Covers the study of (mostly homogeneous) macroscopic systems from a heat/energy/entropy point of view. Maybe combine with [tag:statistical-mechanics].

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Mixed Gas Absorbtion

Consider a gas misture that contains two type of atom, A and B. The gas is in equilibrium at temperature $T$. If on the surface of the gas container there are M sites that can absorb an atom gas, and ...
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131 views

Work done by an ideal gas expressed as change in potential energy of fluid

I get confused in problems where it is necessary to evaluate the work done by a gas that someway moves a mass. I'll make an example. Consider the tube containing mercury and an ideal gas in A (...
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46 views

Work done on gas problem with movable set

I found two different version of an exercise where the work is considered in a different way. Consider a gas in a tank divided in two parts by a movable set. The set in $B$ is also movable. If a ...
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35 views

What is the heat transfer ability from a specific temperature to a solid surface area that changes according to ambient temperature?

I am looking for a formula to find the efficiency of using $55^\circ$ ground water to prevent a concrete pad with dimension of 14' x 28' from falling below $25^\circ$ Fahrenheit during sub freezing ...
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1answer
18 views

Water evaporation rate: temperature vs humidity

I have a hot tub which I keep at 100 degrees F, and the water has "a lot" of dissolved salts in it. If I leave it open, will it evaporate faster when it is hot and humid outside, or when it is cold ...
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52 views

Canonical partition function and counting

That's a silly silly question, so my apologies, but in this moment I could not reach out! Let's have a system made of a particle reservoir $R$, and a subsystem $S$. The total particle number is $N$. ...
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1answer
129 views

Starting from an expression of E(V) and P(V) for the Birch-Murnaghan's equation of state, is there a way of obtaining an expression for E(P)?

I have a function, an equation of state named the Birch-Murnaghan's equation of state, in which the Energy ( $E$ ) is a function of the Volume ($V$), where $E_{0}$, $V_{0}$, $B_{0}$ and $B_{0}^{'}$ ...
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45 views

In heat conduction, what does it actually mean to be in the steady state?

I have read about the method of heat conduction and I have some questions related to this topic: If I consider a metal bar and supply heat in one end, the heat will flow through the bar and if I ...
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372 views

Is information entropy the same as thermodynamic entropy?

Context In one of his most popular books Guards! Guards!, Terry Pratchett makes an entropy joke: Knowledge equals Power, which equals Energy, which equals Mass Pratchett is a fantasy comedian ...
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37 views

Calculating the Total number of States for a microcanonical system

Please note before flagging, I do not need help solving as the math is simple algebra. Where I am lost is understanding what the math means and why/how it is applied. Problem 2.4 from Reif ...
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41 views

How to find entropy production of opening the windows in the winter?

Every time you open the windows in the winter (to bring in healthy and fresh air), room's warm air goes to Atmosphere. How to find entropy production of opening the windows in the winter? where the ...
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57 views

Which one is better at keeping you warm? [closed]

Does Glass feel warmer during winter when you keep your feet on it or Wood?
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52 views

Heat Developed in a Resistor

What does the graph that represents the total heat developed from time t = 0 by a resistor carrying a steady current look like (where heat is on the y-axis and time is on the x-axis)? The answer ...
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30 views

Heat Production in a Current Carrying Wire

The rate of heat production in a wire carrying an electric current is proportional to... The answer is meant to be current with a power (e.g. the square root of current, just current, current ...
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40 views

What is the region of instability of a reduced equation of state?

What is the region of instability of a reduced equation of state? I'm asked to give the region of instability given a reduced equation of state, $$\ln\left(\sqrt{\dfrac{\widetilde{p}}{\widetilde{T}}}\...
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29 views

Calculate the heat transfer for system expands over a straight line

Exercise 7.4-23 "Thermodynamics and an Introduction to Thermostatistics", Herbert B.Callen, 2nd Edition 1985. A system expanded along a straight line in the $P-v$ plane, from $(P_0, v_0)$ to $(P_f, ...
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63 views

Flame shape and size(length) depending on gravity

How would the shape and size of a flame(from a simple candle for example) depends on the gravity? Suppose all the relevant information is known, like candle dimensions and its chemical composition, ...
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68 views

Conservation of energy in the form of y=kx +b?

I am doing an experiment on method of mixtures and specific heat capacities. During my experiment I have to use the graph as a means of finding the SHC of the subject. So I did the experiment with ...
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26 views

Would a black copper bowl full of water in a hot, sunny room absorb enough heat to evaporate the water?

I'm looking at making my conservatory more humid, it gets a lot of sun and gets very, very hot. If I were to put a black copper bowl in the room full of water would this be a good metal for ...
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19 views

Change in volumetric energy density

I we have an insulated system (i.e. $dQ = 0$, where $Q$ is the heat), then the first law of theormodynamics says $$dU = -pdV.$$ If there system changes volume while there are no other sources of ...
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49 views

Classical Grand canonical partition function derivation

Consider a classical grand canonical ensemble. Let $S_r$ be the reservoir entropy. Suppose it could be expanded at first order: $$S_r \approx S_r(E_t,N_t) + \frac{\mathrm dS_r}{\mathrm dE_i} \cdot ...
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62 views

Definition of heat that does not produce a cyclic argument?

If we are going to define (empirical) temperature from the zeroth law, we need a definition of heat that does not depend on the concept of temperature, else this would produce a cyclic argument. ...
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52 views

How does hot air act in zero gravity?

In an environment with gravity, hot air is less dense than cool air, so it rises. How does hot air interact with cold air in a zero gravity environment, in terms of movement? Does it just stay where ...
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1answer
41 views

Ohnesorge Number - why square root?

I understood the Weber number, but why would the Ohnesorge Number go like this: $$Oh = \frac{\text{viscous forces}}{\sqrt{\text{inertia $\cdot$ surface tension}}}$$ Why the root? There seems to be no ...
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1answer
61 views

Where does energy go in the death of the Universe?

So I thought that energy can't be destroyed or created but can only be transformed into another kind of energy. I read something about the Universe dying because all the stars will burn out and the ...
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19 views

Liquid-vapor saturation curve

I am trying to draw the saturation curve for liquid-vapor region, but I don't have the exact equation. Can someone help?
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1answer
27 views

Why hair dryer can heat up the air (kinetic and internal energies)?

The energy of an object is the sum of the kinetic and internal energies. When a hair dryer heat up its coils, it transfer energy to air molecule via radiation. My understand is that Kinetic Energy ...
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28 views

Joule's “Work-Heat Equivalent” Experiment

I have been reading about the Joule's experiment that is supposed to have shown that work is the equivalent of heat. I can't really find the original paper and I am finding trouble understanding how ...
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62 views

How to calculate the minimum kinetic energy required by a surface molecule to escape the liquid (during evaporation)?

Evaporation occurs when surface molecules have enough Kinetic Energy to escape the surface of the liquid. Given a certain volume of liquid at a certain temperature, is it possible to determine this ...
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4answers
162 views

Does a reversible heat engine exchanging heat with an ideal gas that does a transformation imply that transformation is reversible?

Consider a reversible heat engine working between two sources. Suppose that one of the sources is a thermostat, while the other is an ideal gas which follows a transformation and exchanges some heat ...
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4answers
781 views

If an isolated quantum system consists of only one particle, is it possible for it to be in a mixed state?

Mixed states are defined as the statistical ensemble of pure states. Classically, I understand the word, "statistical" referring to a system with a large number of microscopic particles. So if I go ...
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90 views

A theoretical model for evaporation occurring when wind is blowing over the surface of water

I've recently done an experiment in which I was studying the variation of the cooling rate of hot water in a draft (wind). The air was blow directly over the surface of the water (kept in a ...
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48 views

Confusion on meaning of fugacity in scientific publication

in my research project in statistical mechanics, in the context of phase transition and condensation, I was reading the seminal paper of Yang and Lee titled: "Statistical theory of equations of state ...
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what is the physical significance of dielectric constant and loss tangent?

I want to know that the significance of dielectric constant and loss tangent behaviour. How it characterises the materials. and possible relation between the dielectric constant and polarisation ?
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52 views

Entropy and Clausius inequality

From the Clausius inequality we can derive that the efficiency of a Carnot (reversible) cycle is given by: $$e= 1 - \frac{T_c}{T_h}$$ Is this true for every reversible cycle? Is the efficiency of all ...
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1answer
56 views

Why can't "cold flow from an area of coldness to hotness? [duplicate]

Why do we always talk of heat flow from a hotter region to a coder region? Would it be wrong to say that cold flows from one place to another?
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75 views

The Zero Electricity Air Cooler : How does it work? [duplicate]

I have seen from a video and a website where they said that, temperature can be reduced by reducing the area where the air passes. But what theory can explain it more precisely? I guess this could be ...
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47 views

Average energy from Boltzmann energy distribution is not the same as average kinetic energy of an ideal gas:

The Boltzmann energy distribution represents the probability of a micro-state taking an energy E. It can be formulated as follows: \begin{equation} P(E)=\frac{1}{kT}\cdot e^{-\frac{E}{kT}} \end{...
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38 views

How do I calculate the amount of heat transfer to agitated air?

Suppose my room is x degrees C. The air in my AC ductwork is a constant y degrees C and is blowing at z m/s. We assume there is no heat transfer from the outside. How can I figure out how long it will ...
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1answer
28 views

Why did this ice explode?

After watching this video of molten copper poured on a block of ice, the whole thing kinda exploded. What would cause ice to explode when subjected to molten copper?
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21 views

Isochoric Kelvin Plank - Clausius Equivalence

As the Clausius statement is underpinned by the assumption that W=P.∆V Therefore ∆V=0 , W=0 Can anyone restate the Kelvin Plank-Clausius Equivalence Proof considering a solely Isochoric process ...
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2answers
61 views

What VOLUME does exactly the $V$ term in ideal gas equation represent?

According to kinetic theory of gases 'the actual volume occupied by the gas molecules are negligible in comparison to the volume of the container.' I believe that this assumption is significant ...
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69 views

Home Work Help: Calculating Entropy for Melting Ice - Clarification on answer

The question states: What is the change in entropy for the process to completely melt 8.0 kg of ice at 0°C? The formulas for Entropy we've been introduced to are: ...
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2answers
68 views

Difference between KE “relativistic” mass and heat mass

I have been told in several answers that the term "relativistic mass" is no longer considered adequate wrt. the mass/energy increase in KE. Yet, I read that 1 Kg of gold's mass ingreases by 10^-14 Kg ...
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22 views

How to convert relative humidity to humidity ratio [duplicate]

I wish to calculate the enthalpy of moist air using a formula which combines sensible and latent heat, specifically: $$h=h_a + x.h_w$$ where $x$ is the humidity ratio (mass/mass). However, I only ...
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2answers
47 views

Confusion on electron volt and Kelvin?

If an element A has a binding energy of X eV with element B, can it be said that it is equivalent to X*11600K as 1 eV approx equals 11600K. I do not think this is correct as temp. is linked to the ...
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Where does the free energy powering this device come from?

I encountered this problem in an IAP course at MIT back in 1971, presented by Prof Pritchard. You have a long tube, at one end of which is a semi-permeable membrane. This membrane allows water to ...
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39 views

Entropy change in mixture of two gases

I'm confused about the entropy change if two gases, initially separated, are mixed togheter in a rigid box. I use the following $$\Delta S_1= n_1 c_{v,1} \mathrm{ln}( \frac{T_f}{T_{i,1}}) + n_1 R \...
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1answer
86 views

Steady state heat equation intuition

I am learning a bit of fourier analysis, with an interest in physics as well. I originally posted this question on the math stack exchange, but perhaps you physicists have more experience in these ...
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1answer
64 views

Is zero heat capacity possible without violating the third law of thermodynamics?

Suppose we have a gapped system i.e. no gapless excitation is possible. If the thermal energy is insufficient to excite atoms from ground state to excited state of any kind (of a single atom or of a ...