1 INTRODUCTION A central aim but also a major challenge in science education is to foster understanding of scientific concepts, that is, supporting the construction of relational knowledge of the concepts in a domain (Goldwater & Schalk, 2016). Learning scientific concepts is typically supported using multiple external representations (MERs), such as manipulatives, figures, diagrams, graphs, and equations (e.g., Ainsworth, 2008; Corradi et al., 2012; Treagust et al., 2017), for several reasons.