Exposing Students to the Idea that Theories Can Change

Abstract

The scientific method is arguably the most reliable way to understand the physical world, yet this aspect of science is rarely addressed in introductory science courses. Students typically learn about the theory in its final, refined form, and seldom experience the experiment-to-theory cycle that goes into producing the theory. One exception to this is the Powerful Ideas in Physical Science curriculum (PIPS) developed by the American Association of Physics Teachers.1 In this curriculum students develop theories based on experiments. The “Heat and Conservation of Energy” unit illustrates the experiment-to-theory cycle in a set of experiments introducing the conservation of energy. The idea of conservation of energy is developed early in the unit; however, students must expand their idea of energy in order to incorporate new phenomenon, namely the specific heat and phase transitions. Yet even with these experiments, the ideas of energy and of a theory remain abstract. In order to address the abstractness of energy, many authors have introduced energy diagrams.2–5 In these energy diagrams, the height of a bar graph represents the amount of different types of energy, nicely illustrating how energy transfers from one form to another. The PIPS curriculum took this one step further and used area to represent thermal energy when mixing different amounts of water. Thus, the conservation of area illustrates the idea of conservation of energy. Using this as a starting point, we have extended the energy/area diagram so that it includes other aspects of thermal energy, making the idea of a theory more concrete. Every new experiment requires a change in the theory and hence a change in the corresponding energy diagram. In this paper we develop this enhanced energy diagram through a series of experiments taken from the PIPS curriculum. While PIPS is designed for nonscience majors, this sequence of events as a lab or as demonstrations would work for any introductory course. The sequence involves four experiments. We will describe each of the experiments the students perform and the typical results. Then we describe the theory building that subsequently adapts the energy diagram to explain new data. This will demonstrate how the theory building takes place and how the energy diagram is developed based on experimental results.