Covers the study of (mostly homogeneous) macroscopic systems from a heat/energy/entropy point of view. Maybe combine with [tag:statistical-mechanics].
3
votes
0answers
26 views
Lattice model completely constrained by boundary data
I am dealing with a lattice model that has the peculiar property that if I specify all the spins on the boundary, by local conservation laws, the whole lattice configuration (throughout the whole ...
1
vote
1answer
70 views
Does brown but transparent swimming pool water heat significantly faster than western style highly chlorinated pools?
Eastern European swimming pools are often brown tinted water. i was told it was the color of the chemical to keep the pools clean, but who knows. These pools did not smell unsanitary and may have even ...
0
votes
1answer
44 views
How does an earthen pot keep water cool?
I understand that evaporative cooling takes place thanks to small pores contained in the pot and that allow some water to go through and evaporate. However I couldn't understand clearly whether water ...
0
votes
0answers
43 views
Air pressure in balloon
I have to calculate the air pressure inside of an hot air balloon. After some searching I found out that I can use the ideal gas law: PV = nRT (from Wikipedia)
So to get the pressure in the balloon I ...
-3
votes
1answer
80 views
Is it possible (theoretically) to divide Black Hole into two parts? [duplicate]
I have read that it's not possible.
1
vote
1answer
35 views
What's the criteria for black hole thermodynamically stability? (And dynamical?)
It looks like usual criteria (positivity of Hessian; what geometrically means a cancave of entropy) is no useful, becouse entropy is not additive and not extensive for black hole. Then what is the ...
3
votes
0answers
39 views
What is the physical meaning of fact, that Reissner-Nordstrom black hole is thermodynamically unstable?
It is known, that Reissner-Nordstrom black hole is thermodynamically unstable [1].
Does it mean, that there is no Reissner-Nordstrom black hole in physical world?
Does it mean, that there may be ...
4
votes
3answers
161 views
Definition of entropy
In physics, the word entropy has important physical implications as the amount of "disorder" of a system. In mathematics, a more abstract definition is used. The (Shannon) entropy of a variable $X$ is ...
2
votes
0answers
19 views
Can one get clear ice crystals from a dirty suspension?
Euteictic freeze crystallization is a method where an electrolytic solution is cooled and separated into a stream of (relativly) clean, pure ice and a salty brine. I know anectdotally of wine ...
4
votes
0answers
70 views
Mechanical Equivalent of Heat
Recently I have been looking up James Joule's experiment regarding the mechanical equivalent of heat. After viewing some drawings of the apparatus, I assumed that the lines holding the weights would ...
2
votes
1answer
45 views
Thermodynamics, PV diagrams?
My teacher told me that the total amount of work done on or by a gas can be represented by the area enclosed in the process in a PV diagram. This is only valid for non isothermic processes, right?
5
votes
2answers
158 views
First law of thermodynamics?
The first law says that the change in internal energy is equal to the work done on the system (W) minus the work done by the system (Q). However, can $Q$ be any kind of work, such as mechanical work? ...
-1
votes
0answers
47 views
Is there axiom of entropy's additivity in thermodynamics? [closed]
I would be glad for some links on books.
0
votes
0answers
20 views
Total massflow through heat exchanger
I am working on a project and I stumbled on a problem. The project is to design a heat pump to replace the old system (actual problem, not some homework problem). There are 100 or so induction units ...
0
votes
0answers
30 views
How connected thermodynamical stability and dynamical stability for black holes?
Criteria for thermodynamical stability is the convex of entropy. But for black hole entropy is non-additive.
1
vote
4answers
84 views
The Preference for Low Energy States
The idea that systems will achieve the lowest energy state they can because they are more "stable" is clear enough. My question is, what causes this tendency? I've researched the question and been ...
2
votes
2answers
31 views
Gas Circulation Using Pressure Difference
Dear all, see attached picture
Please, is it possible to have the gas recirculated from the gas phase to the liquid as described in the diagram assuming the gas is not soluble in the water.
These ...
1
vote
0answers
50 views
Explain to me how this water cooler works?
Goodday all,
I was recently reading up on a few projects that might be of interest to me when I found "CPU Bong water coolers", there isn't much online on them so I figure I would ask y'all.
If you ...
0
votes
0answers
13 views
What is the effect of an increase in pressure on latent heat of vaporization?
What is latent heat of vaporization ($L_v$) in the first place? Wikipedia seems to indicate that it is the energy used in overcoming intermolecular interactions, without taking into account at all any ...
3
votes
1answer
67 views
Error in Sear's and Zemansky's University Physics with Modern Physics 13th Edition (Young and Freeman)?
I was reading up on the Ideal Gas Equation in University Physics with Modern Physics by Young and Freeman when I chanced upon a seemingly illogical mathematical equation.
Can anyone rectify this ...
0
votes
3answers
69 views
How do you determine the heat transfer from a P-V diagram?
I doubt this question has been addressed properly before, but if there are similar answers, do direct them to me.
I am currently studying the First Law of Thermodynamics, which includes the p-V ...
0
votes
0answers
19 views
Heat transfer in fluid between two horizontal plates vs unconfined case
I often see the correlation for turbulent heat transfer between liquid cells published by Globe and Dropkin (1959). In the original paper the fluid was confined between two horizontal plates and ...
0
votes
1answer
679 views
Beginner Thermal Dynamics Question [closed]
A syringe is set up filled with air (mainly N2 and O2) as shown in the diagram below. The surface area of the syringe is 15.3 cm2. The initial pressure inside the syringe is Pi = 114 kPa and the ...
3
votes
1answer
52 views
How can I understand a Vortex Tube and its efficiency?
A Vortex Tube takes a pressurized input stream, most typically of a gas, and creates two output streams with a temperature differential. Apparently, it has been described as a Maxwell's Demon.
Both ...
3
votes
1answer
58 views
Why does compressing a piston increase the internal energy?
When we compress a piston, its total internal energy increases, however I don't understand why.
As the piston compresses, the temperature should change, as the total energy density increases.
As a ...
-2
votes
1answer
42 views
Michaelis-Menten derivation for 2 enzyme substrates
We know that the Michaelis-Menten derivation for the following reaction:
$E + S \rightleftharpoons ES \rightarrow E + P$
However, what if the reaction took place in a different scenario whereby:
$E ...
1
vote
1answer
95 views
Mathematical proof of non-negative change of entropy $\Delta S\geq0$
I understand that we can prove that for any process that occurs in an isolated and closed system it must hold that
$$\Delta S\geq0$$
via Clausius' theorem. My question is, how can I prove this in a ...
1
vote
0answers
48 views
Calculate how hot PLA will become
I am trying to attach the shaft of a brass heating tip to a PLA component. My problem is that the tip will have to reach a temperature of about 200°C and the PLA can only handle a temperature of about ...
4
votes
2answers
74 views
Does it make a sense to speak about age of electron or atom?
It's possible that this question is too soft or even quite senseless for this forum, but I will ask nevertheless.
Everyday (macroscopic) things, like a grandfather's pendulum clock or the grandfather ...
22
votes
6answers
2k views
How do whisky stones keep your drink cold?
From a discussion in the DMZ (security stack exchange's chat room - a place where food and drink are important topics) we began to question the difference between how ice and whisky stones work to ...
1
vote
0answers
27 views
Calculating the change in entropy in a melting process
I have a homework question that I'm completely stumped on and need help solving it.
I have a $50\, \mathrm{g}$ ice cube at $-15\, \mathrm{C}$ that is in a container of $200\, \mathrm{g}$ of water at ...
6
votes
1answer
79 views
Is there a relativity-compatible thermodynamics?
I am just wondering that laws in thermodynamics are not Lorentz invariant, it only involves the $T^{00}$ component. Tolman gave a formalism in his book. For example, the first law is replaced by the ...
0
votes
1answer
44 views
Calculating the coefficient of thermal expansion in liquid
I am trying to write a matlab function that calculates the coefficient of thermal expansion of water from a given temperature. From what I understand the thermal expansion coefficient is calculated as ...
1
vote
0answers
42 views
What defines the adiabatic flame temperature?
In a case, I have to solve, I need to describe the combustion of natural gas (Groningen natural gas to be more specific). However I am having some problems understanding the adiabatic flame ...
0
votes
0answers
39 views
Lambda transition data points of $\require{mhchem}\ce{^4He}$
I'm looking to get some data on the lambda transition of $\require{mhchem}\ce{^4He}$. I need the data points of the specific heat vs. temperature graph, if that makes sense.
-1
votes
0answers
23 views
Finding rms velocity in isothermal process [closed]
I think none of these options are correct, I just need someone to confirm. Please, as no option is matching with $V_{rms}$.
0
votes
1answer
41 views
If a balloon is continuously filled with air and stays at a constant shape and size will there be any empty space in the balloon?
If a container like a balloon but with constant volume is filled, is it possible to pack air molecules so closely together that they don't have any empty space between them? If so, what would this ...
0
votes
1answer
36 views
What is the work done by an ideal gas?
What is the work done by an ideal gas when final pressure and volume are both different from its initial pressure and volume or when both pressure and volume changes ?
-1
votes
1answer
44 views
Heisenberg's uncertainty and $0 K$ temperature
when a body is subjected to $0 K$ temperature, it becomes rigid. hence if we see in terms of quantum the lattice vibration decreases, resulting in no change in the direction of the Random velocity, ...
-2
votes
1answer
38 views
How do I calculate the heat lost or gained by surroundings? [closed]
How do I calculate the heat lost or gained by surroundings (Q surr) given mass ($m$), change in temp ($\Delta T$), and specific heat ($c$)? What equation would I use?
How can I tell whether it's lost ...
-3
votes
0answers
51 views
When do we have $p = -\frac{\partial F}{\partial V}$? [closed]
In what context can we say that :
$$p = -\frac{\partial F}{\partial V}$$
?
0
votes
0answers
30 views
Negative temperature [duplicate]
How can we prove that if a negative-temperature system is in contact with a positive-temperature system, then the heat flow from the first to the second (and finally, the temperature of the second ...
-1
votes
1answer
72 views
The effects of heat on gravitational fields
In boiling soapy water, globs of soap coalesce as the temperature increases to boiling. Does this mean that temperature increases the gravitational pull of bodies?
1
vote
1answer
64 views
Finding equation of state from thermal expansion coefficient and isothermal compressibility
I'm stuck on a problem that I found in a book (Modern Thermodynamic with Statistical Mechanics, Helrich S., problem 5.2).
The text of the problem is that:
Consider a solid material for which:
...
1
vote
2answers
43 views
How is it possible to equate the internal energy at constant volume with the internal energy of an adiabatic process?
I hope my question makes sense. My problem is that, I have read through numerous textbooks that nC(cons. volume)dT = -PdV when deriving the relationship between T and V for an adiabatic process, ...
1
vote
3answers
130 views
Integrating factor $1/T$ in 2nd Law of Thermodynamics
How would you prove that $1/T$ is the most suitable integrating factor to transform $\delta Q$ to an exact differential in the second law of thermodynamics:
$$dS = \frac{\delta Q}{T}$$
Where $dS$ is ...
10
votes
3answers
211 views
The notion of an adiabatic process in thermodynamics -vs- quantum mechanics
I'm confused about the terminology in the two contexts since I can't figure out if they have a similar motivation. Afaik, the definitions state that quantum processes should be very slow to be called ...
0
votes
1answer
48 views
Time constant of ice melt
I'm familiar with problems of "how much ice can you melt given some amount of energy", but I'm writing to get some clarification on the time constant of this event. This question might be somewhat ...
-1
votes
0answers
53 views
Newton's cooling law
I want to know few things regarding the practical of Newton's cooling law.
1). What are the other possible ways of making external conditions constant except using two calorimeters one within one?
...
1
vote
1answer
62 views
Why does Hydrogen molar heat capacity reach 7/2 R?
If a diatomic gas like Hydrogen has 6 maximum degrees of freedom why its molar heat capacity reaches at high temperatures $C_V = \frac{7}{2} R$ and not $C_V = \frac{6}{2} R= 3R$?
molar heat capacity ...
