The First Law in Detail

Abstract

The three terms of the First Law of Thermodynamics, (3.50), relate a system’s internal energy increase to its thermal, mechanical, and diffusive changes. Historically, the study of thermal and mechanical changes enabled heat processes to be harnessed into engines, from the age of steam through to modern automobiles and jet propulsion. Studies of the law’s third term, diffusion, brought chemists an understanding of how to quantify the rates and directions of chemical reactions. In this chapter, we’ll study some important aspects of each of these terms that comprise the First Law.

In which we derive some standard results related to heat, work, and chemical reactions. We follow the mathematics of heat flow, and show what it has in common with diffusion and radar signal processing. We enquire why air escaping a tyre grows cold. We then explore density and pressure in the atmosphere and ocean, determine some melting and boiling points, and examine chemical equilibrium.