Why does it go up? The impact of the MARS curriculum as revealed through changes in student explanations of a helium balloon

Abstract

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.Suppose you have two identical balloons, both inflated and tied. One is filled with helium. The other contains an equal amount of air. If you hold them at the same height and release them at the same time, what will happen? Why?The value of the balloon question is that, although it is easy to grasp and involves a familiar, real-world phenomenon, it can be used to elicit understanding of a variety of concepts including volume, mass, density, weight, gravitational force, buoyancy, balance of forces, and floating and sinking. Moreover, pertinent follow-up questions can get at students' ideas about relationships between concepts. Students who say the helium balloon rises because it is lighter than the air balloon can be asked, "How can one balloon be lighter if they are both the same size?" or "Why does being lighter make the balloon go up?" An item such as the balloon question can be asked before, during, and after a course of study to trace the development of student conceptions throughout instruction.The balloon question is one of the assessment tools used to monitor the effectiveness of a sixth-grade science curriculum created by the Model-Assisted Reasoning in Science (MARS) project. MARS designs and investigates instruction in which students use interactive computer JOURNAL

Models and Modelling: Routes to More Authentic Science Education

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