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Phase changes · Thermodynamics

Phase Change & Latent Heat Calculator

Solve heat, mass, or specific latent heat for melting, freezing, boiling, and condensation.

Formula shown Runs locally Reviewed Aug 11, 2026
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Equation guide

Pure-substance phase change at constant temperature

Latent heat

Q = mL

Useful rearrangements

m = Q/LL = Q/m
Phase-change calculator

Solve Q = mL

Reference values are approximate; temperature remains constant during an ideal phase change. The calculator returns positive energy magnitudes; absorption or release determines the sign of Q. Results use up to three decimals.

Q=mL

The solved phase-change quantity will appear here.

Using the model

Symbols, assumptions and limitations

Interpretation notes

Temperature is assumed constant during the phase change. The calculator returns a positive energy magnitude; energy absorbed by the system is conventionally positive and energy released is negative. Sensible heating before or after the transition must be calculated separately.

Worked examples

See the method in practice

01

Melting ice

Melting 2 kg of ice with Lf = 334 kJ/kg requires 668 kJ.

02

Separate stages

Heating ice, melting it, and heating the water are three separate energy terms.

Questions

Frequently asked

Does temperature change during melting?

For a pure substance at constant pressure, temperature remains at the phase-change point while both phases coexist.

Can L be negative?

Use a positive material property and apply the sign to Q according to whether energy enters or leaves the system.

Sources & review

Equations and examples are checked against the references below. Results are educational and should be independently verified for safety-critical work.

OpenStax Physics — phase change and latent heat

Written by the STEM Hub editorial team · Reviewed August 11, 2026 · Review methodology