Naty1 said:
There is some diversity of usage of the word heat, even in technical scientific writings.[10] In current scientific usage, the language surrounding the term can be conflicting and even misleading. One study showed that several popular textbooks used language that implied several meanings of the term, that heat is the process of transferring energy, that it is the transferred energy (i.e., as if it were a substance), and that is an entity contained within a system, among other similar descriptions. The study determined it was not uncommon for a combination of these representations to appear within the same text.[11] They found the predominant use among physicists to be as if it were a substance.
http://en.wikipedia.org/wiki/Heat#Semantic_misconceptions
Yet even the wiki article itself made some absolutist claims with:
http://en.wikipedia.org/wiki/Thermal_energy#Distinction_of_thermal_energy_and_heat
In thermodynamics, heat must always be defined as energy in exchange between two systems, or a single system and its surroundings.[5] According to the zeroth law of thermodynamics, heat is exchanged between thermodynamic systems in thermal contact only if their temperatures are different. For the purpose of distinction, a system is defined to be enclosed by a well-characterized boundary. If heat traverses the boundary in direction into the system, the internal energy change is considered to be a positive quantity, while exiting the system, it is negative. Heat is never a property of the system, nor is it contained within the boundary of the system.
Constraints were first put on the statements in red with Einstein's paper, and subsequent measurements, on Brownian motion. For modern versions involving macroscopic scales of space and time see "Wang et al. Phys Rev Lett, 89, 050601(2002)" and "Carberry et al., Phys Rev Lett, 92, 140601(2004)". For press rease versions of these references in Nature and NewScientist see:
http://www.nature.com/news/1998/020722/full/news020722-2.html
http://www.newscientist.com/article/dn2572-second-law-of-thermodynamics-broken.html
By separating "thermal energy" from "heat" the wiki article actually implies the same extensive property for kinetic energy it denies for 'heat' in defining it an intensive property. Yet since when is kinetic energy an extensive property? If two rocks in space has a kinetic energy k
e with respect to each other where is this kinetic energy located? If you try to draw a box around these rocks which frame, even if picking a purely Galilean frame, do you associate the box with? They do not even always have the same combined k
e under differing Galilean frames that can be chosen. Even if you choose a box frame that minimizes k
e it almost certainly not be minimized after a particle reflection on the box sides. We can call this k
e a potential energy in terms of the box as a whole, but in terms of the motions of the particles, treated as separate systems, the potential energy of the system is the kinetic energy of its parts, even if those parts also involve frame dependent carriers other than the idealized particles.
In fact what an extensive property depends on for validity is a mean field limit which is itself a frame dependent construct. If this box is allowed to thermally fluctuate then even the frame that defines it is not constant such that the boxes position must be given a mean value fully justified by Newton's 3rd law, rather than the second law.
The second law appears to be nothing more than a very useful inversion of causality, where the inversion results from assuming the second law is itself the fundamental cause. Its usefulness results from the fact that we can use this causal expectation to predict behaviors in which we do not or cannot know the causal subsystems the system consist of. This gets us into trouble when we start trying to attach this inverted causality to an investigation of the subsystems themselves. The second law is not the cause of itself.
