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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Accessibility by reversible processes and the Second Law of Thermodynamics

One common way of motivating the existence of Entropy as a state function is the following. Let us take the Clausius/Kelvin-Planck statement of the second law, from which we can deduce Clausius' ...
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1answer
36 views

Water Boiling Time Calculator

Is there a way to calculate out how quickly a body of water will boil? My primary concern is to measure in relationship to different temperatures. For example, heat at 100 degrees Fahrenheit versus ...
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1answer
58 views

Why does wood go straight into ignition, while other materials melt first?

Background: I was cooking eggs (very difficult) with a plastic spatula which was not very good, so when I set it on the border of the pan it began melting. In order to keep cooking, I reached for a ...
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3answers
86 views

Is work done in isothermal process process greater than work done in isobaric process?

One of my friend was discussing today about the work done by ideal gases in three different processes. They are isothermal, isobaric and adiabatic. We googled to know about the differences between ...
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0answers
19 views

newtons law of cooling [closed]

I need help with this calculus problem i just cant get After 10 minutes in Jean-Luc's room, his tea has cooled to $43^\circ ~\rm C$ from $100^\circ ~\rm C\;.$ The room temperature is $23^\circ ~\...
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1answer
35 views

How to justify a thermodynamic cycle practically? [closed]

I have been working on some new thermodynamic cycle and was managed to create the formulation and the P-V diagram for it but when i showed my work to my professor he said that i am gonna have to ...
3
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1answer
35 views

Moving heat problem: instant toast?

Toast-making usually takes a couple minutes using something like a conventional toaster oven to brown the surface of a piece of bread, making toast. However, this duration may be inconvenient. What ...
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4answers
817 views

Would water, given enough heat, instantly vaporize?

(Please excuse the wrong usage of words, I'm not a trained physicist. Please point out any misuse.) So far, my understanding of water evaporating is the following: Water always evaporates, whatever ...
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2answers
59 views

Reversible processes in which mechanical or thermal equilibrium is not reached

The definition of a reversible thermodynamic process requires in any instant the mechanical equilibrium (equal pressures) and thermal equilibrium (equal temperatures) of the system in a quasi-static ...
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2answers
57 views

Change in entropy of thermodynamic environment during isobaric or isochoric processes

When an ideal gas follows a isobaric or isochoric transformation (no matter if it is reversible or not) I'm not sure what is the change in entropy of the thermodynamic environment. First of all, ...
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1answer
64 views

By how much does the temperature of a cool Cola can increase by condensation of the ambient moisture on its surface?

Assuming standard ambient temperature and pressure, how can we estimate the increase in the temperature of a typical, cool beverage can produced by the condensation of ambient moisture on its surface? ...
2
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1answer
94 views

Two conflicting forms of equation of state of non-relativistic gas

I've run into two conflicting derivations of the equation of state of a non-relativistic gas. However, the derivations of the relativistic equation of state of both sources agree. I think maybe the ...
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1answer
68 views

The exact mechanism of energy release durning bond formation on the atomic level

Image a situation: We have two atomic hydrogen atoms. We magically collide them together dead center and perpendicular. Each atom has exact amount of kinetic energy. We collide them with precisely ...
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4answers
326 views

Can we have air flow without air noise?

I want to have air flow in my room, but I don't want a fan to move the air because of the air noise. I think the noise comes from all air molecules going to the same direction. If I can move the air ...
4
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2answers
62 views

Boltzmann factor and ratio of number of states

When using Boltzmann factor for two states, we see that $$N_1/N_2 = \exp\left(\frac{h\omega}{k_BT}\right)\;.$$ Where $N_1$ is the number of atoms in state with lower energy $E_1$ than atoms in state $...
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0answers
48 views

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 ...
2
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3answers
133 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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3answers
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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0answers
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
34 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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2answers
55 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
132 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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2answers
52 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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4answers
418 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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2answers
38 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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2answers
163 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 outside into Atmosphere. How to find entropy production of opening the windows in the winter? ...
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2answers
63 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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4answers
62 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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2answers
35 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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2answers
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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32 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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3answers
64 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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1answer
73 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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54 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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0answers
63 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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2answers
54 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
53 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
65 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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20 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
29 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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35 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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0answers
67 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
166 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
794 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 ...
5
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0answers
106 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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0answers
50 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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1answer
55 views

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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1answer
59 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
57 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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1answer
95 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 ...