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Entropy Change Calculator

Work out entropy change instantly with clear inputs, formula shown and shareable results.

About Entropy Change Calculator

Because temperature changes during heating, entropy must be integrated: dS = mc ln(T2/T1). Warming 1 kg of water from 300 K to 350 K transfers 209 kJ and raises entropy by 644 J/K. The ratio of heat to entropy gives an effective mean temperature of 324.4 K, slightly below the arithmetic mean.

Formulas

Entropy change on heating

dS = m c ln(T2 / T1)

Heat transferred

Q = m c (T2 - T1)

Worked example

With the default values below, Entropy Change Calculator returns Entropy Change of 645.275. Change any input above and every figure here is recalculated in your browser.

Inputs used

Massminimum 0 kg
1 kg
Specific heat capacityminimum 0 J/(kg K)
4,186 J/(kg K)
Initial temperatureminimum 0 K
300 K
Final temperatureminimum 0 K
350 K

Results

Entropy Change
645.275 J/K
Heat Transferred
209,300.0 J
Temperature Ratio
1.1667
Effective Mean Temperature
324.36 K

Step by step

  1. 1Values used
  2. 2Entropy change on heating
  3. 3Heat transferred
  4. 4Entropy Change= 645.275 J/K
  5. 5Heat Transferred= 209,300.0 J
  6. 6Temperature Ratio= 1.1667
  7. 7Effective Mean Temperature= 324.36 K

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why not simply divide heat by temperature?

That only works at constant temperature. When temperature varies, each small amount of heat is divided by the temperature at that moment, giving the logarithm.

Can entropy decrease?

For one object, yes - cooling it lowers its entropy. The second law requires only that the total including the surroundings does not fall.

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