A gas that behaves as randomly moving, non-interacting molecules. This allows a simplified equation of state.

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Heating during expansion in Joule Thomson - Mechanism? [on hold]

When a real gas(like H2,He) expands through a porous plug into free space, they heat up. How? How does it get the extra energy?
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1answer
53 views

Deriving Ideal Gas law from Hamiltonian Mechanics

I just don't understand the explanation in Wikipedia. Is there a nice & elegant way of arriving at the Ideal Gas Law from Hamilton's Equations?
3
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8answers
243 views

Ideal gas law: Will the piston move at all?

We have the following experimental setup: Before the experiment starts: $$p_1=p_2; \space V_1=V_2; T_1=T_2+\Delta T$$ The experiment starts and both the containers are heated so that the ...
2
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4answers
490 views

Conversion of ideal gas to real gas via $Z$ compression factor

The ideal gas equation $PV=nRT$ can be converted into real gas equation by compression factor $Z$ i.e $PV=Z~ nRT)$. My question is what is $Z$ and how does it arise? Is $PV/nRT$ a compression ratio of ...
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2answers
48 views

Intuitive explanation of the shape of the Maxwell-Boltzmann distribution

At higher temperatures (for an ideal gas), the Maxwell-Boltzmann distribution is spread more widely and has a lower maximum. At lower temperatures, the spread is much more narrow and the peak is much ...
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2answers
63 views

Ideal gas equation and atmosphere of Venus

I'm teaching myself some basics of the ideal gas law and working out simple density equations for atmospheric gases at various altitudes. When I applied the gas law to Venus' atmosphere at its ...
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1answer
307 views

Gas compressed and cooled

If a certain amount of a gas is compressed into a cylinder by the action of a piston that reduces its volume (lets say at a low speed), the kynetic energy of the gas molecules increases, what is ...
2
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1answer
182 views

Bernoulli Equation for isentropic ideal gas flow

If one derives the Bernoulli Equation for the isentropic ideal gas flow you get: $$ \frac{1}{2}v^2 + g z + \left(\frac{\kappa}{\kappa -1} \right) \frac{p}{\rho} = const. $$ Two questions: Is ...
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38 views

Approximating Gas Density

So this was a random thought I had that I thought would be fun to mess around with using an Arduino and some sensors, but after the difficulty I've had I'm just curious to see if it can be done at ...
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2answers
12k views

Work Done in an Isobaric Process

I am given the information that an air parcel undergoes isobaric heating from 0° C to 20° C, and that's all I'm given. I have to determine the work done by the parcel on its surroundings. I know that ...
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2answers
32 views

Density of air using ideal gas law

I need to find the density of air using (I think) the ideal gas law. I have calculated $V$ of an ideal gas at s.t.p. to be $.0224m^3$. I am asked to find the density of air knowing it's temperature ...
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2answers
39 views

Does the increase of pressure of a gas also increase the energy?

It says that in adiabatic process, the heat is constant but the temperature is not. My question is, if you increase the pressure, the temperature is going to rise as pV = kT. But we know that the ...
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2answers
155 views

If I double the amount of oxygen molecules, do I double the paramagnetic force?

Oxygen is well known to be paramagnetic. If I take one molecule, $O_2$, and measure its paramagnetic force due to externally applied magnetic field, and then add another molecule near the first ...
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2answers
219 views

Viscosity for steam in the Reynolds number

In calculating the Reynolds number for a flow of steam in a pipe, this is the general formula I am trying to use: $$Re=\frac{\rho d v}{\mu}$$ with density $\rho$, pipe diameter $d$, flow steam $v$ ...
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2answers
36 views

Mixture of different gases filling their container

If I have a closed container with a mixture of two or more gases $\rho_1$ and $\rho_2$ for instance at thermal equilibrium where $\rho_1>\rho_2$ how would I determine what percentage of the ...
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1answer
13 views

What are the assumptions made when analysing a stretched elastic string from a thermodynamic aspect?

Consider a stretched elastic string. Then conducting a thermodynamic analysis of the elastic string. The approach is very similar to that used for $(P, V, T)$ systems, with the pressure and volume ...
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3answers
238 views

Not Quasi-static, yet reversible process? Is this a valid example?

Imagine a gas (at room temp. and pressure) enclosed in a thermally insulating spherical container. At some instant, the container instantly expands symmetrically (radially outward) to, say, twenty ...
3
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1answer
35 views

Balloon of ideal gas suddenly pops in the vacuum of space - final average energy per atom?

My question is: is the following thinking pretty much correct? I'm interested hearing about anything here that is fundamentally wrong. Of course there is a bit of hand waving and approximation. If a ...
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1answer
37 views

Calculation of internal energy and entropy of ideal gas

I am having some trouble with calculation of entropy and internal energy for ideal gas. All sources which provide such derivations which I managed to find either assume a priori that $U$ is some ...
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2answers
34 views

Why does an ideal gas not consist of identical molecules? [closed]

since the mass , temperature , and number of particles are the same , shouldn't the molecules be the same so that the pressure of the gad is inversely proportional to the volume.
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20 views

If Earth's atmosphere would be cooled, how would its pressure change relative to its temperature?

I have a feeling it would not behave like an ideal gas? For example, if the atmosphere were to cool down at a constant 1 atm to 90 K, oxygen would liquefy. If changing of pressure would be ...
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2answers
94 views

Deriving the Ideal Gas Equation

Im specifically looking at how the IGE can be derived from the kinetic theory of gasses. Most textbooks and webpages I've viewed start off with a wall that the particle is hitting and then writes an ...
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2answers
129 views

physical meaning of pressure derivatives

Is there any physical meaning of the first and second derivatives of pressure with respect to time? If this helps, I am considering ideal gases.
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48 views

Pressure exerted by ideal gas on walls of container

All derivations I've come across are more or less similar to this: All of them take total momentum change as $2mv_{x}$ and divide it by total time to get the force exerted on the wall. That seems to ...
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22 views

Pressure in a balloon as a function of its diameter [duplicate]

Premise #1: Balloon is a perfect sphere Premise #2: We add water in order to increase the diameter of the balloon Is there an equation allowing us to find the pressure in the balloon, as the diameter ...
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1answer
53 views

What height is atmospheric pressure half that at sea level?

$PV = NT$, where T is a constant $P = \rho g h$ but I don't think this equation can hold in this form as the density is most definitely not constant as we go up in the atmosphere $\rho = ...
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2answers
6k views

Work done by isothermal expansion from two different viewpoints

Consider an adiabatic system as follows. It consists of a gas in a container and a piston. Initially, the system is at equilibrium and the gas inside it occupies a volume $V_i$ at a pressure $p_i$ ...
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20 views

Ratio of Stagnation to Normal Flow Properties in Incompressible Flows

I know in compressible flows the ratio of stagnation to normal flow variables is a function of the Mach number and usually the specific heat ratio. Does this ratio mean anything for incompressible ...
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46 views

Is it possible to consider PV diagrams without the equations of state?

Suppose that we have the equations of state for a particular system, or equivalently, that we have the fundamental relation $S = S(U,V,N)$. If we want to write down a PV diagram it will be quite ...
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2answers
108 views

Gases Expanding and Bonding in the Vacuum? Frozen Clouds

Why do gasses expand in space rather than attract forming a liquid? Do some gasses attract or bond when they get colder and what would be the characteristics of it in space? Would it be like powder ...
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0answers
56 views

How to solve PV questions? [closed]

A diatomic gas is expanded according to $PV^{1.3} = constant$. Hence choose the incorrect statement Gas cools at expansion Work done by surrounding is negative Gas expands by absorption of heat from ...
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1answer
46 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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2answers
169 views

How is the degenerate electron gas state “degenerate”?

What is "degenerate" in the degenerate electron gas state? Why is it called degenerate?
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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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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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5answers
50 views

How Heat is constant in adiabatic process

Consider adiabatic cylinder with a piston attached. $Q=0$ in this case and Work done is equal to change in internal energy. If I do work on the piston then its internal energy increases and so its ...
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1answer
54 views

Chemical Potential in the canonical and grand canonical ensemble

I'm studying the ideal Fermi gas from "Statistical Mechanics", by R. K. Pathria. In particular, the following formula, which can be found on page 237: \begin{equation} \mu=\left(\frac{3N}{4 \pi g ...
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2answers
18k views

Calculating work done on an ideal gas

I am trying to calculate the work done on an ideal gas in a piston set up where temperature is kept constant. I am given the volume, pressure and temperature. I know from Boyle's law that volume is ...
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0answers
85 views

Why do we need to suppose the chemical potential is zero in this situation?

I've been working on some statistical mechanics problems and one of them asks to compute the pressure with chemical potential zero of a boson gas whose particles do not interact and whose energies are ...
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2answers
21 views

Would a hybrid mixed medium balloon allow you to use less helium to lift equivalent weight?

Suppose you had two balloons, one inside the other (a inside b). Would filling balloon "a" with the 80% nitrogen/20% oxygen mix you find in the surrounding air at ground level, and then filling ...
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1answer
56 views

Why does the expansion of gas into a vacuum mean that we have less information about the system? (entropy)

I'm reading through Statistical Physics by F. Mandl and in the chapter about the 2nd law of thermodynamics he states that: The basic distinction between the initial and final states in such an ...
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1answer
33 views

Calculating heat absorbed from expanding gas [closed]

I'm trying to calculate the amount of heat absorbed per kg of different types of gas, namely compressed air and carbon dioxide. Starting with carbon dioxide, I found that the Joule-Thompson ...
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0answers
17 views

pipette waterfountain

Place the tip of a pipette in some hot water. Cover the other end with you thumb. Invert the pipette and water sprays out nearly two metres. Is the cool air in the pipette being heated by the hot ...
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1answer
107 views

Compute $\langle x^2\rangle$ for gas of non-interacting particles in a quadratic potential

Consider a 3d gas of $N$ non-interacting identical particles in a quadratic potential, where the Hamiltonian $H$ is: $$ H = \sum_{i=1}^N \bigg( \frac{p_i^2}{2m} + \frac{k}{2}x_i^2 \bigg). $$ After ...
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1answer
49 views

Can't change in momentum be negative?

I was going through a derivation, of Ideal gas equation, PV=1/3 mnc2 and the book showed the following... But I know that change in momentum should be final momentum-initial momentum. But if it is so ...
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1answer
31 views

Calculate the pressure in a container given moles and volume [closed]

Say there are two containers with the same volume. The first has a temperature T and pressure P and contains 1 mole of $O_2$. The second has a temperature 2T and contains 1 mole of $He_2$. I'd like to ...
5
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4answers
2k views

Understanding mathematically the free expansion process of an ideal gas

I'm trying to understand mathematically that for the free expansion of an ideal gas the internal energy $E$ just depends on temperature $T$ and not volume $V$. In the free expansion process the ...
0
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0answers
32 views

Acceleration of an bubble under the sea [duplicate]

An air bubble arises from the bottom of the sea. Find its acceleration if resistance force is proportional to $\rho Av$ where $\rho$ is density of water, $A$ is cross section area and $v$ is velocity ...
3
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1answer
74 views

Can the internal energy of an ideal gas system increase as temperature decreases?

If $\Delta U = Q + W $ Then adding $x$ moles of an ideal gas of lower temperature into a system of internal energy $U$ would increase $U$ as the kinetic energies of the molecules of the colder gas ...
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1answer
54 views

Kinetic theory of physics [closed]

$$E = (3/2) kT$$ For average kinetic energy of a molecule gas.The constant $k$ does not depend on the type of molecule. Can this result be true for both hydrogen and chlorine?