Energy conservation in dissipative processes: Teacher expectations and strategies associated with imperceptible thermal energy

TL;DR

This study explores how teachers' expectations about perceivable thermal energy influence their understanding of energy conservation in dissipative processes, highlighting the use of exaggeration strategies to infer imperceptible thermal energy.

Contribution

It reveals that teachers rely on perceptible indicators of thermal energy and use exaggeration strategies to better understand energy conservation in dissipative scenarios.

Findings

Teachers expect visible warmth to indicate thermal energy presence.

Exaggeration strategies help teachers infer imperceptible thermal energy.

Perceptible indicators strongly influence energy conservation understanding.

Abstract

Research has demonstrated that many students and some teachers do not consistently apply the conservation of energy principle when analyzing mechanical scenarios. In observing elementary and secondary teachers engaged in learning activities that require tracking and conserving energy, we find that challenges to energy conservation often arise in dissipative scenarios in which kinetic energy transforms into thermal energy (e.g., a ball rolls to a stop). We find that teachers expect that when they can see the motion associated with kinetic energy, they should be able to perceive the warmth associated with thermal energy. Their expectations are violated when the warmth produced is imperceptible. In these cases, teachers reject the idea that the kinetic energy transforms to thermal energy. Our observations suggest that apparent difficulties with energy conservation may have their roots in a strong and productive association between forms of energy and their perceptible indicators. We see teachers resolve these challenges by relating the original scenario to an exaggerated version in which the dissipated thermal energy is associated with perceptible warmth. Using these exaggerations, teachers infer that thermal energy is present to a lesser degree in the original scenario. They use this exaggeration strategy to productively track and conserve energy in dissipative scenarios.