A important extensive property of all systems in thermodynamics, statistical mechanics, and information theory, quantifying their disorder (randomness), i.e., our lack of information about them. It characterizes the degree to which the energy of the system is *not* available to do useful work.

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9
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3answers
333 views

Why does $S = k_B \ln W$ not always apply?

I thought for a long time that the Boltzmann formula for entropy, $S = k_B \ln W$, was a universally true statement, or rather the definition of entropy from the perspective of statistical mechanics. ...
13
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2answers
2k views

Why is entropy additive?

Although it seems simple, I can't get the derivation correct. Here is my reasoning: $P(S)=P(A)P(B)$ Where P is the probability and S, A, and B denote different systems. $S_A=-P(A)\ln P(A)$ and ...
7
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5answers
7k views

Difference between heat capacity and entropy?

Heat capacity $C$ of an object is the proportionality constant between the heat $Q$ that the object absorbs or loses & the resulting temperature change $\delta T$ of the object. Entropy change is ...
15
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7answers
2k views

How do you prove the second law of thermodynamics from statistical mechanics?

How do you prove the second law of thermodynamics from statistical mechanics? To prove entropy will only increase with time? How to prove? Please guide.
4
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1answer
66 views

What are the phenomena responsible for irreversible increase in entropy?

https://www.quantamagazine.org/20140416-times-arrow-traced-to-quantum-source This article says that entanglement drives the arrow of time of increasing entropy towards thermodynamic equilibrium: ...
0
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3answers
68 views

A relationship between entropy and temperature

I tried deriving a formula relating entropy (not change in entropy, but entropy itself) to temperature. I’ve only seen two equations really relating to entropy thus far, and only one of them includes ...
11
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3answers
815 views

Does electricity have an associated entropy?

One can certainly measure entropy changes associated with the generation of electricity, but does electricity itself have an associated entropy (maybe related to voltage, current etc.)?
3
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4answers
194 views

Really how does the entropy of the universe increase?

Universe means the system along with its surroundings. I have always got this statement while studying the second law; be it a thermodynamics book (Sears, Salinger) , physical chemistry book (Atkins, ...
5
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0answers
40 views

Is there any useful sense in which entropy fluctuates?

One of the classic distinctions between young Boltzmann and old Boltzmann was his view on entropy. Young Boltzmann had his H-theorem where a mechanical quantity H was supposed to represent entropy. ...
3
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1answer
37 views

About the holographic principle

I read at a book this quote "As the degrees of freedom of a particle are the product of all the degrees of freedom of its sub-particles, were a particle to have infinite subdivisions into ...
0
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1answer
82 views

Replica trick for calculating Entanglement Entropy?

This is probably a simple question. Von Neumann entropy is defined to be $$S_A=-tr_A\rho_A \log\rho_A$$. And it's said that it can be calculate from the "Replica trick": $$S_A=\lim_{n\to 1}\frac{tr_A ...
0
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0answers
31 views

Estimation of an Entropic Path Integral

I'm trying to reproduce some results from a paper (http://www.alexwg.org/publications/PhysRevLett_110-168702.pdf for reference) and basically I need a way of estimating a particular path integral ...
4
votes
2answers
97 views

Does the entropy of a system vary in the equilibrium?

I am not physicist and this question may seem trivial. But I understand that in the equilibrium the magnitudes such as temperature or volumen do not vary. Is the same for entropy? My logical says that ...
2
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3answers
972 views

How is the efficiency of a heat engine related to the entropy produced during the process?

I'm reading Schroeder's An Introduction to Thermal Physics. Regarding heat engines, it is stated: Unfortunately, only part of the energy absorbed as heat can be converted to work by a heat engine. ...
2
votes
1answer
53 views

Entropy generation during irreversible adiabatic expansion

During irreversible adiabatic expansion entropy is generated. It means that the gas expands to as greater volume than that during reversible adiabatic expansion for the same change in pressure. How ...
0
votes
1answer
23 views

entropy changes in common processes?

Can you point me please to a reference that will explain what the entropy undergoes (increase, decrease, etc) in common thermodynamic cycle processes, like adiabatic, isobaric, isochoric, etc?
1
vote
1answer
73 views

Would it be possible that a broken glass can return to its original state spontaneous at 0K?

my teacher said that a broken glass can't fix itself spontaneous because of the second law of thermodynamics, entropy won't decrease in a isolated system. But when the temperature is at 0k, then ...
13
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3answers
3k views

Is this thought experiment violating the the Second Law of Thermodynamics?

There is an adiabatic box, with a board in the middle, which is adiabatic too.The board separates the box into two parts and there is a small hole in it, which is close to a coil and the hole has a ...
3
votes
1answer
70 views

Entropy and gravity

Entropy, at an intuitive level, is often described as a general level of disorder within a system. For example, I have a gas in a container divided in two areas by a divider, the gas all on one side. ...
0
votes
0answers
30 views

Is entropy decreased in this scenario?

I heard one possible definition of entropy $S$ is the number of possible configurations of microscopic variables that satisfy macroscopic variables such as volume and pressure. Suppose I have a box ...
1
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1answer
64 views

What is more important, energy or entropy? [closed]

What decides if something will change or remain the same? Energy or entropy considerations?
1
vote
1answer
58 views

Why is entropy of system same for reversible and irreversible processes? [closed]

I read that entropy change of universe is zero in a reversible process but positive in a irreversible process,then doesn't it mean that entropy change of system of both the processes must be ...
1
vote
1answer
52 views

Is the pressure-gradient force an entropic force?

A gas flows from an area of high pressure to an area of low pressure when there are no other forces preventing it. From a macrosopic perspective you have to infer that an underlying force is ...
1
vote
2answers
82 views

Free expansion of an ideal gas

I am having trouble understanding the transient phase of an ideal gas expanding into vacuum. Firstly, the pressure of any gas is defined only when there is an instrument (barometer/ wall/ piston) ...
-3
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1answer
47 views

What has more randomness? [closed]

Four particles in a line or along a square, which has higher entropy? Just for a minute question. × × × × × × × ×
0
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2answers
287 views

Second law of thermodynamics (in terms of entropy)

Is the second law of thermodynamics (in terms of entropy) for closed systems or isolated systems? I thought it must be valid for isolated systems, such as the Universe. But the book Fundamentals of ...
1
vote
0answers
50 views

What is the relation between Clausius and Kelvin-Planck statement?

What is the relation between Clausius and Kelvin-Planck statement? In second law of thermodynamics, it is said that these two statement are equivalent and inverse to each other. Violation of one ...
0
votes
0answers
26 views

Ice and water mixed and entropy

In any introductory book, everybody has atleast done these type of questions where water at a high temp is mixed with ice and final temp and mass is asked with the understanding that zeroth law define ...
4
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0answers
93 views

Entropy change in a boiling egg

Yesterday in a rather intuitive Q/A session, by a visiting researcher in my town, this question got my attention.What he said was that if you boil an egg, the entropy inside the egg would increase.Now ...
3
votes
0answers
82 views

On the surface, is the law of maximum entropy production the same as principle of least action?

I just have read about the law of maximum entropy production. Someone has idolized it enough to make an whole website just for it: http://www.lawofmaximumentropyproduction.com/ A system will ...
0
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0answers
26 views

What is meant by a “change in volume of a system”?

I keep getting confused when my professor talks about the change in volume of a system. Sometimes it seems as though he's talking about the volume of the gas and at other times he might be talking ...
10
votes
3answers
1k views

Why do we remember the past but not the future?

The question is sometimes referred to as the "psychological arrow of time" (Hawking, 1985). Here the past is understood as a moment or time when the entropy of the universe was lower, and contrarily ...
1
vote
0answers
27 views

Calculate the change in entropy of superheated water [closed]

1 mole of superheated water at 110 degrees Celsius and 1atm is evaporated to a vapour at the same temperature. Find the change in entropy given that i) In the pressure range from 1atm to 1.4atm the ...
1
vote
2answers
92 views

Change in entropy of two isolated systems merged into one system

From Statistical Physics, 2nd Edition by F. Mandl: Two vessels contain the same number $N$ molecules of the same perfect gas. Initially the two vessels are isolated from each other, the gases ...
0
votes
1answer
91 views

A hypothetical equation of state that violates second law of thermodynamics

Suppose for a gas I guess an equation of state in the form $f(P,V,T)=0$. Is it possible that this hypothetical equation of state turns out to violate the second law of thermodynamics. A simple example ...
0
votes
2answers
70 views

If for an isolated system, $\Delta$U is 0, then what is $\Delta$S?

My textbook answers this question as $\Delta$S > 0 but I really don't know why. If system is isolated, then dQ = 0 i.e. S = 0. (S = dQ/T). I don't really get why question has provided an additional ...
18
votes
4answers
7k views

Is there any proof for the 2nd law of thermodynamics?

Are there any analytical proofs for the 2nd law of thermodynamics? Or is it based entirely on empirical evidence?
1
vote
1answer
92 views

Can a coffee cup really jump off the table?

I've been reading Nassim Nicholas Taleb's book The Black Swan which largely concerns the uncertainty of social and economic systems (and the futility of predicting outcome); the Black Swan being the ...
1
vote
0answers
40 views

How to understand better this point of view on entropy?

On the book "Applied Differential Geometry" by William Burke we see a discussion about thermodynamics in which the following is said: A thermodynamic system is a homogeneous assembly that includes ...
0
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0answers
29 views

Does inflation violate the second law of thermodynamics?

Does inflation violate the second law of thermodynamics? It seems like it would, since quantum fluctuations were scaled up and created the varying density field that lead to Galaxy formation. ...
0
votes
1answer
45 views

In situations where we have entropy decrease, are we violating second law?

When we heat a material and this heat solidifies it (eg. when we cook an egg), isn't that decrease in entropy? when we have an endothermic reaction that produces larger molecules (synthesis), don't we ...
4
votes
2answers
168 views

“Violation” of the Second Law

I can't reconcile some facts about entropy and irreversibility. This depresses me, because I feel I can't quite grasp the importance of entropy. I will illustrate my problems with an example given by ...
0
votes
1answer
39 views

Entropy of environment of pendulum?

I remember reading a statement along the lines of: Suppose our system is a simple pendulum. Then the entropy change in it is overall zero because the system is periodic. However, the entropy ...
15
votes
5answers
1k views

Why don't photons split up into multiple lower energy versions of themselves?

A photon could spontaneously split up into two or more versions of itself and all the conservation laws I'm aware of would not be violated by this process. (I think.) I've given this some thought, and ...
1
vote
2answers
100 views

Does heat death of the universe necessarily imply an inability to perform computation?

Wikipedia defines the heat death of the universe as follows: the universe has diminished to a state of no thermodynamic free energy and therefore can no longer sustain processes that consume ...
0
votes
1answer
57 views

Why does the expansion of gas into a vacuum mean that we have less information about the system? (entropy)

I'm reading through Statistical Physics by F. Mandl and in the chapter about the 2nd law of thermodynamics he states that: The basic distinction between the initial and final states in such an ...
1
vote
1answer
64 views

Understanding Entropy

I know that entropy in an isolated system only increase, also is a measure of order. But I can't grasp the idea behind it in a fundamental level. When you try to transform energy from one state to ...
0
votes
1answer
45 views

Is there any difference between heat and entropy here?

This screenshot is from the Carnot Cycle page on Wikipedia. In the "Stages" section, it says that: The gas expansion is propelled by absorption of heat energy, $Q_1$, and of entropy, $\Delta ...
1
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1answer
49 views

Heat, temperature and entropy

I have many questions concerning this topic. I know that temperature measures the tendency of an object to give up its internal energy. The transit of internal energy is called heat. I don't know if ...
0
votes
0answers
59 views

Time Vs Entropy [duplicate]

Entropy is a property of thermodycamical systems. We know that entropy measurement it's determinated by preassure P and temperature T (for simplicity). At the same way we consider that the entropy of ...