Bradbury
Chemistry 112 Laboratory
How to Write a Laboratory Report
The main objective in producing a written laboratory report is to preserve and convey the steps
taken during an experiment, the observations made, the results and the conclusions drawn; as
effectively as possible. The report is a demonstration that the student learned what was expected.
A well-written laboratory report must:
a) Be Reproducible within the acceptable limits of error: Accuracy and detail in recording are the
keys to achieve reproducibility.
b) Be Clearly communicated both in the procedure summary and in the expression of the thought
process in the interpretation of results obtained: Relevant details should not be left out to just
save time or paper space. The report needs to be well organized. Presentation is not everything
but it is very important.
c) Follow the format agreed upon by the scientific community, in order to facilitate
comprehension and minimize ambiguity.
The Accepted Format for Written Scientific Reports:
A full laboratory report should be consisted of the following parts, in the sequence shown below:

Pre-Laboratory procedure

Observations

Calculations: All of the calculations performed.

Results: A simple statement of the main result(s) of the experiment. A table should include any
numeric results

Discussion of results (Conclusions): Analysis, explanation, and interpretation of the results.
Analysis of error, explanation of chemical or physical processes of the experiment.

References: A list of all the literature sources used for the experiment and the report.
Pre-laboratory Write-up:
A pre-laboratory protocol must be completed BEFORE the laboratory. This will be checked and
signed by the instructor before student enters or begins the experiment. It must have the following
parts sequentially:

Date: The starting date for the experiment.

Title: The title of the experiment.
Write the following headings, underline it then indent the next line.
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
Purpose: The main purpose of the experiment, stated in the form of a COMPLETE sentence.
Be concise. No more than 2 sentences.

Chemical Equation for any reactions that occur

Materials: A table of chemical substances, which includes states (aqueous, solid etc.) and
concentrations, the safety information, and the disposal notes.

Apparatus: A table that includes a list of hardware and glassware equipment.

Summary of the procedure: This section will ultimately become your only reference source to
the experimental steps. In order to make the procedure section easy to follow, the summary
should be written on the left half of the notebook pages, and any observation for the steps
should be recorded on the right half, across from its corresponding step. The steps of the
experiment should be broken down into a numbered or bulleted list to make the procedure easy
to follow. Some students prefer to make a box for each step that they then check off when
completed. For some experiments a flow chart will be desirable.

Data tables: Create an organized table before coming to the lab. Title the table with words that
describe the data in the table. Include a box for each piece of data to be collected. Each column
must be clearly titled. Use a ruler. Make sure each box is large enough to fit the data and leave
room for any errors to be re-written. All errors are to be crossed out with one line in ink with a
ruler, and correctly written in the same box. Initial any errors.
During the Laboratory Write-up
Observations:

Write observations on the opposite half of the page and adjacent to the procedure during which
the observed phenomena occurred. Use as few words as possible and be clear. Avoid using the
terms “cloudy” or “clear” Instead write: “Aqua blue solution turned colorless.” “Dark brown
gelatinous precipitate formed.” “Bubbles formed;” If you know the gas then write: “Bubbles
(hydrogen gas) formed.” It is a good idea to include the shade of the color and texture of any
precipitate as this will help you determined what was formed. Observations must use correct
chemical terminology and not ambiguity. You will use the observations and reference them in
your conclusion. Observations must be written directly in your notebook in ink, not on a scratch
paper to be transferred later.
Data:

Write all original data directly into the previously created data table. Do not write on scratch
paper and then transfer the data later. Cross out all errors with a single line using a ruler and
your initials. Include all units.
Post-laboratory Write-up:
Calculations:

All calculations go after the procedure. Number and title each calculation and underline the title
and indent the calculation from the title. Use a ruler for any line drawn. Use generic formulas
with words or clear symbols before showing actual calculations. Line up all equal signs. Be
neat and readable. Show all units and steps in the calculation.
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Results:


Table: Title the table in such a way that it tells the type of results in the table. Put answers to
all calculations into a results table. Tables are to be written in ink with a ruler. Title/label all
columns. Be organized. It is suggested that you make a sketch of the results table before
putting the final table in the lab notebook. Include all units. Do not crowd the information and
do not leave too much empty space.
Paragraph: After the table write a brief paragraph stating the facts of the results. Make no
analysis here. Just summarize the most important results.
Discussion:
In the discussion analysis is made of observations, data, and results. Conclusions are drawn.
Evidence to support those conclusions is given. Reasons for error are given. Technique is
evaluated. Any questions from the lab are answered. Chemical principles demonstrated in the
procedure are used to explain what was observed. Ask yourself: “Why did that happen?” and write
out your explanation. Do not re-state the procedure. It should be demonstrated, with evidence that
the purpose of the experiment was fulfilled and that the student learned the concepts illustrated by
the experiment. It is expected that students will use their best writing skills and correct grammar and
English skills. It is suggested that a rough draft be written first on scratch paper. Each paragraph
should have an introductory sentence, make a claim or conclusion, give evidence, and have a
concluding sentence. Use correct logic. Here is a suggested sequence for the discussion:





Introductory paragraph
Explanation and analysis of results and observations. Conclusions drawn with evidence.
Chemical principles behind the experiment discussed. Demonstration that purpose was
fulfilled.
Explanation and analysis of acceptable error
Evaluation of technique
Concluding paragraph
References:
Any time a textbook, journal, web site, or other source is quoted, paraphrased or
summarized in the lab report it must be noted and given credit at the end of the lab
report. Use standard referencing for this. See the “Citation Guides” on the Cerritos
College Library web site. www.cerritos.edu/library.
Maintaining the Laboratory Notebook:
1. Name: Your laboratory notebook should be labeled with your name on the outside and each
page completed.
2. Page Numbers: Since all the pages are numbered, you should use the pages sequentially. Points
will be deducted fro missing pages or pages out of order.
3. Table of Contents: Dedicate the first two pages of the notebook to the "Table of Contents".
Draw the table first and update it every time you add more experiments to your notebook.
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4. Cleanliness: The notebook has a semi-resistant cover. It is wise, however, to wipe it with a
damp cloth, to keep it in a decent shape as long as possible.
More Pointers…
1. Each section of the laboratory report must be labeled, in order to make the reading of the report
smoother. Write the heading of a section like Procedure and then skip to the next line and indent to
begin the procedure.
2. The report must be written in third person (voice). “the student” or “we”
3. The report must be written in ink (no pencil).
4. If any mistake is made, it should be crossed out (with a horizontal line through it)!and drawn with
a ruler and initialed by the writer of the report.
5. ALL the lines (Including underlined titles, tables, strikethrough, etc…) must be drawn using a
ruler (no free-hand drawing).
6. The report should not convey any personal emotion (positive or negative).
7. Handwriting should be legible, not crowded and not too small.
8. Language and diction should be formal and professional. Correct formal grammar is to be used.
No abbreviations.
9. The report should not look like a rough draft.
10. Write on the lines in the book. Make sure all columns line up.
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