For example, HS-PS1-4 (high school, physical sciences core
idea 1, performance expectation 4) is: “Develop a model to
illustrate that the release or absorption of energy from a chemical
reaction system depends upon the changes in total bond energy.”5
This standard is cross-referenced to the science practice of
constructing models, the crosscutting concepts of matter and
energy, and the disciplinary core idea “Stable forms of matter
are those in which the electric and magnetic field energy is
minimized”.5 The performance expectation is designed to help
teachers, curriculum developers, and assessment developers
address the highly problematic area of “chemical energy”a
concept that is well documented as an area of major conceptual
difficulty for many students. The clarification statement reads in
part:5