The Laboratory Notebook
The Laboratory Notebook
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You will record your data and observations in a laboratory notebook. We
will use the same same principles and guidelines for laboratory
notebooks that are used in colleges and in industry. The purpose of a
laboratory notebook is to show exactly what you did and when you
did it, in case you need proof to back up a claim of a new discovery or
to patent an invention.
Your lab notebook must be a separate notebook. (I.e., you may not
use one section of a multi-subject notebook.) It should have the pages
bound into it in a way that they cannot be easily removed (such as a
composition notebook). Composition notebooks are ideal; loose-leaf
notebooks are not acceptable.
Your laboratory notebook is a diary of your experiment. The goal of a
laboratory notebook is to be able to go back to it later to answer
any question you might have about the experiment.
Every teacher, professor, manager, boss, or company has specific
laboratory notebook formats and guidelines. Not only isn't there any
one right way to keep a lab notebook, there isn't even a compromise
format that will satisfy almost everyone. As you are getting used
to using a laboratory notebook, keeping the goals in mind instead
of the specifics of the particular format will make it a lot easier to
adapt to someone else's style in the future.
In this class, the sections of your lab notebook write-up will exactly
follow the steps of designing an experiment, because the most important
elements you will want to recall about an experiment are usually the
ones that went into designing it:
- What were the objectives of the experiment?
- What was the overall plan?
- What, exactly, did I do? (I.e., what were the specific
- What actually happened? What did I observe? What did I
- What could I conclude from the data? What are the results of
any calculations based on the data?
- How well did the experiment meet the objective? What went
wrong? What should I do differently next time?
To make it easy to find information, you will want each experiment to be
recorded in an organized fashion. For this class, we will use the
The title of the experiment and the date should appear at the top of the
page where the experiment starts. A good title should describe the
relationship between the independent and dependent variables. (For
example, "The Effects of
This is a short description of what you are trying to do. Your
description can be words, chemical reactions, diagrams, or a combination
of all of these. If you are testing a hypothesis, you would state the
hypothesis in this section. The only requirement is that anyone
knowledgeable about chemistry must be able to tell from looking at this
section what your intent was. This section can also include your
motivations (why you are doing the experiment), if they are relevant.
This is a short description of how you intend to accomplish your
objective. It should not be a detailed step-by-step
procedure, though it should give a basic overview of the procedure you
intend to use. This section can include an outline, flow chart, and/or
This optional section is a place to list any information you might want
to have readily at hand during your experiment, such as physical
constants or other data about the compounds and materials that you are
working with. For example, if you were doing a calorimetry experiment
to determine the specific heat of an unknown metal, you would include
the specific heat of water, so you would have it handy for your
You will write this section as you perform the experiment. It needs to
Because this is the only time you will actually write the detailed
description of your procedure, you need to allow yourself enough time to
write down each step before going on to the next one. Do not leave
anything for later, because you are likely to forget important details.
- the names of your lab partners
- the names, concentrations, and quantities of each substance that
you used. (In industry, you would also include the manufacturer and
grade of each chemical.)
- the name & description of any major equipment used, where
"major" means anything larger than an electronic balance. (In
industry, you would also include the manufacturer and model number
for major equipment.)
- a detailed description of each step exactly as it is
Data & Observations
You will also write this section as you perform the experiment. It
needs to include everything you think might be relevant to your
In general, it is easiest to create a table for recording data. Most
data tables should be set up so that the columns represent each of your
independent and dependent variables, and the rows represent each data
Record all analog measurements to one more (estimated) decimal place
than the finest marking. For example, if you have a graduated cylinder
that is marked to the nearest 1 ml, you would estimate and
record the volume to the nearest 0.1 ml. (If the last digit is
zero, be sure to record it, as it is significant.)
You can record observations either in the data table, or in a separate
section. If observations in a separate section refer to entries in a
data table, be sure to include some sort of cross-reference.
Note that you do not have to use complete sentences or worry about
spelling or grammatical errors in this section, though it does need to
be legible and comprehensible. The goal is for anyone reading this
section to be able to verify exactly what you did, and
exactly what happened, with a minimum of assistance or explanation from
You will write this section after completing the experiment. As
described above, this section includes everything you need to answer
your objective, using your data. If the experiment involved
measurements, this section will include calculations from the experiment
(show all work) and your experimental yield (if relevant).
You should always round your calculations off to the appropriate number
of significant figures. Keep a minimum of one extra digit during your
calculations to minimize accumulated round-off errors. If published
data are available, you should always reference the published data and
calculate your percent error.
Your analysis should also consider any possible sources of error
(especially any errors that you believe actually occurred),
considerations to keep in mind the next time you perform a similar
experiment, and suggestions for future related experiments.
If your objective included a hypothesis or goal, you should finish with
a quick mention of whether or not your hypothesis was correct, or
whether or not you accomplished your goal.
The general rules and guidelines for writing in lab notebooks are:
- All entries in a lab notebook must be hand-written, in ink.
- All pages must be numbered consecutively, to show that no
pages have been removed. If your notebook did not come with
pre-numbered pages, you need to number all of them by hand
before using the notebook.
- Start each experiment on a new page.
- At the end of each experiment, sign and date the bottom of the
last page. (In industry, every single page would have its own box
for your signature and the date.)
- When crossing out an incorrect entry in a lab notebook,
never obliterate it. Always cross it out with a single line
through it, so that it is still possible to read the original
mistake. (This is to prove that it was a mistake, and you didn't
change your data or observations. We all make silly mistakes, so
you don't need to feel embarrassed about the original text still
being legible.) If you accidentally scribble something out, write
your initials next to the change.
- Never remove pages from a lab notebook for any reason. If
you need to cross out an entire page, you may do so with a single
large "X". If you do this, write a brief explanation of why you
crossed out the page, and sign and date the cross-out.
- Never, ever change data after the experiment is completed.
Really. I mean it. Your data, right or wrong, is what you actually
observed. Changing your data constitutes fraud, which is a form of
cheating that is every bit as bad as plagiarism. You can still get
an A on an experiment that didn't work; changing or faking your data
will get you the full penalty for cheating, including a zero for the
This also means that you should never change anything on a page you
have already signed and dated. If you realize that an experiment
was flawed, leave the bad data where it is. Just add a note that
says "See page
." with your initials
and date next to the addendum. On a new page, refer back to the
page number of the bad data and describe briefly what was wrong with
it. Then, give the correct information and sign and date it as you
would an experiment.
Remember that your laboratory notebook is your only record of what you
actually did. If you worked for a company that was applying for a
patent, your notebook might be the only proof that someone from your
company had actually invented the substance or process. The more
information you record in your notebook, the more useful it will be. If
you need a more immediate incentive, the more information you have in
your notebook when you are writing that 3-5 page lab report at
3:00 a.m. the night before it's due, the less work you'll have to do to
find everything, and the more sleep you'll get.
Pavia, Donald L., Gary M. Lampman, George S. Kriz, and Randall G. Engel.
Introduction to Organic Laboratory Techniques, A Microscale
Approach. (Philadelphia: Saunders College Publishing, 1990).
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