Latent Heat Calculator
Boiling costs five times more than heating to boiling.
Work out Latent Heat. Boiling costs five times more than heating to boiling. Free, with no account and nothing to install.
Energy required
334.9 kJ
0.093 kWh · 2.8 minutes at 2,000 W
Sensible heat changes temperature; latent heat changes state at a constant temperature. The split matters enormously, because latent heat dominates whenever a phase change is involved. Boiling a kilogram of water at 100 °C takes 2.26 MJ — more than five times the energy needed to heat it all the way from freezing to boiling. That is why a kettle switches off long before the water is gone, why sweating cools so effectively, and why steam burns are far worse than hot-water burns at the same temperature. Heating water to exactly 100 °C brings it to the boil without boiling any of it away, so no latent heat is charged at that boundary. Going even slightly past it adds the full 2.26 MJ per kilogram, which is the discontinuity the numbers above are showing you.
How the Latent Heat Calculator works
Energy to take water through any temperature range, splitting sensible heat from the latent heat of melting and boiling. The latent heat dominates whenever a phase change is involved, and by a startling margin.
Also known as: energy to boil a litre of water · why do steam burns hurt more · energy to melt ice · specific heat of water calculator
Frequently asked questions
How much energy does it take to boil water?
Heating a kilogram from 20 °C to 100 °C takes about 335 kJ. Actually boiling that kilogram away takes another 2,260 kJ — nearly seven times as much for no temperature change at all.
What is the difference between sensible and latent heat?
Sensible heat changes temperature; latent heat changes state at constant temperature. Put a thermometer in boiling water and it reads 100 °C the whole time, however much energy you add.
Why do steam burns hurt so much more?
Because steam releases 2,260 kJ per kilogram as it condenses on your skin, before the temperature starts falling at all. Water at the same 100 °C carries only the sensible heat.
Why does sweating cool you?
The same latent heat, run backwards. Evaporating water takes energy from your skin, and because vaporisation is so energy-hungry a small amount of sweat removes a great deal of heat.
Does heating water to exactly 100 °C include the boiling energy?
No, and this calculator does not charge for it. Reaching 100 °C brings water to the boil; the latent heat is what turns liquid at 100 into steam at 100, and it only applies if the range passes through.
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