A content analysis of the presentation of the mole concept in chemistry textbooks

The goal of this study was to examine the means used by textbook authors to introduce, define, and explain the mole concept in high school and introductory college chemistry textbooks. The analysis was framed by four questions:

• 1 How is the mole defined?
• 2 What concepts about the atom are introduced prior to the mole?
• 3 Is Avogadro's constant presented as an experimentally determined value?
• 4 What is the context for introducing the mole?

Twenty-nine high school and introductory college level chemistry texts were examined. After independent reading of appropriate sections of each text, discussion of differences, second or third readings of texts, and subsequent discussions, both authors reach 100% agreement concerning the results. Major conclusions were

• 1 Two ways of defining the mole dominate the texts. One way defines the mole as Avogadro's number (6.02 × 10²³) particles; the other method defines the mole in terms of carbon-12.
• 2 All texts that present a definition in terms of C-12 introduce and define concepts about the atom prior to introducing the mole.
• 3 Most texts at all levels point out that the value 6.02 × 10²³ is an experimentally determined quantity.
• 4 Nearly all texts discuss the mole in relation to die problem of finding a way to count particles that are too small to be directly weighed. Most texts also use a familiar counting unit, such as the dozen, to introduce the mole by analogy.

Four issues were discussed: (a) the defining attributes of the mole concept itself and the cognitive requirements for comprehending the two most frequently used definitions; (b) the connection between the definition of the mole presented in the text and the concepts about atoms that are introduced before the mole concept is developed; (c) the experimental nature of Avogadro's number; and (d) the context or setting for developing the mole concept.