Latent Heat
Definition and meaning of Latent Heat in chemistry.
Latent heat is the energy required to change a substance's state of matter (from solid to liquid, liquid to gas, or solid to gas) without changing its temperature. Each state transition has a characteristic latent heat value for a given substance.
In more detail
The term latent means "hidden" because the absorbed or released energy goes into breaking or forming intermolecular bonds rather than increasing the kinetic energy and temperature of molecules. The three main types are latent heat of fusion (melting and freezing), latent heat of vaporization (boiling and condensation), and latent heat of sublimation (direct solid-to-gas transition). Latent heat values depend on the specific substance and are typically expressed in joules per gram (J/g) or calories per gram (cal/g).
Key facts
| Field | Physical Chemistry |
|---|---|
| Common units | Joules per gram (J/g) or calories per gram (cal/g) |
| Example for water | H2O: 334 J/g (fusion), 2260 J/g (vaporization) at standard conditions |
| Three main types | Fusion, vaporization, and sublimation |
Water requires approximately 334 J/g of latent heat to melt from ice to liquid water at 0 degrees Celsius, while 2260 J/g is needed for vaporization at 100 degrees Celsius.
Frequently asked questions
Why is it called 'latent' heat?
The term latent means 'hidden' because the heat energy is absorbed or released to break or form intermolecular bonds rather than changing the substance's temperature.
How does latent heat differ from specific heat?
Specific heat is the energy needed to raise the temperature of a substance by one degree. Latent heat changes the state of matter without changing temperature.