Entropy Definition and 999 Threads

I was following along in my Thermodynamic textbook and began playing with some definitions. In the following formulation, I somehow managed to prove (obviously incorrectly) that dq = TdS for even irreversible processes. I was hoping someone could point out where in the proof I'm going wrong...

Homework Statement A 3.5 kg block of cobber at 100 degrees celsius (373 K) is put in 0.8 kg water at 0 degrees celsius (273 K). The equilibrium temperature is 30 degrees celsius (303 K). Calculate the change of entropy for the system of cobber and water. Homework Equations ΔS=\frac{Q}{T}...

Ok so entropy cannot be destroyed, right? So let's say you have a reaction that decreases entropy (s<0) but it also is exothermic (h<0) and that overpowers the entropy decrease so it is spontaneous (ie h-ts=g<0). If that happens, where does the entropy go?

In the Gibbs free energy equation, does the standard change in entropy equal q(sys)/T(system)? Or in math terms: T(surr) * q(sys)/T(sys) = T(surr) * dS(standard) Thus dS(standard) = q(sys)/T(sys) (surr) = surroundings (sys) = systems (standard) = at standard conditions

Homework Statement Is boiling of egg accompanied by an increase in entropy? The Attempt at a Solution I guess entropy decreases because as the egg boils, the stuff inside it gets hardened and changes into a solid mass. So the disorderliness decreases and the entropy should decrease. But...

Homework Statement The temperature at the surface of the Sun is approximately 5 700 K, and the temperature at the surface of the Earth is approximately 290 K. What entropy change occurs when 1 000 J of energy is transferred by radiation from the Sun to the Earth? Homework Equations...

Homework Statement As a model of a paramagnet, consider a system of N fixed particles with spin 1/2 in a magnetic fiels H along z axis. Each particle has an energy e=μH (spin up) or e=-μH Using S=kln(Ω), show that S=k [ (N-E/e)/2 ln( 2N/(N-E/e) ) + (N+E/e)/2 ln( 2N/(N+E/e) ) ]...

"Dumping" Entropy Hello everyone, I am reading Daniel Schroeder's Thermal Physics book. One phrase he uses that I find particular confusing is that a system has to "dump" entropy. As one example, in chapter 5 he briefly discusses how a fuel cell functions, stating, "In the process of...

From Statsitical And Thermal Physics (Reif. international edition 1985) 160 page. (5.4.4) S(T,V;√) = √[∫{cv(T`)/T`}dT` + Rln(V) - Rln(√) + constant] (integral is from T0 to T , cv is specific heat) This is a entropy of system for temperature 'T' , Volume 'V' , Moles '√' <--...

Hi.. Consider a rod which is insulated on its lateral surface, now this rod is brought in contact with a source at temperature T1 and sink at temperature T2 now a temperature gradient sets up in the rod after steady state is reached temperature at some distance X from the source end is given as...

hi to everybody out there, entropy as i know of now is associated with heat which is basically energy in transit(for a rev. process it is indicative of unavailable part of energy) having said that what is meant by entropy change for a system as heat flows into or out of it(for instance consider...

Homework Statement Show using Boltzmann's principle (S=k.lnW), show that with respect to changes in V and T: dS=k.N.\frac{dV}V{}+\frac{C.dT}V{T} Where W=T^{\frac{C}k{}}V^{N}The Attempt at a Solution S=k.lnT^{\frac{C}k{}}V^{N}=k.lnT^{\frac{C}k{}}+klnV^{N} S=C.lnT+N.lnV Now I know that the...

Hello, I'm studying for my exam for tomorrow and we solved an exercise in class , but a question was not answered and I don't know how to solve it. Homework Statement 1 Kg of water is heated at 0 degree C is brought into contact with a large heat reservoir at 100 degrees C. When the water...

One mole of an ideal monatomic gas initially at 298 k expands from 1.0 L to 10.0 L. Assume the expansion is irreversible, adiabatic, and no work is done. Calculate delta S of the gas and delta S of the surroundings. I know that delta dS = dq/T but q = 0 in adiabatic processes right? So does dS...

Hello, Do living beings use food to decrease the entropy of his body? If so, could anyone explain the process of how we do it? (or at least name a couple of keywords that I can search) Thank you very much.

I don't know how to relate the entropies, S1 and S2, to the temperatures in my entropy balance

Homework Statement Hey guys, So I have this equation for the entropy of a classical harmonic oscillator: \frac{S}{k}=N[\frac{Tf'(T)}{f(T)}-\log z]-\log (1-zf(T)) where z=e^{\frac{\mu}{kT}} is the fugacity, and f(T)=\frac{kT}{\hbar \omega}. I have to show that, "in the limit of...

Homework Statement Hey guys, Here's the question. For a distinguishable set of particles, given that the single particle partition function is Z_{1}=f(T) and the N-particle partition function is related to the single particle partition function by Z_{N}=(Z_{1})^{N} find the following...

There is a container containing water (state 1) which is being stirred. There is a temperature rise (state 2) due to stirring. It is required to find out change in entropy of the system if the process is reversible. Since, there is no heat transfer there would be no change in entropy due to...

It is well-known that with known marginal probabilities a_{i} and b_{j} the joint probability distribution maximizing the entropy H(P)=-\sum_{i=1}^{m}\sum_{j=1}^{n}p_{ij}\log{}p_{ij} is p_{ij}=a_{i}b_{j} For m=3 and n=3, a=(0.2,0.3,0.5), b=(0.1,0.6,0.3), for example, \begin{equation}...

Homework Statement Ten kmol per hour of air is throttled from upstream conditions of 25°C and 10 bar to a downstream pressure of 1.2 bar. Assume air to be an ideal gas with Cp= (7/2)R. (a)What is the downstream temperature? (b)What is the entropy change of the air in J mol-1K-1? (c)What...

The 2nd law of thermodynamics state that entropy increases with time and entropy is just a measure of how hard it is to distinguish a state from another state (information theoretical view) or how hard it is to find order within a system (thermodynamic view). There are many ways to view entropy...

To preface my question, I know it is related to the Gibbs paradox, but I've read the wikipedia page on it and am still confused about how to resolve the question in the particular form I state below. Suppose a completely isolated ideal gas consisting of identical particles is confined to a...

I've always been slightly confused by the Second Law of Thermo. For example, with Maxwell's Demon, where a demon controls the partition between two gas chambers to select all the fast moving particles into one chamber, the Second Law is not violated because the demon's actions and thought...

Why entropy is highest at lowest energy? Entropy is disorderness.So low energy means low disorderness.But why it is highest?

Homework Statement A compressor processes 1.5kg/min of air in ambient conditions (1 bar and 20ºC). The compressed air leaves at 10bar and 90ºC. It is estimated that the heat losses trough the walls of the compressor are of 25kJ/min. Calculate: a) The power of the compressor b) The...

1. A photon that emerges when an electron jumps one orbital down -- will have a fixed energy ...i.e. the different between the (potential) energy of the orbitals. However a "free/unbound" photon can have any energy level. Is that correct? 2. What is the lowest level of energy a...

Hi, Under standard conditions, why does water have higher entropy than helium? Isn't helium a gas? I understand that water has more atoms, but it seems more ordered and is a liquid. I'm not sure how a qualitative analysis could lead to the conclusive result that water is higher in entropy...

Homework Statement One end of a metal rod is in contact with a thermal reservoir at 695K, and the other end is in contact with a thermal reservoir at 113K. The rod and reservoirs make up an isolated system. 7190J are conducted from one end of the rod to the other uniformly (no change in...

Homework Statement Calculate the variation of entropy in the following processes: a) Heating of 18 kg of water from 15 to 40ºC at ambient pressure. b) Compression of 9 kg of water from ambient pressure to 7atm at the temperature of 15ºC. Homework Equations ΔS=Cp*ln(T_final/T_initial)...

For a thermodynamic system there exists a function called entropy S(U,N,V) etc. We then define for instance temperature as: 1/T = ∂S/∂U μ = ∂S/∂N etc. When taking these partial it is understood that we only take the derivative of S wrt the explicit dependece on U,N etc. right? Because...

If we have a qubit in a mixed state, let say 1/2(+><+)+1/2(-><-) and we measure it. Is then the result a pure state + or - ? If this is the case, then the entropy of the system decreases. Now the question another way round is : Suppose we measure a quantum system without gaining...

Hello, I am trying to understand a short literature article (doi: 10.1021/ja01635a030). I am not sure how much liberty I have to reproduce its contents here, and I can't explain it here because I don't understand it -- which is why I have this question. I believe it is proposing that a...

I'm interested in the ultimate fate of the universe. And it seems that the most prevalent theory is the Big Freeze. From what I can gather the BF is caused by dark energy making the universe expand to the point that stars can no longer form, resulting in cold dark space filling the universe...

Hello Community, I have a question that I'm struggling to get clarification on and I would greatly appreciate your thoughts. Big bang theories describe an extremely low thermodynamic entropy (S) state of origin (very ordered). Question: Is the big bang considered to be a high or low shannon...

Homework Statement Considering entropy as a function of temperature and volume and using the Maxwell relation; $$ \left(\frac{\partial S}{\partial V}\right)_T = \left(\frac{\partial p}{\partial T}\right)_V$$ Show that the entropy of a vessel is given by; $$ S= R...

Hello everyone, I've been reviewing some concepts on Thermodynamics and, even though I feel like I am gaining a level of comprehension about the subject that I could not have achieved before as an undergraduate, I am also running into some situations in which some thermodynamic concepts seem to...

Hi everyone! I have a little problem for an upcoming exams, and I think I need just small hints to solve it. My problem is that I have to write about ten/fifteen pages about SUPERDENSE CODING and QUANTUM CRYPTOGRAPHY, and my professor has taken for granted that these are strongly linked to...

Quantum entropy and ...?? Homework Statement My problem is that I have to write about ten pages about SUPERDENSE CODING and QUANTUM CRYPTOGRAPHY, and my professor has taken for granted that these are strongly linked to quantum entropy. He never told us why! Indeed he talked about that as...

Is entropy a measure of "disorder"? In textbooks I never saw a definition of entropy given in terms of a "measure of disorder", and am wondering where this idea comes from? Clausius defined it as an "equivalent measure of change", but I do not see the relation with a concept of "order" or...

Okay, I am considering a cycle, where the working fluid is an ideal gas, with heat capacities Cv and Cp, the cycle consists of: isochoric increase in volume, adiabatic expansion back to initial pressure and a isobaric compression back to initial conditions. Questions: - q1) I am asked to...

This article insinuates that the physics community had forgotten Gibbs entropy long ago and has used Boltzmann entropy since. Isn't this nonsense? For me it was always clear that Boltzmann entropy is problematic...

Evening all. I've seen this equation written down but can not for the life of me find it on tinterweb, is it correct? L = Tconst(S2-S1)

Greetings folks, I'm new to this forum and to physics in general so apologies if I come off like a greenhorn or if I am posting these questions in the wrong place. I have an Arts background and have never really "gotten" science, but my interest in post-Enlightenment philosophy has led me to a...

From what I've been taught, the entropy of a system is the amount of microstates a macrostate can have. A microstate refers to the configuration of a system on a microscopic level (energy of each particle, location of each particle), a macrostate refers to the external parameters of that system...

in my thermo class when we were formalizing the definition of temperature (\frac{1}{T}=\frac{∂S}{∂U}), we drew out all the combinations of various slopes and concavities of the ∂S/∂U graphs. http://imgur.com/cR4V8K8 The shape of this graph i figure should be a reflection of the...

Homework Statement A system of N distinguishable particles is arranged such that each particle can exist in one of the two states: one has energy \epsilon_{1}, the other has energy \epsilon_{2}. The populations of these states are n_{1} and n_{2} respectively, (N = n_{1}+n_{2}). The system is...

Good night, maybe this is a dumb question, but: how was the entropy before the Big Bang? 1. I know, entropy increases or remains constant, so, was the entropy before the Big Bang, and existence of time an space constant? 2. Why is the entropy in our universe not constant but increasing...

To encode a symbol in binary form, I need 3 bits ,and I have 6 symbols. So I need 6*3=18 bits to encode "We are" into binary form. As shown in http://www.shannonentropy.netmark.pl/calculate My question: 3 bits to encode one then I have to use 16 bits, _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _. How to...

Homework Statement When 1.70 ✕ 105 J of heat enters a cherry pie initially at 20.0°C, its entropy increases by 470 J/K. What is its final temperature? Homework Equations The Attempt at a Solution I have no clue