Students’ Representations of Chemical Reactions: Does the Type of Chemical Equations Matter?

Abstract

Different forms of chemical representations facilitate reasoning of different aspects of chemical phenomena. This study investigated students’ submicroscopic representations of a reaction (Mg + HCl as a case in point) when they were given different forms of equations in different order. Nine Grade 12 students were selected from a school in Hong Kong based on their previous chemistry examination results. Three students were selected each from the top 10th, 45th-55th, and the bottom 10th percentile of their cohort respectively. During the semi-structured interviews, each student was asked to draw to represent and explain the reaction based on the given full equation, net ionic equation and full ionic equation, but in different order. The drawings and oral responses were analyzed based on the two models of reactions proposed in Cheng and Gilbert (2017). Students in general make a few or no changes to their drawings when different equations were provided. Yet some of the changes were remarkable. It was found that some students, when provided with a full equation, represented the reaction as spatial rearrangement (particle model of reactions) switched to an inclusion of ‘electron transfer’ (atomic model of reactions) after they were provided with ionic equations. It may mean that ionic equations but not the full equation facilitated these students in representing a more sophisticated model. If ionic equations better support the learning of changes at the submicroscopic, it would challenge the common teaching sequence of different types of equations (i.e., from full equations to ionic equations).