Development of a learning progression for the particle model of matter

Prior research indicates that one of the most difficult concepts for students to understand is that of the particle nature of matter. The How can I smell things from a distance? chemistry unit takes the approach of building students' ideas through the construction and revision of models. The purpose of this study is to describe the changes in students' understanding of the particle nature of matter as they were engaged in an eight-week model-based curriculum. One teacher and her two 6th-grade classes in a midwestern school district were the focus of the study. Data sources include pre- and posttests, students' artifacts, and video recordings of the curriculum enactment, including students' creation of models of various phenomena. Results from this study were used to help develop a learning progression for the particle nature of matter.