# Thermodynamics

Thermodynamics. It is the science that studies energy, its properties, the mutual transformations between thermal and mechanical energies, and the different correlations between the properties of substances.

Summary

[ hide ]

• 1 Fundamentals of thermodynamics
• 2 Thermodynamic potentials used in thermodynamics
• 3 Common thermodynamic potentials
• 4 Ideal and real gases
• 5 See also
• 6 Source
• 7 Bibliography

Fundamentals of thermodynamics

Heat energy is transformed during the combustion process, using the energy provided by water , wind and the sun . In turn, this is transformed into the mechanical energy necessary to start machines , trucks, planes , etc. It is used to obtain electrical energy , which through the use of special machines and equipment we can transform into work or thermal energy again.

The different types of energy (mechanical, thermal, electrical, etc.) can transform each other.

Thermodynamic potentials used in thermodynamics

In thermodynamics, a thermodynamic potential is a state variable associated with a thermodynamic system that has energy dimensions. The term “potential” is due to the fact that in a certain sense it describes the amount of potential energy available in the thermodynamic system subject to certain restrictions (related to the natural variables of the potential). Furthermore, the potentials serve to predict under the imposed restrictions which thermodynamic changes will be spontaneous and which will need energy input.

Common thermodynamic potentials

1. Isochoric -isothermic
2. Isobaric-isothermal
3. The internal energy
4. Enthalpy

The first four are combined under the general name of thermodynamic potentials, but this term is often used in a more imitated sense, referring only to isothermal potentials, especially isobaric – isothermal . The four potentials are as follows:

• The potential internal energy

U ou

• The isochoric – isothermal potential. This potential is the Helmoltz function

A = U-TS or A = u-TS

The Helmholtz function or the isochoric -isothermal potential is frequently represented by F (particularly in physics), although the IUPAC prefers the symbol A (which is used primarily in chemistry).

• The enthalpy potential defined as:

H = U + pv oh = u + TS

• Isobaric-isothermal potential. This potential is the Gibbs function

G = H-TS or g = h-ts

Thermodynamic potentials determine criteria about the possibility of a process occurring spontaneously as well as criteria about stable equilibrium under certain conditions of the system’s existence.

Ideal and real gases

All bodies in nature are made up of small particles called molecules , which in turn are made up of atoms . These particles are invisible and remain in constant motion, hence the essence of the bodies’ heat energy . Cohesion forces act on the molecules of any body, the magnitude of which depends on the intermolecular distances. To all the bodies that are in the different states of matter ( solid , liquid , gaseous) correspond to different intermolecular distances and cohesion forces, depending on the magnitude of the molecules. The speed of the molecules’ movement is dependent on the temperature . The magnitude of the cohesion force of the molecules in the gases is much less than in the rest of the aggregation states, as the temperature increases, the gas will become less dense and the less the cohesion force between the particles.

Ideal gases are those that do not have cohesion forces between the molecules, they themselves represent the material points, so the volume is negligible. They are also known as perfect gases, although they do not exist, their study is important in practice, since in the technique they are applied when studying those gases in which the cohesion forces between the molecules and the volume are negligible.

Gases in which the cohesion forces of the molecules and their volume are not negligible are called real gases.