This study examines the effectiveness of a new constructivist curriculum model (Powerful Ideas in Physical Science) in improving prospective teachers' understanding of science concepts, in fostering a learning environment supporting conceptual understanding, and in promoting positive attitudes toward learning and teaching science and chemistry in particular. A non-equivalent pretest-post-test control-group design was employed. Analysis of covariance and repeated-measures analyses of variance were performed to analyze the scores on concept tests and attitude surveys. Data from videotaped observations of laboratory sessions and interviews of prospective teachers were analyzed by employing a naturalistic inquiry method to provide insights into the process of science learning and teaching for the teacher trainees. The interpretations were made based on the findings that could be corroborated by both methodologies. Conclusions and limitations of the present study as well as recommendations for future implementation of constructivist science curriculum in general are also included.