1. Introduction

Whether we make tea, dissolve sugar in coffee or get a beer from the fridge - we always have to deal with the phenomena of temperature, thermal energy and their changes.

When we turn on the light and read a good book on a cold winter's evening, we owe this pleasant atmosphere to the inventions of light bulb and central heating.(...and, of course, not to forget Johannes Gutenberg in this context!)

In our summer holidays we enjoy making a journey through beautiful landscapes in a traditional train pulled by a steam engine.

Stove, refrigerator, central heating, steam engine, electric bulb ... the list might be continued for a long while. A large number of gadgets we are using every day, testify that we have learned to handle temperature and thermal energy quite well. We are so familiar with these phenomena that these terms from the sciences have become part of colloquial language. During the 20th century especially the term energy has become a trendy term.

1.1. Isoenergetic Thermodynamics -
The Key to Understanding!

In contrast the term entropy hardly occurs in colloquial language. Even among scientists there is no agreement on the meaning of this term. Some natural scientists, however, express the opinion, that entropy is of greater importance for the phenomena referred above than the term of energy. They say:

"Entropy is the ruler of energy".*

It would be even better to say "entropy is the ruler of temperature" because the phenomena indicate:

given the same amount of thermal energy, the greater entropy of a substance causes the lower temperature. See chapter 3.2. The graph ' Temperature as a function of the entropy ' is discussed in a series of measured data.

Today, there is no universally accepted interpretation of the entropy phenomenon. However, upon careful analysis of the various arguments, it becomes clear that the problem of understanding is not the entropy, but the misinterpretation of the temperature phenomenon. If you would like to know more about this question, read this train of thought.

The most important aid in thermodynamic investigations is the calorimeter, in which temperature changes with constant energy are usually investigated. It is therefore a good idea to develop interpretations of the experimental findings from the point of view of the first law of thermodynamics, namely the assumption of constant energy. Isothermal interpretations as offered by classical thermodynamics led away from phenomena: processes such as heating, cooling or exo- and endothermic processes are not isothermal. In Chapters 6 and 7 you will find the corresponding experiments.

In the preface of their thermodynamics textbook the authors Charles Kittel and Herbert Krömer (see 9 Software and Literature) state:
"The physics of heat is one of the areas which is substantially simplified by the introduction of quantum mechanics concepts. What is astonishing about this is only one: how little formal (ie. mathematical) quantum mechanics is really necessary.

The basic idea of "quantization without extended mathematics" is implemented on this website in such a way that a didactic concept is created that can accompany students from secondary school to university degrees. Two models are used, both of which are characterized by the fact that they provide analogies for thermodynamically relevant phenomena on the model side:

  • thermal energy
  • temperature
  • entropy and thermal capacity
  • thermal radiation

Both models, the shelf and the fluid model, are far superior to the purely statistical models (coin toss, flea jump game, etc.), because the latter suffer a lack of these analogies on the model side.

 * F.BADER, Entropie, Herrin der Energie, Schroedel Verlag 1993