What's the difference between entropy and specific entropy?

Entropy (S) has units J/K—it's an extensive property depending on amount of substance. Specific entropy (s) is entropy per unit mass (J/kg·K)—an intensive property independent of amount. s = S/m. Molar entropy (J/mol·K) is entropy per mole.

Why does specific entropy increase during boiling?

Boiling dramatically increases molecular disorder—gas molecules are far more randomly distributed than liquid molecules. The entropy of vaporization for water is about 6.1 kJ/kg·K at 100°C. This large entropy change is why boiling requires so much heat (latent heat).

How is specific entropy used in power plant analysis?

Steam tables list specific entropy at various temperatures and pressures. Isentropic (constant entropy) processes represent ideal expansion/compression. Comparing actual vs isentropic specific entropy shows process efficiency. T-s diagrams visualize the cycle and calculate heat transfer.

Entropie spécifique Converter

About Specific Entropy Conversion

Specific entropy is entropy per unit mass—an intensive property that allows comparison of thermodynamic states independent of the amount of substance present. While total entropy (J/K) depends on system size, specific entropy (J/kg·K) characterizes the material's state itself. This makes it essential for analyzing working fluid cycles in power plants, refrigeration systems, HVAC equipment, and chemical processes where fluid properties matter more than total quantities.

The SI unit is joules per kilogram kelvin (J/kg·K). Specific entropy is a fundamental property listed in steam tables, refrigerant property charts, and thermodynamic databases alongside temperature, pressure, enthalpy, and density. The T-s (temperature vs specific entropy) diagram is perhaps the most powerful visualization in thermodynamics—area under curves represents heat transfer, and the cycle shape immediately reveals efficiency and irreversibility. Isentropic (constant specific entropy) processes represent ideal, reversible compression or expansion.

Our converter handles all standard specific entropy units used in thermodynamic analysis, power engineering, and refrigeration system design.

Common Specific Entropy Conversions

From	To	Multiply By
J/kg·K	kJ/kg·K	0.001
kJ/kg·K	J/kg·K	1,000
J/kg·K	BTU/lb·°R	0.000239
BTU/lb·°R	J/kg·K	4,187
kJ/kg·K	kcal/kg·°C	0.239
kcal/kg·°C	kJ/kg·K	4.184
J/kg·K	cal/g·K	0.000239
cal/g·K	J/kg·K	4,184
kJ/kg·K	BTU/lb·°R	0.239
BTU/lb·°R	kJ/kg·K	4.187

Specific Entropy Unit Reference

Joule per kilogram kelvin (J/kg·K) – The SI unit for specific entropy. Has the same dimensions as specific heat capacity (J/kg·K) but represents a fundamentally different property—disorder per unit mass per degree rather than heat capacity. Values range from near-zero for low-temperature solids to thousands of J/kg·K for high-temperature gases. Used in scientific thermodynamics and international engineering standards.

Kilojoule per kilogram kelvin (kJ/kg·K) – The practical unit for engineering thermodynamics, giving convenient single-digit values for common substances. Steam tables universally list specific entropy in kJ/kg·K: water at 25°C is about 0.37 kJ/kg·K; saturated steam at 100°C is about 7.35 kJ/kg·K. The large entropy increase during vaporization reflects the dramatic increase in molecular disorder.

BTU per pound degree Rankine (BTU/lb·°R) – US engineering unit for specific entropy, standard in American steam tables, HVAC calculations, and power plant engineering. 1 BTU/lb·°R = 4.187 kJ/kg·K. US-origin equipment, software, and engineering handbooks commonly use this unit. Rankine maintains consistency with Fahrenheit-based temperature measurements.

Calorie per gram kelvin (cal/g·K) – Older unit with the same dimensions as specific heat capacity. 1 cal/g·K = 4.184 kJ/kg·K exactly. Found in older thermodynamic tables, chemistry literature, and some food science applications. Numerically identical to kcal/kg·K.