Using AACT Resources to Teach Thermodynamics

Concepts related to thermodynamics, including enthalpy and entropy are outlined in the AP Chemistry Curriculum Framework in Big Idea 5, shown below.

Many teachers find topics related to the role of energy in chemistry difficult to teach. The Energy Foundations for High School Chemistry resources from ACS can help you teach the big ideas about energy to your students.

The AP framework states that students must have an understanding of Hess’s law. This includes knowing that the sign of enthalpy is reversed when a reaction is reversed and that summing the enthalpy for a series of reactions will be the enthalpy for the net reaction. This standard is covered by Learning Objective 5.8: The student is able to draw qualitative and quantitative connections between the reaction enthalpy and the energies involved in the breaking and formation of chemical bonds.

The following AACT resources can help your student meet this standard:

• In the Hess’s Law lesson plan students learn about the concepts of the law and how to solve problems involving them. It includes a teacher’s guide, a PowerPoint for the lesson, student activity sheet, and answer key.
• The December 2003 ChemMatters article “Hydrothermal Vents and Giant Tubeworms” can provide students who are already familiar with this concept, with “real life” problems involving Hess’s law. Refer to the Connection to Chemistry Concepts section of the teacher’s guide for sample calculations.

The framework also requires that students have an understanding of the concept of entropy and must be able to make predictions about changes to it. This standard is covered by Learning Objective 5.12: The student is able to use representations and models to predict the sign and relative magnitude of the entropy change associated with chemical or physical processes.

The following AACT resources can help your student meet this standard:

• The Entropy activity helps students define entropy and recognize entropy changes in chemical processes. PowerPoint slides are included with this activity.
• Students must understand entropy differences and reason with ΔG= ΔH–TΔS for the AP Chemistry exam. However, even students in “physics first” programs do not have the physics required to grasp the entropy concept well. In the Connecting States to Entropy activity, students model different states of matter and Kinetic Molecular Theory to understand the concept of entropy.
• The ChemMatters article “Hot & Cold Packs” includes a sidebar discussion of how entropy and enthalpy are related in portable hot and cold packs.