Concerns persist regarding science classroom learning environments and the lack of development of students' metacognition and reasoning processes within such environments. Means of shaping learning environments so that students are encouraged to develop their metacognition are required in order to enhance students' reasoning and learning. Interventions should account for the nature of the subject material to be learned. This study employed a mixed-methods approach to investigate the efforts of university researchers and a classroom teacher to change the learning environment of a year 11 chemistry classroom. Changes in participants' perceptions of their learning environment and corresponding changes in their metacognition and associated reasoning are documented. The teacher's use of language that explicitly targeted students' metacognitive knowledge altered their metacognition. Students reported changes in their learning environment and an increased awareness of how they considered chemistry might be learned. Classroom environment instruments can act as reliable indicators for monitoring changes in psychosocial dimensions of classroom environments that can be directly related to students' metacognition.