Science & engineering · Heat
Water phase change energy calculator.
Add up warming ice, melting, warming water, boiling and warming steam for a mass of water at 1 atm.
Inputs
Energy
Enter a mass.
How much energy does it take to turn ice into steam?
Add five parts: warm the ice (c = 2.09 J/g°C), melt it (6.01 kJ/mol at 0°C), warm the liquid (4.18 J/g°C), boil it (40.67 kJ/mol at 100°C) and warm the steam (1.86 J/g°C). Moles are mass divided by 18.015 g/mol. Temperature stays constant during melting and boiling while the energy goes into the phase change.
Worked example. 135 g from −15°C ice to 120°C steam needs about 415 kJ here; the OpenStax Example 10.10 rounds each step and reports 416 kJ.
Assumes pure water at 1 atm. Pick the phase for 0°C or 100°C endpoints, since the temperature alone does not say whether it has melted or boiled.
Frequently asked questions
How much energy does it take to melt ice?
6.01 kJ per mole at 0°C, which is about 0.334 kJ per gram (6.01 divided by 18.015 g/mol).
How much energy does it take to boil water?
40.67 kJ per mole at the boiling point, about 2.26 kJ per gram, far more than melting.
Why does the temperature stay constant while ice melts?
The added heat goes into breaking intermolecular attractions rather than raising kinetic energy, so the temperature holds until the change of state finishes.
Does this work for substances other than water?
No. The specific heats and latent heats here are for water at 1 atm only.
Sources
Checked
Specific heats of ice, water and steam, enthalpy of fusion and vaporization, and the 416 kJ example are from the source above. Molar mass 18.015 g/mol from standard atomic weights. Runs entirely in your browser. Nothing you type is sent or stored.
Scope
Education reference for water at 1 atm. Specific heats vary slightly with temperature and the source uses single constant values.