Writing a Science lab report

Many of your Science units will require you to write a formal laboratory report. The purpose is to report on what you did, what you learned from an experiment and why the findings matter.

The marker is looking for evidence that you:

  • understand what happened, why it happened and what it signifies in relation to the experimental aims
  • can structure and present your lab report in accordance with discipline conventions.

Disclaimer:

Please note that many units require students to record notes and observations in logbooks in the laboratory. These have their own purpose and conventions and are different from lab reports.


Lab report structure

Lab reports can vary in length and format. These range from a form to fill in and submit before leaving the lab, to a formal written report. However, they all usually follow a similar basic structure.

Click on the links below to find out more about the different sections of a lab report.

Title

Your title needs to reflect the purpose of the experiment. Check with your demonstrator or lecturer for specific requirements.

PHS1022 Week 5 Laboratory

The Period of a Simple Pendulum

Abstract

An abstract provides a brief overview of the experiment, including its findings and conclusions. In general the abstract should answer six questions:

  • Why was the experiment conducted? (big-picture/real-world view).
  • What specific problem/research question was being addressed?
  • What methods were used to solve the problem/answer the question?
  • What results were obtained?
  • What do these results mean?
  • How do they answer the overall question or improve our understanding of the problem?

The most important thing to remember when writing the abstract is to be brief and state only what is relevant. No extraneous information should be included. It also must be clear enough so someone who is unfamiliar with your experiment could understand why you did what you did, and the conclusions you reached, without needing to read the rest of the report.

An abstract is usually only one paragraph (200-300 words max).


Tip

An abstract should be written last (even though it appears as the first section in your report), as it summarises information from all the other sections of the report.

Introduction

The Introduction should:

  • provide the context and motivation for the experiment
  • briefly explain relevant theory in sufficient detail
  • introduce any relevant laws, equations or theorems
  • clearly state the aim or research question that the experiment is designed to address.


Tip

  • Always write the introduction in your own words; don’t just copy from the lab notes.
  • Some brief lab reports do not require an introduction and will just begin with an aim/statement.
  • Always check with your lecturer/demonstrator if you’re not sure what is expected.

Activity

Method

The method section is where you describe what you actually did. It includes the procedure that was followed. This should be a report of what you actually did, not just what was planned. A typical procedure usually includes:

  1. How apparatus and equipment were set up (e.g. experimental set-up), usually including a diagram,
  2. A list of materials used,
  3. Steps used to collect the data,
  4. Any experimental difficulties encountered and how they were resolved or worked around.

If any aspects of the experimental procedure were likely to contribute systematic error to the data and results, point this out in sufficient detail in this section.

Experimental set-up and materials

Your description of the experimental set-up should be sufficient to allow someone else to replicate the experiment themselves. You will usually begin with a description of the materials used and/or the apparatus set-up accompanied by:

  • an image showing the relevant features of any object or material under investigation
  • a diagram of the experimental setup, with each component clearly labelled

Procedure

When you carry out an experiment, you usually follow a set of instructions such as these, which may include extra information to guide you through the steps.

Lab handout example

Week 5 Laboratory instructions

Procedure

  1. Use a clean pipette to measure 25ml of HCl(aq) into the conical flask.
  2. Rinse a burette with standardised NaOH(aq).
  3. Fill the burette to the 0.0ml marking with standardised NaOH(aq). Remember to take the reading from the centre of the meniscus, and from eye level. Record the actual reading in Table 1.
  4. Place a sheet of white paper under the burette. This is to make it easier to observe the colour change during the reaction.
  5. Place the conical flask onto the white paper...

Lab report example

Procedure

The equipment was arranged as shown in Fig. 2.

25.0ml HCl(aq) was pipetted into a 100ml conical flask. A burette was clamped to a retort stand and filled with standardised NaOH(aq) and the initial measurement was recorded. The conical flask was placed below the burette, on top of a piece of white paper. Five drops of universal indicator solution were added to the flask...

image of experimental set-up for titration

Figure 2. Experimental set-up for titration (taken from Carroll 2017)


Lecturer's comment

When writing up the procedure, you must report what was actually done and what actually happened, and omit any extra information such as helpful hints included in the instructions. Your goal for this section should be to include enough detail for someone else to replicate what you did and achieve a similar outcome. You should also explain any modifications to the original process introduced during the experiment.


Tip

In the Procedure section you should use:

  • the past tense when you are reporting on something you did.

While most science units require that you report in the passive voice, some require the active voice. In the example below, the first person is used e.g. "we initiated". This is accepted in some disciplines, but not others. Check your unit guide or talk to your unit coordinator.

Instruction

Your report

Initiate the bicarbonate feed pump.

We initiated the bicarbonate feed pump. (active voice)

 

The bicarbonate feed pump was initiated. (passive voice)

Activity

Lecturers have different preferences for using active/passive voice and you will likely have to write in both voices. Read samples of student reports below and identify which examples are written in passive voice, and which use active voice.

Results and analysis

In this section, you present the main data collected during your experiment. Each key measurement needs to be reported appropriately. Data are often presented in graphs, figures or tables.

This section often also includes analysis of the raw data, such as calculations. In some disciplines the analysis is presented under its own heading, in others it is included in the results section. An analysis of the errors or uncertainties in the experiment is also usually included in this section.

Tables, graphs and figures

Most numerical data are presented using tables or graphs. These need to be labelled appropriately to clearly indicate what is shown.

Titles and captions

  • Tables should be labelled numerically as Table 1, Table 2, etc.
  • Everything else (graphs, images, diagrams etc.) is labelled numerically as Figure 1, Figure 2,  etc. (References to figures in the main body of the text are usually written in abbreviated form, e.g. ‘see Fig. 1’).
  • Table captions appear above the table. Figure captions appear below the figure.

Example table labelled as "Table 1. Circular cylinder data". Tables are labelled above the table. Unites are given in the column headings

Sample graph labelled "Figure 3. Lift and drag co-efficients at various angles of attack". Figures are labelled below. Label both axes including units. Provide a key to symbols.

Note that in Fig. 3, above, the student has omitted error bars on the data points. For most experiments an error analysis is important, and errors should be included in tables and on graphs.

Also, it is always best to draw figures yourself if you can. If you do use figures from another source, indicate in the citation whether you have modified it in any way.

Data can be presented in other formats, such as images:

Microscopic image labelled "Figure 4. Scanning electron micrograph of the surface of an AI-Si-Ge alloy illustrating Si-Ge core-shell particles on the surface of the material". Provide magnification value for microscopic images. This can be included as part of the caption. Figure titles should state what the figure is and what it contains.

Calculations

When showing calculations, it is usual to show the general equation, and one worked example. Where a calculation is repeated many times, the additional detail is usually included in an appendix. Check the requirements given in your unit guide or lab manual, or ask your tutor if you are unsure where to place calculations.

In some disciplines, if formulae are used, it is common to number them as equations:

sample report section containing formulae with each formula marked with a number to the right


Lecturer's comment

In some schools, like Biology, calculations that are too detailed to go into the main body of the report can be added in an appendix. The purpose of such appendices is to present the data gathered and demonstrate the level of accuracy obtained.

Results

A chromatogram was produced for the unknown compound U, and each of the known compounds, A-E. Rf values for each substance are listed in Table 1.

Table 1: Rf values for known compounds (A-E).

Compound

Rf value

Present in U?

A

0.95+/-0.03

Y

B

0.75+/-0.10

Y

C

0.88+/-0.04

N

D

0.45+/-0.06

N

E

0.33+/-0.05

Y

Note: U is the unknown compound.

Error analysis

As well as presenting the main findings of your experiment, it is important that you indicate how accurate your results are. This is usually done through determining the level of uncertainty. The sources of error that you need to consider will vary between experiments, but you will usually need to factor in both random and systematic errors. Your error analysis should identify the main causes of uncertainty in your measurements, note any assumptions, and show how you have calculated any error bars. Check with your demonstrator, tutor or lecturer if you are unsure about how to determine uncertainties or whether error bars are required for your experiment.

Discussion

The discussion section is where you:

  • comment on the results you obtained
  • interpret what the results mean
  • explain any results which are unexpected.

Your discussion section should demonstrate how well you understand what happened in the experiment. You should:

  • identify and comment on any trends you have observed
  • compare the experimental results with any predictions
  • identify how any sources of error might impact on the interpretation of your results
  • suggest explanations for unexpected results, and
  • where appropriate, suggest how the experiment could have been improved.

The discussion example below is from a first-year Biology unit. The aim of this experiment was to identify decomposition rates of leaf breakdown to establish rates of energy transfer.

Discussion

It was expected that the leaves would show a far higher rate of decomposition in the shore zone, where there are more chances for sediments to rub against them. However the two zones show no significant difference in leaf breakdown, although these results are non-conclusive due to the limitations of this experiment. The two zones of leaf decomposition were physically too close, and over the incubation period reeds were observed growing close to the limnetic zone. This may have negatively affected the accuracy of the results by reducing the differences in habitat at these sites, as seen in other experiments (Jones et al. 2017). The results also had large standard deviations, possibly due to these physical constraints or human error in weighing leaves. Further studies with more diverse zones and precise procedures should be undertaken in order to explore leaf decomposition and rates of energy transfer more effectively.

Activity

Drag each description of each component of the Discussion section to its example. Notice the order in which the components make up a coherent Discussion section.

Conclusion

The conclusion section should provide a take-home message summing up what has been learned from the experiment:

  • Briefly restate the purpose of the experiment (the question it was seeking to answer)
  • Identify the main findings (answer to the research question)
  • Note the main limitations that are relevant to the interpretation of the results
  • Summarise what the experiment has contributed to your understanding of the problem.


Lecturer's tip

In brief lab reports, the conclusion is presented at the end of the discussion, and does not have its own heading. This type of conclusion can also be thought of as the sentence that answers the question “So what?”. Note that a conclusion should never introduce any new ideas or findings, only give a concise summary of those which have already been presented in the report.

Click the icons next to each paragraph to show the lecturer’s comments. Click again to hide the comment.

Legend:

Good Problem Suggestion Question

Conclusion

Show/hide lecturer's comment 1 Show/hide lecturer's comment 2 Show/hide lecturer's comment 3 Show/hide lecturer's comment 4 The concentration of salicylic acid in commercially available aspirin tablets was determined through UV spectroscopy. Lecturer's comment 1:
indicates to what extent the aims of the experiment were achieved.
The mean concentration from three different tablets was determined to be 301.1+/-4.36 mg per tablet, which is within commercially permitted limits. Lecturer's comment 2:
elaborates how the aim of experiment was achieved
The results for individual tablets were found to be dependent on the accuracy of measurements during the process, and the purity of the other reagents. Lecturer's comment 3:
summarises the main reasons for any discrepancies and recommends improvements to overcome experimental limitations
Standardised solutions might further improve the accuracy of the results. These findings show that analytical chemistry techniques such as spectrometry can be used for fast, accurate determination of compound composition. This is important in many industries, where consistency is crucial for effective use of the product, or is vital to the safety of the product. Lecturer's comment 4:
briefly recaps key findings

References

It is quite possible that you may have in-text citations in your lab reports. Typically these will be included in the introduction to establish evidence of background for current theories or topics. Your discussion section will often include in-text citations, to show how your findings relate to those in the published literature, or to provide evidence-based suggestions or explanations for what you observed.

When in-text citations are incorporated into your lab report, you must always have the full citations included in a separate reference list. The reference list is a separate section that comes after your conclusion (and before any appendices).

Check your lab manual or unit guide to determine which referencing style is preferred. Carefully follow that referencing style for your in-text references and reference list. You can find examples and information about common referencing styles in the Citing and referencing Library guide.

The following is an example of a reference list based on the in-text citations used in the Introduction and Conclusion sections in this tutorial. It has been formatted in accordance with the CSIRO referencing style.

References

Jones T, Smith K, Nguyen P, di Alberto P (2017) Effects of habitat overlap on population sampling. Environmental Ecology Journal 75, 23-29. doi: 10.5432/1111.23

Tian M, Castillo TL (2016) Solar heating uptake in Australia: rates, causes and effects. Energy Efficiency Reports. Report no. 10, The Department of Sustainability and Environment, Canberra.

Appendices

An appendix (plural = appendices) contains material that is too detailed to include in the main report, such as tables of raw data or detailed calculations.

Each appendix must be:

  • given a number (or letter) and title
  • referred to by number (or letter) at the relevant point in the text.

Example text

The calculated values are shown in Table 3 below. For detailed calculations, see Appendix 1.

In summary

Many of your Science units will require you to write formal laboratory reports. The purpose is to report on what you did, what you learned from an experiment and why the findings matter.

Activity

Review the components of the Science laboratory report.  Select the report section that relates to the statement.