Entropy Definition and 999 Threads

Trying an example from a textbook but I don't understand Legendre transform at all. "construct Legendre transforms of the entropy that are natural functions of (1/T, V, n) and (1/T, V, μ/T)". I don't really understand where to start. An example prior to this exercise just states: A = E - TS =...

I just have this confusion which is completely eating me up. They say entropy of a system is a state property. Then they say that for a completely isolated system, entropy either increases or remains zero depending on the process being irreversible or reversible. So, let's say for an...

Hello I was wondering, with regards to the Tds equation Tds = de + pdv: 1. All of my textbooks state that integrating this equation, although derived for a reversible process, will give the entropy change regardless of the process or whether or not the process is reversible. However, I...

Homework Statement We have a piston in a cylinder containing Helium. The initial states are: P1=150kPa T1= 20°C V1=0.5m3 Following a polytropic process, the final states are: P2=400kPa T2=140°C V2 is unknown. We're also given R=2.0769 kPa.m3.(kg.K)-1 And Cp=5.1926kJ.(kg.K)-1 As...

We know that if we brought a body at temperature T' in contact with a heat reservoir at temperature T (where T' < T) entropy of the universe increases. What if we brought a body at temperature T' in contact with a reservoir at temperature T ( where T' > T)? It is supposed also that the entropy...

Entropy -- can only calculate entropy only at constant temperature? Is that possible to calculate entropy when dq=+100J , temperature change from 271K to 273K ? Ice melt until 273K , not an isolated system. Or I can only calculate entropy only at constant temperature? Thank you

There have been some discussions here as to what type of processes create entropy rather than just move it around. It is established that a gradient of temperature can create entropy. However, the issue moved to partial pressure, and then even away from that. The previous discussion...

"change" in entropy While reading a textbook on introductory thermodynamics , I came across the following- "When a system is in equilibrium, the entropy is maximum and the change in entropy ΔS is zero " And also "We can say that for a spontaneous process, entropy increases till it reaches a...

Hi there, I have to solve this problem: Use the following data to estimate the molarity of a saturated aqueous solution of ##Sr(IO_3)_2## So, I think I should use the Van't Hoff equation in some way, but I don't know how. I also have: ##\Delta_r G=\Delta G^o+RT\ln K## ##K## is the...

Homework Statement 1 kg of water with specific heat (C) of 4180 Joules /kg/degree is given at 0°C. It is taken to 100°C by two methods :- (i) by bringing it in contact with a reservoir at 100°C. (ii) by bringing it in contact with a reservoir at 50°C , and then with another reservoir at...

From theory, we know that Boltzmann entropy for a given distribution, defined through a set of occupancy numbers {ni}, of the macrostate M, is given by: S=k log(Ω{ni}) where omega is the number of microstates for the previously given set of occupancy number, {ni} . Assuming that the system...

Entropy is a measure of energy availiable for work ? "Entropy is a measure of energy availiable for work". Can someone explain this to me? Give some examples that show in what sense it is true. It has to come with a lot of caveats, proviso's etc. because its simply not true on its face. I...

How do I go from the entropy of a system, S(U,V,N), to its internal energy, U(S,V,N)? For instance, for an ideal classical gas, we have S=(3/2)N*R*ln(U/N) + N*R(V/N) + N*R*c where R is the Boltzmann constant, N is the particle number, V is the volume and "c" is a constant. How can I...

Hi PF, I would like to implement different random number generators using AVR microcontroller (both PRNG and TRNG). So I would like to get suggestions about different sources of entropy for TRNG and algorithms for PRNG. Also wanted to test the randomness. And What is chaos theory...

What exactly is entropy?

For a system that is completely isolated from its surroundings, basic thermodynamics requires that the quasi-static heat flux dQ and the entropy change dS be related by: dQ = TdS and since the system is isolated...

Given a system of multiple free electrons. Say 2 of the electrons accidentally collide and become joined (opposite spin) by the weak force. So, the positions of those 2 electrons are now correlated. Was the total entropy of the system reduced by those 2 electrons joining? Thank you...

A friend asks me this. If considering the equation: ∫\frac{dQ}{T}, then it is technically feasible to work out some forms of expressions with measurable physical quantities like temperature and specific heat, therefore it is possible to work out a precise value for entropy change. But is there a...

Homework Statement Hello everyone. My problem is as follows: In a spontaneous process where two bodies at different temperatures T_{1} and T_{2}, where T_{1}>T_{2}, are put together until they reach thermal equilibrium. The number of atoms or molecules of the first is N_{1} and N_{2} for the...

I am asking this question because I am trying to understand what entropy is and I just can't seem to get it clear. Now I think the asnwer is 0.5. The pressure of the can is 30. the Atmospheric pressure is around 15. You divide the pressure in the can by the atmospheric pressure and you...

Homework Statement I have the equation Z=1/N!h3N∫∫d3qid3pie-βH(q,p) How can I get the entropy from this equation assuming a classical gas of N identical, noninteracting atoms inside a volume V in equilibrium at T where it has an internal degree of freedom with energies 0 and ε What...

Entropy is the measure of ored and disorder. But who tells that what is order and what is disorder? Isnt it a relative or subjective thing? How to define it in general, or it can be definet only for thermodinamic systems?

If 12007 kJ of heat is lost to the surroundings with an ambient temperature of 25 degrees centigrade during a cooling process, and the ambient temperature of the surroundings is unaffected by the heat addition, what is the entropy change of the surroundings? If Δs=∫δQ/T, then Δs=ΔQ/T=12007...

Common extensive quatities such as mass, charge, volume can be defined for general systems. I can imagine that we can measure and define them without any problem in case of any kind of complex system as well. However, I do not know the general definition of the entropy, only the thermodynamic...

Does entropy in a closed system always increase OR remain constant ( in equilibrium ). I have a friend arguing it is ALWAYS increasing. His latest argument was, "if no energy enters or leaves an isolated system, the availability of the remaining energy decreases."

I'm wondering if there's an expression/correction for finding the entropy of a density using histograms of different bin sizes. I know that as the number of bins increases, entropy will also increase (given a sufficient number of data points), but is there an expression relating the two? All I...

I'm a little confused about entropy and it's increase along the arrow of time. My perception of entropy is that it is a measure of order in a system and that high entropy represents dissorder. The final result given sufficient time. From what I have read, the universe has began with low and...

Why is the standard entropy of aqueous ions negative? I thought it could be no less than 0, which represents a perfect crystal at 0 K? Is it negative so that calculations can be performed properly? Or is it because it because ions solutes actually have less entropy than a perfect crystal?

Reading popular books (written by Hawking, Penrose, Greene, Linde, Guth and certainly many more) one finds numerous statements like entropy was low after the big bang ... Weyl-curvature hypothesis ... entropy increases with time ... black holes violate unitarity and therefore entropy or phase...

Greetings, I want to ask you somthing if i understood well this subject. Lets say we have an order 1 binary source. H(a)=-Paa*log(Paa)-Paa*log(Pab) bit/symbol. From what i understand this is the average information of a symbol generated after an "a", like aa or ab. Is it right?

I just heard about entropy from another thread, so I had to go and google it, I lightly skimmed this wiki page...

Assuming a mini-universe with the same laws as our current one. A gas within that universe reaches a state of maximum entropy. Would it remain in that state of maximum entropy once it is reached? Maybe the question does not make much sense. In that case, forgive my ignorance. edit: the...

Entropy of molten lead "freezing" Lead melts at 327.5 C.° The latent heat of melting of lead is 24.1 J/g, and the heat capacity of solid lead is 0.14 J/g °C. You take 100 grams of molten lead at a temperature of 327.5 C° and pour it on the sidewalk. The lead freezes and then comes into thermal...

Homework Statement I am having trouble working out the change in Entropy. The question is as follows: A mass of 1 kg of air is initially at 4.8 bar and 150 degC and it is enclosed in a rigid container. The air is heated until the temperature is 200 degC. Calculate the change in entropy...

Homework Statement One body of constant pressure heat capacity C_P at temperature T_i it's placed in contact with a thermal reservoir at a higher temperature Tf. Pressure is kept constant until the body achieves equilibrium with the reservoir. a) Show that the variation in the entropy of the...

Hi everyone, I've hit a bit of a snag with part c of this problem (can't figure out how to invert a function T(ν)), so I'm starting to question whether I have the previous parts correct. Homework Statement Consider a system of N identical but distinguishable particles, each of which has a...

entropy = jouls/kelvin supose 1 liter of ideal gas is allowed to freely expand into a 2 liter volume in an isolated system the energy in the system would remain the same, the temperature in the system would remain the same therefore if entropy =jouls/kelvin the entropy would remain the same...

Homework Statement Supercooled water is water that is liquid and yet BENEATH the freezing point. a) A sample of 131 g of supercooled liquid water freezes to solid ice at a temperature of -8.00 ° C. Using the following, Cp,ice = 38.09 J/molK Cp,liquid = 74.539 J/molK fusH° (at T=0 °...

Homework Statement This is an issue I'm having with understanding a section of maths rather than a coursework question. I have a stage of the density function on the full phase space ρ(p,x); ρ(p,x) = \frac {1}{\Omega(E)} \delta (\epsilon(p,x) - E) where \epsilon(p,x) is the...

1. Assume that one mole of H2O(g) condenses to H2O(l) at 1.00atm and 95 Celcius. Calculate q, w, ΔH, ΔS of the system, ΔS of surroundings. BUT I AM NOT ASKING HOW TO CALCULATE THESE VALUES, SEE LAST SENTENCE OF POST. Homework Equations q = nCΔT ΔH = n(Cp)ΔT W = -PΔV ΔS = [q_reversible] / T Cp...

Hello there, I have a question on the dissipation and entropy. Let us consider a Newtonian dampener with viscosity coefficient η, pulled at a fixed rate e', immersed in an infinite bath at temperature T. The mechanical work input in time dt is then dW = ηe'*e'dt, and is all dissipated...

I asked a question on this forum a few days ago about the entropy change of the surroundings, and am grateful for the insight provided. However, something faulty in my conceptualization is preventing me from solving this problem. Let's say you have a set processes shown in the following...

Hello, I am taking a biochemistry course right now, and I am so confused by this 'hydrophobic effect' and how it relates to entropy. Hydrophobic effect: THe exclusion of hydrophobic groups or molecules by water. (I get this part!) This appears to depend of the increase in entropy of solvent...

Homework Statement You mix 1 liter of water at 20°C with 1 liter of water at 80°C. Set up an equation to find the change in entropy for one of the volumes of liquid in terms of initial temperature (T1) and the temperature after the two volumes of water mixed (T2) Homework Equations...

Hello, I was just reading how the second law of thermodynamic is the only principle of physics that is irreversible, and that fact appears to have a correlation with how we view time and how time can only move in one direction, being the same as the flow of entropy. So, are entropy and time...

According to my textbook, during an irreversible process, the entropy change of the surroundings is given by \frac{q}{T} where q is the heat transferred to the surroundings during the process. Why are we allowed to use this equation, considering that this equation only holds for reversible...

The spectrum of the Cosmic Microwave Background radiation - the flash of the Big Bang, aligns almost precisely with the shape of the Black Body radiation curve. This means that the CMB radiation came from a state that was in thermal equilibrium. Since thermal equilibrium is a state of maximum...

For a reversible process, I imagine it is correct to say that dS = \frac{dq}{T} where all quantities refer to system quantities (not the surrounding). However, for an adiabatic process, dq = 0 . Thus, should it be the case that for an adiabatic reversible process, dS =...

Homework Statement A container is divided into two parts by a thermally conducting wall. There are N atoms of a monatomic ideal gas on the left side, 2N on the right. The gas on the left is initially at absolute temperature 200K, the gas on the right at 500K. a. After thermal equilibrium...

Hello, This is a question I've been working on out of blundell and blundell, http://imageshack.us/a/img560/3342/entwopy.jpg The red box is my answers to the question which I am pretty sure are ok. I am having trouble with the very last part of the question. By the logic of the...