The “mole” is a fundamental concept in quantitative chemistry, yet research has shown that the mole is one of the most perplexing concepts in the teaching and learning of chemistry. This paper provides a survey of the relevant literature, identifies the necessary components of a sound understanding of the mole concept, and unpacks and presents these components in the form of a concept map. The concept map incorporates the atomic–molecular concept with the mole concept, and connects the two concepts by two linking ideas: the number aspect of the SI definition (linking idea 1) and the connection between relative atomic–molecular mass and molar mass (linking idea 2). This concept map not only provides a conceptual framework for making meaning in relation to the mole but also sheds some light on how the concept might be better taught and learned.

ABSTRACT:This study attends to the possibilities of analyzing students' writings at a lexicogrammatical level in terms of their use of linguistic resources, and the insights afforded by this approach into the challenges students faced when they employed the language of school science related to the phenomenon of expansion. For the purpose of this study, the data consist of Grade 7 students' written assignments generated from a sequence of lessons on the topic of "States of Matter." We analyzed the language by employing the Systemic Functional Linguistics framework. The analysis reveals similarities and differences in the use of linguistic resources among the students, from which we identified several patterns of language use that appeared to be significant for realizing scientific meanings. These patterns of language use suggest that students face challenges not just in learning to use language as both a cognitive and a semiotic tool but also in interpreting the requirements of task when employing the language of school science. The findings demonstrate the productivity of this approach in expanding our understanding of the conceptual and representational challenges that students face when learning the language of school science.C 2011 Wiley Periodicals, Inc. Sci Ed 95: 852 -876, 2011

Models are important both in the development of physics itself and in teaching physics. Historically, the consensus models of physics have come to embody particular ontological assumptions and epistemological commitments. Educators have generally assumed that the consensus models of physics, which have stood the test of time, will also work well as teaching models, and for many topics this assumption is at least unproblematic and in many cases productive. However, in the case of electric circuits the consensus models are highly abstract and consequently inaccessible to beginning learners. Certain historically derived analogues for the consensus models are accepted in texts, but these are demonstrably ineffective for helping learners grasp the fundamental concepts of electric circuits. While awareness of other models circulates informally in the teaching community, these are not well documented in the science education literature and rarely referred to in authoritative texts, possibly because the models do not share the ontological assumptions and epistemological commitments that characterise consensus models. Consequently these models have not been subjected to a disciplined critique of their effectiveness for teaching purposes. In this paper I use criteria drawn from the science education literature to reflect on why I have found particular models valuable in teaching electric circuits. These criteria contrast with the epistemological and ontological features that characterise the consensus models of science, and my reflection leads me to attend explicitly to the ways in which meanings are created within physics. This suggests that all models, whether consensus models or not, can be used more knowingly for important educational ends.