“…Krajcik et al, ). In terms of the idea that understanding corresponds to an increasingly complex knowledge structure (Bernholt & Parchmann, ; Geller, Neumann, Boone, & Fischer, ; Neumann et al, ; see also Bransford, Brown, & Cocking, ), these findings might be interpreted as while students develop knowledge about each of the four ideas individually, there is a particular overlap in the knowledge elements and connections between them. That is, in order to understand aspects of chemical reactions (e.g., covalent bonding), some knowledge about the structure and composition of matter is needed (e.g., the structure of atoms and behavior of electrons) whereas no immediate knowledge is needed about physical properties and change (e.g., phase state changes).…”