Entropy Definition and 999 Threads

Homework Statement I am to show that ΔS=Q/T for the isothermal expansion of a monoatomic ideal gas, when the expansion is so slow that the gas is always in equilibrium. Homework Equations 1. law: ΔU=Q+W (We mustn't use dQ and dW - our teacher hates that :( ). Ideal gas law: PV=NkT We need the...

Homework Statement A liter of air, initially at room temperature and atmospheric pressure, is heated at constant pressure until it doubles in volume. Calculate the increase in its entropy during this process. so Ti= 300K, Volume which is 2Vi=Vf; Pressure is constant Homework Equations ΔS...

Homework Statement Initial pressure: 140kPa Temperature: 25C or 298K Volume: 0.14m^3 Final Pressure:1.4MPa or 1400kPa It uses index compression, n=1.25. So PV^1.25 = constant. c_p = 1.041kJ/kg.K and c_v = 0.743 kJ/kg.K Homework Equations ¥ = c_p/c_v ΔS=c_v*ln(Tf/Ti) + R*ln(Vf/Vi) [i...

Homework Statement http://puu.sh/c09sc/b1d02302bd.png Homework Equations Conceptual question. The Attempt at a Solution The answer is isothermal expansion(D). but heat does not decrease due to isothermal process and expansion leads to lesser collision of particles on walls of container. So...

I am teaching myself Stat Mech / thermo from Swendsen's "An Introduction to statistical mechanics and thermodynamics". To this point I find the book interesting and clear to follow. But in section 4.6, Probability and Entropy, he confuses me by concluding that the entropy that he defines there...

Hi. Say you have a canonical ensemble, and its zustandssumme is ##Z = \sum_j e^{- \beta E_j}##. Then $$d \: ln(Z) = \frac{-d\beta}{Z} \sum_j e^{- \beta E_j} E_j - \frac{-\beta}{Z} \sum_j e^{- \beta E_j} dE_j$$ Further, my book says the second term is given by the work ##dW## done on the...

Sean Carroll has stated several times that the reason we can remember the past and not the future is because entropy is increasing, i.e. because there is an arrow of time. Is this statement justifiable? Remember that life and its processes, including memory, require negentropy. In other words...

A few months ago my door broke, so can I say the Entropy of the door is increased? This is because I read that Entropy is wear and tear. So the door broke due to wear and tear.

Homework Statement A piston‐cylinder initially contains 0.5 m3 of an ideal gas at 150 kPa and 20 degrees. The gas is suddenly subjected to a constant external pressure of 400 kPa and it is compressed in a manner that the final temperature is also 20oC. Assume the surroundings are also at 20...

I have a conceptual question that I am trying to clear up. A reversible process means that the net change in entropy is zero. If we have two scenarios, where case 1 has a ΔS= 0.1 J/K and case 2 has a ΔS= 0.5 J/K. Is it a correct statement to say that case 1 is "less irreversible (i.e...

Certainly fission is a prime example of entropy. But what about fusion? Doesn't fusion look like a process that goes from a disordered state to an ordered one? Out of chaos comes order!

If dark matter affects normal matter (by gravity), does that mean that normal matter also affects dark matter? I think it does... In which case; Black holes could attract BOTH dark and normal matter? Does this give any opportunity to "information loss"? What if some information in normal...

Do different observers, say, inertial and accelerated, moving thru the same point in space, agree on the entropy of the same isolated system they observe? I am interested in it in the context of Unruh effect. If we switch between inertial and accelerated frames, we switch Unruh particles...

Assuming a big crunch theory were to be true (I know it's not too popular a theory these days) I figure a collapsing universe would need to have decreasing entropy. If entropy is decreasing, would the arrow of time flip? Also, because physics is just as valid with time moving backwards, would...

Homework Statement I know that the equation ΔSsystem = Q/T is only valid for a reversible process but whenever i see problems involving a irreversible isothermal expansion of ideal gas, the ΔSsurroundings is taken as -Qirr/T. Why is that equation valid for surroundings, is it because the...

Homework Statement Calculate the entropy change of an ice cube of mass 10g, at an initial temperature of -5°C, when it completely melts. cice = 2.1 kJkg-1K-1 Lice-water = 3.34x105 Jkg-1 Homework Equations dQ = mcdT dS = \frac{dQ}{T} ΔS = \frac{Q}{T} Q = mL The Attempt at a...

Homework Statement A well-insulated rigid tank contains 7 kg of a saturated liquid-vapor mixture of water at 150 kPa. Initially, three-quarters of the mass is in the liquid phase. An electric resistance heater placed in the tank is now turned on and kept on until all the liquid in the tank is...

Homework Statement Imagine that the temperature of 255 g of aluminum sitting in the sum increases from 278 K to 294 K. By how much has its entropy increased? Homework Equations Q=mcΔT ΔS=Q/T The Attempt at a Solution Q=(255 g)(.90 J/gK)(294 K -278 K) Q=3672 J ΔS=Q/T...

Homework Statement If 25.0 g of gallium melts in your hand, what is the change in entropy of the gallium? What about the change of entropy in your hand? Is it positive or negative? Is its magnitude greater or less than that of the change in entropy of the gallium? The melting...

Homework Statement Premium gasoline produces 1.23×108 J of heat per gallon when it is burned at a temperature of approximately 400ºC (although the amount can vary with the fuel mixture). If the car's engine is 25.0% efficient, three-fourths of that heat is expelled into the air, typically at...

Im not satisfied with the answer: that's just what it is... Because it kinda doesn't explain anything. Please help me, anyone?

I have seen in a number of thermodynamics lectures that the entropy change of a system as it falls approximately isothermally from some height h to the ground is: ΔS = mgh/T (The proof basically has you conceive of a reversible process between the same two states where some upwards force acts...

Homework Statement S(E,V) = kln(\Gamma(E) )\\ S(E,V) = kln(\omega(E) )\\ S(E,V) = kln(\Sigma(E) )\\ S entropy, k Boltzmann's constant. Prove these 3 are equivalent up to an additive constant. Homework Equations \Gamma(E) = \int_{E<H<E+\Delta}^{'}dpdq\\...

Combining first and second law of thermodynamics we can get the following equation TdS=dU-PextdV First question: Is this equation available for irreversible process that dS≠dQ/T? Second question:If the system temperature Tsys is smaller than the surrounding temperature Tsur, which...

The usual "proof" entropy is a state property is like that: "Consider a system which undergoes a reversible process from state 1 to state 2 along path A, and let cycle be completed along path B, which is also reversible. Since the cycle is reversible we can write: ∫1-2 δQ / T + ∫2-1 δQ / T...

Hello guys, I was watching video about physical basis for arrow of time.. ..as well as several other videos and articles about physics of time. I am puzzled with this picture here (seen in 35:07 in video above)...

I'm having trouble getting my head around entropy. In an isolated system, entropy can only remain the same or increase. Is this the same for a thermodynamics cycle? What I mean is, if I drew a cycle on a PV diagram, would the entropy keep increasing? I can't see how that would work, that would...

When: - Vacuum had an absolute mass, relatively limiting expension of all universal matter - Newton's second law could be overridden or negated - [Anything else I couldn't think of]

I am presented a review of data which gives: vapour pressures of a liquid have been measured and fit to the following equation: Log10 (mmHg) = -3571/T + 8.999 The melting point has been determined to be 392.7 K. A Cp value given for the liquid is 250 J/mol K and the ΔSvap is 117 J/mol K...

Homework Statement Homework Equations The Attempt at a Solution I don't know what is the difference between the change in entropy of the gas vs the thermal reservoir??

1) What is the reason why dH!=0 for an adiabatic(q=0) reversible process? The mathematical argument is irrefutable and it is clear that it has to do with the process not being isobaric: ΔH=ΔU+PΔV+VΔP , ΔU=work=−PΔV Therefore, ΔH=VΔP and this is not 0. However, I do not understand it...

Hello. I was reading Hyperphysics website and could not get one particular part. I am providing a picture of the equation I am having trouble with: http://i.snag.gy/W3CC3.jpg The particular part that puzzles me is the relation around the third equation sign. From the formula there one can think...

Homework Statement From the 2nd TD law: TdS= d(\rho V) + P dV - \mu d(nV) find that: S= \frac{V}{T} (\rho+P- \mu n) Homework Equations \frac{dP}{dT}= \frac{P+\rho - \mu n}{T} The Attempt at a Solution TdS= d(\rho V) + P dV - \mu d(nV) TdS= d[(\rho+ P- \mu n) V] -...

Homework Statement Vapour pressures of a liquid have been measured and fit to the following equation: Log10 P (mmHg) = -3571/T + 8.999 The melting point has been determined to be 392.7 K. A Cp value given for the liquid is 250 J/mol K and the ΔSvap is 117.20 J/mol K Homework Equations...

We Now From Information Theory That Entropy Of Functions Of A Random Variable X Is Less Than Or Equal To The Entropy Of X. Does It Break The Second Law Of Thermodynamic?

Homework Statement vapour pressures of a liquid have been measured and fit to the following equation: Log10 (mmHg) = -3571/T + 6.124 The melting point has been determined to be 392.7 K. A Cp value given for the liquid is 250 J/mol K and theΔSvap is 117 J/mol K Homework Equations...

Homework Statement The vapour pressures of a liquid have been measured and fit to the following equation: Log10 (mmHg) = -3571/T + 6.124 The melting point has been determined to be 392.7 K. Calculate the standard entropy of the liquid at the melting point. Homework Equations...

No heat exchange is facilitated during an adiabatic process. Change is heat is zero. How does this relates to the entropy being zero? ∫dQ/T? But this could really just mean that the integral is of any constant.

okay so I suck at La-Tex so I'm not going to put the actual equation, but it's not important for my question. In the equation the entropy is dependent on the natural log with mass in the numerator of the argument. Why is mass involved when talking about entropy at all? I mean I think of...

I have a short question which I have been discussing with a fellow student and a professor. The question (which is not a homework question!), is as follows: If you shift all the energies E_i \to E_i + E_0 (thus also shifting the mean energy U \to U + E_0), does the entropy of the system remain...

Calculate the change in entropy of the Universe as a result of the following operations: (a) A copper block of mass 0.4kg and thermal capacity 150JK-1 at 100◦C is placed in a lake at 10◦C. dS=dQ/T dQ=mCdT Tried simply combining these equations and integrating to find change of entropy of...

Hello, I am looking for some clarity on the second law of thermodynamics. I am an amateur physics student and only just beginning and so my understanding is currently very basic! I have watched Brian Cox's Wonders of the Universe, where he talks about the second law of thermodynamics being...

Homework Statement Suppose we put N atoms of argon into a container of volume V at temperature T. Of these N atoms, Nad stick to the surface, while the remainder Ngas = N - Nad form an ideal gas inside the container. Assume that the atoms on the surface are not able to move and have an...

There is one paragraph that says: " Our starting assumption is directly motivated by Bekenstein's original thought experiment from which he obtained is famous entropy formula. He considered a particle with mass m attached to a ctitious "string" that is lowered towards a black hole. Just...

Hello Homework Statement From the expression of the partition function of a fermi dirac ideal gas ln(Z)=αN + ∑ ln(1+exp(-α-βEr)) show that S= k ∑ [ <nr>ln(<nr>)+(1-<nr>)ln(1-<nr>) Homework Equations S=k( lnZ+β<E>) <nr>=-1/β ∂ln(Z)/∂Er <E>=-∂ln(Z)/∂β The Attempt at a Solution I...

1.0 mol of N2O4 placed in a constant pressure vessel at P = 1bar and T = 298 K. The system is allowed to slowly (reversibly) come to equilibrium. Given gibbs energy of formation, enthalpy of formation and entropy (the values are below) calculate the entropy change to the surroundings. N2O4...

Homework Statement Four moles of an ideal gas expands at constant temperature until its pressure is reduced to half of its initial value. What is the change in entropy of the gas? Homework Equations ΔS=Q/T (For constant T) pinitial=p pfinal=.5p Q=W W=pdv nrTln(vf/vi) The Attempt...

Any state analytic in energy (which includes most physical states since they have bounded energy) contains non-local correlations described by the Reeh-Schlieder theorem in AQFT. It is further shown that decreasing the distance between wedges will increase the entanglement as measured by a...

Homework Statement a)A stone at 400K with heat capacity ##c_p## is placed in a very large lake at 300K. The stone cools rapidly to 300K. Calculate the entropy change, due to this process, of the stone and lake. b)An insulated cool-box of a Carnot refrigerator at temperature T loses heat...

Homework Statement For a box containing 1m^{3} of nitrogen at S.T.P., estimate the number of microstates which make up the equilibrium macrostate. Homework Equations S = Nk_{b}(ln\frac{V}{N} + \frac{5}{2} + \frac{3}{2}ln\frac{2πmk_{b}T}{h^{2}}) where the entropy of a volume, V ...