How do I use verb tenses?
Engineering papers tend to be written primarily in the past and present tenses. Professional engineers, however, differ in they way they use these tenses in their reports, and the mixed precedents often confuse beginning ChE writers. Therefore, in an effort to keep consistent standards for your undergraduate ChE laboratory reports, we are setting these rules:*
1. Use the past tense to write up what was done or what happened in the experiment.
Example: We mixed the red chemical with the green chemical.
2. Use the present tense to write up
(a) statements of general, accepted knowledge in your field,
(b) facts that are always true, and
(c) accepted findings in published work.
a. Carbon dioxide levels influence global climate change.
b. Water is wet.
c. Carbamate ions react with H2O to form MEA and bicarbonate ions (Hoff, et al., 2000).
3. Use the present tense to refer to figures, tables, appendices, equations or other parts of the report.
Example: Fig. 1 demonstrates the trend.
These guidelines may seem simple, but many writers run into difficulty applying them. Shifting tenses in a paragraph may seem awkward. Here are two examples of how to shift tenses:
Example: The red chemical was mixed with the blue chemical. These reacted to produce a white crystalline product that has a melting point of 120 degrees C and has an adsorbance maximum at 230 nm.
Note: The procedure is described in the past tense because it took place in the past (Rule 1). It is a fact, however, that the white crystalline product has certain properties, so those properties are described in the present tense (Rule 2b).
These guidelines should suffice for most Technical Memos and Laboratory Reports. Your Research Reports may demand a more sophisticated use tenses, particularly in the Introduction. See the annotated example of the Research Report.
* These guidelines simplify Robert A. Day’s Scientific English: a Guide for Scientists and Other Professionals (Westport, CT: Oryx, 1995), pp. 74-75.