Helge Strömdahl
Title: On mole and amount of substance: A study of the dynamics of concept formation and concept attainment/
Language: English
Keywords: Amount of substance, analogy, metaphor, physical quantity, stoichiometry, chemistry, physical chemistry, qualitative method, mole, phenomenography, conception, conceptual change, learning, teaching, teachers' conceptions
Göteborg: Acta Universitatis Gothoburgensis, 1996
ISBN: 91-7346-293-4
Email: Helge Strömdahl
At the 14th meeting of the General Conference on Weights and Measures (Conférence Générale des Poids et Mesures, GCPM) in 1971 1 mol was adopted as the unit of the base physical quantity amount of substance within the International System of units (Le Système International d'Unités, SI).
On the other hand it is empirically found that only 3 among 54 chemistry educators, acting on different levels of the Swedish educational system in the late 1980's, recognise 1 mol as an SI unit for the base physical quantity amount of substance. This thesis aims to provide an answer to the question: Why have the educators not attained the 1971 convention?
Two main routes have been followed to grasp the conceptual situation. One empirical and synchronic manifested in the overt statements individuals have made concerning the actual concepts, and one theoretical and diachronic, coincident with the formation of the scientific concepts.
The first route deals with semi-structured open-ended individual interviews comprising a theoretical sample of 54 Swedish Chemistry educators on different levels in the Swedish educational system from upper secondary school to university level. A contextual analysis of the transcribed interviews has generated results mainly in the format of categories of descriptions accounting for the variation of conceptions among the respondents. This kind of qualitative research approach is denoted phenomenography.
The second route comprises a historical account of the formation of the concepts 'the mole' and amount of substance and a conceptual analysis of the contemporary scientific convention.
In the encounter between the two routes a theory is elaborated to model the process of concept attainment.
Via the theory it is shown that the defaulting attainment of the 1971 convention among the educators is a consequence of a non-apprehension of the base physical quantity amount of substance, and thereby the conceptual habitat of the SI unit 1 mol. A vast majority of the educators comprehend 1 mol as the unit measure of number of elementary entities (atoms, molecules, ions, etc.) in portions of matter. This conception belongs to discontinuum physics. However, the 1971 definition of 1 mol belongs to continuum physics since amount of substance is a continuous physical quantity. This is not generally noticed by the educators acting and interpreting within the frames of the grand theory of matter, the atomic theory, which is foundational in explaining chemical events. The non-attainment of amount of substance and its unit 1 mol is an example of the fact that concepts are theory-laden and can only be attained within the theories to which they belong.
The accounted conceptual situation also reflects an ongoing scientific controversy about the nature of the physical quantity amount of substance and whether number should be used instead of amount of substance. This is a matter of didactical choice and convention. The decision ought to be made under conceptual transparency. Hence, the representatives of the International Union of Pure and Applied Chemistry (IUPAC) are addressed to reconsider the commentary on amount of substance and the unit 1 mol in the IUPAC manual, inter alia in view of the results of the present investigation.
Some educational implications of the conceptual situation are discussed.