What does «energía interna» mean in Spanish?
- In thermodynamics, a system is any object, any quantity of matter, any region, etc., selected for study and mentally separated from everything else which is then called its environment. The imaginary envelope that encloses the system and separates it from its environment is called the boundary of the system. In this article, the boundaries will be called the walls of the system. The internal energy of a system is simply its energy. The term was introduced into thermodynamics in 1852 by W. Thomson (the later Lord Kelvin). The adjective "internal" refers to the fact that some energy contributions are not considered. For example, when the total system is in uniform motion, it has kinetic energy. This overall kinetic energy is never considered part of the internal energy; it could be called external energy. Or, if the system is at a constant non-zero height above the Earth's surface, it has a constant potential energy in the Earth's gravitational field. Gravitational energy is only taken into account when it plays a role in the phenomenon of interest, for example in a colloidal suspension, where gravitation influences the upward and downward motion of the small particles that make up the colloid. In all other cases, it is assumed that gravitational energy does not contribute to the internal energy; it can be referred to again as external energy. On the other hand, a contribution to the internal energy that is always included is the kinetic energy of the atoms or molecules that make up the system. In an atomic gas, it is the energy associated with the translations of the atoms; in a molecular gas the molecular translations and rotations contribute to the internal energy. In a solid, the internal energy acquires contributions from vibrations, among other effects. Except in ideal gases, the potential energy of molecules in the field of others (see intermolecular forces) is also an important component of the internal energy.