6 x 1 hour lessons

This module extends your understanding of energetics into the field of thermodynamics. You'll explore how ionic compounds form and why their lattice enthalpies differ, then learn to construct and use Born–Haber cycles to calculate enthalpy changes. You'll also cover enthalpy of solution and hydration, and how to calculate overall energy changes in dissolving processes using Hess cycles.

The second half of the module introduces entropy — a measure of disorder — and explains how entropy change and enthalpy change combine in the Gibbs free energy equation to predict the feasibility of reactions. You'll learn how to calculate ΔG and interpret the effect of temperature on reaction spontaneity.

By the end of this module, you’ll be able to:

• Define lattice enthalpy and explain factors affecting its magnitude

• Construct and interpret Born–Haber cycles

• Calculate enthalpy of solution using hydration and lattice enthalpies

• Define and calculate entropy change (ΔS)

• Use the Gibbs free energy equation ΔG = ΔH – TΔS to determine feasibility

• Understand the effect of temperature on ΔG and reaction feasibility

OCR (A) specification points covered: 5.2.1 Lattice enthalpy 5.2.2 Enthalpy and entropy