Four Laws that Drive the Universe

By: Peter Atkins, read in 2012

3 "Thermodynamics, like much of the rest of science, takes terms with an everyday meaning and sharpens them—some would say, hijacks them—so that they take on an exact and unambiguous meaning. We shall see that happening throughout this introduction to thermodynamics."
7 "...the zeroth law of thermodynamics: if A is in thermal equilibrium with B, and B is in thermal equilibrium with C, then C will be in thermal equilibrium with A."
13 "The precise form of the distribution of the molecules over their allowed states, or the balls over the shelves, is called the Boltzmann distribution. This distribution is so important that it is important to see its form. To simplify matters, we shall express it in terms of the ratio of the population of a state of energy E to the population of the lowest state, of energy 0: (Population of state of energy E ) / (Population of state of energy 0) = e-βΕ."
15 " just a parameter that summarizes the relative populations of energy levels in a system at equilibrium.
29 "...the first law of thermodynamics[:]...the internal energy of an isolated system is constant."
30 "In thermodynamics heat is not an entity or even a form of energy: heat is a mode of transfer of energy. It is not a form of energy, or a fluid of some kind, or anything of any kind. Heat is the transfer of energy by virtue of a temperature difference. Heat is the name of a process, not the name of an entity."
35 "...a reversible process in thermodynamics is one that is reversed by an infinitesimal modification of the conditions in the surroundings."
37 "...reversible changes achieve maximum work."
49 " other scientific law has contributed more to the liberation of the human spirit than the second law of thermodynamics."
49 "The second law is of central importance in the whole of science, and hence in our rational understanding of the universe, because it provides a foundation for understanding why any change occurs. Thus, not only is it a basis for understanding why engines run and chemical reactions occur, but it is also a foundation for understanding those most exquisite consequences of chemical reactions, the acts of literary, artistic, and musical creativity that enhance our culture."
49 "...whereas U is a measure of the quantity of energy that a system possesses, S is a measure of the quality of that energy: low entropy means high quality; high entropy means low quality."
50 "...although the second law was established by observations on the lumbering cast-iron reality of a steam engine, when expressed in abstract terms it applies to all change."
50 "All our actions, from digestion to artistic creation, are at heart captured by the essence of the operation of a steam engine."
52 "Efficiency = 1 – Tsink / Tsource"
53 "...the Kelvin statement of the second law of thermodynamics is as follows[:] cyclic process is possible in which heat is taken from a hot source and converted completely into work."
54 "In thermodynamics spontaneous means not needing to be driven by doing work of some kind." Or, as Greylorn has observed, the laws of thermodynamics are time independent.
54 "Thermodynamics is silent on rates."
55 "...the Clausius statement of the second law of thermodynamics[:]...heat does not pass from a body at low temperature to one at high temperature without an accompanying change elsewhere."
60 "Change in entropy = heat supplied reversibly / temperature
61 "For our initial encounter with the concept, we shall identify entropy with disorder" Atkins fails to keep his promise from page 3. He should define 'order'. I claim it can't be cogently defined without introducing the notion of consciousness. A judge is required.
61 "The analogy I have that of sneezing in a busy street or in a quiet library." Even in this analogy, the sneeze is only disruptive and is only noticeable to conscious minds.
62 "A change in entropy is the ratio of energy (in joules) transferred as heat to or from a system to the temperature (in kelvins) at which it is transferred" Does 'to or from' mean 'either'? In which case the absolute value of the energy is used? Or does the sign change in the two cases? If so, how is the direction established?
62 "...the second law: the entropy of the universe increases in the course of any spontaneous change."
65 "Now consider the Clausius statement in terms of entropy. If a certain quantity of energy leaves the cold object as heat..." How does that happen?
65 "The same quantity of heat enters the hot object." Likewise, how does that happen?
65 "Overall, therefore, there is a decrease in entropy, and the process is not spontaneous, exactly as Clausius's statement implies." AND the process is not spontaneous?? How do we know? The logic here seems to be incomplete or nonsense.
65 "The first law and the internal energy identify the feasible change among all conceivable changes: a process is feasible only if the total energy of the universe remains the same. The second law and entropy identify the spontaneous changes among these feasible changes: a feasible process is spontaneous only if the total entropy of the universe increases."
66 "Quantum mechanics can be used to calculate these allowed energy levels (it boils down to computing the wavelengths of the standing waves that can fit between rigid walls, and then interpreting the wavelengths as energies)." What waves? Sound waves propagated by the gas? Surely not EM waves? Or, do we mean De Broglie matter waves?
67 "This increased uncertainty of the precise energy level a molecule occupies is what we really mean by the 'disorder' of the system..."
85 "The only criterion of spontaneous change in thermodynamics is the increase in total entropy of the universe."
87 "...only heat transactions result in changes in entropy.:
89 "The Gibbs energy, which is denoted G, is defined as G = A + pV."
90 "at constant volume, a process is spontaneous if it corresponds to a decrease in Helmholtz energy . at constant pressure, a process is spontaneous if it corresponds to a decrease in Gibbs energy."
94 "Our bodies live off Gibbs energy."
103 "...the whole of thermodynamics can be expressed in terms of these three quantities[:]...the temperature, the internal energy, and the entropy. ...the enthalpy, the Helmholtz energy, and the Gibbs energy...are just convenient accounting quantities, not new fundamental concepts."
103 "...there are two approaches to the definition of entropy, the thermodynamic, as expressed in Clausius's definition, and the statistical, as expressed by Boltzmann's formula. They are not quite the same: the thermodynamic definition is for changes in entropy; the statistical definition is an absolute entropy. The latter tells us that a fully ordered system, one without positional disorder and without thermal disorder—in short, a system in its nondegenerate ground state—has zero entropy regardless of the chemical composition of the substance, but the former leaves open the possibility that the entropy has a value other than zero at T = 0 and that different substances have different entropies at that temperature."
104 "The third law is the final link in the confirmation that Boltzmann's and Clausius's definitions refer to the same property and therefore justifies the interpretation of entropy changes calculated y using thermodynamics as changes in disorder of the system..."
105 "...the third law of thermodynamics: no finite sequence of cyclic processes can succeed in cooling a body to absolute zero."
110 "...the third law[:]...the entropy of every pure, perfectly crystalline substance approaches the same value as the temperature approaches zero. Note that the experimental evidence and the third law do not tell us the absolute value of the entropy of a substance at T = 0. All the law implies is that all substances have the same entropy at T = 0 provided they have nondegenerate ground states—no residual order arising from positional disorder of the type characteristic of ice. However, it is expedient and sensible to choose the common value for the entropy of all perfectly crystalline substances as zero, and thus we arrive at the conventional 'entropy' statement of the third law: the entropy of all perfectly crystalline substances is zero at T = 0."
117 "All the laser-equipped devices we use around the home, as in CD and DVD players, operate at temperatures below zero."
123 "The zeroth law introduced the concept of temperature, the first law introduced internal energy, and the second law introduced entropy. The first law circumscribed the feasible changes in the universe: those that conserve energy. The second law identified from among those feasible changes the ones that are spontaneous—which have a tendency to occur without us having to do work to drive them. The third law brought the molecular and empirical formulations of thermodynamics into coincidence, uniting the two rivers."
124 "I [have not] touched on the extraordinary, and understandable, analogies in the field of information theory, where the content of a message is closely related to the statistical thermodynamic definition of entropy." A shame. I still don't think it can be extended to that domain without introducing consciousness into the mix.

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