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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Why internal energy is considered as disordered energy? [closed]

Why internal energy is disordered energy? How can the kinetic energy of a system as a whole ordered?
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27 views

Energy contribution due to matter transfer

I have a very important question that lingers in my mind for a long time: In the fundamental relations of Gibbsian Thermodynamics, I simply don't understand how the last term appears. I have ...
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60 views

Good thermodynamics/statistical mechanics books that treat the apparent paradoxes in the theory

I am working on a small project mainly concerning the Gibbs and mixing paradoxes arising in thermodynamics/statistical mechanics. Still cannot find good literature on the topic. Any suggestions (I ...
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1answer
36 views

Under what conditions does Latent Heat hold?

Let us say I have a liquid of mass $m$ at its boiling point and add heat to increase to cause turn it all into a vapour. Under what conditions will the heat I actually add be equal to: $$Q=ml$$ Where ...
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2answers
95 views

Multivariable calculus and Thermodynamics

Somewhere in my thermodynamics text I read the following. $\left(\frac{dU}{dP}\right)_{V} = \left(\frac{\partial U}{\partial T}\right)_{V} \left(\frac{\partial T}{\partial P}\right)_{V}$ Is it ...
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1answer
59 views

how can we reduce the temperature below -60 degree celsius? [closed]

To reduce the temperature below -60 degree celsius. we have to do a project based on this subject.
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1answer
67 views

What actually makes boiling happen?

Boiling can be breezed over easily with a few rudimentary diagrams and a couple equations, but I seek a deeper explanation. The definition of boiling is that the vapor pressure in the liquid is ...
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5answers
86 views

When a gas is compressed by a piston, where is the heat added to the gas?

Suppose an ideal gas is being compressed by a piston inside a cylinder in an adiabatic compression process. Does the gas closest to the piston heat up first as the gas molecules collide with the ...
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1answer
37 views

Equation of state in General Relativity versus microscopic description of the fluid

I can't find the answer to the following question. Consider matter fields in General Relativity, assume it to be a perfect fluid. Then its equation of state is, by definition: $$ w=\frac{p}{\rho} = ...
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1answer
44 views

Filling of a gas in a cylinder

The problem statement is as follows: An insulated rigid vessel of volume $V$ initially contains $N_i$ moles of an ideal gas at temperature $T_i$. A pipe is now connected to the vessel and the same ...
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2answers
42 views

How could be modelled this heat transfer problem?

I have been puzzled the other day by a young boy who asked me about the phenomenon making that, when arriving to the shower, water is cold. Simple, isn't it? I started describing, in simple words, ...
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1answer
36 views

Liquid/solid to plasma?

During a phase change we can go from solid to gas via the process of sublimation. The diagram given below indicates that there is no analogous process for the transition from solid (or liquid) to ...
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23 views

How can I determine maximum efficiency of a process?(like Carnot did) [closed]

I was thinking about developing an "engine" for energy production from "waste". And then I thought why not develop it like Carnot did. So, is there any way I can develop the "most efficient ...
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28 views

Why there is no wall resistrictive to magnetic moment? [closed]

I was reading callen and in chapter 1 he mentions the need to a walls restrictive of energy. He notes that if such walls did not exist, quantitative study of energy will not be possible. Next in ...
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35 views

Thermodynamic derivation of condition for equilibrium of triple line

Edit:(4/1/2016) Okay, I get how the required equation arises from force balance. All forces are acting on the same length, so the length cancels out of the equation and what we've got is essentially ...
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32 views

Why dynamic equilibrium exists?

We know that at equilibrium Gibbs energy is minimum. We also know that at equilibrium both forward and reverse reactions occur simultaneously, and also we know that for a reaction to be spontaneous ...
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1answer
55 views

Statistical mechanics of ideal gas in a box with adsorption states on surface [closed]

Assume we have a cubic box of side length 1m with ideal gas particles inside. We assume the binding energy of a gas molecule to the wall is 1eV. One can make the simplifying assumption that: ...
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34 views

Derivation of a equation in closed, phases coexisting system

I'm trying to show that for a closed system consisting of two phases coexisting in equilibrium at a temperature $T$ and under a pressure $P$. $$(\frac{\partial P}{\partial ...
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1answer
43 views

Adiabatic expansion of ideal gas and dependence of temperature on volume

We know that for an ideal gas $$PV=nRT,$$ where $P$ is pressure, $V$ volume, $n$ amount of substance in moles, and $T$ the temperature of the gas. We can easily derive that, for a (non-free) ...
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1answer
36 views

Thermal Energy in a pV diagram

I'm studying for an exam in thermodynamics and therefore going through old exams, but I am stuck on one assignment. One kilomole of ideal monoatomic gas under standard conditions is processed ...
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23 views

Double check my understanding of the eventual state of the universe according to current theory

According to current orthodox physics theory, no energy is being created and put into the universe, and the universe's energy is finite. As stars like our sun expel energy in every direction, then we ...
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2answers
22 views

Thermodynamics Availablity why use surrounding pressure?

The formula for availability in thermodynamics is given by: $$A=U+p_sV-T_sS$$ Where $p_s$ and $T_s$ are related to the surroundings. I understand why we use the temperature $T_s$ instead of the ...
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45 views

What is the best material to use in a solar heater box to convert solar energy into heat energy?

Suppose you want to design a solar heater box with the dimensions: 1 sq meter x 30.48 cm H. 5 sides of the box's interior will be insulated and the interior will be totally black. Ideal glass will be ...
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3answers
43 views

How do you calculate oxygen temperature as atm pressure changes? [closed]

I know that when gases are decompressed the atoms suddenly have a bunch of space and absorb all the heat around them thereby giving the effect that it is cool but how do you calculate this for oxygen ...
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3answers
45 views

When can we consider temperature and pressure as two independent properties of a pure substance?

I thought that pressure and temperature were always dependent properties on each other.But is there any state of a surrounding or condition when these two properties behave independently of a pure ...
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1answer
72 views

Harmonic oscillator with heat bath

I need to calculate the expectation value for a harmonic oscillator coupled to a heat bath using the trace method. I know that the density operator looks like: $$\rho = \frac{e^{-H / k_B ...
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1answer
62 views

Compression vs. Friction - what happens when space objects enter earth's atmosphere

When reading about what happens when cosmic debris enters the earth's atmosphere, some sources say friction, others say compression. For example: On space.com it says: Meteor showers occur when ...
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1answer
51 views

How to calculate the entropy change in an adiabatic process? [closed]

A 2 cm long, 10 mm diameter and 1.5 kW electric heater is used to heat 30 kg water in an insulated container.The initial and final temperatures of the water are 25 C and 90 C respectively. Calculate ...
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21 views

Existence of statistical ensemble with fixed energy but varying volume

To me, every statistical ensemble in statistical physics was introduced beginning with the microcanonical ensemble, in which every microstate is equally probable. A canonical ensemble is described by ...
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1answer
79 views

how thermos flask get broken when subjected to cold water?

I saw my mother washing thermos flask with warm water. I ask to her why she do so. She replied: " because if you wash it with cold water, then may it get broken." I wondered how but she had no reply. ...
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2answers
48 views

Heat Losses from water pan due to vaporisation before boiling

I'm studying heat transfer from an electric heater to a cooking pan (Stainless steel) filled with water; specifically, my problem is related to water vaporisation, as I've already found good models to ...
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0answers
21 views

At what point does a cigarette stop burning [closed]

Temperatures of [cigarettes] reach 900°C during a puff and fall to about 400°C between puffs (Guerin 1987). Puffing burns the tobacco on the periphery of the cigarette, and tobacco in the core ...
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3answers
67 views

If an Ising model is in contact with two thermal reservoirs, would it still experience a phase transition if one of the reservoirs is below Tc?

For example; Two reservoirs are at each end of a one dimensional or even two dimensional lattice. One of the reservoirs has the temperature T < Tc. Would the lattice site have a phase transition ...
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1answer
84 views

Will physics ever be able to answer the question: “What caused the universe to come into existance”? [closed]

Or is this just the flip side of a metaphysical question "why does the universe not exist", if the opposite was the case and nothing existed i.e. a universe devoid of all energy, matter forces, ...
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2answers
64 views

Book recommendation for nonequilibrium thermo/stat mech

I'm doing an undergrad research project that lies at the intersection of biology and nonequilibrium thermodynamics, but I'm starting to realize almost none of my equilibrium thermo/stat mech knowledge ...
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2answers
76 views

What is polytropic index?

What is polytropic index? What is the connection between it and work of an adiabatic system? I tried surfing but didn't able to find a proper answer for that.
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55 views

Dissipative forces and reversible processes

A book that I have contains the following lines: For a process to be reversible, the dissipative forces such as viscosity and friction should be absent. My question is why?
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59 views

What will a glass look like in 500 years?

The glass is in a metastable state. It is changing constantly. So what will a piece of glass look like in 500 years in room temperature?
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In stochastic thermodynamics, can you define the notion of equilibrium for microstates/individual trajectories?

Recently there has been quite some research on interpreting statistical thermodynamical quantities at the level of microstates/individual trajectories. Although I did not find any ...
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4answers
142 views

Why do dark objects emit more than lighter ones?

For the purposes of this question, "lighter" and "darker" refer to the absorptive qualities of the objects. Darker objects absorb more light, and therefore appear darker. I'm trying to understand the ...
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1answer
25 views

Dilemma on work done by gas in isothermal contraction

Consider an ideal gas inside a cylinder undergoing reversible isothermal contraction. Now if we consider the forces acting on the gas inside the cylinder the force acting is $P_{ext}\cdot A$, however ...
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2answers
37 views

Stuck at Thermodynamics problem [closed]

So I was trying to solve this problem: "What is the pressure generated in the tramcar pneumatic pump tank, after blowing air 250 times, if the tank capacity is 30 liters and the pump takes 600 ...
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55 views

Reverse-engineering an equation of state

Suppose we have a fluid of some kind with a (let's keep it simple) barotropic equation of state: $p = p(\rho)$. Typically, I see that one starts with a function $p$ and $\textit{then}$ solves the ...
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10 views

Specific heat capacity for Adiabatic process

We can define infinite number of specific heat capacities between two temperatures(e.g $c_p ,c_v$) . Could we do that for an adiabatic process. As for adiabatic process heat addition or removal is ...
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1answer
65 views

Which thermal expansion coefficient to use?

I wanted to solve this problem: In a glass there is 1 liter water at $5^\circ\ C$. How much water will spill out when the system is heated to $85^\circ\ C$? Then I thought, OK I know $V_0$ which ...
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1answer
97 views

Has there been any experimental verification of Jeremy England's theory of dissipation-driven adaptation?

In this paper, Jeremy England discusses about dissipation-driven adaptation, which proposes a mathematical explanation for the origin of life. While there is almost general consensus on the ...
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0answers
56 views

Is it possible to trap hot air at 50 degrees for an year or more [closed]

I have this question that has been running in my mind for days now. Lets say i have some air which i have heated to 50 degrees Celsius. Is there a storage mechanism i can lock this air in and store it ...
3
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1answer
79 views

A mass falls to the ground from a height. What's the change of the entropy of the universe?

A mass $m$ falls to the ground from a height $h$. The temperature $T$ is constant. What's the change of the entropy of the universe? It's an example in Carter's Classical and Statistical ...
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56 views

How is Temperature and Pressure related to when a tire rolls on the ground?

Actual observation: Here in Canada it is known that even when 'dry' snow is on the ground, and when a car drives over it that small amount of dry snow instantly becomes ice (NOT GOOD). Anyways as an ...
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1answer
64 views

Thermodynamics equation that involves time? [closed]

There are principles in thermodynamics—e.g., that heat transfers from hot to cold—and equations like $$Q=mc\Delta T,$$ but is there any equation in thermodynamics related with time?