Case 1
- Mass changing phase
- 1kg
- Specific latent heat
- 334000J/kg
334,000J
Open with these valuesLatent Heat Calculator
334,000J
Result: 334,000 JA phase change costs energy without changing the temperature: Q = m × L. Melting one kilogram of ice takes 334000 J; boiling the same kilogram away takes about 2260000 J, nearly seven times more. Enter the mass in kilograms and the specific latent heat in joules per kilogram.
The numbers at a glance
Held fixed: Mass changing phase 1.000 kg.
| Specific latent heat (J/kg) | Result (J) |
|---|---|
| 0 | 0 |
| 100,000 | 100,000 |
| 200,000 | 200,000 |
| 300,000 | 300,000 |
| 334,000Your value | 334,000 |
| 400,000 | 400,000 |
| 500,000 | 500,000 |
| 600,000 | 600,000 |
Worked examples
Case 2
- Mass changing phase
- 0.5kg
- Specific latent heat
- 2260000J/kg
1,130,000J
Open with these valuesCase 3
- Mass changing phase
- 2kg
- Specific latent heat
- 334000J/kg
668,000J
Open with these valuesHow it's calculated
Q = m × L
- StepEnter the mass that changes phase, in kilograms.
- StepEnter the specific latent heat of the substance, in joules per kilogram.
- ResultRead the heat in joules; divide by 1000 for kilojoules.
Reference table
| Mass, latent heat | Same in kJ | Heat in J |
|---|---|---|
| 0.145, 2260000 | 327.7 kJ | 327700 |
| 1, 334000 | 334 kJ | 334000 |
| 2, 334000 | 668 kJ | 668000 |
| 0.5, 2260000 | 1130 kJ | 1130000 |
| 10, 2260000 | 22600 kJ | 22600000 |
Questions
How do I calculate latent heat?
Multiply the mass by the specific latent heat of the substance: Q = m × L. Kilograms and joules per kilogram give joules — melting 1 kg of ice needs 334000 J, or 334 kJ.
What is latent heat?
It is the energy a substance takes in or gives off while it melts, freezes, boils or condenses, with no change in temperature. The energy goes into rearranging the bonds between particles rather than making them move faster, which is why a melting ice cube stays at 0 °C until the last of it is gone.
What is the difference between fusion and vaporisation?
The latent heat of fusion covers the solid–liquid change and is about 334000 J/kg for water. The latent heat of vaporisation covers the liquid–gas change and is far larger, roughly 2260000 J/kg, because pulling particles apart into a gas costs much more than loosening them into a liquid.
Joules or kilojoules?
This calculator returns joules, the SI unit; divide by 1000 for kilojoules, which is how most tables quote latent heats. The reference table below shows both readings side by side.
Why does the temperature stay the same?
All the energy goes into breaking or forming bonds instead of speeding the particles up, so the thermometer does not move. That is why the formula has no ΔT term, unlike sensible heat, where Q = m × c × ΔT.
Sources and last check
Information, not professional advice.