Thermodynamics
Entropy Change
Entropy change for reversible isothermal process.
Variables
ΔSJ/K
Entropy change
Change in entropy
In SI units: kg·m²/(s²·K)
QrevJ
Reversible heat
Heat in reversible process
In SI units: kg·m²/s²
TK
Temperature
Absolute temperature
Allowed values: greater than 0
Derivation
dS = δQ_rev/T. For isothermal: ΔS = Q/T.
Your notes
0/5000
Check value
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- Qrev = 2 J (Reversible heat)
- T = 3 K (Temperature)
Result: ΔS = 0.66666667 J/K
Other thermodynamics formulas with the same quantities
- Clausius Inequality (Second Law) shares Entropy change, Temperature
- Stefan-Boltzmann Law (Heat & Temperature) shares Temperature
- Work (Isothermal Process) (First Law) shares Temperature
- Internal Energy (Ideal Gas) (First Law) shares Temperature
- Ideal Gas Law (Kinetic Theory) shares Temperature
- Ideal Gas Law (Molecular) (Kinetic Theory) shares Temperature
Where this formula is listed
- Thermodynamics formulas, under Second Law, alongside Heat Engine Efficiency, Coefficient of Performance (Refrigerator) and Coefficient of Performance (Heat Pump).
- In the thermodynamics list it comes after Enthalpy and before Carnot Efficiency.
- Thermodynamics formula sheet, one of 34 formulas printed with symbol keys and SI units.
- The full formula index, grouped by category and topic.
Common questions
What is the Entropy Change formula?
Entropy Change is written ΔS = Q_rev/T. Entropy change for reversible isothermal process. It belongs to Thermodynamics, under Second Law.
What are the units in ΔS = Q_rev/T?
In SI units, ΔS is entropy change, measured in kg·m²/(s²·K); Q_r ev is reversible heat, measured in kg·m²/s²; T is temperature, measured in K.
How is the Entropy Change formula derived?
dS = δQ_rev/T. For isothermal: ΔS = Q/T. The result is ΔS = Q_rev/T.