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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When heat is applied to the top of a stack of pennies, why does the bottom penny melt first?

I just watched this video where a blow torch is used on the top of a stack of pennies. I'd like to know why the bottom penny melted first.
6
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2answers
590 views

Is it possible to disprove water memory with an entropy argument?

Water memory was a controversial experiment claiming to provide an explanation supporting homeopathy. The results were largely dismissed as being tainted by experimental error. One possible mechanism ...
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0answers
30 views

When did the casual definition of the three laws of thermodynamics first appear? [closed]

Who is credited as the source, and when were the laws first stated in this form? (1st Law) You can't win. (2nd Law) You can't break even. (3rd Law) You can't get out of the game.
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1answer
39 views

Does $\delta W=pdV$ hold for non-ideal gases

I have that for quasistatic processes, $$ \delta W= \textbf{f}\cdot d\textbf{x} $$ so for a gas $\delta W=pdV$. Does this only hold ideal gases or will it hold for van der waal's gas?
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80 views

Finding Maxwell relations

I feel I am missing something about deriving Maxwell relations. I have read http://ocw.mit.edu/courses/physics/8-044-statistical-physics-i-spring-2013/readings-notes-slides/MIT8_044S13_notes.Max.pdf ...
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1answer
14 views

Cooling effect of sipping

Is the primary action of cooling of a sipped hot fluid explained by the reduced flow of the hot fluid, the air cooling of the fluid as it is sipped or another factor?
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14 views

Equation of State of PVT system

Find the Equation of State of a fluid with Volume expansivity $\alpha_P$ and an isothermal compresibility $\kappa_T$ are given by $$\alpha_P=\alpha_0 \Big(1-\frac{P}{P_0}\Big) \\ \: \: \: \: ...
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2answers
364 views

Temperature of space

What will be temperature inside an isolated box in empty space? By isolated I meant light from stars cannot enter the box and there is no matter inside the box.(no vibrations or movement of molecules ...
0
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1answer
60 views

Entropy and the $2^{nd}$ law of thermodynamics

I have just been introduced to the word "entropy" and as it is my understanding that it is a measure of the randomness and chaos of particles in as system. My textbook list the 2nd law of ...
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0answers
19 views

Isothermal Expansion in Real Gases

I understand that for a ideal gas in the case of reversible isothermal expansion, $\Delta U=0$ and $-Q=W$ but in case of a real or van der Waal gases, how can I find $Q$, $\Delta U$ and $\Delta S$?
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1answer
43 views

What sort of math deals with thermodynamics inside of semiconductors?

That is to say, how would one consider the thermodynamics of a complex chip like a modern CPU? I hear that designing the thermal efficiency of such systems is very difficult. I'm not sure why, ...
0
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1answer
34 views

How to thermodynamically understand process of burning a piece of coal?

Let's imagine that I have a match in hand and nugget of coal on my desk. Then I light up the match and place it for few seconds near the coal so a tiny piece of nugget catches fire. Then another piece ...
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1answer
31 views

Dielectric heating - does EM field transfer energy to polar molecules?

In AC field, polar molecule are trying to align with external field. At high freguencies, changes of field are so quict, that molecules cannot align with it. This leads to increasing kinetic energy of ...
0
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1answer
25 views

What assumptions can be made using a $pV$ diagram?

In this question I am asked to find the volume of a gas at $V_3$ I have some parts that am not clear on. Is it reasonable to assume the temperature at $3$ is $657^{\circ}C$ Work is done by the ...
0
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1answer
33 views

Heat transfer through radiation and its relation with temperature

My question is: if a body and the surroundings have the exact same temperature, will that body still lose heat in terms of radiation? If so then what exactly is heat. Heat is defined as energy flow ...
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3answers
173 views

Does placing a cold bottle next to an incubator cool the incubator through convection or radiation?

Context for question: My girlfriend who is studying to be a nurse asked me to explain the difference between radiation and convection in context of the above question. My answer: Radiation is the ...
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0answers
24 views

Callen Thermodynamics 2.8-2 help? [closed]

A two component gaseous system has a fundamental equation of the form $S=AU^{1/3} V^{1/3} N^{1/3} + \frac{BN_1N_2}{N}$ where $N=N_1+N_2$ and $A$ and $B$ are positive constants. A closed cylinder of ...
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1answer
57 views

What is thermodynamic equilibrium?

The state of thermodynamic equilibrium is typically defined referring to the system's behaviour in the future. Can the definition be formulated in terms of measurable quantities?
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1answer
32 views

Pressure, Momentum and Energy: A 'Peculiar' Relation

Is the following possible? $$ P = \frac{p^2}{3E} $$ where $P$ is pressure, $p$ is momentum and $E$ is energy. In what convention is the above relation acceptable? EDIT: The source paper can be found ...
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2answers
40 views

What is the heat sink in an internal combustion engine?

I believe that the heat source is the spark plug because it heats up the fuel-air mixture and that the working substance is the fuel-gas mixture. Then, I know that the explosion created by the fuel ...
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1answer
71 views

Is information a form of energy? [closed]

To better describe my question, do the following experiment: Calculate x=12+26+67+71 Now you might have spent some time in getting the answer. You burnt sugar, you used up energy to get the ...
2
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1answer
117 views

How does this new theory of a possible infinitely old universe not violate the second law of thermodynamics

I read the following article: http://phys.org/news/2015-02-big-quantum-equation-universe.html And followed it back to this journal reference : http://arxiv.org/abs/1404.3093 It appears to be ...
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2answers
112 views

Extensive variables in thermodynamics

Extensive variables in thermodynamics are those which scale linearly with the system size. It is known that a ratio of two extensive variables is an intensive variable. Now, the number of particles ...
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1answer
66 views

How to heat water at very high temepratures?

I am working on a project and recently came through a situation where I'll be working with water evaporation. On searching the internet I found that water heated at 350Celsius would generate almost ...
3
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2answers
575 views

Why does ice become sticky the colder it gets? [duplicate]

I noticed that ice becomes stickier the colder it gets. I am reminded of the fool who stuck his tongue to a cold galvanized steel pole and got stuck to it. I am guessing that the pole was so cold that ...
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0answers
37 views

Can energy be extracted indefinitely from a mass dipole/mass negative mass pair in perpetual motion?

Some days ago I have read this short piece of article by Hammond which caused me to revisit the theoretical properties of negative mass. It is known that a pair consists of ordinary mass and negative ...
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35 views

Is the system in equilibrium?

If the time derivative of the Liapunov functional related to free energy of my system is zero, can I say my system is in chemical equilibrium?
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1answer
41 views

Thermodynamics vs Kinetics

As a chemical reaction approaches equilibrium, one of forward or backward reactions dominate the other. According to thermodynamics, this is because the gibbs free energy change for one is negative. ...
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1answer
42 views

Entropy and Gibbs Free Energy

I've been struggling with the notion of entropy and gibbs free energy for almost three days now. Different sources on and off the internet say different things about entropy. Gibbs Free Energy is ...
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1answer
25 views

What are the units in the heat equation?

If we write the heat equation as: $$ \frac{\partial}{\partial t}u-\alpha \nabla \cdot (\nabla u) = f $$ Then, Temperature of the material: $u: m^3\times s\rightarrow K$ Thermal diffusivity: ...
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2answers
73 views

How does a radiometric infrared camera estimate an objects temperature?

Say we have an infrared camera which measures some amount of radiation, in a spectral bandwidth which is given, between wavelength $\lambda_1$ and $\lambda_2$ from a perfect black body. How is it ...
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0answers
43 views

Calculating the heat transfer into CO$_2$ gas at a constant pressure

I am having trouble with a homework question and I am just not sure how to attack it. We have not covered how to deal with non-ideal gases yet, and we are expected to answer this question without that ...
2
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1answer
42 views

Accessible system where specific heat and thermal conductivity vary in different ways?

I'm teaching undergrad thermo this semester and to my surprise several students are having trouble conceptualizing heat capacity and thermal conductivity as different properties; they can apply them ...
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0answers
25 views

reflecting foil on window

Assumptions: A house window acts as a cavity resonator, and so can be treated as a blackbody. If the room temperature is 20 C then the outgoing radiation is 418 W/m2 If the outside temperature is ...
0
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1answer
18 views

Rankine Cycle pressure

I don't understand why in (Ideal) Rankine Cycle we assume that pressure remains constant at the boiler and the condenser. Shouldn't water pressure change, when water goes from liquid to vapor (boiler) ...
0
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1answer
46 views

Decrease in system pressure do to gas dissolution?

A system of fixed volume contains two fluids as illustrated in the figure below, in equal volumes. Their pressures are both equal and high (much greater than atmospheric pressure). Initially the ...
0
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1answer
22 views

Why is work done on the system considered when calculating the work output?

The thermodynamic efficiency $\eta$ is calculated by $\eta= \frac{W_{out}}{Q_{in}}$ Using the first law of thermodynamics we usually say that $W_{out}$ is $Q_c+Q_h$, where $Q_c$ is the heat ...
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0answers
46 views

What happens to running water in sub-zero environment?

Many rivers in sub-zero winter temperatures don't freeze (photo). For simplicity let's discuss a (small) water pipe/canal with uniform cross section, inclined by an angle $\theta$. It seems that: ...
2
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1answer
42 views

What is thermal radiation? How does it move through space?

Assume that by some mysterious(at the lack of a better word) way I was able to make a bonfire on the moon and was able to sit next to it without a space suit. I will not be able to feel the heat form ...
0
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1answer
47 views

Adiabatic processes and the First Law

The first law of thermodynamics in my notes is : $\Delta E=\Delta Q +\Delta W $. Then later in my notes for an adiabatic process: $\Delta Q \implies dE=-pdV$. Then for a monatomic gas ...
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0answers
26 views

Necessity of infinitesimal steps for reversible processes

Is there a mathematical proof for why a reversible process is one that has many infinitesimal equilibrium steps, rather than fewer large steps? Maybe something along the lines of this?: ...
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0answers
30 views

What are the Fermi and Debye temperature constants?

What are the Fermi temperature and Debye temperature constants? We were discussing these in class and I don't fully understand what these constants are or why we have them. Can anyone explain?
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0answers
135 views

Confusing Chemical potential of mixtures

I feel that there are very few textbook that treat the chemical potential of mixtures in an understandable clear way, which is why I wanted to ask here about certain things? Although I do not have a ...
0
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1answer
62 views

Can I manually speed up convection?

Let's say, I have half bucket of boiling water and I have added equal amount of freeze cold water to it. I want to have equilibrium temperature reached as quick as possible. Can I speed up the ...
4
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1answer
120 views

For $N$ particles acting under gravity, how long until they settle into a virial equilibrium?

As the title says, if I have a system of particles interacting only due to gravity, over what timescale do we expect them to fall into a virial equilibrium? By virial equilibrium I mean a system that ...
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1answer
42 views
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39 views

Ising Model with All Spins Interacting with All Other Spins

I am studying the Ising model with all spins interacting with all other spins and have formulated $Z$. I am trying to understand what it means to study at large N but not infinite N. I know that at ...
29
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3answers
4k views

Why does a Pewter mug keep a beverage hot better than a foam cup?

I know my subject sounds improbable and that's why I posted it. I helped my daughter with a science project for school. We tested five different materials to determine which would keep hot water ...
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0answers
22 views

Can a gas be modelled as a low density blackbody, if we want to consider how detectable it will be in space?

The answer to this question taught me about the sort of parameters I need to consider if I want to consider how "detectable" an object in space is. I want to consider the detectability of a ...
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2answers
32 views

first law of thermodynamics change in internal energy

Change in state {for example from liquid to gas} is an isothermal process but the change in internal energy is not zero in this process isn't this contradictory?