# 1: Applying Models to Thermal Phenomena


In this chapter we introduce the Energy-Interaction Model, which is the primary focus of this course. We will apply this model together with the Three-Phase Model of Pure Substances in order to understand various physical phenomena. We will analyze pure substances going through temperature and phase changes and chemical reactions.

• 1.1: Where are we Headed?
The Energy-Interaction Model tells us what is energy, how is it conserved, and how is it transferred. We will see that by applying the Energy-Interaction Model to seemingly very strange thermal phenomena, we can make sense of them, we can explain what is going on, and we can answer all kinds of questions about the phenomena. In this Chapter we will apply Energy-Interaction Model to substances going through temperature changes or phase changes and to several chemical reactions.
• 1.2: Three-Phase Model of Pure Substances
We start our analysis of energy by studying what role it plays in the three-phases of matter: solids, liquids, and gases.  We will first provide a brief overview of the three phases of matter and explain which properties of a substance change when energy is either added or removed from the substance.  Specifically, we will graphically depict how the temperature of a substance changes as energy is being added or removed from the substance.
• 1.3: Energy-Interaction Model
The scientific meaning of energy is rather tricky to convey in a sentence or two. There is a good reason for this: energy is an abstract concept that took scientists a long time to figure out. Although the concept of energy is truly universal in the sense that energy changes are associated with nearly all phenomena and processes, energy is not related to a single property of matter.
• 1.4: Working With the Energy-Interaction Model
Some examples are presented using the Energy-Interaction Model and the Three-Phase Model of Pure Substances to explain behavior of pure substance and chemical reactions.  A tool, called Energy-Interaction Diagrams, is used as a helpful guide of applying these models.
• 1.5: Units, Data Tables, and Equations
This section is a good reference for useful units in this course, a table of melting and boiling temperatures, heats of melting and vaporization, and specific heats for numerous substances, and a list of equations for different types of energies.