Fundamental thermodynamic relation and chemical potential
For a simple compressible equilibrium system, U(S,V,{N_i}) has differential dU=T dS−p dV+Σ_i μ_i dN_i.
Key knowledge
For a simple compressible equilibrium system, U(S,V,{N_i}) has differential dU=T dS−p dV+Σ_i μ_i dN_i. Temperature, pressure and chemical potentials are the corresponding partial derivatives of U; particle-number changes are distinct from heat transfer.
Values and equations
dU=T dS−p dV+Σ_i μ_i dN_i; μ_i=(∂U/∂N_i)_(S,V,N_j≠i)
- U,μ_i
- Internal energy and energy per particle J
- T
- Thermodynamic temperature K
- S
- Entropy J K⁻¹
- p
- Pressure Pa
- V
- Volume m³
- N_i
- Particle count of species i
Conditions and scope
- Equilibrium state functions, specified species and no additional electrical, magnetic, surface or elastic work coordinates.
- N_i counts particles; using amount n_i in mol instead gives molar chemical potentials in J mol⁻¹. This state differential is not a reversible-path requirement on every actual process.
Sources · 2
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Thermodynamics and Statistical Mechanics (2016): Internal energy: Equations 6.82–6.86 for fixed composition. Statistical Thermodynamics: CHEM_ENG 404 review: Printed pages 13–14, section 2.10: composition term and chemical-potential derivatives; unrelated glossary and process claims excluded.
2026-10-10 · Independent AI editorial review: All 136 unique authored Physics compact statements, all hypotheses and displayed equations/variable/units tables, all 192 Physics-origin semantic links, exact 165 author inspection matrix and mapped retained conceptual claims have been independently read. Three Physics-tagged Measurement realization records are delegated to root Measurement review. Scientific source verification combines exact author section inspection with independent whole compact-content/semantic review and targeted primary rechecks recorded below; it does not claim each full source body was independently reread. Independent AI editorial review is not human specialist certification or experimental replication. Field inventory is approved after independently reviewing the two added source-inspected band-construction methods. Receipt: physics-independent-content-inventory-review.1.
Entry details
Permanent link to this entry ↗- Record identity
- physics-thermodynamic-fundamental-relation
- Revision
- university-core.1
- Structured reference record
- University core expansion