Writing Laboratory Reports for Chemistry Experiments Tutorial

Key Concepts

The term "Laboratory report" is usually abbreviated to "lab report".

Scientific Integrity: A Lab Report is a permanent and true record of the experiment you performed.
(DO NOT change the results of an experiment just because you don't like the look of them or you think they are wrong.)

Scientific Language: The language used in a Lab Report is important:
A Lab Report is written in the third person passive style.
(DO NOT use words like; I, you, we, us, me, my, your, etc)
A lab report is a summary of your experiment with the information organised under several different headings:

Heading	Information contained in this section
Title :	Name your lab report so people can refer to your work.

Introduction :	Explain why you did this experiment. Discuss what you expected to find by doing this experiment.

Materials and Method :	Describe how you performed the experiment.

Results and Discussion :	Describe what you found out by doing the experiment (results). Discuss how you interpreted the results of your experiment. Discuss the implications of the conclusion you made about the results of this experiment.

References :	Write bibliographic information for every source you cited in the lab report.

Note: different courses have different requirements for the presentation of Lab Reports.

Your teacher will provide you with the details of what is expected from you in your Lab Reports.
Read these instructions carefully BEFORE you begin to write your Lab Report!
If you do not understand an instruction, ask your teacher to explain it to you.

The following discussion is about the features that will be common to ALL Lab Reports.

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Lab Reports are Written with Scientific Integrity

You must truthfully record the results of your experiment.

You must not change the results of your experiment because you think they are wrong, or because they don't agree with the textbook, or because you spilled some of the reactant and didn't go back and measure it again, or for any other reason!

If the results of your experiment do not agree with published results, for example data in a textbook, then you can try to explain why in the discussion section of your lab report.
If you spilled some product of a reaction before you had a chance to weigh it, then, in an ideal world, you would have to discard this part of the experiment and start again.
In the real world of the school laboratory you probably won't have time to re-do the experiment, so you will have to explain the impact of this loss on your results in the discussion section of your lab report.

There are many examples in the history of Chemistry in which a Chemist got strange results, but, instead of changing the results to what was expected, the Chemist truthfully recorded the results so that the whole scientific community could investigate the strange results.

In fact, the 2011 Nobel Prize in Chemistry was awarded to a man because he didn't falsify his data so that it would agree with the scientific theory current at the time, instead, he spent years trying to convince other scientists that the theory was wrong because his data was good. Scientists opposed the "correctness" of his data so much that he even lost his job. Eventually, however, other Chemists reproduced his results, and the evidence became so overwhelming that a complete revision of the scientific theory was necessary!⁽¹⁾

So the moral of the story is that you MUST NOT falsify your results, you never know what you might miss out on if you do!⁽²⁾

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Scientific Language Used in Lab Reports

The focus of a lab report is the science, not you!

For this reason, lab reports are written in the third person passive style.

A quick grammar lesson for chemistry students: What does third person passive style mean?

Compare the following examples of language below:
First person active:	talking about yourself or others doing something by using the words I, me, my, mine, we, us, our	Example: I poured 10 mL of water into a 100 mL beaker. Example: We poured 10 mL of water into a 100 mL beaker.
Third person active:	removes reference to specific people by name or pronoun	Example: The author poured 10 mL of water into a 100 mL beaker.
Third person passive:	completely removes reference to people	Example: 10 mL of water was poured into a 100 mL beaker.

So, third person passive simply means that the people who perfomed the experiment are not referred to in the Lab Report.

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Components of the Lab Report (Sections of the Lab Report)

The purpose of the lab report is to provide other people with enough information about the experiment so that they can reproduce the experiment and get the same results.
The general form of the lab report you will be required to write in High School is no different to the general form used by professional Chemists to report their findings to the scientific community in scientific journals.

The components that are common to all lab reports, and in the order in which they are written, are:

Title

Introduction

Materials and Methods

Results and Discussion

References

Your completed Lab Report will have a number of different sections. Each section, except the title, will have a heading. The heading of each section will be the name of one of the components listed above.

(a) Title

The title of your lab report should be:

brief (less than a sentence)

informative (tells the reader something about the experiment)

interesting (to people interested in chemistry)

Think of the names (titles) of the best movies you have ever seen. What are the things that all those names (titles) have in common?

brief (less than a sentence)

informative (tells you something about the movie)

interesting (encourages people to go and see the movie)

You want people to read your lab report, so just like a movie title, you need a short, informative, interesting title.

Example: In an experiment in your laboratory you measured the temperature of 10 mL of water in a 50 mL beaker. You then added 10 grams of ice to the water and measured the temperature of the water every minute until all the ice had melted and the beaker contained only liquid water.
The experiment was about finding how the temperature of water changed as the ice melted, so the key words to include in the title are temperature, water and ice.
A suitable title for the lab report might be, "Effect of Melting Ice on Water Temperature", or, "Temperature of an Ice-Water System".
It's probably advisable to avoid humorous titles, what you think is funny might not seem funny to someone else (you could even offend someone with your "humorous" title).⁽³⁾

(b) Introduction

The introduction is your chance to tell the reader why you did the experiment.
(and the reason is NOT because your teacher said you had to!)
Experiments are designed to answer, or at least to investigate, scientific questions.
The introduction to your Lab Report must tell the reader what scientific question you are trying to answer (or investigate).

If your teacher has provided you with the method (or procedure) for the experiment, and you "followed the directions", then all you probably need to do is write the aim (goal or objective) of the experiment instead of a complete introduction.
The aim (goal or objective) is a brief statement about what you hope to achieve by doing the experiment.

Here are some common phrases that are often used to begin the Aim:
To observe
(used if no measurements are taken and you are reporting on what you observed or sensed, that is what you saw, heard, smelt, physically felt)

To measure
(used if you will be taking measurements but not doing any calculations)

To determine
(used if you will be taking measurements, doing calculations or otherwise manipulating the raw results)

To synthesize
(used if you are making a new compound)

Example: In an experiment in your laboratory you measured the temperature of 10 mL of water in a 50 mL beaker. You then added 10 grams of ice to the water and measured the temperature of the water every minute until all the ice had melted and the beaker contained only liquid water.
The experiment involves measuring the temperature of the water so the aim of the experiment could be, "To measure the effect of melting ice on the temperature of water".
If you are going to graph the results, that is manipulate the raw results, a better aim would be, "To determine the effect of melting ice on the temperature of water."

Your Lab Report will now have 2 sections:

Title

Aim (with the heading Aim)

If you had to undertake some research yourself, and you designed the experiment that you then performed, you are going to need more than just an "Aim" for your introduction. You are going to have to write a much more detailed introduction.
The introduction needs to explain why it is important to do this experiment. Who will benefit from the results of this investigation? How is this experiment relevant to the community in which you live?
For example, think about our experiment in which we measure the temperature of water while the ice melts in it.
Why is it important to know how melting ice in water effects the temperature of water?

To start with, it is an interesting phenomenon.
When the ice is added to the water the temperature of the water falls to a minimum and stays constant until all the ice has melted.
This has many important benefits.
For example, you are going on a picnic in summer and you want to keep your sandwiches cold so they won't spoil. You pack some ice in an eski, place the well-wrapped sandwiches in the eski, put the lid on and head off. As the ice melts, the temperature of the water formed remains at the same low temperature, keeping your sandwiches cold and fresh for hours. You don't need to keep emptying out the water and adding fresh ice in order to keep the sandwiches cold. This is going to save you lots of time, so you can enjoy the picnic more, and will save you money because you won't need to go and buy more ice, so you can afford to buy drinks to wash the sandwiches down :)
Most importantly though, the bacteria that cause food to spoil don't like low temperatures, so your sandwiches won't spoil and you won't get sick when you eat them.

The introduction to your Lab Report could include some background information about how many people suffer illness as a result of eating spoilt food each year, the link between temperature and food spoilage, then a discussion about how ice can be used to keep the temperature of stored food low enough so that it won't spoil.

You Lab Report will now have 3 sections:

Title

Introduction (with the heading Introduction)

Aim (with the heading Aim)

(c) Materials and Methods (or Procedures)

This section of your Lab Report must include enough information so that someone else can follow the directions in order to replicate the experiment and get the same results.

Keep it brief!

Materials
DO NOT write sentences.
DO write a list of all equipment and reagents that are required to perform the experiment.
Example: think about our melting ice in water experiment. We will need:

50 mL beaker
10 mL measuring cylinder (or a 10 mL pipette)
electronic balance
retort stand
10 mL liquid water
10 g water ice
thermometer
stopwatch (or watch, or clock)

You may be required to write another section with the heading "Hazards", "Safety" or "Risks" etc
In this section you will describe the hazards of each chemical reagent you use, or produce, during the experiment (you may need to refer to the MSDS sheets).
Also write down any special precautions or safety equipment needed, for example, gloves, fume cupboard (fume hood).

Method (Procedure)
If the equipment you are using is of the type found in any chemistry laboratory, you do not need to explain how to set up the equipment.
All you need to do is:
(i) write, "Set up the equipment as in the diagram"
(ii) draw a labelled diagram of what the equipment looks like at the start of the experiment

(iii) give a suitable instruction, for example, "Record the temperature of the water every minute until all the ice has melted."

If you have designed and built your own equipment, you will need to explain how to construct the equipment.

Any written instructions you provide in this section should be in numbered point form, or presented as a set up of steps to be followed.

Step 1: Clean and dry a 50 mL beaker.
Step 2: Add 10 mL of liquid water to the beaker.

Step 3: Position the thermometer in the water 3 mm above the bottom of the beaker and secure it in place using the clamp on the retort stand.

etc

Each step in the method or procedure will start with a verb (a doing-word or action-word).

So far, your lab report will have the sections:

Title

(Introduction if you are required to design and perform an experiment yourself, with the heading Introduction)

Aim (goal or objective, with the heading Aim)

Materials (with the heading Materials)

(Hazards if required with the heading Hazards)

Method (or procedure, with the heading Method or Procedure)

Results and Discussion

Results are presented first, followed by the Discussion.

Results
Describe what happened during the experiment in the results section.
When measuring physical or chemical quantities, use the appropriate number of significant figures when you record these measurements in your results.
If the 10 mL measuring cylinder is graduated (marked) in 1 mL intervals, you will read it to the nearest 0.5 mL (half the limit of reading) so there will be 2 significant figures, eg, 5.0 mL, 5.4 mL etc

You should also record the tolerance of any measuring equipment you use (you will find this written on volumetric glassware, otherwise assume the tolerance is half the limit of reading)
Tolerance is given as a ± value and tells us how reliable the measurement is likely to be,
eg, 5.5 mL ± 0.5 mL (the volume is definitely known to be between 5.0 and 6.0 mL, but there is some uncertainty about the exact volume)

Do tabulate the data wherever possible.

Do include graphs wherever possible.

Do show any calculations that are needed (sometimes you might be asked to put calculations under a separate heading)

Do show all relevant chemical equations.

Example: our melting ice in water experiment would have a table of results (time and water temperature), and a graph of the results, followed by any other observations you made during the experiment (for example, you might have noticed how the volume of water changed as the ice melted)

Discussion
In the Discussion section section you need to analyse your results.
In particular, you need to discuss the reliability of your results.
What type of errors are associated with this experiment, how do they effect the results of the experiment? You may be required to calculate the errors.
Are there problems with the method used? What are the problems?
If you have drawn a graph, you will describe any trend that it shows.

If you have performed any calculations, you will need to discuss the meaning of these calculations.

Conclusion
You may be required to have a separate heading for the conclusion.
If you are not required to have a separate heading for the conclusion, then your discussion above will end with the concluding statement or paragraph.

Read your Introduction and/or Aim section, do the results of your experiment support the stated aim?
If the results support your aim, write a sentence or two that reflects this:
Example: "The temperature of water can be maintained at a temperature low enough to prevent food spoilage by the addition of ice to the water."
If the results do not support your aim, write a sentence or two that reflects this:
Example: "The temperature of water can not be maintained at a temperature low enough to prevent food spoilage by the addition of ice to the water."
The conclusion should also include any suggestions you have for improvements to the design of the experiment, or, suggest further investigation of any new questions raised by your experiment.
The melting ice in water example raises lots of possibilities for future investigations.
What would happen if you changed the substance, for example, used ethanol-ice and liquid ethanol, would you get the same results?
What would happen if you added a soluble substance, such as sodium chloride, to the ice and water, would you get the same results?
What would happen if you added an insoluble substance, such as vegetable oil, to the ice and water, would you get the same results?
What would happen if you added added ice to boiling water, would you get the same results?
I'm sure you will be able to think of even more possible questions to be investigated.

So far, your lab report will have the sections:

Title

(Introduction if you are required to design and perform an experiment yourself, with the heading Introduction)

Aim (goal or objective, with the heading Aim)

Materials (with the heading Materials)

(Hazards if required, with the heading Hazards)

Method (procedure, with the heading Method or Procedure)

Discussion (with the heading Discussion)

(Conclusion if required, with the heading Conclusion)

References

The source of any information you have used (actually cited) in your Lab Report must be written down in the reference section.
This enables someone who is interested in your experiment to look up the information for themselves.

If you have copied any text word-for-word from someone else's work, you must cite this in-text (that is, where it occurs in your Lab Report) by placing quotation marks around "the text" and by placing the referencing information inside (brackets) or by adding a footnote (depending on the instructions you have been given), and then add the full bibliographic information for this source in your Reference section.
Similarly, if you have copied any diagrams you will need to reference those.

There is more than one way to cite and reference sources.
You teacher will provide you with the details of how you are to cite and reference sources in your Lab Report.

Your completed lab report will have the sections:

Title

(Introduction if you are required to design and perform an experiment yourself, with the heading Introduction)

Aim (goal or objective, with the heading Aim)

Materials (with the heading Materials)

(Hazards if required, with the heading Hazards)

Method (procedure, with the heading Method or Procedure)

Discussion (with the heading Discussion)

(Conclusion if required, with the heading Conclusion)

References (with the heading References)

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Checklist : Have you missed anything in your written lab report?

Before submitting your Lab Report for marking, check that you have:

If this is a major assessible project, then, when you are satisfied that your Lab Report fulfills all the requirements, you should do 2 things:

Make a copy of the completed Lab Report before you submit it.

Keep the copy in a safe place!

Why should you make a copy?
Because it takes a long time to write a good Lab Report. If the original is, for any reason, misplaced, you will always have the copy to re-submit!

The best example I know of for why you should make a copy of anything that is important comes from the world of Mathematics (Number Theory).
In 1637, Pierre de Fermat wrote, in the margin of a book, that he had found a proof for the conjecture that no three positive integers can be found that will satisy the equation
aⁿ + bⁿ = cⁿ

for n > 2

but, that the proof was too large to fit in the margin.
Since he didn't keep, or indeed publish, this proof, it was lost to the world, until Andrew Wiles successfully proved it in 1995.⁽⁴⁾
If Fermat had kept a copy of the proof and published it, Mathematicians could have devoted more than 350 years to other useful research, and who knows how far advanced mathematics would be now!

Footnotes:

(1) Dan Shechtman first noted a "forbidden symmetry" in crystals in 1982 (forbidden by the prevailing theory at the time). No scientific journal would be prepared to publish his results until 1984. It wasn't until 1992 that the International Union of Crystallography was convinced enough to change the official definition of a crystal!
You can read more about this discovery in the December 2011 AUS-e-NEWS.

(2) Unfortunately the history of science also includes the names of people who did falsify results, or at the very least did not practise good scientific technique, or of those who were, at best, self-delusional.
Rather than provide examples of "poor science", why don't you read one of the many interesting books available about this?
I'm rather fond of "Bad Science" written by Ben Goldacre and published by HarperCollins Publishers in 2009, and I also like "Sorting the Beef from the Bull: The science of food fraud forensics" by Richard Evershed and Nicola Temple, published by Bloomsbury Publishing in 2017.

(3) Yes, OK, you caught me out! One of the reasons I LOVE the book, "Sorting the Beef from the Bull", cited above is because of the title which I find to be both clever and amusing. If you don't find the title humorous that's OK, ignore the title and enjoy reading the book anyway.

(4) If you happen to be a clever mathematician you can read the proof in the May 1995 issue of "Annals of Mathematics".
If, like me, you would prefer to read an account of how the proof came about, try reading "Fermat's Last Theorem: Unlocking the secret of an ancient mathematical problem" by Amir D. Aczel available in Penguin Books (1997).