The Price of Precision: Significant Figures and the Student Experience

General chemistry is often regarded as difficult due to its math-intensive nature. Mathematical computation in general chemistry differs from other introductory STEM courses due to the emphasis placed on significant figure (SF) rules. These rules are found in general chemistry textbooks and enforced by online homework systems. Instructors may not understand the impact of enforcing SF rules because their effects on students have not been studied. In this work, we quantitatively investigated how the inclusion of SF rules impacted students’ mental workload while solving chemistry problems. We found a statistically significant increase in self-reported cognitive load associated with the application of SF rules. We further found that inclusion of SF rules exacerbated the relationship between mental workload and math anxiety in students. We also conducted interviews with students to find out how they describe their experiences with significant figures, and how they are engaging with these rules. Responses were analyzed using expectancy value theory. Interviews revealed that students have largely negative perceptions of SF rules. As a result, participants frequently did not engage meaningfully with the rules, abandoning them in favor of guessing or lower-effort mental shortcuts. These results suggest that the standard textbook approach to teaching SF rules is both burdensome and ineffective, substantiating concerns previously raised in the literature. Considering these findings, we would urge instructors and homework platform providers to be judicious in their enforcement of SF rules, emphasizing them when the context supports it.