# Questions tagged [ideal-gas]

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

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### Does Humid Air Rise (neglecting the effects of weather turbulence-for example in a closed environment like a sealed room)

An internet search will find many people claiming that Humid Air (water vapor) rises. However, I am skeptical because if lighter molecules rose then, it follows that the air would be stratified by ...
1answer
362 views

### How to find the work done by compressing gas?

What is the work done by the piston when the piston is compressed and there's no internal energy/heat lost from the gas(thermally insulated)? The reason I can't solve this problem is because I have ...
1answer
513 views

### External or internal pressure in the gas laws

Does pressure in the ideal gas law and other gas laws (Boyle’s, Charles’s, and Gay-Lussac’s) mean the external or internal pressure?
1answer
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### Plotting a $PV$ diagram for free expansion — why is it undefined?

Apparently trying to plot a $PV$ diagram for an adiabatic free expansion of ideal gas is undefined. I'm taking issue as to why this is the case. From what I understand using my diagram attached as my ...
0answers
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### How was the ideal gas equation derived?

How did people come up with the formula: $$PV = nRT = k_BT \qquad$$? I see two possible ways: 1.) We did some measurements and defined $$kB:=\frac{PV}{T},$$ remarking that $\frac{PV}{T}$ is ...
1answer
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### Kinetic theory for Charles' Law: does frequency and time interval of collisions change?

So I was given this table in class about Charles' Law: The table I got from class says that the time interval and frequency of collisions increases. However, if the velocity of molecules and volume ...
2answers
119 views

### Ideal gas with sticky wall

A collection of $N$ point particles is held inside a cubic box of side $L$. The walls of the box are sticky. This means that when a particle collides with a wall, it stays attached for a short period ...
1answer
137 views

### Velocity for a straight line collision

I get that the force of a collision is m(Δv/Δt). What I do not get is why the change in velocity for a straight-line collision m(2v/Δt). Why is this?
2answers
379 views

### Does the internal energy of single-phase materials depend primarily on temperature or does it depend on pressure as well?

I am confused about the relation between the internal energy and temperature of ideal gases and single-phase materials. The following two statements from two distinct sources are mainly the reasons: ...
1answer
2k views

### Derivation of the virial expansion

It is easy to derive the ideal gas law form the kinetic theory of gases, but how do you derive the other coefficients of the virial expansion? Is it even possible to get a closed-form formula for the ...
3answers
1k views

### Why does the specific heat of a real gas depends on temperature but not for the ideal gas?

The specific heat of a real gas, unlike an ideal gas, depends on temperature. How can we physically understand this? Thanks.
1answer
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### Different ways to perform an adiabatic expansion

In this Wikipedia article https://en.wikipedia.org/wiki/Joule_expansion#Entropy_production, three ways to perform an adiabatic expansion are mentioned. Irreversible non-quasistatic Irreversible ...
1answer
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### Model to predict temperature of the Sun?

In a homework problem, we were to assume the Sun is a sphere with uniform density and use the hydrostatic equilibrium equation to compute the pressure at the center of the Sun? Upon doing this, I was ...
1answer
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### Confused about ideal gas law with two types of gases

Suppose I have a ideal gas mixture consisting of two different types of ideal gases, say $A$ and $B$, in a container with volume $V_{tot}$. There are $N_A$ particles of gas $A$ and $N_B$ particles of ...
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### Collisions of gas molecules with walls of a container [closed]

I am to calculate the rate of collision of gas molecules with the walls of a container with dimensions $3m\times4m\times2m$ at room temperature (20°C) and pressure 1atm. For reasons of simplicity I ...
1answer
398 views

### When do ideal gases stop behaving like ideal gases?

Sometimes I don't know which method I should use to calculate the volume of the gas in a system, I'm not sure if I should use the table values for the specific volume, or if I should calculate by ...
2answers
9k views

### Why is $PV^\gamma$ constant in an adiabatic process?

In non isolated systems where there is no adiabatic process, $PV$ is constant. But the graph gets steeper in adiabatic process because of the $\gamma$ over the $V$. Why is it there in adiabatic ...
3answers
425 views

### What does happen if I push a piston in an adiabatic cylinder containing an ideal gas?

What does happen if I push a piston in an adiabatic cylinder containing an ideal gas? According to Ideal Gas Equation: $$PV=nRT$$ Is it possible to predict what's going to happen? Will Temperature ...
0answers
263 views

### Sod shock tube - Contact Discontinuity

sorry for bothering with my question. https://en.wikipedia.org/wiki/Sod_shock_tube I have trying to understand, how is it possible to have a discontinuity on Density and not on Pressure. I don't ...
1answer
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### Nebulas and Ideal Gas Equation confusion

I was wondering how stars form and watched this video: https://youtu.be/mkktE_fs4NA?t=18s The lady says: "Gravity brings matter together. And when you bring matter together, when you squeeze ...
3answers
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### If pressure is proportional to temperature, why aren't compressed gases always hot?

When you compress a gas, say within a deodorant can, it temporarily heats up, but then cools to room temperature whilst in the can. It will then cool down to below room temperature once decompressed. ...
2answers
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### Ideal Gas and Thermodynamics

The question is : Let M and N be specific heat at constant pressure and specific heat at constant volume. M - N = a for hydrogen gas M - N = b for nitrogen gas Then find the relation between a and ...