Latent Heat Calculator

Created by Miłosz Panfil, PhD
Reviewed by Małgorzata Koperska, MD and Steven Wooding
Last updated: Jan 18, 2024


The latent heat calculator helps you compute the energy released or absorbed during a phase transition like melting or vaporizing. In the text below, we explain what is specific latent heat and present a simple latent heat calculation.

Specific latent heat

Specific latent heat is energy hidden in the internal structure of a substance. As we saw in the sensible heat calculator, if we transfer heat to water, its temperature increases according to its specific heat.

Once the temperature reaches the boiling point, something interesting happens. The temperature stops increasing, and instead, the water vaporizes. This process of turning water into vapor takes some energy. This is the latent heat. Once all the water is turned into vapor, a further transfer of heat will simply increase the temperature again.

Condensation is the reverse process of vaporization, where gas turns into liquid. The latent heat released during condensation is equal to the latent heat absorbed during vaporization.

A change from a liquid to a gaseous phase is an example of a phase transition. Another common phase transition is from a solid to a liquid phase. Specific latent heat is the amount of energy absorbed or released during the phase transition per 1 kg of the substance.

🔎 If you need to know the temperature at which the phase transition occurs, make sure to check our boiling point calculator.

Latent heat calculation

All we need to know to compute the latent heat is the amount of substance and its specific latent heat. The formula is:

Q=mL,Q = mL,

where:

  • m [kg]m\ \rm [kg] – Mass of the body;
  • L [kJ/kg]L\ \rm [kJ/kg] – Specific latent heat; and
  • Q [kJ]Q\ \rm [kJ] – Heat absorbed or released depending on the direction of the transition.

The specific latent heat is different for solid-to-liquid transition and liquid-to-gas transition. For example, if we want to turn 20 g\small 20\ \rm g of ice into water, we need Q=20 g×334 kJ/kg=6680 J\small Q = 20\ \rm g \times 334\ kJ/kg = 6680\ J of energy. To turn the same amount of water into vapor, we need Q=45294 J\small Q = 45294\ \rm J.

Latent heat calculator

The computation of latent heat is simple with our calculator. It provides the specific latent heat for a few substances. If the substance that you're after is not on the list, just give the specific latent heat by filling in the appropriate field.

It's amusing to observe that it takes less energy to go from solid-state to liquid phase than to go from liquid phase to gas. It means that liquids are more like solids than gases.

FAQ

How to calculate latent heat?

To calculate latent heat, you need to multiply two numbers:

  • Specific latent heat, the energy absorbed or released during a phase transition per kilogram of substance; and
  • The mass of the substance.

latent heat = specific latent heat × mass.

What is the difference between latent heat, and specific latent heat?

Latent heat is the total energy released or absorbed during a phase transition of a substance.
Specific latent heat, on the other hand, is the energy released or absorbed during a substance's phase transition per 1 kilogram.

What is the difference between latent heat and specific heat capacity?

Latent heat is the total energy released or absorbed during a phase transition of a substance. You find it by multiplying the specific latent heat of a substance by its mass. It's also known as the heat of transformation.
Specific heat capacity is the energy released or absorbed with the change in temperature by exactly 1 kelvin per 1 kilogram of substance. The same substance has different heat capacities in different phases (i.e., water and ice).

What is the latent heat of the fusion of 5 kg of water?

The latent heat of the fusion of 5 kg of water is 1670 kJ. To find this number on your own, you need to multiply the specific latent heat of the fusion of water (334 kJ/kg) times the mass of the water (5 kg).

latent heat = specific latent heat × mass

Miłosz Panfil, PhD
Mass
oz
Substance
Water (vaporization)
Specific latent heat
kJ/kg
Latent heat
J
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