Questions tagged [thermodynamics]

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

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Derivation of the velocity distribution function in kinetic gas theory

I'm reading a book and got stuck at how one formula during the process of deriving the velocity distribution function. $$ \Omega\left(v_{x}, v_{y}, v_{z}\right)=f\left(v_{x}\right) f\left(v_{y}\right) ...
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Coupling engines together

Annoyingly, I once found a paper about this, but I cannot locate it after several hours. Hopefully someone can help. Imagine I have a hot reservoir and a cold reservoir. Rather than connecting these ...
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Energy balance paradox

Consider a closed system consisting of a room surrounded by walls at temperature $T$ (infinitely big, so $T$ remains fixed). In this room, we place a power source with a wire of a particular material, ...
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How much energy i need to convert 100 gramm of sand to 100 gramm of water

As I understand, at least in theory, we can disassemble matter to some basic particles, and assemble these particles back to something another, the whole process will cost energy for me. So question. ...
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Overall pressure and movement in Earth making heat because of gravity

my last account was deleted so don't get mad if this is a duplicate. There are three sources of heat in the Earth's core, impacts of the planet when it was created (impacts made heat), radioactive ...
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Why is the probability of a microstate independent of its energy in Boltzmann statistics?

Intuitively, I would think that the bigger the energy, the less probable it is to have a particle in this microstate, but Boltzmann hypothesis is that the probability of all microstates is the same. ...
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Time in the second law of thermodynamics versus relativity [duplicate]

I recently had a debate with someone about time and argued that the most concrete definition of time would be an increase in entropy. The entropy of a localized area of space might reduce, but that of ...
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41 views

Gravity creates heat?

There are three sources of heat in the Earth's core, impacts of the planet when it was created (impacts made heat), radioactive decay of elements, and the extreme amounts of pressure and friction ...
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Derivation of Perturbation Terms in Thermodynamic Perturbation Theory

In the "A critical evaluation of perturbation theories by Monte Carlo simulation of the first four perturbation terms in a Helmholtz energy expansion for the Lennard-Jones fluid" paper by T. van ...
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3answers
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Boiling water on gas stove

Does boiling water really heats room faster than just gas stove? I know that is not true, but I need some more detailed explanation.
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Are neutron star cores thought to be stiffer than photon gases?

The weak energy condition allows anything from -1 to 1 (meaning that the magnitude of the pressure can be at most equal to the density). Cosmic inflation and dark energy are very close to the limit of ...
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Partition function of a two level system

So I have a system made up of $N$ indistinguishable fermions that interact with each other. Also, the system is made up of two energy levels, and their gap is $D$. Therefore, trying to write down ...
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How does Cosmic microwave background radiation provide temperature to the outer space?

We define temperature as average kinetic energy of atoms. We know that outer space has vacuum that is it lacks matter and hence the temperature should be 0 K. But because of CMB radiation, the ...
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The driving force of entropy

In Gibbs free energy, entropy is treated as a sort of energy. The increase of entropy can generate work and release energy. However, normally energies are associated with actual forces. Light is due ...
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Does the equation of state include all the possible states that a system can exhibit?

For a given amount of a chemically defined homogeneous fluid, the equation of state is often represented as $$f(p, V, T) = 0.$$ But, does this include all the possible states that the fluid can be in?...
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Temperature relation to Gibbs free energy

The equation to calculate gibbs free energy includes the absolute temperature of the system. However isn't it the energy needed to raise temperature independent of the initial temperature? Why does ...
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Is hot oil more harmful than hot water? [on hold]

I would like to know the medical influence of hot oil and hot water in comparison. Maybe another place is suited better but I think the reasons can be better explained from a deeper understanding of ...
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Did R. Feynman know about the different notations for exact and inexact differentials? [on hold]

I remember reading a long time ago, the story of a student taking R. Feynman for responsible of her (I think it was a woman, not sure though) fail at an exam of physics because what was written in her ...
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Limits to natural convection in a non-infinite medium

I'm trying to understand the temperature profile of a fluid in an underground vertical pipe without flow. The fluid is subject to a boundary condition of the form: $$Q = h[T_e(z) - T],$$ where $Q$ ...
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What is a total multiplicity of particles in box? [on hold]

Consider two systems: A with 10 particles and B with 4 particles. In both systems, each particle has two possible energies $\epsilon = 0$ or $\epsilon = 1$. (a) Suppose UA $= 2$ and UB $= 2$ ...
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Is the entropy a concave function of the number of particles $N_j$?

Suppose we have a thermodynamic system which has $c$ components and the number of particles of each component are $N_1\cdots N_j\cdots N_c$. Suppose that the only work coordinate is $V$. Then, ...
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Undamped reflection of soundwaves in a medium of maximum (thermal) density, possible? [on hold]

Looking for both experimental results in setups similar to further described and/or a solid theoretic counterargument, to the supposition. The counterargument could be mounted against the sub-...
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Entropy in the SYK model

Reading about the SYK model I encounter a trick that should help to calculate the thermal entropy of the system. I am not able to understand what they are doing though. Particularly the part from eq....
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2answers
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How do you define volume for gases? [on hold]

Straight forward question. If atoms forming a gas float far from each other, how can we assign a volume to it? if it is in a container, perhaps we'd say the atoms, or molecules, reach every corner and ...
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Is it possible to calculate the skin temperature of an object passing through a gas?

If you have an object passing through a gas at a certain velocity, is it then possible to calculate the temperature of that object using properties like velocity, density, mass and/or others?
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Paradox regarding phase transitions in relativistic systems

The main question I would like to ask is whether quantities such as density are dependent on the frame of reference. I have searched several forums and the answer is somewhat controversial. Some ...
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Why do things cool down?

What I've heard from books and other materials is that heat is nothing but the sum of the movement of molecules. So, as you all know, one common myth breaker was "Unlike in movies, you don't get ...
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What value does the specific humidity obtain when all the mass being considered is water vapor?

I am working on creating a dynamic model of a condenser for a steam turbine and was entertaining the idea of using specific humidity to determine the point at which the steam condenses, $$\omega = \...
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if we could simulate every particle of the universe that we could discover? [closed]

If we could simulate each particle (take a snapshot of the universe) on a computer what could we do?
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Calculating resulting force in a medium from a nuclear weapon's shock wave

If the mass of the fission products produced by the reaction is equal to some quantity (say, 4*10^-4 grams for an ultra-small device) and the energy released by the detonation is equal to 10 MWth (...
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Is my understanding of physics/ my theory possible? If not, why? [closed]

WARNING: LONG POST, PLEASE READ ONLY IF YOU HAVE TIME I was never a fan of particles and Einstein’s time dilation. It just does not seem right to me that forces have speeds and mass - attributes ...
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Filling of empty tank with gas/liquid reference problem

Let's say we had an empty insulated tank with no non PV work involved and a liquid/gas is injected into it via a pipeline whose temperature and pressure remain constant. So via energy conservation ...
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117 views

Was Chernobyl Explosion a Small Nuclear Detonation?

The Chernobyl reactor was designed to produce a maximum of 3.2 megawatts of power. It is now estimated to have produced 3.2 gigawatts of power in the final second of its life. The original ...
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Understanding radiation of objects

I am trying to understand Greenhouse effect. I have heard that during the day the earth absorbs heat from the sun and during the night it looses heat in the form of infrared radiation. Does earth ...
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Gibbs theorem and partial molar volume

In the above, it's mentioned that any quantity other than MOLAR VOLUME can be written that way. But how can we say generalize it with certainty when molar volume itself doesn't fit in or to say any ...
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How much hydrogen does Earth lose in an hour? [closed]

CONTEXT: Escape velocity is the minimum speed needed for a free, non-propelled object to escape from the gravitational influence of a massive body. The escape velocity from Earth is about 11186,1 m/s. ...
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Conservation of energy violation Convection currents [closed]

There are three sources of heat in the Earth's core, impacts of the planet when it was created (impacts made heat), radioactive decay of elements, and the extreme amounts of pressure and friction ...
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Thermodynamics equation of state [closed]

Please help with my physical chemistry question.
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Temperature of an opaque body with known reflectance

Assume we have an opaque body, irradiated from all sides with a spectral irradiance $E(\lambda)$ [W/m2]. Furthermore, we know its reflectance $R(\lambda)$. (It's in vacuum, and in no thermal contact ...
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How much time it will take to reach equilibrium temperature on mixing of air? [closed]

1 cubic meter of air at Temperature 20 degree Celsius and 20% humidity is mixed with 1 cubic meter of air at Temperature 30 degree Celsius and 15% humidity. How much time it will take to reach ...
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Doubt about Entropy of solar radiation on Earth

This paper $[1]$ gives the following statement: On Earth, the low-entropy energy is provided by solar radiation and the high-entropy energy is disposed as infrared radiation emitted into the cold ...
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Deriving simple equation for volume and pressure, adiabatic exponent

I have $$VT^\frac{f}{2}=\text{constant}\tag1$$ and $$V^{\gamma}P=\text{constant}.\tag2$$ Where $V=\text{volume}, \ P=\text{pressure} , \ T=\text{temperature},$ $f=\text{number ...
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Thermodynamic planks temperature [duplicate]

There is a limit of temperature that is about $0$ K = $-273.15$ $^\circ$C. Is there any maximum limit?
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Potential energy of an ideal gas

According to equipartition theorem, for ideal gas in thermal equilibrium, each vibrational mode will get $kT/2$ for kinetic energy and $kT/2$ for potential energy. But at the same time, we assume ...
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Calculate the change in the helium's energy content a process

Imagine some helium in a cylinder with an initial volume of 1 liter ant initial pressure of 1 atm. Somehow the helium is made to expand to a final volume of 3 liters, in such a way that its ...
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Unit confusion - How Pressure and Volume combines to Joule

Imagine some helium in a cylinder with an initial volume of $1$ liter ant initial pressure of $1$ atm. Somehow the helium is made to expand to a final volume of $3$ liters, in such a way that its ...
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55 views

Efficiency of a reversible thermodinamic cycle

1 mole of ideal monoatomic gas completes a reversible ABC cycle, in which AB is a VOlume constant tranformation, BC an adiabatic expansion(Q=0) and CA an isotherm(Temperature during tranformation is ...
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So what, exactly, is latent heat?

I am given to understand that the energy is stored in the molecule in the form of changes to bond angles. With water, the bond angle between the hydrogen atoms changes by a degree or so during ...
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What does it mean for the grand potential $\Phi$ to be minimised for a process at constant $T,V,\mu$, when $\Phi$ is a function of $T,V,\mu$?

I've read from a few places like Kjellander, R. (2019). Statistical Mechanics of Liquids and Solutions: Intermolecular Forces, Structure and Surface Interactions Volume I. p.83. and this Physics Stack ...
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Real world heat transfer?

I would appreciate it if someone can advise me if my idea of heat transfer is correct. I would like to transport frozen products and below is my idea of insulating them. From what Ive found online ...