Latent Heat Calculator (Melting and Boiling Energy)
Enter the mass and choose the phase change.
Your numbers
Your results
Energy needed (kJ)
Energy needed (kJ)
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In kWh
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In kilocalories
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Latent Heat Calculator (Melting and Boiling Energy) by TheCalcTools
How the Latent Heat Calculator (Melting and Boiling Energy) works
Melting or boiling takes energy without changing temperature, because it breaks bonds between molecules. The energy is Q = m × L, where L is the latent heat for that substance and phase change.
Water’s latent heat of vaporisation is about seven times its heat of fusion, which is why boiling a pan dry takes far longer than bringing it to the boil.
The formula
Q = m L
Worked example
Using the default values shown in the calculator:
| Mass (kg) | 2 |
|---|---|
| Phase change | Melting ice (water, 334 kJ/kg) |
| Latent heat (kJ/kg) | 855 |
- Melting 2 kg of ice takes 668.0 kJ (0.1856 kWh).
Result:
| Energy needed (kJ) | 668.0 |
|---|---|
| In kWh | 0.1856 |
| In kilocalories | 159.7 |
Frequently asked questions
How much energy to boil away 1 litre of water?
About 2,265 kJ (0.63 kWh) once it is already at 100 °C.
Sources and further reading
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