Energy Tracking Diagrams

Abstract

Energy is a crosscutting concept in science and features prominently in national science education documents. In the Next Generation Science Standards, the primary conceptual learning goal is for learners to conserve energy as they track the transfers and transformations of energy within, into, or out of the system of interest in complex physical processes. As part of tracking energy transfers among objects, learners should (i) distinguish energy from matter, including recognizing that energy flow does not uniformly align with the movement of matter, and should (ii) identify specific mechanisms by which energy is transferred among objects, such as mechanical work and thermal conduction. As part of tracking energy transformations within objects, learners should (iii) associate specific forms with specific models and indicators (e.g., kinetic energy with speed and/or coordinated motion of molecules, thermal energy with random molecular motion and/or temperature) and (iv) identify specific mechanisms by which energy is converted from one form to another, such as incandescence and metabolism. Eventually, we may hope for learners to be able to optimize systems to maximize some energy transfers and transformations and minimize others, subject to constraints based in both imputed mechanism (e.g., objects must have motion energy in order for gravitational energy to change) and the second law of thermodynamics (e.g., heating is irreversible). We hypothesize that a subsequent goal of energy learning—innovating to meet socially relevant needs—depends crucially on the extent to which these goals have been met.

University student conceptual resources for understanding energy

“…This practice might be promoted by using energy tracking representations such as those described in the literature [120,129,134,135], or simply by asking students to describe energy transfers and transformations as we did in our free body diagram and story questions. …”

“…Literature on students' (and teachers') ideas about energy implies several ways in which instructors might build on this conceptual resource. For example, representations for tracking energy through a system [120,129,134,135] may encourage students to draw on this resource in order to determine when and where energy transfers and transformations occur. Energy bar graphs [90,114] enforce the identification of forms of energy at particular instants; pairing such representations with requests for evidence for the presence of each form of energy may also encourage students to associate forms with indicators.…”

“…Instructors may also elicit these ideas by asking students to make explicit connections between force and energy representations, or by introducing representations that enforce the identification of mechanisms for energy transfers and transformations, such as Energy Tracking Representations [120,134,135].…”

Identifying content knowledge for teaching energy: Examples from high school physics

“…Her students are using a representation called Energy Theater [31][32][33], in which units of energy are represented by people, and objects in the scenario (such as the box, or the hand of the person doing the pushing) are represented by areas on the classroom floor. Forms of energy are indicated by hand signs or body movements; for example, these students indicate motion energy by pumping bent arms as in jogging.…”

Drawing energy: Evidence of Next Generation Science Standards for energy in diagrams

“…We use this rubric to assess the alignment of four different energy diagrams with the NGSS: an energy bar chart, an energy flow diagram, an Energy Tracking Diagram [2], and a learner-invented diagram. Finally, we demonstrate how this rubric allows us to document a class's increased facility with NGSS-aligned energy representations.…”