Latent Heat Calculator

Latent heat is calculated using the formula Q = mL, where Q is the energy absorbed or released (in joules), m is the mass of the substance (in kg), and L is the specific latent heat (in J/kg). Simply multiply the mass by the specific latent heat for the relevant phase transition.

Specific latent heat (L) is the amount of energy required per unit mass of a substance to change its phase without changing its temperature. It is measured in J/kg. Different substances have different specific latent heats for fusion (melting/freezing) and vaporization (boiling/condensation).

Latent heat (Q) refers to the total energy absorbed or released during a phase change for a given amount of substance. Specific latent heat (L) is the energy per unit mass — it is a property of the material itself. Total latent heat depends on both mass and the specific latent heat: Q = mL.

Specific heat capacity describes the energy needed to raise the temperature of a substance by 1°C, and it applies when no phase change is occurring. Latent heat describes the energy involved in a phase change (e.g. melting or boiling) where temperature remains constant despite energy being added or removed.

Water has a specific latent heat of fusion of approximately 334,000 J/kg. For 5 kg of water: Q = 5 × 334,000 = 1,670,000 J or 1,670 kJ. This is the energy needed to melt 5 kg of ice at 0°C without raising its temperature.

Latent heat of fusion refers to the energy required to change a substance from solid to liquid (or liquid to solid). Latent heat of vaporization refers to the energy required to change a substance from liquid to gas (or gas to liquid). Vaporization typically requires much more energy than fusion for the same substance.

No — during a phase transition, the temperature of a substance remains constant even as energy is being added or removed. All the energy goes into breaking or forming intermolecular bonds rather than increasing kinetic energy. This is why it is called 'latent' (hidden) heat.

Water has an unusually high latent heat of vaporization (about 2,260 kJ/kg) because of strong hydrogen bonds between water molecules. A large amount of energy is required to break these bonds and convert liquid water into steam, which is why sweating is such an effective cooling mechanism.