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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155 views

Physics of boiling an egg - what am I missing? (heat capacity and coagulation question)

Update: 1) I originally posted this because the numbers seemed to make no sense to me (seemed very counterintuitive to only need 60-100ml of water to cook an egg when you usually have to boil it ...
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4answers
46 views

Why work is done on the system in this case?

Consider the following situation: The system is the air contained within a bicycle tire along with a tire pump connected to it. The pump plunger is pushed down, forcing air into the tire. Assume ...
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1answer
83 views

Deriving Enthalpy from Stat Mech

One can derive all the numerous thermodynamic potentials (Helmholtz, Gibbs, Grand, Enthalpy) by Legendre transformations, but I'm interested in seeing each from Stat Mech instead (ie taking the log of ...
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2answers
37 views

Definition of atmosphere unit and relation to temperature and gravity

I've seem sometimes the atmosphere unit for pressure be defined so that $1\ \mathrm{atm}$ would be the mean atmospheric pressure at sea level. I've seem on the other hand the following definition: ...
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0answers
46 views

Why does cold air feel even colder when you are moving through it quickly?

My question is the following: Why does it feel colder (i.e. why does your body transfer more heat to the surroundings) when you are moving through the air at a high velocity, f.ex. when you are ...
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1answer
29 views

Relationship between thermal conductivity and reaching the steady temperature

The diagram is for three materials with 3 different thermal conductivities, i think the material with higher thermal conductivity is the number 1 because it transfers the heat much better so it gets ...
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1answer
45 views

The average value of the electric polarization of an ideal gas

An ideal gas consisting of $N$ molecules possessing an electric dipole moment $\mathbf{d}$, placed in a constant electric field intensity $\mathbf{E}$. Need to calculate the average of magnitude of ...
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3answers
113 views

Which is the second law of thermodynamics?

There are many statements. https://en.wikipedia.org/wiki/Second_law_of_thermodynamics#Various_statements_of_the_law But how do they say the same thing ? I don't understand. Why all of them are the ...
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2answers
102 views

Why rough surfaces promote nucleation of CO2 in carbonated drinks?

Glassware with scratched/etched surfaces generate more bubbles (video 1, video 2). Why these rough surfaces allow easier heterogeneous nucleation?
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1answer
30 views

Pumping water vapor into liquid water [closed]

Do liquid water and water vapor count as different types of matter? How does Second law of Thermodynamics apply when I pump water vapor into liquid water? What would happen when water vapor goes into ...
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1answer
30 views

Internal energy. Mechanics and Thermodynamics

Internal energy is defined in thermodynamics as a function of state, in such a way that, in an adiabatic process, the variation of internal energy equals to the work done, regardless of the way it has ...
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0answers
8 views

what are the things that affect the ion mobility of a particular material?

what factors are important in ionic transition in a substance? please use easy word to answer as I am a high school student.
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0answers
18 views

Computing the energy of a heat source

My son and a friend are doing a science fair project on thermoelectricity. While they understand ZT, the figure of merit conceptually, they do not know how to calculate efficiency. It's easy for ...
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1answer
29 views

Transfer of heat from ice to water in a beaker

How does the transfer of heat takes place from ice below 0 degree celcius to water at room temperature? Does it take place by conduction? Does temperature of water rises uniformly throughout or it ...
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0answers
47 views

What is the relation between Clausius and Kelvin-Planck statement?

What is the relation between Clausius and Kelvin-Planck statement? In second law of thermodynamics, it is said that these two statement are equivalent and inverse to each other. Violation of one ...
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0answers
32 views

Validity of Gibbs-Dalton Law

I know that the Gibbs-Dalton law valid for an ideal gas mixture of ideal gas components. Does it also hold in the case of ideal gas mixture of real gas components? For example, could I say the ...
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0answers
22 views

Expressing thermal efficiency for a closed Brayton cycle in terms of static enthalpies

I have a Brayton cycle made of a compressor (stage 2 to 3), a heat exchanger (stage 3 to 4) and a turbine (stage 4 to 5). The turbine and compressor are connected through a shaft. The cycle is closed ...
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0answers
25 views

Ice and water mixed and entropy

In any introductory book, everybody has atleast done these type of questions where water at a high temp is mixed with ice and final temp and mass is asked with the understanding that zeroth law define ...
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0answers
80 views

Entropy change in a boiling egg

Yesterday in a rather intuitive Q/A session, by a visiting researcher in my town, this question got my attention.What he said was that if you boil an egg, the entropy inside the egg would increase.Now ...
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1answer
46 views

Heat and Thermodynamics [duplicate]

What is the temperature of air in the upper part of our atmosphere? I read somewhere that it is of the order of 1000 K, but then, why is it cold there? My question is different from the ...
2
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1answer
60 views

how is it proved $\frac{Q_c}{Q_h}=\frac{T_c}{T_h}$? [closed]

I know how to prove that the efficiency is $1-\frac{Q_c}{Q_h}$, but how do I go from that to $1-\frac{T_c}{T_h}?$ i.e. what is the proof that $\frac{Q_c}{Q_h}=\frac{T_c}{T_h}$?
0
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1answer
51 views

Can you concencrate paralel laser beams?

I've seen some videos of laser toys but they all seem to use either one laser or lens with some specific range of focus. What I was thinking is this: But it seems like it might violate the 2nd law ...
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0answers
23 views

What could be the anharmonicity effect if phonon interact with a tilted interface?

If Phonon propagates through c-axis grown structure and at the end reach a tilted interface of GaN, what phenomena will appear there? How anharmonicity is going to effect the phonon propagation ...
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1answer
50 views

Why a balloon explodes by itself? [duplicate]

I was wondering why a balloon explodes after some time by itself with no specific reason. yesterday I was doing my chores and to my amazement the balloon far in the corner of house pop with no obvious ...
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2answers
95 views

When sailboats sail faster than the wind, why are they not violating the 2nd Law of thermo?

There is a related question here, but it doesn't explain the implications of / on the 2nd Law of Thermo. One of the effects of the 2nd Law of Thermo is that no matter how many zillion particles ...
3
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0answers
26 views

How does air going through silica gel change its humidity

Assume that the properties(temperature,humidity,velocity and so on) of the incoming air flow stay constant. The air flow goes through a silica gel plate. Humidity of the air will decrease, but how to ...
2
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1answer
96 views

Does high heat make a boiling pot of water evaporate faster?

According to another answer, the rate at which water evaporates depends on the temperature of both air and water, the humidity of the air, and the size of the surface exposed. The air ...
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9answers
14k views

Why does matter exist in 3 states (liquids, solid, gas)?

Why does matter on the earth exist in three states? Why cannot all matter exist in only one state (i.e. solid/liquid/gas)?
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0answers
20 views

What are some good books on foundations of Thermodynamics [duplicate]

I am not looking for some introductory texts, graduate text, etc. I am looking for something that addresses to foundational problems in thermodynamics and statistical mechanics.
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3answers
82 views

Boiling as apparent violation of the second law of thermodynamics

One of the statements of the second law is that no agency can be built whose sole effect is to convert some amount of heat entirely to work. But in case of boiling, the temperature being constant, ...
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0answers
23 views

What is meant by a “change in volume of a system”?

I keep getting confused when my professor talks about the change in volume of a system. Sometimes it seems as though he's talking about the volume of the gas and at other times he might be talking ...
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2answers
50 views

What Statistical Mechanics does in classical regime

In a book of Dipankar Home, "Foundations of Quantum Mechanics", he has mentioned that A newer theory should not only predict all the results that are already predicted by it's predecessor where ...
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0answers
11 views

What are the limitations of velocity selective coherent population trapping?

I'm somewhat familiar with limitations of Doppler cooling, particularly with the one photon recoil limit, but what I was curious about was what is the next barrier to cooling approaching absolute ...
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1answer
79 views

Help me solve a heat conduction/emission transfer problem. Mathematica has failed me

My problem: A thin-walled tube (length $L$, diameter $D$ and wall thickness $t \ll D$) is in a vacuum. It is held on one end (at $x=0$) by a heat source at constant temperature $T(0)=T_0$. The only ...
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1answer
67 views

Fluid filled open container in space/vacuum

I have water in a bottle, as I open it in space(or vacuum for that case ). From what I have read in books the water will instantly vapourize,as the vapour pressure of the water inside, far exceeds the ...
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0answers
29 views

Why changes in the degrees of freedom implies changes in the internal energy?

In Thermodynamics we describe equilibrium states of macroscopic systems. For those equilibrium states we make a description giving one macroscopic coordinate for each measured degree of freedom (like ...
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1answer
43 views

Free expansion of ideal gas, transient phase (3 questions)

We all know the classic scenario of free expansion. A contained gas expands into a vaccum and in the end we have $\Delta T = \Delta U = \Delta H = 0$ and $\Delta S = R \ln \frac{V_2}{V_1}$. This is ...
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0answers
26 views

Calculate the change in entropy of superheated water [closed]

1 mole of superheated water at 110 degrees Celsius and 1atm is evaporated to a vapour at the same temperature. Find the change in entropy given that i) In the pressure range from 1atm to 1.4atm the ...
2
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1answer
30 views

Coefficient of Linear Expansion (Formula)

Quoting directly from my textbook: We define average coefficent of linear expansion in the temperature range $\Delta T$ as: $$ \bar \alpha = \frac 1L \frac{\Delta L}{\Delta T} $$ The ...
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1answer
24 views

Calculating Effects of Added Insulation on Rate of Temperature Change

I have recently begun tracking the temperature data available from my Nest thermostat. Among other things, the hope is to use this data to measure the effectiveness of additional insulation and other ...
0
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1answer
79 views

Why does pressure decrease as velocity increases?

Bernoulli's principle states that as velocity increase pressure decreases. But higher the velocity, greater is the temperature and pressure must be high. Can you explain the situation in both the ...
0
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1answer
87 views

A hypothetical equation of state that violates second law of thermodynamics

Suppose for a gas I guess an equation of state in the form $f(P,V,T)=0$. Is it possible that this hypothetical equation of state turns out to violate the second law of thermodynamics. A simple example ...
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2answers
59 views

If for an isolated system, $\Delta$U is 0, then what is $\Delta$S?

My textbook answers this question as $\Delta$S > 0 but I really don't know why. If system is isolated, then dQ = 0 i.e. S = 0. (S = dQ/T). I don't really get why question has provided an additional ...
2
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2answers
84 views

Does invariant mass depends of temperature? [duplicate]

From special relativity theorie we know that $E = mc^2$. When a system acquires energy, mass becomes greater. That is clear for kinetic energy, because we have a formula that gives m as a function of ...
2
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1answer
55 views

Is heat radiation an instance of electromagnetic radiation?

From school physics I recall the following means by which heat spreads out: conductance (particles bump against each other), radiation and the original heated mass moving (for example: sea currents). ...
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2answers
62 views

Internal energy, Enthalpy, and Heat

Setting a general background for my question: We know that the equation of state for an ideal gas is given by: $$pv=RT$$ where: $p$ is the absolute pressure of the gas. $v$ is the volume per ...
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0answers
14 views

Increase in temperature of metal piece during filing explain by the Gibb's equation?

When we file the metal the surface of the metal gets worn out in the form of small pieces of metal. The file acts as medium to transpher the energy from the body to the metal piece in the form of ...
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1answer
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2answers
80 views

Change in entropy of two isolated systems merged into one system

From Statistical Physics, 2nd Edition by F. Mandl: Two vessels contain the same number $N$ molecules of the same perfect gas. Initially the two vessels are isolated from each other, the gases ...
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1answer
47 views

Difference between throtling and adiabatic expansion

Throttling process is an isoenthalpic process.$$U+PV=constant.$$ during throttling process does the gas do work at the cost of internal energy such that its temperature decreases? Then what is the ...