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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How can hot water dislodge stuck objects on a flat surface when cold water can't?

The question Why does hot water clean better than cold water? is almost what I want to ask but it focuses on small particles and oil. I just washed a vegetable knife which had a piece of vegetable ...
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Is this hot tub working? [closed]

everyone.I meet an interesting hot tub-wood fired hot tub.It use a stainless steel coil to burn wood and thus heat water,like this article: https://www.smartclima.com/stainless-steel-coil-heat-...
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Ideal Vacuum Stirling Engine

Under an ideal pressure to prevent water just below from changing to gas, can water in a container in space to boil in the sunlight causing water to move to another container in an, ideally shaped, ...
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Why doesn't a moving object spontaneously slow down and heat up? [duplicate]

This may seem like a silly question. Imagine an object moving at uniform velocity in isolation. Since this is an isolated system, the total energy (kinetic + internal) will remain constant, according ...
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25 views

What would an information-lossy universe be like?

What properties of our universe depend on the nontrivial fact that information can't be lost? (Previously, I posed this question in terms of time-reversibility, which is a sufficient condition for no-...
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Does thermal equilibrium imply that a body can be approximated as a black body?

I have read this post and from it was my understanding that the definition of a blackbody is: Black body means a body which ABSORBS all wavelengths completely. After reading this answer on ...
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How do I calculate work done when change in enthalpy is given?

The question is $$C_2H_4(g)+H_2(g)\longrightarrow C_2H_6(g)$$ Where $\Delta H=-620KJ$. We have to find the pressure volume work done. How do I relate enthalpy and work? $$\Delta H=\Delta U+\Delta n ...
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66 views

Third law of thermodynamics - A contradiction?

The third law of thermodynamics states that a system in equilibrium has entropy $\to$ 0, as its temperature $\to$ 0, which essentially means the system is in ground state. However consider the case ...
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Internal energy change in isothermal process vs. adiabatic process with $\gamma$ approaching 1

This might be a somewhat academic question (since there's no gas with $\gamma = 1$), but I am still interested in this. Let's consider ideal gas and polytropic process with index $n$. We know, that ...
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Why does Wheeler's bag of gold solution contradict the holographic principle and a black hole does not?

The interior volumen of a typical black hole is greater than the one we expect when measuring its external area and calculating its volume: https://plus.maths.org/content/dont-judge-black-hole-its-...
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How to define non-equilibrium phase transitions?

I have some difficulty to understand how it’s possible to define phases and phase transitions of matter in non-equilibrium. My main issue is that most thermodynamics properties behave differently ...
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Definition of an ideal gas

Zemansky and Dittman's Heat and Thermodynamics (6th ed, p. 108) defines an ideal gas as one that satisfies the equations: $PV=nRT$ and $(\partial{U}/\partial{P})_T=0$. However, Rossini and Frandsen's ...
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What does crook's fluctuation theorem exactly say?

As far as I understand, entropy production fluctuation theorems such as crook's fluctuation theorem give an expression for ratio of probabilities of happening of forward event to backward event ...
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Entropy production in isolated system

My question relates to the stereotypical example for understanding the first and second laws: an isolated system filled with a gas of non-interacting molecules with constant ($E$,$V$,$N$) has two ...
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Irreversible, Compression and expansion work for a piston with ideal gas

How can we calculate the work done by the piston or on the piston by including the internal pressure of the piston and not the external one. Because if the external pressure is doing work, the ...
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Transmission of heat from fluid flowing through a pipe

If we hold a pipe, filled with almost scalding water (say 50 °C), does it make any different whether the water is flowing along the pipe and, if yes, at what speed?
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Splitting kinetic energy into micro and macro contributions

Reading J.N. Reddy - Introduction to Continuum Mechanics, the first law of thermodynamics is stated as $$\frac{D}{Dt}(K+U)=W+H$$ Where $K$ denotes the kinetic energy, $U$ the internal energy, $W$ ...
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Derivative expansion in hydrodynamics and the definition of the temperature

Thermodynamic quantities are well defined at equilibrium. a fluid at zeroth order can be approximated by a perfect fluid and conserved currents such as electric current and energy momentum tensor is ...
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Overall heat transfer coefficient

I'm trying to design a liquid fueled rocket engine, with copper walls cooled by kerosene. While designing it, the following formula comes out: $$Q=qA=wc(T-T(0))$$ Where: Q = total heat transferred ...
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1st Law of Thermodynamics, Newton's 3rd Law and the Work-Energy Theorem

I came across $ΔU=Q+W_o $ where $W_o$ represents the work done on the system. I also came across the formula $ΔU=Q-W_B$ where $W_B$ represents the work done by the system (gas). My question is, ...
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Is there any intuitive explanation as to why is entropy is a state function?

In my textbook there is a proof that entropy is a state function but there is no intuition given there. What is the intuition behind entropy(∫dQ/T) being a state function. Why would we have ...
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Why only isothermal and adiabatic for Carnot engine?

What is the reason behind choosing adiabatic and isothermal process for carnot engine? My book states the following reason. I am not able to understand it. It would be great if you could put it in ...
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Sign convention in thermodynamics [closed]

My approach The efficiency equals to W/Q1 where Q1 is the temperature of the source 1/10=-10/Q1 Q1=-100J (W is taken negative as work is done on the system) Now, Q1-Q2=W and solving this with ...
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Why are people capturing Carbon dioxide from the air? [closed]

I am not really sure if this is the correct platform to ask this question. In the recent times, there seems to have more discussion on how to combat global warming and one of the problem is to reduce ...
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How can wind feel colder than normal air if it has more energy? [duplicate]

So I asked my science teacher how wind could feel colder than normal air when the particles would be moving faster than normal air particles, meaning that they would have more kinetic energy and a ...
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First Law of Thermodynamics as a rate equation

In a standard engineering thermodynamics textbook (Fundamentals of Thermodynamics, Sonntag, et. al, 6th ed) the First Law of Thermodynamics is differentiated with respect to time, and written as a ...
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What is the equation of state for compressible liquid nitrogen?

So far I managed to find this. Are there any newer results?
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Change in entropy due to the change in volume

If its given that $N$ no of Ideal gas atoms are in $V$ volume. What will be the change in entropy in units of $N\cdot kb\cdot\ln2$ when the volume is increased fourfold, i.e. $V \to 4V$, keeping ...
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Ericsson Cycle - How to Calculate Heat Transfer

Let's consider a Ericsson Cycle with working body an ideal gas, e.g.: https://www.theengineerspost.com/ericsson-cycle/ I still haven't figured out how to calculate the heat transfer between process $...
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51 views

What about the grand canonical ensemble allows you to use it to describe quantum gases as compared to the canonical ensemble?

Probably an obvious question but this is my understanding so far: Ideal classical gas - gas where occupancy of an SPS <<1. Ideal quantum gas - cold dense gas where occupancy of SPS can be ...
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Increasing thermal efficiency in cooking pasta

Odd question, I know, please don't bash me. Hopefully somebody can help me get a better understanding on this matter. Pasta is usually cooked by dropping it in boiling water (either salting water to ...
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What are intuitive definitions of the 4 thermodynamic potentials?

So out of the 4 thermodynamic potentials only the internal energy seem to make intuitive sense to me. My understanding of enthalpy is that it is a state function which represents the total heat ...
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What is meant by the temperature of an atom? [duplicate]

Does it make sense to ask 'what is the temperature of an atom?'. Why not?
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Ideal gas cycle efficiency in $p$-$H$ diagram [closed]

We have a thermodynamic cycle of an ideal gas in a $p$-$H$ (pressure-enthalpy) diagram with known temperature $T_{1}, T_{3}$ and pressure $p_{1}, p_{3}$ (see the picture below). What is the ...
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Confusion with work done in isochoric process

So recently I've come up with this thought In an isochoric process, many books state that the work done is zero because there is no change in volume i.e. the gas isn't expanding nor it is contracting....
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How long will it take for a Schwarzchild Planck mass BH to evaporate? [closed]

My late-night calculations for the question "how long will it take for a Schwarzchild Planck mass BH to evaporate" predict 4.7 septillion years. I'm sceptical. Are my calculations true, according to ...
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About Feynman's treatment of entropy

Feynman said in this chapter that if a system absorbs (rejects) an amount of heat $d Q$ at a temperature $T$, then we say the entropy of the system increased (decreased) by an amount $dS=d Q /T$. And ...
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86 views

Conceptual block on energy transfer [closed]

I recently posted a question about energy transfer in oblique elastic collisions between equal mass balls, asking how much energy the slower ball can transfer to the faster ball. The correct answer ...
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51 views

Use of the solid angle in deriving the Maxwell-Boltzmann distribution

This is from a course in statistical mechanics, specifically the derivation of the Maxwell-Boltzmann distribution. We have an integral over the momentum space $$Z = \frac{V}{(2\pi \hbar )^3}\int d^3p ...
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Operation Of A Constant Volume Gas Thermometer

Concerning the mechanism of a constant volume gas thermometer, I was wondering how the adjustment of the second tube upon the open side increases the pressure. I know how the gas placed in the ...
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reverse osmosis membrane

We are second year cram schoolers , we are currently working on a project tackling water desalination by reverse osmosis and are required to do an experience. During the process, we encountered some ...
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79 views

Can regular air conditioner be used as heater? [closed]

In winter season, the normal room temperature is generally 6 to 10 degree Celsius, if the air conditioner is working at 25 degree Celsius will it be working as a heater, making the room warm (relative ...
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Surface temperature variation with distance [closed]

So here is the question I'm troubling with: We estimate that the temperature varies approximatively with that relation:
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Query about maximum temperature you can raise a block in an isolated system of 3 blocks [closed]

Set up: Consider an isolated system of 3 blocks: 1,2 and 3. At temperatures 100K , 300K and 300K respectively. The blocks all have identical properties other than temperature, i.e specific heat ...
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Does vapor latent heat depend on temperature? [duplicate]

Adding energy to water makes it's temperature increase. This continues until it reaches 100 °C (at 1 atm) when it turns to vapor with a vaporization energy of 2257 kJ/kg. But if we lower the pressure ...
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After I pour a cup of tea, I can't drink it for 10 minutes. Will it stay warmer if I add the milk at the start, at the end or does it not matter? [duplicate]

So preface, I work in engineering so I'm familiar with the basic principals of most fields in physics, but specialise in Civil Engineering so my knowledge of thermal physics is poor and I haven't ...
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Second-order partial derivative of Helmholtz Potential

So the lecture notes to my thermodynamics course contain this relation: $$\left(\frac{\partial^2F}{\partial T^2}\right)_{V,N}=-\frac{1}{\frac{\partial^2U}{\partial S^2}}$$ With no further explanation ...
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The first law of Thermodynamic in curved space

As we know, the first law of thermodynamic is $ dE=TdS-PdV+\mu dN $. is it true for a generic metric? what is the covariant form of this equation? for example, I think chemical potential and number ...
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Grunesian Parameter vs. Effective Debye Temperature

Both the grunesian parameter and "effective" debye temperature account for changes in lattice due to thermal expansion. Does this mean both can be used interchangeably? In other words, If I use an "...
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When we push on a wall, can we say work is being done on the atomic particles in contact with our hand?

Since textbooks say work is act transfer of energy, it led me to think of the following assumption: Work is being done on the the atoms in the wall, in contact with the hands, when we push (hard) ...