Thermal Energy vs Heat: Understand the Difference

[bsmm11]

According to my textbook...

Thermal energy is the kinetic energy of the component particles of an object and is measured in joules.
Heat is the thermal energy that is absorbed, given up or transferred from one object to another.

But later on the book there is a small chapter called THERMAL ENERGY (HEAT) and it says...
"Students should understand that the term thermal energy refers to the non-mechanical transfer of energy between a system and its surroundings." ⓒ IBO 2007

I thought heat is the transfer of thermal energy but all of sudden it says thermal energy is also a transfer of energy. So what is the difference between thermal energy and heat then?

 

[Drakkith]

I think it's saying that thermal energy is transferred by non-mechanical means, not that thermal energy IS energy transfer. Not sure though.

 

[Naty1]

not an easy subject...will take more than one minute to grasp so be patient...I still find it confusing at times...

Good explanations here:
http://en.wikipedia.org/wiki/Thermal_energy#Distinction_of_thermal_energy_and_heat

"Students should understand that the term thermal energy refers to the non-mechanical transfer of energy between a system and its surroundings."

is explained above...like

Thermal energy is the part of the total internal energy of a thermodynamic system or sample of matter that results in the system's temperature. The internal energy, also often called the thermodynamic energy, includes other forms of energy in a thermodynamic system in addition to thermal energy, namely forms of potential energy....

maybe also read 'heat' in wiki...and keep in mind they may have been written by different authors... especially: Semantic Misconceptions

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

 

[my_wan]

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.

 

[Naty1]

my wan...this verall subject is definitely "above my paygrade"...and although I did not understand all your points, it's an intersting post...and subject...

probably when starting it's best to keep to first semester physics and
thermodynamic texts...I may have been better off then!

Another issue regarding frames of reference and heat: If two observers pass locally, one one accelerating and one inertial, the acelerating observer measures a higher temperature
than the inertial observer as the former has a horizon...this is the Unruh effect...so "counting particles" and making temperature observations is not so simple as once thought.