Demonstrating chemistry phenomena and back-and-forth thinking between phenomena, concepts, and various representations and visualizations.

Johnstone's (1993, 2009) “chemistry triangle” comprises three levels of processing to describe and explain chemical phenomena: Macro-, Micro-, and Symbolic-level. Experienced chemists can easily switch between the different levels, but learners often struggle to do so. Pupils have to learn to think back-and-forth between phenomena and theory, and switch between the three levels of description and explanation of phenomena. In this article we describe the relationship between hands-on and minds-on approaches to learning chemistry concepts through teacher demonstrations. We provide guidance and a strategy to facilitate smooth switching between the different levels. In Section 1 we introduce "meaning-making" through Thinking Back-and-Forth (TBF) between the Domain of Observables (phenomena, objects and observations) and the Domain of Ideas (concepts, theories and models). In Section 2, the back-and-forth thinking model (Abrahams & Millar, 2008; Spaan et al, 2023) is expanded to incorporate the various levels of processing as outlined in Johnstone's "Chemistry Triangle" (1993, 2009). Finally, in Section 3, we conclude with some strategies for visualizing the micro level. To illustrate the back-and-forth thinking between phenomena, concepts, and visualizations we used the example of the reaction between a copper(II)nitrate solution and iron nail/ steel wool.