Latent energy

Latent heat is (thermal) energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process - usually a first-order phase transition.

Latent heat can be understood as heat energy in hidden form which is supplied or extracted to change the state of a substance without changing its temperature. Examples are latent heat of fusion and latent heat of vaporization involved in phase changes, i.e. a substance condensing or vaporizing at a specified temperature and pressure.

The term was introduced around 1762 by British chemist Joseph Black. It is derived from the Latin latere (to lie hidden). Black used the term in the context of calorimetry where a heat transfer caused a volume change while the thermodynamic system's temperature was constant.

In contrast to latent heat, sensible heat involves an energy transfer that results in a temperature change of the system.

The terms ″sensible heat″ and ″latent heat″ are specific forms of energy; they are two properties of a material or in a thermodynamic system. ″Sensible heat″ is a body's internal energy that may be ″sensed″ or felt. ″Latent heat″ is internal energy concerning the phase ( solid / liquid / gas ) of a material and does not affect the temperature.

Both sensible and latent heats are observed in many processes of transport of energy in nature. Changes of Latent heat is associated with the change of phase of atmospheric water, vaporization and condensation, whereas sensible heat is energy that reflects the temperature of the atmosphere or ocean, or ice.

The original usage of the term, as introduced by Black, was applied to systems that were intentionally held at constant temperature. Such usage referred to latent heat of expansion and several other related latent heats. These latent heats are defined independently of the conceptual framework of thermodynamics.

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