Now that we have applied all of our tools to analyze gasses, we want to finish by looking at a more pragmatic application, heat engines. The basic heat engine converts heat into work.

We will start by defining heat and work. We will revisit the thermodynamic identity with our new vocabulary. We will show how the fundamental differences between heat and work give rise to inefficiency in engines and the Carnot inequality. We will look closely at the basic heat engine, keeping track of heat, energy, and entropy in the process.

We will turn to more commonly-used appliances and relate them to the heat engine, namely refrigerators, air conditioners, and heat pumps.

We will examine a simplified model of most real engines, known as the Carnot cycle, and investigate it graphically. Finally, we will look at isothermal and isobaric processes.