Abstract
High school chemistry should be accessible to all students in a manner that builds understanding and appreciation for chemistry while explaining observed phenomena, making predictions and solving problems. This research project has culminated in the development of a year-long high school chemistry course that implements model-based reasoning to build a progressively complex and coherent conceptual understanding of chemistry. The MBR course engages students with a constructivist approach to learn chemistry in a manner that resembles the iterative nature of scientific progression. Learning is centered on observed phenomena that drive the construction of models to develop explanations. The concepts are spiraled during the year to continue developing, applying, refining and extending models to construct a deeper understanding. Connections are explicitly made to build coherent interconnected understanding.