How this calculator works
During a first-order phase transition at a fixed pressure, transferred energy changes phase rather than temperature. Specific latent heat L gives the energy per kilogram transformed. Water presets use OpenStax Table 1.4 values at approximately one atmosphere: 334 kJ/kg for fusion and 2256 kJ/kg for vaporization. Heating before or after the transition adds a separate sensible-heat term. Outputs here are positive magnitudes.
Formula
|Q| = mL; m = |Q|/L; L = |Q|/m.
Worked example
Melting 2 kg of ice at 0 C requires 668000 J. Vaporizing 0.5 kg of water already at 100 C requires 1128000 J using the listed boiling latent heat.
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Frequently asked questions
What is the heat sign?
Melting and vaporizing absorb heat; freezing and condensing release the same magnitude under the same conditions.
Does pressure affect the value?
Yes. Transition temperature and latent heat change with pressure, especially for vaporization.
Can I use only the mass that melts?
Yes. Enter transformed mass, which may be smaller than the total sample mass.