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Entropy Calculator and Specific Entropy Calculator

What is Entropy?

Entropy is a property that follows from the Second Law of Thermodynamics – the entropy of a system increases during a natural thermodynamic process. Entropy is related to the number of microscopic configurations of a thermal system. The second law of thermodynamics states that the specific entropy of a system cannot decrease unless it is to increase another system. 

Entropy is defined as the natural logarithm of the number of microscopic systems and the Boltzmann constant:

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Where:

S = Entropy
kB = Boltzman Constant
Ω = Configurations

Change In Entropy

The change in Entropy of a system can also be defined as the change in heat over temperature:

Where:

𝛿s = change in entropy (kJ/K)
𝛿Q = change in energy (kJ)
T = Absolute temperature of the system (K)

Change in Entropy Calculator

Change in Energy (kJ)
Absolute Temperature (K)

Change in Entropy (kJ/K)


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Specific Entropy

Specific entropy is a measure of entropy per unit mass, and is defined by:

Where:

​S = Specific Entropy (kJ/kgK)
m = Mass (kg)
s = Entropy (kJ/K)

Specific Entropy Calculator

Mass (kg)
Entropy (kJ/K)

Specific Entropy (kJ/kg K)



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Specific Values of Entropy

The below table has a selection of values of Entropy at 25°C (298K):

Description of Material	Entropy Value at 298K ​S° (J/(mol.K)	Reference
Oxygen O(2)	205	IST
Carbon Dioxide (CO2)	213.8	UWSP
Nitrogen (N2)	191.6	UWSP
Water (H2O) (Gas)	70	TES
Water (H2O) (Liquid)	189	TES
Quartz (SiO2)	41.5	Lumen
Potassium (K)	64.7	opentext
Hydrogen (H2)	130	UWSP