BPS2026 – Student understanding of the chemistry and physics in introductory chemistry problems

Often, students find answers to problems in introductory chemistry by memorizing an equation, and writing down whatever comes out of a calculator as the answer. The student may not understand what the equation means, or whether the answer is reasonable. An incorrect button push may give an answer off by an order of magnitude or worse without the student noticing. An extreme example would be multiplying atomic weight by Avogadro’s number instead of dividing when determining the weight in grams of an atom, getting something like the mass of the moon. While this case is fortunately rare, slightly less egregious cases are not rare. If the student has a good memory, she or he may leave the course with a decent grade, but without understanding the content of the course, and thus with no foundation for more advanced courses. To remedy this, I have prepared problems in which the student is required to consider the actual physical situation that the problem deals with before starting to calculate, and whether an answer to a problem is reasonable. Sometimes estimating an answer may cure this, or even doing a one significant figure calculation without a calculator. It is also useful to have a discussion of units and of arithmetic approximation. Some problems may use physical conditions that are impossible, such as determining the properties of a solid at a temperature above the melting point, so the student must consider whether the conditions in the stated problem are physically possible. I will discuss a new book that deals with these questions and gives examples from essentially all quantitative subjects in chemistry; there are multiple approaches to getting the student to think about the physics and chemistry inherent in a problem.