Lowther
AP Chemistry
Lab Report Guide
AP Chemistry Laboratory Notebooks:
A Writing Guide
Composition Books make excellent lab notebooks.
Wide or narrow, lines or graph, the decision is yours.
Your Laboratory Notebook
Maintaining a well-kept and accurate lab notebook is the most important component of good
laboratory performance. The effort invested in developing good habits of notebook use now will
be repaid many times over for students pursuing a career in the sciences. Furthermore, some
universities now require submission of your A.P. Chemistry notebook before they will grant A.P.
credit in chemistry even if you score a "5" on the A.P. chemistry exam.
Lab Notebook Basics
 A lab notebook must be permanently bound. Ringed binders or spiral bound books are
not suitable. (At a professional level, lab notebooks may become a legal document for
many reasons. In that case a spiral notebook in which pages could be torn out without
notice would not hold up in court.)
 Ink Only, No WhiteOut: Use permanent blue or black ink for all entries. Think about a
reasonable layout for your data (a table perhaps) before putting pen to paper. Get in the
habit of writing everything in your lab notebook (no scraps of paper to lose). Do not
erase, scribble-over, or whiteout anything; simply cross out errors with one line so they
are still legible (e.g. 0.503 g 0.530 g). You WILL get better at this.
 Your name and contact information should be written on the front cover.
 Number all pages on the upper right hand corner in ink (right pages only). The organized
and neatly written lab goes on the right-hand side of each page. The left-hand side is for
scrap and preliminary calculations (and to avoid bleeding through).
 Pages Numbered and Dated: When you begin writing on a new page, record the date in
the upper right corner below the page number.
 Leave two pages (pg 1 and 2) for your Table of Contents, which should include
experiment titles and corresponding page numbers as they are performed. Leave one
page (pg 3) for your “Contact List”; names, emails, phone numbers of lab partners go
here.
 All graphs must be properly labeled, computer generated and permanently glued into
your notebook or they will not be graded.
 Percent errors greater than 10% may result in point deductions on lab reports.
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AP Chemistry
Lab Report Guide
The Format of Your Lab Report
For each lab we do in A.P. Chemistry, you will write up a formal lab report in your lab notebook.
The lab report is a formal document, so use proper grammar and punctuation. For the purposes
of this class, your target audience is other A.P. Chemistry students who have NOT done the lab
you are writing up. Therefore, write on a level such that students with similar background
knowledge to yours could use your lab report to repeat your procedure and verify your data and
conclusions without having access to the lab manual or handout you used. Every lab report
should include the following sections with headings:
**Items 1-4 and empty data tables when applicable (item 5) are the required Pre-Lab for
every experiment**
1. Title: Placed at the top of the first page, this should include the title of the experiment,
the name(s) of the person(s) performing the experiment, and the date it was performed.
2. Introduction/Objective: In a sentence or two, describe the reasons or objectives for
completing the lab. Use your own words; do not paraphrase the lab handout. Why are
you doing this lab? What are you trying to find out? Of course the objectives are always
“to learn” but you will need to be specific and detailed—use the content vocabulary.
3. Equipment & Safety: A bulleted list of all the equipment and chemicals you will use in
this experiment. A bulleted list of all safety concerns should be included.
4. Procedure: Briefly summarize the procedure to be followed; use a flow chart, or outline,
and/or drawings. If you number the steps, you will be able to refer to them later in the
Data/Observations section. You do NOT need to write out the procedure in complete
sentences and do NOT copy directly from the lab manual. The first time you do an
unfamiliar technique, include a description of how to assemble or operate any apparatus.
Write the procedure with enough detail that a trained chemist could reproduce your
results from what you wrote (for example, be sure to include elapsed times, instrument
name, solution, concentration, colorimeter wavelength, voltage, etc.).
5. Data / Observations: Record the data during the experiment; do not record on scraps of
paper for later transfer into your notebook. Be sure to use the correct number of
significant digits and label all data with appropriate units. Be sure to record actual
measurements—for example, initial and final burette readings, starting and ending time,
not the difference done in your head. Use data tables when appropriate; simple
calculations may be included in the data table. Be sure to label all tables with a title;
“Data Table” is fine, or “Data Table II” if there is more than one. Also record any
observable occurrences ((color change, precipitate, gas evolution, heat generation, etc.).
6. Calculations: Include all pertinent calculations. For all calculations, express the
equations in words first before showing the numbers used in the equation, or label each
line. For example: concentration of substance = mass of (substance + beaker) – mass of
beaker/molar mass/volume of solution, = x.x M. Do not show calculations of molar mass
(e.g. H2O = 2 x 1.01 + 16.00) unless it is an intrinsic part of the experiment. Show work
for calculations and express all answers to the correct number of sig figs and include
units. You must show at least one sample calculation for each piece of data in your table
that was not simply a measured value. For example, if you record the number of moles
of NaCl, but you obtained that from measuring the mass of NaCl, you must show in the
calculations section how you got the number of moles from the mass. If you did this step
in five different trials, only one calculation is necessary. Summarize calculations in a
table when appropriate. Be sure to label all tables.
7. Data Analysis: This is the main part of the lab report where you:
a. present the data you collected
Lowther
AP Chemistry
Lab Report Guide
b. discuss how you obtained the data (explain calculations, but don’t restate
procedure)
c. analyze why the data is relevant and explains the chemistry concepts.
This section of the lab should contain only statements you can support with your data,
NOT your opinions. Every statement should be backed up by quoting your data and/or
referencing by title, relevant tables, charts or graphs within your report. For example, in
your “data” section you recorded the freezing point of unknown sample #1 to be -5oC. In
the “data analysis” section you will further analyze that data: "We used an electronic
temperature probe and determined the freezing point of sample #1 to be -5oC as noted
in Figure 2 by the flat portion of the curve. This shows that the addition of a solute (NaCl)
lowered the freezing point by 5oC when compared to the curve of the pure sample
shown in Figure 1." This will undoubtedly be the longest and most difficult section to
write up in every lab report.
You can also include any graphs you generated in this section. Make graphs an
appropriate size so they are clearly legible; all graphs must have a descriptive title.
Typically you will show a best-fit line or curve; often you will need to calculate the
equation of the best fit line. I recommend using a computer-generated graph.
If it is appropriate, you can also rewrite the analysis/conclusion questions from the lab
sheet and answer each question, but this is not the only thing you should do.
Additional Tips:
Data Analysis Section
DO
DON’T
present the data you collected
give opinion that your data was good or bad
discuss how you obtained your data and explain
describe details of the procedure again or explain
complex calculations
every addition or subtraction step in words
refer to data tables, charts, and graphs by their
use the phrase, “our graph shows…” or start
title (i.e. Figure 1-2)
sentences with numbers
analyze how your data supports or rejects your
assume the reader will understand your data
hypothesis or objective
without an explanation
focus on facts you can support with your data
describe what you think or what you think should
and/or observations
have happened
compare your results to known or expected
expect the reader to trust your results without
values by calculating percent error, difference,
proof
standard deviation, etc.
8. Conclusion: This is a brief paragraph where you interpret the data you obtained. What
do the calculations/observations/graphs reveal? What theory was demonstrated? You
should:
a. restate your hypothesis/objective
b. quote data that proves you met or did not meet the objective
c. Compare your results with accepted values, or with the class values, and list
percent error when applicable (show as a calculation also). State whether your
results were too high or too low.
d. Suggest possible sources of error and how they affected your data
e. Hypothesize why the errors occurred and what might be changed to avoid these
errors. Random error exists in all measurements and should NOT be mentioned.
Human error (e.g. spills) and mistakes in recording data are NOT the same as
Lowther
AP Chemistry
Lab Report Guide
experimental error; usually they are addressed by repeating the experiment.
For example, "We showed that solutes lower freezing points of pure substances
because when we added NaCl, the freezing point dropped by 5 degrees Celsius." Also
use this section to analyze sources of error and how those errors influenced your data.
Instrumental and human error exist in all experiments and should never be mentioned as
a source of error. If human error ruined your data, then the experiment should be
repeated before it is written up.
Conclusion Section
DO
DON’T
briefly restate the objective (“In this
list procedural steps, give opinion that
lab we…”)
this lab was good or bad, fun or not
fun
state whether or not you met the
write, “We met the objective.” and fail
objective and provide simple data to
to support this statement with proof
support this statement
list/explain any significant errors and
write, “human error messed up our
how they influenced the data
lab” or unjustly blame the equipment
make suggestions for improving the
criticize the procedure or equipment
procedure, process and/or outcome of without offering an idea for fixing the
this experiment if you were to repeat it problem
Lab Notebook Rubric. AP labs are chosen to aid your understanding of chemical principles,
practice manipulation of some typical lab apparatus, and teach you about scientific problem
solving. Getting the “right answer” is much less important than understanding why an
experimental result is questionable.
Discussion with your lab partner is expected. However, everything should be in your own words,
especially the Introduction and Conclusions. I will not grade every section of every lab and
certain sections are weighted more heavily than others. Lab notebooks will most likely be
collected after every lab, but sometimes every other lab. Points may be deducted for wrong
answers resulting from lack of preparedness, inattention, or gross sloppiness. Remember that
labs are in the 80% Summative category, so your attention to detail and understanding content
is crucial. The approximate point distributions are:
Introduction 5 pts
Conclusions 5 pts
Procedure 10 pts
Data/observ/calculations 10 pts
Total 50 pts
Analysis 15 pts