During a phase change, heat goes into breaking bonds rather than raising temperature. Melting ice absorbs 334 kJ per kilogram – which is why ice cools drinks so well – and boiling water absorbs nearly seven times more.
How to use the Latent Heat Calculator
- Mass m
- Substance
- Phase change
- Latent heat L
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Choose the substance and the phase change, and enter the mass.
Tips
- Use absolute temperature (K) in gas laws and efficiency formulas.
- Temperature differences are the same in K and °C.
- Heat = mass × specific heat × temperature change when no phase change occurs.
- Phase changes need latent heat at a constant temperature.
Common mistakes to avoid
- Using °C in pV = nRT.
- Forgetting latent heat during melting or boiling.
- Confusing heat capacity (J/K) with specific heat (J/(kg·K)).
Inputs explained
| Field | What to enter |
|---|---|
| Mass m | Units: kg, g, mg, t, lb, oz |
| Substance | Choose one: Water / ice, Ethanol, Ammonia, Mercury … |
| Phase change | Choose one: Melting / freezing (fusion), Boiling / condensing (vaporisation) |
| Latent heat L | Units: kJ/kg, J/kg, J/g |
Example values
How the main result changes when Mass m changes and everything else stays at the example values above:
| Mass m (kg) | Energy Q (J) |
|---|---|
| 0.5 | 167,000 |
| 0.75 | 250,500 |
| 1 | 334,000 |
| 1.25 | 417,500 |
| 1.5 | 501,000 |
| 2 | 668,000 |
Formula
Q = m·LWorked example
Inputs — Mass m: 1 kg; Substance: Water / ice; Phase change: Melting / freezing (fusion).
Results — Latent heat used = 334,000 J/kg; Energy Q = 334,000 J.
Key terms
- Latent heat
- Energy for a phase change at constant temperature.
Frequently asked questions
Why doesn't temperature change during melting?
Energy goes into breaking bonds between molecules.
Why is the latent heat of vaporisation larger?
Molecules must be fully separated.
Why do steam burns hurt so much?
Condensing steam releases 2,257 kJ/kg on your skin.
What is the latent heat of ice?
334 kJ/kg.
What formula does the Latent Heat Calculator use?
Q = m·L.