Abstract
‘The mole’ is one of the fundamental concepts in quantitative chemistry. However, previous research has shown that because of its abstract nature and the anomalous evolution of the definition in scientific history, the mole is generally acknowledged to be one of the most troublesome concepts in chemistry teaching and learning.
Adopting a sociocultural view of learning, this study aimed to explore how the mole concept is presented and understood in secondary science classrooms. The study was conducted in two countries, Australia and Taiwan, in order to maximize the possibilities of seeing differences in instructional approaches to the teaching of the mole. Two Australian year 11, and several Taiwanese year 8 and 10 classrooms provided the research sites for this study. Data generation methods included videotaping, interviewing, questionnaires, and the collection of relevant documents.
Through reflection and a re-conceptualization of the mole concept, I developed a ‘concept map’ of the mole. The concept map makes it clear that the mole is a complex concept. The mole concept subsumes several major sub-concepts and links together many aspects of chemistry. The principal meaning of the mole concept derives from the purpose of using the mole in chemistry (stoichiometry): to use weights of substances to ensure the correct ratio of particles participating in a chemical reaction. Based on this meaning, two linking ideas were identified as essential for a sound conceptual understanding of the mole: (1) the SI definition of the mole, including the number aspect and the mass aspect, and (2) a connection between molar mass and relative atomic mass. In addition, an important proposition emerged as underlying both the two key components: the magnitude of the number in 12 grams of 12C is irrelevant to stoichiometric calculations. “All that matters is that the number should be the same in one mole of every substance” (Gorin, 1994, p. 116).
In the scientific domain, two conceptually incommensurable paradigms, the equivalentist paradigm and the atomistic paradigm that shaped the historical development of the mole concept, are in fact sedimented in the SI definition of the mole. The underlying concepts derived from the two paradigms, such as the rationale behind the choice of 12 grams of 12C in defining one mole and the connection between molar mass and relative atomic mass, shape the way the mole concept is understood by the scientific community. However, they seem to be understood by scientists and teachers at a subliminal level.
In the educational domain, the mass aspect and the number aspect of the SI definition of the mole are presented in ways that distort the meaning of the concept. My empirical findings show that in both countries, the mole concept was defined and conceptualized with emphasis on the mole as a number. Neither the SI definition in terms of 12 grams of 12C (the mass aspect of linking idea 1) nor the connection between molar mass and relative atomic mass (linking idea 2) was explicitly explained in any of the participating classrooms. The students’ conceptions of the mole generally mirrored their teachers’ instruction. Most of the Australian and Taiwanese students defined the mole in terms of the number aspect. Few of them were able to make a connection between molar mass and relative atomic mass. Although the teachers in the two countries adopted somewhat different teaching strategies in the lessons, the way the mole concept was presented, and the way the students conceptualized it, were actually very similar. It was also significant that there were no obvious differences in the students’ conceptions of the mole between Taiwanese junior and senior levels. This uniformity of conception of the mole, independent of cultural setting or grade level, suggests an underlying difficulty with the concept that is independent of either culture or student intellectual maturity.
The differences in how the mole concept has been conceptualized between the scientific and the educational domains led me to suggest that through their training, chemists and teachers learn to use the mole concept as a ‘tool’. Their associated conceptual understanding becomes so ingrained that its importance goes unrecognized. As a consequence, it seems that the teachers’ lack of explicit awareness of the underlying concepts resulted in some ambiguities in their classroom instruction, and this could explain some of the difficulties the students encountered when learning the mole concept.
The findings identify some essential knowledge for teaching and learning the mole concept, and provide specific suggestions for teachers, curriculum designers and researchers. Importantly, the example of the mole concept raises the possibility that other significant scientific concepts might also be conceptualized differently in scientific and educational contexts. This opens up the whole question of the need to recognize the distinctive goals of the science classroom in comparison with the scientific laboratory.
Full Reference of the thesis
Fang, S. (2011). Teaching and learning the mole concept: an investigation of science secondary classrooms in Australia and Taiwan. Unpublished PhD thesis, Melbourne Graduate School of Education, The University of Melbourne.
Correspondence
Dr. Fang SuChi
Email: suchhii@msn.com
Phone: +886 920328538
