Entropy Definition and 999 Threads

How to calculate entropy from positions and velocities of gas molecules? lets say we have 2 different gases. entropy should be bigger after mixing them, than before when these are separated. But how to calculate exact entropies by knowing only positions and velocities of gas molecules?

A short background: My question focuses solely on the part of the refrigeration cycle to do with the compressor, where the cycle begins. The first state is before the refrigerant enters the compressor, and the second state is after the refrigerant leaves the compressor. My goal is to obtain...

Hello everyone, I have to write a paper about entropy and how it relates to the laws of thermodynamics, energy, and work. I have taken a deductive approach starting from the zero-th law to the second law of thermodynamics as follows. Entropy is the disorder of a system (Class Video, 2019)...

I'm kinda confused on the concept of entropy of everyday, low entropy states like macroscopic objects. It is said that the entropy is a measure of disorder, or distinguishability between macroscopic states. Can two objects which are macroscopically distinguishable/look different have the same...

According to Everett-interpretation or many world interpretation of quantum mechanics, each decision an observer makes, the world splits into two parallel universes, let’s say an observer in some point in Spacetime is tests the Schrödinger’s cat experiment, in one branch of the universe the cat...

for a)##\Delta S=\mp \int_{T_i}^{T_0}\frac{C(T)}{T}dT## and ##\Delta S_{th}=\int_{T_i}^{T_0}\frac{dQ}{T_0}dT## so ##S_{univ}=\Delta S_{th}+\Delta S##. What is ##dQ## equal to ? I don't know how to answer question b). Thank you for your help.

If you take a system with fixed entropy S0 and let it evolve, it reachs equilibrium. Let Ueq be the energy of the system at equilibrium. Now take the same system with fixed energy U=Ueq (S is not fixed anymore), how do you know that the equilibrium reached is the same as before, that means with...

I know that the entropy of a system is the same in different inertial frames. Is this still the case for non inertial frames? For example, is the entropy of a body as seen from a rotating reference frame the same as the entropy seen from a fixed frame?

A hypothetical question. Heat Q is transferred from water to a metallic solid. Both have same heat capacities and the same initial temperature. Now since molecules in a liquid are more randomly oriented than a solid, will the entropy decrease of the liquid be more than the entropy increase of...

Why when we supply energy for biological body then the body can keep entropy not increase?Because we know that by definition temperature equals partial derivative of internal energy to entropy.So that when temperature being constant,if internal energy increase(supplying energy for body) then...

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Dear admins and moderators, I am sure this subject has come up many times before, and could well be a stupid question. If so, could you direct me to the relevant thread(s)? Setting aside its itinerant electron, (Hydrogen Atom,) the Proton is THE building block of the Universe. "...Despite...

Hi. Processes involving a friction force whose direction somehow depends on the direction of the velocity, such as ##\vec{F}=-\mu\cdot\vec{v}##, aren't symmetric with respect to time reversal. If you play it backwards, this force would be accelerating. On the other hand, friction dissipates...

What is the entropy change of the system in the Gibbs Free Energy Equation? The general expression for entropy change is ΔS=q/T The only exchange between the system and the surroundings is ΔH done reversibly, with no PV work and no matter transfer, therefore q(syst) = ΔH(syst) therefore surely...

The text says: "Steel bullet of 25kg with a Temperature of 400 Celsius, is being dropped on the bottom of an oil liquid of 100kg at a temperature of 100 Celsius. The system is isolated. Calculate a) The change of entropy of the bullet, b) the change of entropy of the oil, c) the total change of...

What about if we allow for a temperature and volume change in a solid or a liquid? Would the entropy change still only depend on the temperature change or also on the volume change. For a solid I would think that the volume change doesn't matter since it doesn't change the "amount of disorder"...

Problem Statement: 1 kg of water at 273 K is brought into contact with a heat reservoir at 373 K. When the water has reached 373 K, what is the entropy change of the water, of the heat reservoir, and of the universe? Relevant Equations: dS=Cp*(dT/T)-nR*(dP/P) dS=Cv*(dT/T)+nR*(dV/V) I am...

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In a recent study (https://phys.org/news/2018-08-flaw-emergent-gravity.html) it has been discovered an important flaw in Emergent/Entropic Gravity because it has been discovered that holographic screens cannot behave according to thermodynamics... But then, doesn't this also invalidate...

The multiplicity of states for a particle in a box is proportional to the product of the volume of the box and the surface area of momentum space. $$ \Omega = V_{volume}V_{momentum}$$ The surface area in momentum space is given by the equation: $$p^{2}_{x}+ {p}^{2}_{y}+{p}^{2}_{z} =...

Although I've read many papers that propose a relation between action and entropy, I've been told that there is no generally accepted relation in physics. But how/why are these concepts unrelated? What about nobel laureate Frank Wilczek? He proposes that entropy and action are closely related...

So I get into these discussions on other ... less scientific ... fora, and then run into trouble and have to come here for correct answers. I state these as assumptions but they are really questions. Please correct. Entropy is usually applied in a thermodynamics context, but it can be applied...

If we reversed the second law of thermodynamics, and entropy decreased, and also managed to reverse the motion for all matter in the universe, so that in 24 hours, everything would return to the state it was at then, would time be said to be flowing backwards? Or would time still be flowing...

Hi, consider an adiabatic irreversible process carrying a thermodynamic system from initial state A to final state B: this process is accompanied by a positive change in system entropy (call it ##S_g##). Then consider a reversible process between the same initial and final system state. Such...

I tried following: $$ dS_{\text{total}} = |\frac{dQ}{T_c}| |\frac{dQ}{T_H}| $$ where ## T_h ## is temperature of hot water and ## T_c ## is temperature of cold water. Coefficient for water wasn't provided in the assignment so i used following value c = 4190 J/kgK. $$ dS_{\text{total}} =...

Help! Hi, I need in the secodn law of thermodynamic, we have the ENTROPY "S". Well, I need help for this: We have dS ≈ dQ Then we have dS = λ *dQ where we have λ = λ (T, ... ) I have to demostrate that : λ = 1/T , where T = temperature. Thanks for the advices and help!

I saw another post about dS = dQ/T, but the subject of question was different - not related to the entropy of universe. This is what i understand from this formula: As the temperature goes down, the entropy goes up. Is this not the opposite (contradictory) to what entropy (disorder) is about...

My understanding is that to define the entropy of a system what you have to do is as follows: Define the boundaries of your system. Define a set of "microstates" of the system. Define a partition of microstates of the system where each element of the partition is measurable and known as a...

Hi, I am also having problem with the assumption Entropy makes about the movement of molecules in a 3D space. Does it assume that gas molecules could have equal chance of going in any direction? If so then how is it possible outside a free-fall lab as Gravity bias would always make all the...

This is my first post and I need to preface my question by saying I have no physics background, so I'm genuinely asking for help in understanding. A thought occurred to me about the continuing expansion and acceleration of the universe and I'm asking for your help in understanding where my...

Hey guys, so I am reading this book and on pages 89-90, the author says: "Increasing temperature correspond to a decreasing slope on Entropy vs Energy graph", then a sample graph is provided, and both in that graph and in the numerical analysis given in page 87 the slope is observed to be an...

i don't really understand why S of the universe must be always positive,i know that only reversible process have constant entropy but why real proceses always increase S in the universe? sorry for bad english I am not from USA or UK

Homework Statement A gas sample containing 3.00 moles of Helium gas undergoes a state change from 30 degrees celsius and 25.0 L to 45 degrees celsius and 15.0 L. What is the entropy change for the gas (ideal gas)? For He, Cp = 20.8 J/k*mol Homework Equations ΔS = Cv*ln(Tf/Ti) + nR*ln(Vf/Vi) =...

Hi everyone, I have a few questions I'd like to ask regarding what I have read/heard about these two definitions of entropy. I also believe that I have some misconceptions about entropy and as such I'll write out what I know while asking the questions in the hope someone can correct me. Thanks...

If a reservoir is in thermal contact with a system, why is the entropy simply Q/T ? Shouldn't this equation only valid for reversible process? Why is it reversible?

Homework Statement [/B] What is the contribution of the conduction electrons in the molar entropy of a metal with electronic coefficient of specific heat? I can't figure out how to comprehend this, which relation/theory might lead to this? and How this answer is relevant to the point of molar...

There are two aspects of uncertainty (a) how far different from the situation where all possibilities are of equal probability (b) how spread out the values are. In discussions about (Shannon) entropy and information, the first aspect is emphasized, whereas in discussions about the standard...

I am still confused on what exactly entropy is, any help?

I never really understand the concept of entropy through classical thermodynamics. Here are a few questions. 1. The change in entropy dS in an isolated system is always >=0, but how does it imply the system tends to a state with maximum entropy? How to know that there exist a maximum? 2. Why is...

Homework Statement 2.Relevant equations[/B]The Attempt at a Solution How does a reversible process in the universe imply the entropy doesn't increase? I understand that the change of entropy in a closed reversible cycle is 0 in the system, but I don't get why a not closed reversible process...

Sir Roger Penrose in his book Cycles of Time on page 19 states the result of a calculation of probability of mixing red and blue balls as an illustration of entropy as state counting and the Second Law. He assumes an equal number of each. There is a cube of 10^8 balls on an edge subdivided into...

Many people talking about there are similarities and common positions in quantum entaglement and superposition with entropy. I need to know about this phenomenon

Hello, The state | W \rangle = \frac { 1 } { \sqrt { 3 } } ( | 001 \rangle + | 010 \rangle + | 100 \rangle ) is entangled. The Schmidt decomposition is : What would the Schmidt decomposition be for | W \rangle ? I am also intersted in writing the reduced density matrix but I need the basis...

1. Homework Statement if a rigid adiabatic container has a fan inside that provides 15000 j of work to an ideal gas inside the container, does the change in entropy would be the same as if 15000 j of heat are provided to the same rigid container (removing the insulation)?2. Relevant equations...

My background is that I'm an applied mathematician and engineer, self-taught in GR and QFT. It's an old idea, in some dozen or so SciFi books. But I'm looking for a mathematical framework for handling it. The second law of thermodynamics, that entropy always increases in a closed system, can be...

Imagine there is an radiation concentrator (winston cone) surrounded with extremely many layers of foil for radiation insulation, except at the smaller opening. Every part of the setup is initially in thermal equilibrium with the surroundings. The amount of thermal radiation flowing through the...

Hi, Could you please help me to clarify a few points to understand entropy intuitively? Entropy is defined as: Please have a look at the attachment, "entropy111". Source of attachment: http://faculty.chem.queensu.ca/people/faculty/mombourquette/chem221/4_secondthirdlaws/SecondLaw.asp The...

Homework Statement When the air outside is very cold and dry, your climate control system must humidify the cabaret air so that the singers don't lose their voices. The climate control let's pure water evaporate into the dry air and raises the moisture content of that air. As this evaporation...

Homework Statement During the fall, the outside air's temperature is comfortable but its humidity is too high for direct use inside the cabaret. The air feels clammy and damp. So your climate control system chills the outdoor air to extract some of its moisture and then reheats that air back up...