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Discovering the etymological origin of the term enthalpy takes us to the Greek and is that it is the result of the sum of several lexical components of that language:
-The prefix "en-", which can be translated as "inside" or "en".
-The verb "thalpein", which is synonymous with "warm up".
-The suffix "-ia", which is equivalent to "quality".

The enthalpy a is a thermodynamic magnitude which is equivalent to the sum of the internal energy of the body plus the multiplication of its volume by the external pressure. This magnitude is symbolized with a H capital letter.

What the enthalpy does is reflect the amount of Energy that a body exchange with the environment . Its fluctuations, thus, reveal the energy level that the body releases or absorbs.

The enthalpy variations, in short, express the amount of heat that a thermodynamic system (a body) loses or gains during the development of a isobaric process (that is, at constant pressure). He system in question, as the case may be, it provides or receives energy that it exchanges with the external environment.

In addition to everything indicated, it is important to know that there are several types of enthalpy, among which we can highlight the following:
- Enthalpy of decomposition, which we can establish is the amount of energy that is released or absorbed at the moment in which a complex type substance ends up generating substances that turn out to be simpler.
-Combustion enthalpy, which occurs when the burning of one mole of substance takes place. Specifically, what happens is that in that case, with the presence of gaseous oxygen, it is the release or absorption of energy.
- Formation enthalpy, which refers to the energy that is absorbed or released when one mole of substance proceeds to create a compound substance.
-Neutralization enthalpy, which refers to the energy absorbed or released when the mixture of a basic solution and an acid solution occurs.

However, we cannot ignore the existence of other kinds of enthalpy either, among which we can emphasize the so-called enthalpy of dissolution and the one known as enthalpy of phase change.

At International System of Units , the enthalpy is expressed in joules , While in the Unit Technical System , appeals to calories . Within the framework of Anglo-Saxon Unit System , on the other hand, the enthalpy is calculated in BTU (unit of energy whose full name is British Thermal Unit ).

It is known as standard enthalpy variation (HO ) to the enthalpy change that occurs in a thermodynamic system when an equivalent unit of matter undergoes a transformation through a chemical reaction. The result is usually expressed in kJ / mol . These standard enthalpy variations can be of training (he hot ceded or absorbed in the production of one mole of a compound), of neutralization or of combustion .

It should be noted, finally, that enthalpy variations can be used by magnetohydrodynamics to generate electricity .

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