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The concept of gravitational mass is usually introduced to chemistry students as a measure of the amount of matter in a given object. Although this definition can be useful as a starting point for quantitative investigations in chemistry, it does not refer explicitly to the direct experimental observations upon which the concept is actually based. This traditional approach also misses an opportunity to help students connect observations in the see-touch world with inferences about the atomic realm, and may contribute to the incomplete understanding exhibited by many high school and first-year college students of mass and other fundamental concepts, like weight and density. This paper presents a Socratic dialog between a hypothetical instructor and student, which uses experimental evidence and operational definitions to introduce these concepts. The student's responses are based on those of many individuals in a college freshman chemistry course, and point out the difficulties associated with learning the concepts. The question sequence has evolved to its current form based on student feedback obtained over the course of several years. A theoretical basis for this type of instruction is discussed, as well as the benefits and challenges associated with its application to this particular material.
DePierro et al. (2003) studied this question.