Example method section for a chemistry laboratory report: Preparation of Methyl 3-Nitrobenzoate
The nitration of methyl benzoate was conducted as follows: concentrated sulphuric acid (12 mL) was cooled to 0 °C and 5.6 mL of methyl benzoate was added. The nitrating mixture (a 50:50 mixture of concentrated sulphuric acid and concentrated nitric acid; 8 mL) was cooled to 5 °C and added dropwise to the methyl benzoate solution with regular temperature checks to ensure the temperature of the solution was maintained between 5-15 °C. The mixture was swirled thoroughly after each addition of nitrating mixture to encourage reaction. Once all the nitrating mixture had been added to the methyl benzoate solution, the temperature of the reaction mixture was allowed to increase to 18-20 °C using a warm water bath and kept at room temperature for 15 minutes to allow the nitration to occur. To collect the methyl 3-nitrobenzoate after nitration had been completed, approximately 50g of cracked ice was weighed into a beaker and the reaction mixture poured over the ice, forming solid methyl-3-nitrobenzoate. The product was collected using Büchner filtration, washed twice using 10 mL ice-cold methanol and dried in a drying oven prior to weighing to calculate the yield.
Writing a method section for the sciences
It is important to understand how to write a method as early as possible in your scientific based studies. Although this example is for chemistry, science based methods have some commonality across comparable science disciplines.
Often, to make the process of learning method writing easier, your tutor may give you the majority of this information in the 'materials and apparatus' section of a laboratory practical script. However, it still requires some conversion. To explain this further, this example was actually written for inclusion in a Laboratory book (often referred to as 'Lab book'), and was created from a combination of a student following the materials and apparatus section and their own observations from the experiment. E.g. perhaps used slight variations of the suggested apparatus.
Regarding the structure and flow of the writing, note how it provides just enough detail to allow another scientist to carry out the same experiment. Equally, the units of measurement are in the same format. Why? For example, switching between lb (pounds weight) and Kg (kilograms) only makes comparisons difficult, keeping to Kgs would be much easier to read. However, it is preferred that scientists use the same units of mass, volume, temperature, etc throughout their reports; always adhering to the International System of Units (abbreviated SI), a recognised metric system agreed by all the sciences, industry, and also medicine worldwide.
Hints and tips:
1) For those not working directly in chemistry, look at examples from science journal articles in your disciplines and see how it compares. Alternatively, ask your science tutor what they consider to be good examples.
2) Sometimes you are not required to write a method section for University based laboratory reports, because a reference to the 'materials and apparatus' section provided in the practical script is often enough. However, always ask your marking tutor if this short cut is allowed, as you may find that part of your learning outcomes for the practical or assignment included the ability to write a method!
3) Writing method sections are excellent practice for when you have to write for external reports or publication in journal articles during or after your studies, which is the main reason you are encouraged to write and practise them at University.
3) Finally, note that the overall writing style is clear, simple and avoids ambiguity, a typical characteristic for science-based writing.
Note that volume is consistently in millilitres (mL) and temperature is in centigrade °C. There is also sufficient information for another to repeat the first part of this nitration of methyl benzoate.
Use of the simple term 'to collect' indicates the next stage, and that an approximate weight of 50g of ice is sufficient.
This section describes how the mixture was added, note that is uses the term 'dropwise' and indicates the best temperature conditions. This is well written, clear and precise, again allowing another scientist to replicate.
This describes the next step. Note how the start of the sentence is clear about moving from one stage to the next. It is important in science writing to ensure clarity of stages, never assume that others will be able to repeat the procedure without your insights. There is no doubt that nitration will only occur under those conditions.
The last stage is evident as here the use of word 'product' indicates that the experiment is complete and all that is required is filtration and washing. Note that in this case it is indicating the best filtration approach using a Büchner. Highlighting that washing in ice-cold methanol is needed twice, and drying, before measuring the final yield.
This although descriptive, indicates to others an important step, as without swirling of the mixture the reaction is likely to be slow or incomplete.
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