Transcript: Thermodynamics is the study of heat and the way it flows. In this field of physics a strong connection is made between large scale or macroscopic behavior and small scale or microscopic behavior. On the large scales we can study behavior of a perfect gas and the well known relationships between the temperature, density, and pressure of the gas when it undergoes changes. These laws extend simply to the behavior of stars. On the small scale the idea of temperature is related to the microscopic motion of atoms and molecules where temperature is simply a measure of the instantaneous velocity of subatomic particles.