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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322 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 ...
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3answers
437 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 ...
2
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0answers
119 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
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2answers
191 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 ...
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6answers
8k 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 ...
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2answers
322 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 ...
9
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1answer
392 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 ...
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1answer
1k 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 ...
2
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1answer
408 views

What defines the adiabatic flame temperature?

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 specific). However, I am having some problems ...
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0answers
57 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.
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1answer
151 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 ...
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1answer
505 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 ?
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1answer
66 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, ...
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1answer
1k 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 ...
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3answers
388 views

How can anything be hotter than the Sun?

I've heard that if a space shuttle enters the atmosphere from a bad angle its surface will become so hot that it will be hotter than the surface of the Sun. How can that be? It seems to an uneducated ...
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0answers
48 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 ...
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1answer
146 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?
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1answer
33k views

Conduction, convection, & radiation examples (besides vacuum flask)

I am studying heat transfer And understanding the vacuum flask example that involves conduction, convection, and radiation Do you know other example that involves these 3 phases? we can name some by ...
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1answer
2k 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: ...
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3answers
2k 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 $$nCdT = -PdV$$ (where $NC$ is constant volume) when deriving the relationship between $T$ and $V$ for ...
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5answers
416 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 ...
12
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3answers
833 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 ...
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1answer
481 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 ...
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1answer
621 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 ...
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1answer
44 views

Gas transformation for different molar number

When a gas at normal conditions (1atm, 273K, 22.4L) we say like the $$\frac{PV}{T} = 0.0820...$$ And by the know equation: $$PV = nRT$$ Where R is equals to $0.08205...$ and $n$ is the number of mols ...
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6answers
2k views

Why does the Boltzmann factor $e^{-E/kT}$ seem to imply that lower energies are more likely?

I'm looking for an intuitive understanding of the factor $$e^{-E/kT}$$ so often discussed. If we interpret this as a kind of probability distribution of phase space, so that $$\rho(E) = ...
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1answer
356 views

Does electrically heated water have an adverse effect on hair?

I know I should have asked this question on a different site. but this was the most suitable site available right now for my question. Perhaps after this proposed site goes on Beta, we can move it ...
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2answers
1k views

How temperature gradient is a vector?

Everyone knows Temperature gradient is a vector quantity having direction from cold to hot.My confusion: why is temperature gradient vector if its direction is always fixed (as in the case of ...
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2answers
488 views

Emissivity and thermal equilibrium

Lets say I enter a closed room with the walls and everything in it (including me and my eyes) at thermal equilibrium. Its a very hot room, but my super-eyes still work at 5000 degrees Kelvin. I have ...
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2answers
383 views

phase transition by sublimation

Why do sublime solids sublimate in the first place? Is it that their melting point and their liquid's boiling point are the same so that they manage to magically skip the liquid phase? (if so, why ...
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1answer
58 views

What is the coefficient $\mu_\text{air}$?

I am answering some exercises in thermodynamics, and I am still in trouble with some values and constants. In the exercise, it is given: $\mu_\text{air}=1.8\cdot10^{-5}~\text{kg/m s}$. What for is ...
5
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2answers
341 views

Solidification by the application of heat

When you add heat to a liquid (or a fluid), can it be solidified? If not, why in the world does an egg's stuffs become solid (or at least no more a liquid) when you 'boil' it in water?
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1answer
40 views

How can I find the temperature of this system?

A system was given a small amount of thermal energy dE, and its number of states G grew by 25%. How can I find the system temperature? The system contains gas particles, I know that $dE << ...
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2answers
218 views

Does the black body emit more than any other type of body?

I found this on Wikipedia article on black bodies: A black body in thermal equilibrium (that is, at a constant temperature) emits electromagnetic radiation called black-body radiation. The ...
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1answer
344 views

What happens to pipe outlet temperature here?

I have a fluid flowing through a pipe in the ocean and there is heat transfer from the ocean to the fluid in the pipe. I prepared a simulation and the results show that if I increase the mass flow ...
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7answers
9k views

Does an empty refrigerator require more power to stay cold than a full one?

Given that everything else is equal (model of fridge, temperature settings, external temperature, altitude), over a given duration of having the door closed, does it require more electricity to cool ...
6
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1answer
330 views

How is the index of refraction dependence in Planck's law compatible with thermodynamics?

In various formulae for black-body radiation where $c$ appears, there is an implicit index of refraction dependence, since $c=c_0/n$, where $c$ is the speed of light, $c_0$ is the speed of light in ...
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2answers
106 views

Why not assimilate nuclear waste into “igneous” rock?

I was reading a question about why not to drop nuclear waste into volcanoes; the short answer is it would come back out and not be rendered safe. Ignoring the cost and energy requirements, why can't ...
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0answers
550 views

what's the difference between linear n-atom molecule and nonlinear n-atom molecule?

I am reading a material about the degree of freedom for linear n-atom molecule and nonlinear n-atom molecule. Here is my analysis for a diatomic molecule, if there are two atoms, we have to use 3 ...
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0answers
37 views

Henry's Law in metals

For fixed temperature the concentration of a gas dissolved in a solution is directly proportional to the gas pressure $p$, i.e. $c_s (T,p) = f(T)p$. Since $H_2$ only dissolves in metals as single ...
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2answers
199 views

Heating and Recooling of an Object

Consider a piece of metal of length $L$ and linear thermal expansion coefficient $\alpha$. We eat the metal $\Delta T$ degrees, causing the metal to increase to length $$ L' = L + L \alpha \Delta T$$ ...
4
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1answer
188 views

What happens at the interface between two universes with opposite thermodynamic arrows of time? [closed]

I was trying to think but cannot figure it out. For instance, if the interaction is small, for instance limited to a windows, the observers in each universe will see that the other goes in reverse. ...
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0answers
109 views

What temperatures can be reached in an air-to-air thermocompressor nozzle and why?

People are generally of the opinion that the boiler injector cannot be redesigned to run on air. In other words, an air-to-air thermocompressor that puts fresh air into a tank without a mechanical ...
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1answer
150 views

Uncertainty and Thermodynamics

Dilemma The uncertainty principle of energy and the 2nd law of thermodynamics don't add up : the uncertainty principle of energy says that $\Delta \tau \cdot \Delta E \ge \frac{h}{4\pi} = ...
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2answers
548 views

Computer cooling with dry ice, ideas and question; thermodynamics

I am designing a cooling system for my computer and had a few questions. So I have a computer water cooling radiator and I want to cool it as much as I can. My first two ideas were an old window A/C ...
3
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2answers
805 views

What are the units of these virial coefficients?

I'm reading some papers for calculating the vapor pressure of alkali metals as a function of temperature, and I've come across some familiar-looking virial expansions, but when I tried to work out the ...
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6answers
2k views

Why isn't temperature measured in Joules?

If we set the Boltzmann constant to $1$, then entropy would just be $\ln \Omega$, temperature would be measured in $\text{joules}$ ($\,\text{J}\,$), and average kinetic energy would be an integer ...
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1answer
155 views

Maximizing Multiplicity of Einstein Solid == (Temperature = $\infty$)?

If I have a system consisting of 2 Einstein solids (A and B) is it equivalent to say that maximizing the multiplicity of the ...
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0answers
49 views

Heat of adsorption from fugacity data

I have a set of data relating the fugacity ($\approx$ pressure) to the loading for a given set of temperatures. There are three temperature sets each having five fugacity vs. loading points. The ...
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0answers
62 views

Increase in number of micro states explanation or restatement of second law?

Is the boltzmann's expression of entropy as log of micro states leading to the formulation that system is more likely to be in a macrostate with more no. Of micro states really is an explanation or ...