When writing a lab report, it is often a good idea to begin by writing the Materials and Methods section. This section is usually very straightforward, and writing it first helps many people establish the proper thought process and understanding of the work that will allow the rest of the report to flow more smoothly. Following this section, it is generally recommended to write the Results section, followed by the Discussion, and finally the Introduction. Although this strategy is only a recommendation, and although it may seem illogical at first, many have found this approach very effective for writing scientific papers.
The Materials and Methods section is a vital component of any formal lab report. This section of the report gives a detailed account of the procedure that was followed in completing the experiment(s) discussed in the report. Such an account is very important, not only so that the reader has a clear understanding of the experiment, but a well written Materials and Methods section also serves as a set of instructions for anyone desiring to replicate the study in the future. Considering the importance of "reproducible results" in science, it is quite obvious why this second application is so vital.
There are several common mistakes that are often found in the Materials and Methods section of a lab report. One major concern is deciding upon the correct level of detail. (Pechenik, p. 55) It is often very easy for a writer to get carried away and include every bit of information about the procedure, including extraneous information like the number of times he\she washed their hands during the experiment. A good guideline is to include only what is necessary for one recreating the experiment to know. Keeping this in mind will lead to a Materials and Methods section that is thoroughly written, but without the kind of unnecessary detail that breaks the flow of the writing. Another common mistake is listing all of the materials needed for the experiment at the beginning of the section. Instead, the materials and equipment utilized during the experiment should be mentioned throughout the procedure as they are used. Enough detail should be included in the description of the materials so that the experiment can be reproduced. Finally, it is generally recommended that the Materials and Methods section be written in past tense, in either active or passive voice. Many are written in third-person perspective but check with the professor to be certain what verb tense and perspective the report should use. This is demonstrated throughout the example of a well written Materials and Methods section.
Materials and Methods examples
Sample 1: In preparing the catecholase extract, a potato was skinned, washed, and diced. 30.0 g of the diced potato and 150 ml of distilled water were added to a kitchen blender and blended for approximately two minutes. The resulting solution was filtered through four layers of cheese cloth. The extract was stored in a clean, capped container.
Four individually labeled spectrophotometer tubes were prepared using different amounts (as represented in Table 1) of the following reagents: a buffer of pH 7, a 0.1% catechol substrate, and distilled water. The wavelength of the Spectronic 20 spectrophotometer was set at 540 nm. To calibrate the specrophotometer at zero absorbance, a blank control tube prepared with no catechol substrate and labeled "tube 1" was inverted and inserted into the spectrophotometer.
It is important to note that the extract to be tested was added to each tube immediately before placing the tube into the spectrophotometer. 1.0 ml of catecholase extract was pipetted into tube 2. Tube 2 was immediately inverted and placed in the spectrophotometer. The absorbance was read and recorded for time zero (t0), the ten minute mark (t10), and each minute in between. Tube 2 was removed from the spectrophotometer and the same measurements were taken for tube 3 and tube 4 using the same protocol.
Sample 2: A potato and a knife were obtained for this experiment. Also, distilled water, a blender, cheese cloth, a clean container with a cover, and eight spectrophotometer tubes were used. A Spectronic 20 spectrophotometer was used for this experiment, as were buffers of pHs 4, 6, 7, and 8. Catechol substrate, Parafilm coverings, KimWipes, a black pen, and pipettes were also obtained for this experiment. Finally, a pencil and pad were obtained for recording results.
Sample 3: In preparing the catecholase extract, a potato was skinned, washed, and diced. A balance was used to obtain 30.0 g of the diced potato. 150 ml of distilled water was poured into a beaker. The water was added to the diced potato. The cover of a kitchen blender was removed. The potato and water were added to the blender. The solution smelled like potato. The cover was placed on the blender and the power button was depressed. The clock was observed until the second hand circled twice. The power button was pushed again to stop the blender. The resulting solution was filtered through four layers of cheese cloth. The extract was stored in a clean, capped container.
Explanations of the Example Links
Diced potato: In sample one the writer gives enough detail about the procedure so that is can be understood, but not so much that there is an excess of unecessary detail. (return to sample 1)
Calibrate: Calibration is a small but important detail to include in this section so that the experiment would be able to be repeated by anyone reading the report. Keep this in mind while deciding what to include in this section. (return to sample 1)
Distilled water: This example has a list of materials at the beginning which are not necessary in the materials and methods section. The body of the section should mention the materials and equipment used during the experiment so that it is not necessary to list them in order to know what was used for the procedure. (return to sample 2)
Extraneous detail: This is extraneous detail that is not needed to explain the procedure. The reader would know how to turn the blender on and off without being told that a button was pushed, and knowing that the solution smelled like potato is completely unrelated to knowing how to perform the experiment. (return to sample 3)
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All citations from Pechenik, Jan A. A short guide to writing about Biology. pp. 54-102, Tufts University: Harper CollinsCollege Publishers. 1993.