Chemistry · Ch 7 — Thermodynamics

Introduction

Every time a fuel burns to release heat, a circuit carries current, or a cell metabolises glucose for energy, an energy transformation is taking place -- and thermodynamics is the branch of chemistry that lets you analyse and predict these transformations quantitatively, without needing to know every microscopic detail of how they happen.

What this unit sets out to do. By the end of it you should be able to:

distinguish a thermodynamic system from its surroundings, and classify systems as open, closed or isolated;
distinguish state functions from path functions;
describe how internal energy, work and heat relate to one another;
state the four laws of thermodynamics;
correlate internal energy change ( $\Delta U$ ) and enthalpy change ( $\Delta H$ ), and how each is measured;
calculate enthalpy changes for different types of reactions, and apply Hess's law to find the lattice energy of a crystal;
define spontaneous and non-spontaneous processes;
relate the state functions enthalpy (H), entropy (S) and Gibbs free energy (G) to one another;
list the factors that determine whether a process is spontaneous;
link $\Delta G$ to spontaneity, and connect $\Delta G^{0}$ to the equilibrium constant.

Note

Albert Einstein once wrote that classical thermodynamics is "the only physical theory of universal content" he was convinced "will never be overthrown." That confidence comes from how the subject is built: its laws rest on careful bookkeeping of energy, not on assumptions about what matter is made of at the smallest scale -- which is exactly why they still hold even where later physics (like quantum mechanics) has revised almost everything else.

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