Why Does It Go Up? The Impact of the MARS Curriculum as Revealed through Changes in Student Explanations of a Helium Balloon

The Model-Assisted Reasoning in Science (MARS) project created a model-centered, computer-supported sixth-grade science curriculum organized around the theme balance of forces. To help monitor effectiveness during implementation in a public middle school, individual student interviews were conducted after each of the curriculum's three sections. In each interview, students were asked to explain why a helium balloon floats up. This article describes an analysis of student responses to the balloon question and what it reveals about the impact of the curriculum. The article begins with an overview of research on children's ideas about floating and sinking. Following a description of MARS instruction, procedures used to analyze responses to the balloon question are described, and results of the analysis are presented and discussed. The article concludes by examining implications for science education. J Res Sci Teach 35: 547–567, 1998.