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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94 views

Deriving the Ideal Gas Equation

Im specifically looking at how the IGE can be derived from the kinetic theory of gasses. Most textbooks and webpages I've viewed start off with a wall that the particle is hitting and then writes an ...
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1answer
46 views

Cross-differentiation to derive the maxwell relation $\left(\frac{\partial T}{\partial V}\right)_S = -\left(\frac{\partial P}{\partial S}\right)_V$ [closed]

How can I use $T=\left(\frac{\partial E}{\partial S}\right)_V$ and $P=-\left(\frac{\partial E}{\partial V}\right)_S$ to derive $$\left(\frac{\partial T}{\partial V}\right)_S = -\left(\frac{\partial ...
3
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1answer
72 views

Quantum field theory: zero vs. finite temperature

I have recently been made aware of the concept of thermal field theory, in which the introductory statement for its motivation is that "ordinary" quantum field theory (QFT) is formulated at zero ...
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0answers
29 views

Enthalpy in MIT open courseware

I am watching Statistical Mechanics I in MIT open course ware. I have question on one of the lectures and I appreciate it if Mark or someone familiar with this topic can help me. (this is about ...
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0answers
14 views

Pressure and temperature in Nozzle

I'm trying to calculate the change in pressure per temperature in a chamber before a nozzle throat, which will choke the flow at M = 1. I have a linear increase in temperature from 300K to 2500K. I ...
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4answers
75 views

Why does heat engine need to reject energy to environment?

The most efficient thermodynamics cycle is the Carnot cycle, it involves 1/ Receiving heat from hot source, expanding and doing work on the surround 2/ Receiving work from environment, being ...
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0answers
29 views

Is quantum entanglement related to the thermodynamic equilibrium?

https://www.quantamagazine.org/20140416-times-arrow-traced-to-quantum-source "Today, Lloyd, Popescu and others in their field see the arrow of time differently. In their view, information ...
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2answers
48 views

Pressure exerted by ideal gas on walls of container

All derivations I've come across are more or less similar to this: All of them take total momentum change as $2mv_{x}$ and divide it by total time to get the force exerted on the wall. That seems to ...
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3answers
63 views

A relationship between entropy and temperature

I tried deriving a formula relating entropy (not change in entropy, but entropy itself) to temperature. I’ve only seen two equations really relating to entropy thus far, and only one of them includes ...
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3answers
53 views

What physical properties can't be predicted based on index of refraction? [closed]

If I tell you the real and imaginary parts of the index of refraction for all frequencies, name a property that can't be predicted based on that information. If you're assuming this is a gas, specify ...
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1answer
68 views

Statistical Physics: How do we derive this equation?

I'm reading through Statistical Physics by F. Mandl and there is a step in arriving at an equation that I don't follow. He uses $$P = \sum_r p_r \left(-\frac{\mathrm dE_r}{\mathrm dV} \right) ...
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1answer
61 views

What are the phenomena responsible for irreversible increase in entropy?

https://www.quantamagazine.org/20140416-times-arrow-traced-to-quantum-source This article says that entanglement drives the arrow of time of increasing entropy towards thermodynamic equilibrium: ...
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1answer
30 views

Is there a limit to the difference between the boiling and melting points of any material?

Is there a mathematical limit to the difference in the temperatures, a substance acquires before changing states, in this particular case, is there a limit to the difference between the boiling and ...
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0answers
20 views

Optimal two-stage warming up of a bottle of baby milk

Here's a common two-stage method to warm up a bottle of baby milk to avoid uneven milk temperature: 1) Heat up a bowl of water in a microwave oven. 2) Put the bottle into the bowl of heated water to ...
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3answers
788 views

Does electricity have an associated entropy?

One can certainly measure entropy changes associated with the generation of electricity, but does electricity itself have an associated entropy (maybe related to voltage, current etc.)?
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2answers
29 views

Calculating the time for two bodies to reach thermodynamic equilibrium

If we have two bodies a and b, with temperatures $T_a$ and $T_b$ respectively, with $T_a > T_b$ and we also know that body b is surrounded by body a completely. How do we calculate the relaxation ...
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1answer
29 views

Dalton's law of additive pressures

In a mixture of ideal gases, if the pressure of the mixture is doubled, what happens to the partial pressure of each gas? Please explain. Thanks a lot. We start with the expression for the pressure ...
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0answers
13 views

Can vaporization heat added to the whole volume of liquid before vaporizing it?

It seems, for example a volume of water is heated to boiling point, then part of the water is vaporized, while the remainder need much more heat to vapor, which means that part doesn't receive latent ...
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0answers
44 views

How much time it takes to boil water in a rigid body?

I have a question that bothers me. If we have a rigid container containing water at $P_1 = 1$ $atm$ and $T_1 = 25$ $C°$. If we add an electric resistance to heat the water inside, we go through ...
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2answers
69 views

Can first law of thermodynamics be explained in terms of entropy?

Can first law of thermodynamics be explained in terms of entropy? I am bit confused. I need help.
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0answers
21 views

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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0answers
30 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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1answer
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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0answers
22 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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1answer
25 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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0answers
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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1answer
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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2answers
23 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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0answers
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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0answers
23 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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0answers
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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0answers
20 views

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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2answers
35 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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1answer
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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0answers
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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0answers
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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1answer
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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1answer
22 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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1answer
55 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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0answers
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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2answers
201 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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1answer
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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0answers
18 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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0answers
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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1answer
23 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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1answer
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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0answers
15 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 ...
2
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0answers
18 views

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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1answer
38 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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3answers
2k views

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 ...