A

Absolute Entropy of a Substance

Quick Reference
Formula / Notation
Also Known AsStandard molar entropy; Third-law entropy; S° (standard entropy)

What is Absolute Entropy of a Substance?

The absolute entropy of a substance is the total entropy measured from absolute zero (0 K), where a perfect crystal has zero entropy according to the Third Law of Thermodynamics. It quantifies the degree of disorder or randomness in a system at a given temperature and pressure.

Formula & Notation

Other Names / Synonyms: Standard molar entropy; Third-law entropy; S° (standard entropy)

Properties & Characteristics

Always positive above 0 K; measured in J/(mol·K); increases with temperature; gases > liquids > solids; depends on molecular complexity and mass

Uses & Applications

Calculating Gibbs free energy (ΔG = ΔH − TΔS); predicting spontaneity of reactions; thermochemical and thermodynamic calculations; standard entropy tables for reference

Safety Information

No hazard — purely a thermodynamic concept. Standard values are tabulated in reference books.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Absolute Entropy of a Substance
Formula
Synonyms Standard molar entropy; Third-law entropy; S° (standard entropy)

Frequently Asked Questions

The absolute entropy of a substance is the total entropy measured from absolute zero (0 K), where a perfect crystal has zero entropy according to the Third Law of Thermodynamics. It quantifies the degree of disorder or randomness in a system at a given temperature and pressure.

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