“…Equally important, students need to master certain abilities and skills such as visualizing a chemical reaction at the molecular level, reasoning about a macroscopic phenomenon using chemical representations, and coordinating multiple representations (Ben-Zvi, Eylon, & Silberstein, 1987;Gabel & Samuel, 1987;Hesse & Anderson, 1992;Kozma, 2000Kozma, , 2003Krajcik, 1991;Yarroch, 1985). Finally, students need to develop a coherent conceptual framework that integrates their knowledge and skills to establish a scientiÞc theory of the entities and processes that underlie a given observed phenomenon (Kozma, Russell, Jones, Marx, & Davis, 1996;Russell et al, 1997). For example, although Nakhleh et al (2005) found that more than half of the nine middle school students they interviewed had some understanding of the particulate nature of matter, their conceptual framework was rather fragmented.…”