The following case study involves a classroom of seventh graders struggling to understand a set of new and difficult concepts. It focuses on a specific domain of scientific knowledge—the nature and properties of matter, including gases. At least some of this material will be unfamiliar to most educators—in fact, most adults struggle with the properties of gases and air pressure. Focusing on a specific example of teaching that incorporates all four strands demonstrates the power of using the strands together to engage kids in actively doing science. It also makes it possible to dig deeper into some of the new perspectives on conceptual understanding and scientific proficiency that offer so much potential for science education.
Michelle Faulkner, a seventh-grade science teacher, was beginning a unit on air, called “Molecules in Motion,” as an introduction to the atomic-molecular theory of matter.
THE ATOMIC-MOLECULAR THEORY OF MATTER
The atomic-molecular theory is a well-established body of scientific thought that helps make clear the properties of substances, what things are made of, and how things change (and do not change) under varied environmental conditions, such as heat and pressure. The atomic-molecular theory accounts for visible as well as invisible (microscopic) aspects of substances.
Ms. Faulkner had two reasons for starting with air pressure demonstrations at the outset of this unit. The first was that the textbook she used in class introduced the atomic-molecular theory with dramatic air pressure demonstrations. Her second reason was that she knew these demonstrations would produce surprising and unexpected outcomes that would elicit students’ thinking about experiences they’ve had with air pressure. The students were likely to think they knew what was happening in the demonstrations, because they would be observing and working with everyday objects and situations familiar from their own lives. This familiarity and assumed knowledge would elicit a number of predictions and theories from them. Ms. Faulkner knew, however, that her students would quickly discover that their usual explanations or assumptions did not, in fact, work well to explain what was going on. This, in turn, would encourage them to be more open to exploring new tools and models and to developing new explanations.
The air pressure demonstrations were dramatic because, although air is invisible, air pressure pushes in every direction with 14.7 pounds per square inch at sea level—a huge amount of force. Once students began to discover how air pressure works, Ms. Faulkner hoped they would be motivated to greater exploration and mastery of other related scientific phenomena, such as the nature of molecular motion and the effects of heat.
Ms. Faulkner’s seventh graders loved to see chemical reactions, and the grander the better. The problem with many of the demonstrations in their science textbook was that they never really understood the concepts behind the outcomes they produced. They predicted what would happen, invariably found the results surprising and interesting, but due to time constraints were forced to move