Entropy Definition and 999 Threads

Homework Statement Consider two fixed volume bricks of mass m1=2kg and m2=1kg with initial temperatures T1=400K and T2=100K. They are enclosed in a system thermally isolated from the surroundings and are made from a material with a heat capacity cv = 1kJ/kg/K. A) In Process 1, the bricks are...

I am a general chemistry student and I find thermodynamics fascinating. However, I have a hard time visualizing entropy. Can somebody please explain how an increase in entropy can make a process that is endothermic spontaneous? The typical demonstration of entropy that I have seen is on in...

So from the first law for a closed system, dU=dQ-dW=dQ-PdV From the second law, dS=dQ/T + Sgenerated (i.e. the entropy generated) Putting expression of dQ from second law into first law, dU=T*dS-T*Sgen-PdV If s and v are constant, dU= -T*Sgen>0 Hence dU<0 This is a...

Homework Statement 45g of H2O(g) are condensed at 100 degrees C, and H2O(l) is cooled to 0 degrees C and then frozen to H2O solid. Find the Change in Entropy H2O(l): 4.2 J K-1g-1 vaporization at 100 degrees C: 2258 J g-1; fusion at 0 degrees C: 334 J g Homework Equations dS=dq/TThe...

∫dQ/T≤∫dQ(rev)/T * , where both integrals are evaluated between the same thermodynamic coordinates- A and B , say. - I am having trouble interpreting this inequality. -( I understand the derivation in my textbook via the Clausius diagram(considering a reversible and an ireversible process...

I posted this question a couple days back, but it got removed because it looked like a homework question (which, I suppose, is flattering, since I came up with it on the way home from work, and I'm not even a student, let alone a teacher)...so I'm going to try to rephrase it -- but because this...

Hi all, could somebody look over my answer please. I'm pulled the equation I used off the internet but can't remember where so I'm not sure what it's called. I took a picture of my answer as I thought it would be easier to read than fiddling with symbols here. QUESTION ANSWER ATTEMPT...

Hi all, could somebody have a look over my answers for this question please? The value I got for the second part seems quite feeble. Homework Statement The Attempt at a Solution [SIZE="4"]Part a) Key m = mass cs = specific heat bronze cm = specific heat molten bronze Tfus...

I think I actually have solved it. I was right with the PV=nkT, I believe I previously messed up with the algebra. Homework Statement Using the same meathod as in the text, calculate the entropy of mixing for a system of two monatomic ideal gases, A and B, whose relative proportion is...

Fractals are just many iterations of a very basic formula, so they can be described with little information, and yet they are extremely complex given enough iterations. Can they be described as low entropy despite their complexity?

In statistical mechanics the macro-state of a system corresponds to a whole region in the microscopical phase-space of that same system, classically, that means that an infinity of micro-states relate to a single macro-state. Similarly, given a hamiltonian, a whole surface in the microscopical...

Homework Statement So as a part of a very long question on homework for thermodynamics, I and some of my friends got into a debate about how to write an expression for entropy at a particular state. Homework Equations delS(state 1 to 2)= Cv*ln(T2/T1)+R*ln(V2/V1) (from constitutive...

Hi, can I know what are the ways to show that the ground state particles of a Bose Gas possesses 0 entropy?

I've got a couple of questions about reversible cycles: So if we have two gaseous systems and have a reversible cycle working between them, then the entropy generation within each gaseous system is zero, right? Do turbines execute reversible cycles? Thanks a lot for your help!

Homework Statement A system with 100,000 molecules has 2 energy levels, A and B. At first, the 2 energy levels are populated equally. After a reversible process, energy level A is populated by 65% of the molecules and the system is at 293K. a) What is the difference in energy between the two...

Hi all, I've been doing some pretty complex problems on closed systems in thermodynamics, and a few questions pooped up in my mind about Sgen (entropy generation). Please help me out with them.. 1. When work is done on a system (like a paddle wheel in a cylinder containing gas), there is...

As I understand it, the entropy inside a horizon, the black hole event horizon or the cosmological event horizon, is limited by the entropy proportional to the surface area of that horizon. My question is: does that entropy limit always allow the possibility for maximum entropy of the material...

I know this is elementary, but I'm having trouble understanding the definition of entropy. If someone could better clarify the term for me it would be much appreciated.

When collagen binds to bone, the entropy of the system increases. Why does the entropy not decrease, since it seems more logical that the entropy decreases since it seems to become more ordered?

show that \frac{d\hat{r}}{dt}=\hat{θ}\dot{θ} also, \frac{d\hat{θ}}{dt}=-\dot{θ}r i've tried finding the relationship between r and theta via turning it into Cartesian coord.s, and I've tried the S=theta r but still no luck. S=theta r dS/dt=d(theta)/dt r which is similar to the RHS...

What is the definition of entropy of a thermodynamic irreversible process? In the case of reversible process from initial state 'a' to final state 'b' ,one may define entropy by 1) Constructing infinitely many reservoirs having temperatures corresponding to the temperature at every...

During a physics competition, I came across this question. My work was \begin{align*}\Delta S &= \frac{Q}{T} \\ \Delta S &= \frac{1.25 \times 10^3 \, \mathrm{J}}{348 \, \mathrm{K}} \\ \Delta S &= 3.59 \,\,\mathrm{\left( J/K\right )} \end{align*} but I was stuck in between two answer choices...

Homework Statement The Entropy of a probability distribution is given by, S = -k_B \sum _{i=1}^N p(i)\ln{p(i)} I've shown that the extremum of such a function is given by, S' = k_B \ln{N} (which is a positive quantity) Now I want to show that this is a maximum by showing that S' - S...

Dear sir, Hi, Everyone. I have a question about entropy. If the object falls without air resistant (vacuum system) , Is entropy changed? If ΔS=0, it means reversible, is it possible that the object can go back to the original height? I know that it is impossible but can we explain that ΔS...

This is the problem: Consider a system of two Einstein solids, with NA = 300, NB = 200, and qtotal = 100. Compute the entropy of the most likely macrostate and of the least likely macro state. I only have a doubt. Is the most likely macro state when each solid has half the energy (in this...

This is for my Chemical Engineering class, but it comes down to a thermodynamics question. I need to calculate the gibbs free energy for a few reactions, problem is some of the compounds (1-Buten-3-yne and Styrene) do not have standard entropy values that I can find. Without a standard entropy I...

Homework Statement Explain why, for an ideal mixture, the mixing entropy is given by ΔSmixing = k ln( Binomial Coefficient ( N, NA ) where N is the total number of molecules and NA is the number of molecules of type A. Use Stirling's Approximation to show that this expression is the same as...

This question was prompted by reflecting after reading the standard textbook explanation that "the greater acidity of RCOOH vs ROH is due to the greater stability of the delocalised RCOO- ion causing the position of equilibrium to be further to the right". The equilibria can be written as...

I'm struggling to understand the implications and origins of the 2nd law. Entropy is such a slippery subject. Wikipedia has many many definitions of entropy. I've been studying Professor Susskind physics lectures, so I'm most interested in his favorite definition: that information is...

I am a mechanical engineering student, but have yet to take thermodynamics. For months now, I have been reading up on thermo and am actually quite interested in it. However, I am still quite confused with the concept of entropy. Its pretty much the consencus that the "disorder" explanation is...

Ok so the thread I was looking at is closed and I cannot pose this question there. The question was posed if light will travel forever or if it will degrade over time and the answers that were given were a bit incomplete. Here is a link to that thread...

Black holes have an entropy, but they evaporate. At the end of the evaporation, the entropy is greater than the entropy at the beginning of the evaporation. I am looking for an example of a quantitative result for the entropy of the black hole after evaporation (or the entropy difference...

Homework Statement I have question on entropy for which I have no idea about, please help me out... a) Change of entropy of a gas is given with usual notations by: s2-s1=cvln(T2/T1)+Rln(V2/V1) using this relationship, show that for a polytropic process, entropy change can be expressed as...

Homework Statement Suppose the entropy of a system is given by the relation: S(E,V,N) = a(E,V,N)^(1/3) Determine three equations of state for this system Homework Equations there were no equations given on the sheet but I'm assuming that this might help...

Can someone conceptually explain to me how Temperature and Entropy are conjugate variables? I would imagine that Temperature and Internal Energy would be more appropriate, as I understand Heat flow causes changes in Internal Energy, some of which is used to change the translational motion of...

I'm having problems understanding the trace of tensor products when the density matrix is expressed in its reduced density operators. The proof of subadditivity is quite simple. S(ρAB||ρA\otimesρB) = Tr(ρABlogρAB) - Tr(ρABlogρA\otimesρB) = TrAB(ρABlogρAB) - Tr(ρAlogρA) - Tr(ρBlogρB) This...

Apologies if this is in the wrong forum: I am reading Biocentrism by Robert Lanza, and one of his arguments is that time has no real existence outside of animal perception. He says is is the process by which we perceive changes in the universe. The books argument is that everything is a...

Consider the vacuum state that is hypothesised to precede the moment of inflation in classical inflationary theory. The theory assumes that quantum fluctuations in this vacuum are magnified because of the process of inflation and have gone on to form the real energy structures that we witness...

According to the third law of thermodynamics, one could argue that a vacuum has zero entropy, since it has only one ground state and a temperature at absolute zero. However, assuming the accelerated expansion of the universe to result in a 'heat death', i.e. a state of absolute thermal...

When reading about entropy it states that ball does not automatically bounce up because of entropy. It is just not favorable. I don't get this. Isn't the correct reason gravity? Ball does not bounce up because of gravity! Where does entropy come from?

So in my physics textbook, the 2nd law of thermodynamics stated in terms of entropy reads "the entropy of a closed system can never decrease." Now, shouldn't it indicate the entropy of an isolated system can never decrease. All other sources I've looked at note an isolated system, as well...

Everybody says entropy of the universe is increasing. But after the big bang, matter formed, it came together, stars and galaxies were formed, on a small planet called Earth atoms/molecules came together to form unicellular organisms and then higher life. Our brains are organizing even more...

Hello, I have a doubt about the distribution of random variables that maximize the differential entropy in a set of inequalities. It is well known that the Normal distribution maximizes the differential entropy. I have the following set of inequalities: T1 < I(V;Y1|U) T2 < I(U;Y2) T3 <...

According to theory of superconductivity, resistivity almost zero. Below critical temperature the entropy decreases markedly with cooling . why resistivity zero when entropy not equal to zero? my doubt is when there is an entropy there is a disorder. then how can move conducting electron...

So we learn in basic thermo that for any system, the derivative of entropy with respect to volume is pressure over temperature: ∂S/∂V＝P/T. Suppose we have a box with two partitions, and a moveable wall in between the partitions. The box and wall are both insulated to prevent heat transfer...

So we know that at the moment of the big bang the universe was relatively low in entropy; as the universe has expanded entropy has increased, but what about further down the line? What about when the universe is so cold that it's nothing more than a collection of black holes, and further more...

Homework Statement 1 mol of monoatomic ideal gas (temperature T1) is inside a cylinder with a moving piston (all are isolated). The initial external pressure on the piston is P1. at some point the external pressure is changed to (2/3)P1, the gas undergoes (irreversible) adiabatic expansion...

Sen 2013 says, How serious a problem is this for LQG? Does this mean that LQG doesn't have GR as its semiclassical limit? Does that mean it's a dead theory, or maybe just that it needs to be modified? Is the technique using Euclidean gravity reliable? Since I'm not a specialist, I'd be...

Can someone explain to me why Cpln(T2/T1) = 0? Thank you.

In 250gr water at 23 oC(degrees celsius) we throw in 27gr ice at 0 oC. Find the change in entropy. (sorry if that was a bad translation but English is not my native language) The answer is 0.78 calories/oC. But I'm not sure how do this. The formula I have for entropy is: S=δQ/T I find the...