Why internal energy is a function of temperature only – quora e gaskell north and south

The energy associated with temperature is either externally supplied by EMS or kinetic collision into local system entropy. Temperature is the dynamic motion and behaviour of energy-driven molecules and fundamental building units like electrons and protons.

Science doesn’t know what energy is or why it pulses molecules into motion. It is strongly suspected that, like am/fm radio broadcast and reception, specific molecules are tuned to receive and dynamically react to specific EMS wavebands, most usually infrared.

Ignoring kinetic molecule collision and deflection, the energy from the Sun that reaches Earth interfaces with and energizes molecules into multi-axial motion and rectilinear travel. The EMS pulses molecules into remarkably fast velocity while oscillating and spinning. Three bonded atoms, for example, do a dance at Mach 2.0. But this EMS energy has no temperature through its travel from the Sun to Earth. Only on interface with material mass does temperature result.

When one looks at a bulb thermometer reading, could be anything, say 25 Celsius, a nice Summer day. This “25” is molecular impact pressure by innumerable gas molecules, all local systems, hitting the bulb in compliance with Zeroth Law. The reading isn’t true temperature but impact pressure. Way over head, about 50 miles up, molecules tear through the thermosphere at velocity of 1500 Celsius. With enough of these, at or around Earth surface, organic life couldn’t exist.

Temperature is molecular motion by external energy source. Molecules don’t create or destroy energy. And not one molecule in the known universe has ever been discovered to be energy-less or ground state. Every local system molecule is always pulsed by some quanta of energy.

By definition and according to kinetic theory of matter, Internal Energy is merely the summation and manifestation of all the kinetic energies associated with all the energetic random motion and vibrations of the individual atoms and subatomic entities making up the system and it is this motion that gives rise to the sensation of hot or cold, which is temperature. If the temperature of the material changes, then it means, the kinetic energy of these atoms or subatomic entities changes and therefore affect the internal energy of the system. This can happen by heating the system, and/or by doing work on the system and the the atoms and subatomic entities become more vigorously energetic in their motions and vibrations (therefore temperature goes up) and if the system does not do work on the surrounding as result of this increased atomic activity, then the internal energy of the system will increase) and vice versa. Therefore the only way the motion of atoms and subatomic entities can change is by changing the temperature of the system and this can be done either by heat transfer (to or from the system) or by work done (on the system or by the system) or both. That’s how the internal energy of the system arises from the kinetic and vibrational motion at atomic and subatomic level of the ideal system. Therefore in an IDEAL gas system, the internal energy is only the function of temperature and nothing else . For other systems, the internal energy gets affected by changes in pressure, volume in additional to temperature changes.