The purpose of this study was to enhance the teaching and learning of matter and its properties for grade 6 students. The development of a conceptual change approach instructional unit was undertaken for this purpose. Pre- and post-concept surveys, classroom observations, and student and teacher interviews were used to collect data. The teaching activities not only challenged and encouraged students' conceptual change but also indicated that teachers needed to develop their content knowledge and teaching strategies. The participants developed more scientific conceptions and were able to apply these in appropriate contexts. This study illustrates how a conceptual change approach can be accomplished in the Thai context.