish strong habits that will serve you well in college and throughout your career (assuming your major and career will be in science and/or engineering).

Your notebook should be like a diary, recording what you do, and why you did it in chronological order.

You should feel free to record your mistakes and difficulties performing the experiment- you will frequently learn more from these failures, and your attempts to correct them, than from an experiment that works perfectly the first time. It is extremely important that your notebook accurately record everything you did. Could someone else, with an equivalent scientific background to your own, use your notebook to repeat your work, and obtain the same results? For that matter, could you come back six months later, read your notes, and make good sense of them? If you can answer yes to these two questions, you are keeping a good notebook!

Revised excerpt taken from: Massachusetts Institute of Technology, Department of Mechanical Engineering. IW Hunter and BJ Hughey, 2007.

How to Keep a Notebook - General Guidelines [Dartmouth College]

The laboratory notebook is a permanent, documented, and primary record of laboratory observations. Therefore, your notebook will be a bound journal with pages that should be numbered in advance and never torn out. Write your name, the name of your teacher, and your lab section on the cover of your notebook. All notebook entries must be in ink and clearly dated. No entry is ever erased or obliterated by pen or “white out”. Changes are made by drawing a single line through an entry in such a way that it can still be read and placing the new entry nearby. If it is a primary data point that is changed, a brief explanation of the change should be entered (e.g. “balance drifted” or “reading error”). No explanation is necessary if a calculation or discussion is changed; the section to be deleted is simply removed by drawing a neat “x” through it.

Your notebook should be your primary source of information. Everything you do in the laboratory should be included in your notebook, from procedure to calculations. When notebooks are examined, the professor will look for the following points in almost all cases:

  • Pre-Lab write-up that shows that you were prepared for lab before beginning the experiment.
  • Data and associated graphs and calculations quantitatively gauge how successful your laboratory technique was. All units clearly shown on all numbers!
  • Enough explanatory information so that someone else with your knowledge of chemistry, biology, or physics could, from the lab notebook alone, enters the lab and repeats your work.

Revised excerpt taken from: Dartmouth College, Chem. Lab Notebook Requirements.

Academic Magnet High School - Advanced Placement Chemistry

Specific Practice for Laboratory Notebooks

Most of the writing in the notebook should completed during class time and not afterwards. Your teacher may be initialing your lab notebook throughout the lab to verify you are putting entries into your lab book while you are doing actual work. You will have an opportunity to do pre-lab at home before the lab to help you prepare. Post-lab work will include calculations or writing short (1-3 sentence) summaries or conclusions. The pre-lab and post-lab sections must be labeled as such.

It is not necessary to “pretty up” your lab notebooks for me. Your notebook should be clear and organized, but it is not a formal lab report!

Adapted by L. & M. Eicher from Stanford University, “Maintaining a Lab Notebook”.

Each experiment should begin on a new page and should contain the following:

1) Date- Month should be written out! Example: August 18, 2014

2) Title – Full Title (The title should clearly describe the lab!)

3) Primary Question for Investigation–Often generated by the Experiment Overview section of the lab sheet or pre-lab discussion.

4) Hypothesis: If/Then Statement. The hypothesis is a one-line sentence where you discuss how you’ll solve the problem at hand. The statement after “if” is the independent variable. The statement after “then” is the dependent variable. You may decide to use a null hypothesis.

5) Rationale for Your Hypothesis: This is a brief explanation of the scientific concepts you used in order to make your prediction (generally summarized from the Background Section).

6) Proposed Experimental Design: Strategies for testing your hypothesis. This should include identification of the independent and dependent variable, the control (if you have one) and the constants. You must also include any safety issues you should anticipate with your experiment.

Safety Example: Use of caustic 12M hydrochloric acid – gloves and goggles required

7) Procedures: You need to detail the steps you are using in your experiment. You will need to be sure to write this part in as you are working in the lab so it should be a running commentary. [DO NOT SIMPLY COPY THE LAB PROCEDURE!]Make sure you put the actual date by the procedures when you are doing them. Each step should be short (only one sentence) and should have multiple steps summarized into a single entry [DO NOT SIMPLY COPY THE LAB PROCEDURE!].

Example: Spectrophotometer was set to 670 nm.

You should record everything that happens during your experiment. This means any deviation from the protocol whether it was planned, an accident, an error or a mistake, needs to be written down.

Example: You heated a substance for 3.5min instead of 3 min.

8) Results: This is where you will write down your raw data. It should consist of quantitative data arranged in charts and qualitative data (like observations) written out as sentences. This commentary should be recorded in the lab as the experiment proceeds. If the experimental work is done jointly by your lab group, it must be noted and reported independently. Your notebook must list your co-workers and identify who did what. The results section may be combined with the procedures since you will be doing both the procedures and the results in your notebook during the actual lab.

Permanently affix with glue any attachments (like pictures of your data or computer printouts) to the pages of the notebook. Date and sign both the notebook page and the attachment

9) Analysis of Results: This is where you explain the meaning of your results (generate graphs/charts and perform calculations). You should also explain why something happened here. The analysis section is the part of the lab where you explain how the data does or does not support the hypothesis. Any statistical tests performed will also be included in this section.

10) Conclusions/Discussion: You may have an “interim conclusion” written at the end of each lab day even if your experiment is notcomplete. If you will be continuing your experiment another day, the conclusion should be 2-4 sentences briefly describing what you have learned from the day’s experiments, what things were particularly difficult, interesting, or useful, and how the work you did for the day gets you closer to your final goal of answering the primary questions.

If you completed an experiment, the conclusion should include a sentence that states if you are rejecting the hypothesis or if the data supports the hypothesis, etc. Calculations of precision, theoretical yield, percent error, etc. are appropriate for this section. You should summarize your findings and discuss possible errors that occurred as well as the impactof the error on the results (claim…evidence…reasoning). Record any additional questions for further investigation.

Error Analysis Example:

During the titration, the endpoint was passed[CLAIM]and too much base flowed into the flask resulting in too pink of an endpoint [EVIDENCE]. This would incorrectly increase the number of moles of base required which would incorrectly increase the calculated number of moles of acid neutralized yielding a smaller molar mass for the unknown acid (grams/moles)[REASONING].

Pre-Lab: You should do numbers 1-6 in your lab notebook before starting the lab. Be sure you label these steps as pre-lab in the lab notebook. You should date the pre-lab section.

During Lab: You should do numbers 7-10 during the actual lab. You need to make sure to put the date of experimentation and the members of your group. If you do not finish an experiment in one day, you need to write a brief conclusion describing what you learned from the day’s experiment. The next day, continue the experiment in the procedures and results and state that it is a continuation from day___. Identify the members of your group again! This could change from day to day if someone is absent! Your teacher will be initialing your lab book throughout the lab to verify you are putting entries into your lab notebook during actual experimentation!

Post-Lab: You will have the opportunity to work further on your results and your conclusions after experimentation but you must identify the section of your lab notebook as post-lab to identify work done outside of the laboratory. (This may be done as the lab proceeds over multiple dates.

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