Discusses students' understanding of the qualitative conservation of matter and how this understanding is influenced by previous instruction in chemistry and task variables. Results show the influence of group membership, task content, and problem context on students' performance. (ZWH)

Using the US national sample from the Third International Mathematics and Science Study (TIMSS) and the Rasch modeling method, this study identified the conceptual progression sequence of various matter concept aspects, and compared students' latent abilities against the sequence. We found that the four matter aspects, i.e. conservation, physical…