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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Phase diagram binary mixture

The Gibbs Phase Rule states: F = C - P + 2. From this it is possible to construct a phase diagram. In case of a 1-component system C=1 and where P denotes the number of phases in equilibrium. In case ...
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31 views

Explanation of chemical potential

I made a NVT Lennard Jones Monte Carlo simulation. In this simulation I calculate the chemical potential of my system with $$\mu = \mu_{id} + \mu_{ex} $$ Where $\mu_{id}$ is the chemical potential of ...
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16 views

How to find the temperature difference over a specific plate given temperature difference between two plates?

I'm having trouble solving this question where two metal plates are in thermal contact with each-other. I'm given the type of metals in each plate, the thickness and the overall temperature difference ...
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23 views

Maximum work delivered by a heat engine

I've been solving some Thermodynamics problems and found this one: A thermal machine works between a tank containing a volume $V$ of water and a river at a constant temperature of $T_R$. If the ...
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26 views

Specific heat capacity for solids of changing temperature

I was reading the following post: If the specific heat capacity depend upon the temperature, what formula we should use instead of $Q=mc\Delta T$ and I understand that the total energy needed is ...
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22 views

Heat transfer with a small airgap - conduction v convection v radiation

I have a transducer approx 25mm dia x 25mm length which will sit inside a brass casing, but stood off from the walls by around 0.5mm. Obviously the brass is a far better conductor than the plastic of ...
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16 views

Why is the pressure value of an ideal gas for a fixed density and constant temperature of gas more than that of the same real gas?

I solved a question- Under what pressure will carbon dioxide have the density 500g/l at the temperature 300K? Carry out calculations for ideal and Van der Waals. On solving for pressure, I get For ...
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24 views

Consequences of $T_{sat}$ and $P_{sat}$ dependence

I understand that boiling point increases as pressure increases. This means that if you boil water at higher pressure it is going to need much more energy to break the bonds and thus boil at higher ...
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20 views

Sign convention when proving the equivalence between Clausius principle and the 2nd law

I have a question about sign convention of work and heat in a proof of the equivalence between Clausius principle and the 2nd law. My lecture note brings up a model where two heat engines are combined ...
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25 views

The driving force for first order phase transition

The driving force for the solidfication is said to be the free energy difference, but phase transition actually happens due to change of temperature toward the critical temperature. It seems that ...
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35 views

Violations of Onsager reciprocity?

As far as I understand it, the modern statement of Onsager reciprocity is that the linear-response transport coefficient matrix, when transposed, is equal to that of the time-reversed system (reversed ...
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Quanta exchange between 2 harmonic oscillators during an Otto cycle

The focus of my current studies lies on the "Quantum Otto cycle" (e.g. presented on the first pages of this paper). The "machine" as well as the "baths" are represented by harmonic oscillators. Both ...
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36 views

Turning Work into Thermal Energy in Joule’s Experiment

In Joule’s famous experiment where he determined the specific heat capacity of water, he used a paddle to increase the temperature of the water. That is, the kinetic energy of the paddle went into the ...
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33 views

Dissipation and first law of thermodynamics

Consider the following situation: a certain gas is contained in a well-insulated cylinder with a well-insulated piston head. Now, in this case the piston is not frictionless. In order for the piston ...
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28 views

Could Something Infinitely Heat Up?

If there was a perfect environment, and something was able to continue to heat up indefinitely, what would happen?.. What would be the outcome of something continuously heating up?
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41 views

Are there any liquid that becomes solid on heating under room temperature?

The title says it all. When I searched around, there are answers which involve extra steps like super cooling and then heating or exposing the liquid to high pressure. But I would like to know if ...
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30 views

Would High Explosive helped free Shackleton's ship, trapped in pack ice?

This question is based on physical concepts regarding presssure waves and crystallography, but I thought it might be helpful to include a brief historical context first. From Wikipedia: Loss of Polar ...
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23 views

Thermal imaging

If we have thermal imaging camera and the sound is wave is produced and propagates in hot air can we see the electromagnetic emission of molecules producing pressure packets of sound wave?
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56 views

Model of a heating system in an industrial hall

I want to model a heating system in an industrial hall. The system consists of: a heating plant, a pump, 2 pipes (each pipe is 500meters long) and a machine tool. The required heat for the ...
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27 views

Reason behind the heat capacity of water

Water has a high specific capacity. Why can water release a large amount of energy without a great change in temperature?
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208 views

Is there a limit to how hot an object can get?

If heat is the measure of how fast the atoms are moving in an object, than isn't there a limit to how hot that object can get as nothing can go as faster than the speed of light. So because the atoms ...
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307 views

Why is pyrite so explosive when heated? [closed]

I watched this video where fool's gold was heated using a hydrogen torch. The results were surprisingly explosive. I was expecting it to just melt into a puddle. Is there something special about ...
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19 views

Linear thermal expansion from statistical mechanics?

I came across a question recently regarding work done by an expanding metal and the origin of the energy used for the work, and most of the responses pointed the person to look more at the enthalpy ...
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21 views

Microscopic Definition of Heat and Work

If I am given a statistical System, then I can define state-variables like Energy, Entropy or other Observables, and then I can (at least for equilibrium states) give the Change of Energy as: ...
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25 views

Black body radiation curiosity

Wich one of the two cases will be more suitable A hotter body for instance candle with its flame with the pic in infrared region of emissivity will emit more microwave radiation or a colder one with ...
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21 views

Thermodynamic degrees of freedom of a wire

In Equilibrium thermodynamics by C.J Adkins he mentions an example about degrees of freedom of a thermodynamic system -- Very often for a simple system it is possible to say immediately that how ...
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17 views

Calculating optimal heat dissipation/air-flow out-of/into an enclosure - hole size vs number of holes

I am not sure if this is the right place to ask, but I figured it would be a physics question. Essentially I have an enclosure that I will be using to house the components to build a computer. I am ...
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Constancy of Coefficients of Additive Integrals Throughout Subsystems of a Closed System

I'm studying Landau and Lifshitz's Statistical Physics, Part 1, 3rd edition and am looking for clarification on the following statement, which appears on page 11 in the section on The Significance of ...
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41 views

Minimisation of thermodynamic potentials?

An alternative formulation of the second law is that the energy of the system $U$ is minimised if the temperature and entropy of the system are held constant. However, $$dU=TdS-pdV$$ which means ...
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Why does water feel cooler than air?

My first assumption was based on "evaporation causes cooling" but I realized that it is not the case as it is cooler even if I am submerged under it. Are all liquids generally cooler than air ? Just ...
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1answer
49 views

Reversible process, equivalence of two definitions?

There are two common definitions of a reversible process: A reversible processes is quasistatic with no dissipation. And A process where an infinitesimal change in conditions would reverse ...
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39 views

Adiabatic expansion on $(P,T)$ diagram

Consider a certain substance which is described by pressure $P$, volume $V$ and temperature $T$. In one thermodynamics exercise I was asked to draw one adiabatic expansion from $V_1$ to $V_2$ in a ...
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12 views

How the degrees of freedom for gas molecules affect energy

It seems a bit unclear to me how degrees of freedom help judge the amount of kinetics energy in the system. from the formula for the energy of molecule ε = u0 + (v/2)kT it can be inferred that the ...
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128 views

Ice in contact with a heat reservoir at $0^\circ \textrm{C}$?

Let us say I put ice starting at a temperature $T \lt 0^\circ \textrm{C}$, and held at constant pressure of $1atm$ in contact with an infinite heat reservoir at temperature exactly $0^\circ ...
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891 views

What leads to the existence of critical temperature?

We know that $T_c$ is the temperature above which no amount of pressure could force a gas to liquefy. But why is this? Somehow I don't buy the point that the gas molecules exert too much pressure ...
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48 views

What is the minimum energy a quantum can bear? …and more

Here are my assumptions: Energy can be transferred only in limited dosages. When two particles collide, they exchange energy, so that the more energetic particle carries less and the less energetic ...
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1answer
18 views

Derivation of Internal Energy of an Ideal Gas

I have so far derived that $$E_K= \frac{3k_BT}{2} $$ where $E_K$ stands for the average random kinetic energy possessed by particles of an average gas. Now we can take one step further by using this ...
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21 views

Calculating heat distribution along 1D line segment?

I want to calculate temperature distribution where the heating power of $P_0$ is uniformly distributed over 1D bar TO calculate, there is heat equation. $$ \frac{\partial T}{\partial ...
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1answer
30 views

How the mechanical equivalent of heat is employed in this situation?

Reading a little about the "mechanical equivalent of heat" what I understood is that we can convert units between calorie and $J$ by setting $$1\mathrm{\ J} =4.1860 \mathrm{ \ cal}.$$ Now, I saw a ...
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22 views

Energy inside a box of air with temperature variation

How to find the energy of a column of air enclosed in a box (assume adiabatic) with a temperature variation $T(z)$ in the vertical ($z$ direction) in a uniform gravitation field? I think the total ...
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37 views

Why do different color materal differ temperature in the same sunlight?

I have a blue, red, and green cup and put a thermometer in each. Of the 3 the blue cup had the coldest temperature inside, then green, then red. I understand there may be differences in the ...
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Radiative equilibrium in orbit of a black hole

According to Life under a black sun, Miller's planet from Interstellar, with a time dilation factor of 60,000, should be heated to around 890C by blue-shifted cosmic background radiation. How they ...
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1answer
24 views

Can a piston-like displacement be miscible?

I have a question regarding miscibility and piston-displacement of fluids. My question is as follows: I am given that a fluid is displaced miscible. At the same time, I am also given that the ...
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23 views

Relations between Maxwell-Boltzmann's distribution and the n-body problem velocities distribution

Solving the n-body problem numerically and finding the velocities distribution, one finds that it's quite similar to Maxwell-Boltzmann's velocity distribution. This is quite suprising because of the ...
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Confusion about the number of micro states and approximating it for large number of particles

Hopefully after reading the meta site, I can now rephrase the question as more relevant to this site, this is a question related to statistical physics: Let us suppose we are given a system with ...
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1answer
75 views

Ultraviolet catastrophe in a classical world

In the real world, the ultraviolet catastrophe doesn't happen because the quantization of photons modifies the classical behavior of light at frequencies comparable to and higher than the temperature. ...
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1answer
35 views

Gas/liquid pressure equilibrium of water in an exotic environments

So I'll preface this by saying this is not some evil homework assignment, this came about from some idle talk of colonizing the moon by a couple of software engineers when we realized we had no idea ...
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2answers
31 views

Emissivity and Final Temperature of a Black and White object

Objects can be categorized as blackbodies (emissivity $\epsilon = 1$), grey bodies (emissivity $\epsilon < 1$) and white bodies (emissivity $\epsilon = 0$). If we placed two objects (identical ...
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3answers
85 views

How is pressure kept constant in Charles' Law?

Generally, a piston is kept on top of a cylinder containing the gas. The gas is heated and it expands causing a change in the volume. I was wondering how might one keep the pressure constant. Websites ...
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79 views

How to make Temperature vs. Energy graph representing a phase change?

As we know that phase change graphs generally show a variation in the Temperature and time.The graph roughly looks like this. I guess that the shape of the curve will be the same. This is because ...