Many students struggle with writing effective lab reports. Although the exact formatting of a lab report varies by school and even by instructor, the underlying principles that constitute a solid report tend to apply universally.
A problem statement is a short statement --- ranging from a sentence to a paragraph --- that clearly identifies the problem that an experiment will address. In other words, the problem statement establishes the reason for conducting the experiment. Some instructors allow students to phrase the problem statement as a question.
Generally, scientists write papers and lab reports in the third person, past tense. Future tense is acceptable if the student writes the problem statement before carrying out the experiment. Writing in the third person often necessitates use of the passive voice.
The problem statement for a chemistry experiment to determine the amount of acetic acid in vinegar might read as follows:
"The mass percent of acetic acid in commercial vinegar varies from 5 to 10 percent. The percent acetic acid in store-bought vinegar will be determined to a precision of 0.01 percent by titration of the vinegar with standardized sodium hydroxide solution in the presence of a phenolphthalein indicator."