In the “Molecules in Motion” unit, students began with many ideas about air based on their personal experience. For example, some students began the unit thinking that air was nothing, except when you could feel it as wind. For most of the students, the investigations with air pressure entailed building on their preexisting concepts of air and elaborating on them—the first type of conceptual change described earlier in this chapter.
After eliciting ideas from the students for the “What We THINK We Know About Air” chart, Ms. Faulkner introduced some new facts about air molecules. The students grappled with these facts as they attempted to understand and explain why water stayed in a glass as it was pulled, upside down, out of an aquarium full of water. After the first group discussion and demonstration, all of the students were certain that air was something—something that took up space in an “empty” glass. “Something” is a concept that the students entered with and that they elaborated on to include air once they were persuaded that air qualified as something. This was an important development for their continued learning and understanding of matter. Helping students elaborate the concept that air is something took only a modest instructional intervention.
At this point, the students were beginning to rethink and restructure the network of existing concepts about air, molecules, forces, and pressure—the second type of conceptual change we discussed above. Many questions, conjectures, and divergent ideas were made public. Over several days of investigation and discussion, students learned to embrace and apply the notion that air pressure pushed the water up into the glass, and that asymmetrical levels of air pressure within a system would predictably result in such movement. This entailed developments in their thinking about air, the way it pushes in all directions, and the magnitude of force with which it pushes.
Ultimately, the students would go on to build new levels of explanation, the third type of conceptual change, either in Ms. Faulkner’s class or in subsequent grades. That is, they will come to understand atomic-molecular theory and use it to explain phenomena like air pressure. The students will also learn to understand increasingly more complex material explanations. Once they master macroscopic explanations, they will go deeper into atomic-molecular theory and develop an explanation of phase change and motion at the molecular level. They will learn that molecular theory is a basic and broadly applied idea that can help them