Entropy Calculator
Evaluate the entropy change for a reversible step using the classical relation DeltaS = qrev divided by temperature.
Use negative values for heat leaving the system.
Absolute temperature is required for thermodynamic consistency.
Leave blank if you only need total entropy change.
Entropy change
4.195 J/K
Entropy increases (system becomes more disordered).
How to Use This Calculator
Specify heat transfer
Enter the reversible heat exchanged by the system. Use a negative value if the system releases heat.
Enter absolute temperature
Provide the Kelvin temperature at which the reversible step occurs.
Optionally supply moles
Include the amount of substance to report entropy change per mole.
Interpret the result
Positive entropy change indicates more disorder; negative indicates increased order.
Formula
DeltaS = qrev / T
For per mole values, divide DeltaS by the number of moles present. This formula assumes a reversible process at uniform temperature.
Example
If 1250 J of heat enters a system at 298 K, DeltaS equals 1250 / 298 = 4.19 J/K.
Full Description
Entropy quantifies energy dispersal at a specific temperature. For reversible, isothermal steps, the change is directly proportional to heat transfer.
Engineers and chemists use DeltaS to evaluate spontaneity, assess process reversibility, and balance thermodynamic cycles alongside enthalpy calculations.
Frequently Asked Questions
What sign convention is used?
Positive heat means energy enters the system. Negative heat indicates the system releases energy.
Can I use Celsius or Fahrenheit?
No. Convert temperatures to Kelvin before calculating entropy changes.
Does this handle irreversible processes?
Irreversible steps have larger entropy changes. Use this calculator on the corresponding reversible path to estimate DeltaS.
Why allow negative entropy results?
Processes that release heat or compress gases can decrease system entropy, even though total universe entropy still increases.
How accurate is this method?
It is exact for reversible isothermal steps. For temperature changes, integrate qrev over T or use heat capacity data.