Entropy, free energy, and chemical change
What students will learn
Combine matter and energy dispersal with enthalpy and composition to explain chemical favorability, equilibrium and physically connected energy coupling.
Before this topic
- Energy transfer, enthalpy and equation addition
- Chemical equilibrium and Q/K
- Kelvin temperature and consistent energy units
Read and connect
Read: Introduction to Entropy →
Explain entropy changes through accessible arrangements, phase, space and energy without relying on visual disorder.
Read: Absolute Entropy and Entropy Change →
Use absolute molar entropy values and phase-specific coefficient sums rather than formation-enthalpy zero rules.
Read: Gibbs Free Energy and Thermodynamic Favorability →
Combine enthalpy and entropy, compare temperature sign cases and distinguish standard references from actual composition.
Read: Thermodynamic and Kinetic Control →
Draw separate endpoint and barrier differences to explain a favorable but slow or kinetically trapped change.
Read: Free Energy and Equilibrium →
Connect standard free energy to K and distinguish it from zero actual driving force at Q = K.
Read: Free Energy of Dissolution →
Account for lattice, solvent and hydration contributions and the sensitivity of a small net dissolution result.
Read: Coupled Reactions →
Add a connected coupled pathway or identify the external energy source that drives an unfavorable process.
Supporting reading: Reaction Energy Profile →
Revisit activation barriers and reaction coordinates before comparing rate with favorability.
Supporting reading: Introduction to Solubility Equilibria →
Revisit saturated dissolution and free ions before interpreting standard dissolution free energy.
Supporting reading: Cell Potential and Free Energy →
Later electrochemical connection: relate energy per charge to free energy for a balanced redox reaction.
Before this connection: Redox and electrochemistry: balanced half-reactions and cell direction.
Further study: Laws of Thermodynamics →
Further study: the original single-section thermodynamics overview with accepted revisions, including formal state-function language beyond the main-path treatment.
Before this connection: Energy transfer and enthalpy; Entropy and standard free energy.
Check understanding
Use the complete prompt to make student reasoning visible, then consult the separate worked reasoning and criteria. A reading completion tick records reading history.
Explain temperature, reference states and the sign cases →
Calculate free-energy changes and boundaries with matching units; distinguish standard-state references, actual composition, stable phases and reaction speed.
Build a dissolution energy and entropy ledger →
Assign and sum lattice, solvent and hydration contributions, then test how uncertainty can reverse the small net free-energy prediction.
A hypothetical standard-state bookkeeping path is not a measured solubility or a claim about every salt.
Explain what physically couples two changes →
Cancel the shared intermediate, add free energies and identify the mechanism or external energy source; disconnected vessels do not establish coupling.
Standards and earlier reading lists
These topic placements organize reading. Edition-qualified Standards mappings and the existing complete unit task sets retain their reviewed scope.