This bundle of 3 PowerPoints covers IBDP Chemistry HL R1.4 Entropy and Spontaneity for first examination 2025, including entropy changes, Gibbs energy, spontaneity and the link between Gibbs energy and equilibrium. It provides a clear, carefully sequenced set of lessons that helps students move from core thermodynamic ideas to the higher-level calculations and interpretations required for IB exam success.

Entropy and spontaneity are central ideas in thermodynamics. Entropy is a measure of disorder and energy dispersal in a system, and students need to understand how physical and chemical changes can increase or decrease entropy. This bundle helps students predict entropy changes, calculate standard entropy change, ΔS°, and then build on this understanding using Gibbs energy, ΔG, to decide whether reactions are spontaneous under given conditions. It also develops the important idea that spontaneity depends on the balance between enthalpy, entropy and temperature, not just whether a reaction is exothermic.

The bundle includes 3 editable PowerPoint (.pptx) lessons:
Lesson 1: Entropy – predicting entropy changes in physical and chemical processes and calculating ΔS° from standard entropy values.
Lesson 2: HL Gibbs Energy and Spontaneous Changes – applying ΔG° = ΔH° − TΔS°, interpreting the sign of ΔG, and determining the temperature at which a reaction becomes spontaneous.
Lesson 3: HL Gibbs Energy and Equilibrium – using ΔG = ΔG° + RT lnQ and ΔG° = −RT lnK to link thermodynamics with equilibrium and reaction direction.

Across the bundle, students are supported with retrieval starters, clear keyword definitions, step-by-step explanations, worked calculations, conceptual examples and practice questions with answers. This makes the resource ideal for first teaching, revision, or building a complete HL thermodynamics sequence for IB Chemistry.

File types included: editable PowerPoint (.pptx) files.
Last updated: 2026 – improved sequencing, clearer Gibbs energy calculations, and enhanced practice tasks aligned to the IB Chemistry specification for first examination 2025.