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14

I will try to answer these questions from different views. Macroscopic view The "quantitative" rather than qualitative difference in a liquid-gas phase transition is due to the fact that the molecules arrangement does not change so much (there is no qualitative difference) but the value of the compressibility changes a lot (quantitative difference). This ...


10

You are mistaken. You seem to be assuming that there is some kind of inertia in the process of heat transfer, as in water sloshing about in a tank. There is no such inertia here, so there is no oscillation. You write: Since heat has been transferred from A to B, unless I'm mistaken this will place B momentarily at a higher temperature than A. Yes, you ...


8

For a pure substance that can exist in the solid, liquid, and vapor states (i.e., wood is not in this category), let's assume that a closed container is half full of liquid and half full of vapor. As the temperature rises, the liquid expands and the liquid density falls. Also, as the temperature rises, the pressure in the container rises due to the vapor ...


7

The many worlds interpretation has a lot of problems, but this isn't one of them. You're imagining "creating alternate universes" as some energetic event, like a mini Big Bang, but what really happens is a smooth splitting of the wavefunction. For example, suppose we have a spin in a superposition of up and down states, $$\frac{1}{\sqrt{2}} (| \uparrow \...


6

The temperature appearing the the Clausius inequality is definitely the temperature of the "boundary interface (with the surroundings)", or simply the temperature of the sources. One of the best places I have seen this discussion is in Fermi's book, chapter 5, section 11. He is explicit about it. To see this you have to recapitulate the steps in obtaining ...


4

For reference, the diagram is below. First, I'm just going to give a quick explanation of entropy. Before Boltzmann, people knew about entropy, they just didn't explain it correctly; namely, they thought of it as a measure of the uselessness of arrangements of gas. As an example, they thought that if you had a box, and all of the gas molecules in the box ...


2

Real world assumptions: No temperature gradients over the cross-section of the pipe. Plug flow (turbulent flow). Water heat capacity $c_p$ and density $\rho$ are temperature invariant. Consider an infinitesimal mass element $dm$ at temperature $T(x)$ travelling down the pipe at speed $v$. We apply Newton's law of cooling to it: $$\frac{dQ}{dt}=kdA\big(...


2

Good question. I don't have my Widom around, but I'll try to answer from memory. I think the consensus is to say a substance is at its gas state if it could be a liquid at the same temperature. This, as opposed to same pressure, same volume, etc. If the temperature is supercritical, there is no transition between liquid and gas, and the generic term "fluid"...


2

As the steam gets created from the evaporated liquid at the bottom of the liquid drop, it expands and provides additional pressure acting on the bottom of the liquid drop. The steam does move upwards, but new steam is continually being created so the pressure is able to hold the drop slightly above the surface.


2

Energy transfer can be thought to occur via the exchange of a 'virtual particle'. In nature, there are 4 fundamental forces, namely: 1. Electromagnetic force 2. Gravitational force 3. Strong force 4. Weak force Each of these forces have a different exchange particle: For instance, the exchange particle for EM is a photon whereas that for the strong force ...


2

In "Adventures in Friedmann cosmology: A detailed expansion of the cosmological Friedmann equations" by Robert J. Nemiroff and Bijunath Patla in the American Journal of Physics volume 76, on page 265 (2008); http://dx.doi.org/10.1119/1.2830536 the authors call them "cosmic strings" But this is in the context of cosmology, so its for a universe that on very ...


2

Attempting to answer the "why" question intuitively: In a liquid, the molecules experience significant intermolecular force - so much so, that the average energy of the molecules is insufficient to escape the attractive force of the surrounding materials. The result is that it energetically favorable for them to remain close together, even if that means ...


2

There are two definitions of entropy, which physicists believe to be the same (modulo the dimensional Boltzman scaling constant) and a postulate of their sameness has so far yielded agreement between what is theoretically foretold and what is experimentally observed. There are theoretical grounds, namely most of the subject of statistical mechanics, for our ...


2

I have no idea what you are asking in (1). (2) During adiabatic compression, the temperature of the system does change. Starting from the first law of thermodynamics: $$\mathrm{d}U = \mathrm{d}Q + \mathrm{d}W$$ For an adiabatic process $\mathrm{d}Q=0$. If we assume an ideal gas, then the internal energy is $\mathrm{d}U = C_V\, \mathrm{d}T$ and the work ...


2

The 'go to' partial differential equation here is surely the Heat equation (Fourier), here in one dimension: $$\frac{\partial T}{\partial t}=\kappa \frac{\partial^2T}{\partial x^2}+\frac{\dot{Q}(x,t)}{c_p\rho }$$ It can be easily expanded into three dimensions or expressed in polar, spherical or cylindrical coordinates. It's not clear from your question ...


2

Gold will compress to about half of its volume at atmospheric pressure if you compress it to 2 million atmospheres at room temperature, which is something that I'm sure has been done with diamond anvil cells. For many metals, the atomic lattice will also undergo structural phase transitions from one lattice type to another at certain pressures, but I don't ...


1

Leaving this here for now... Will update with more information and references later. Einstein and Debye showed that specific heat is a function of temperature, but is asymptotic at high* temperatures. Here is a simple explanation why: Heat, with regard to everyday applications, is simply a measure of the motion of atoms and molecules. Let's start with ...


1

Why does a critical point even exist? I think this question is equal to this one: "Why the width of the two phase region is bigger at lower temperatures and pressures?" Specific volume of liquids mostly depends on the temperature of them in comparing with their pressure. This means, for a well-defined increment of the pressure, we can neglect its effect ...


1

From a biochemical point of view, heat detection is achieved by proteins at the surface of nerve cells. They basically just trigger a nerve signal above a given temperature. So they DO detect temperature and not a "heat flux". It may seem surprising that nerve cells react so quickly but the increase/decrease in temperature does not need to go all through the ...



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