Chapter 4: Enthalpy, Entropy and Gibbs Free Energy

A-level ChemistryModule 5: Physical Chemistry & Transition Elements9 topicsHigher

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Releases 1 August 2026

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Module 5: Physical Chemistry and Transition Elements: Enthalpy, Entropy and Gibbs Free Energy - Authored Long Answer Questions

Examiner-style long-answer practice with automatic marking, improvement advice and ProofCoach tracking.

4 questions25 marks37.5 min

standard / hard

6 marksdescribestandardOCR A

For Enthalpy, Entropy and Gibbs Free Energy, describe how entropy, Gibbs free energy and feasibility applies to thermal decomposition feasibility.

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6 markscalculatehardOCR A

Using thermal decomposition feasibility, calculate a relevant OCR A Enthalpy, Entropy and Gibbs Free Energy quantity and explain the physical or chemical meaning of the answer. Show equation, substitution, answer and unit.

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7 marksexplainhardOCR A

Enthalpy, Entropy and Gibbs Free Energy: Temperature (K) vs Gibbs free energy change (kJ mol-1)

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The graph for Enthalpy, Entropy and Gibbs Free Energy shows data from thermal decomposition feasibility. Explain the pattern using the data and relevant chemistry principles.

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6 marksevaluatestandardOCR A

In thermal decomposition feasibility, evaluate the experimental method or model assumptions used when applying entropy, Gibbs free energy and feasibility.

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Key learning objectives

Understand the key principles behind Enthalpy, Entropy and Gibbs Free Energy.
Apply these ideas to exam-style questions.
Recall the essential definitions and key terms.