Questions tagged [ideal-gas]
A gas that behaves as randomly moving, non-interacting molecules. This allows a simplified equation of state.
0
votes
0answers
21 views
Derivation of density of states for a gas with $N$ states
I am trying to find any information on the derivation of the density of states for a system with periodic boundary conditions in 3D. I know how it works with 1 particle since I have seen the ...
2
votes
2answers
70 views
Does $PV\propto T$ apply to a photon gas?
For an ultrarelativistic ideal gas, I know that
$p=\frac{u}3$;
$TV^3 =$ constant;
$pV\propto T$.
For a photon gas, I know that the first two results apply as well. However, I am unsure if the third ...
-2
votes
0answers
18 views
Query related to molecular gas dynamics [on hold]
Please refer to the question : https://imgur.com/a/8dk7aj8
And my attempt : https://imgur.com/a/ckE3yOq
Is it correct or not ?
0
votes
1answer
32 views
Bouyancy of ozone gas
If ozone is $O_3$ why is it an outer layer of the atmosphere? It seems $O_3$ would sink in a solution of $O_2$, rather than float on it.
0
votes
0answers
36 views
Ideal gas as balls in boxes in different ensembles
I have some questions about the ideal gas in different ensembles. Often boxes with moving balls are used to explain an ensemble. Now I am confused what the difference would be in the corresponding ...
0
votes
1answer
47 views
Applying ideal gas law to every day problems
Three classical examples of seeing the ideal gas law in action:
crumpled water bottle in cold car
crumpled water bottle after your flight lands
fridge door harder to open a second time after first.
...
0
votes
1answer
29 views
Is the thermal expansion of gas dependent of its nature? [on hold]
First: Is the thermal expansion of gas dependent of its nature, i.e. of its constituing atoms/molecules?
If so : I am looking for a way to find a (real or perfect) gas with high thermal expansion and ...
-1
votes
0answers
22 views
Bernoulli and the Venturi effect vs pressure
I am having a hard time understanding how pressure changes as related to flow, and also as it relates to the ideal gas law, assuming ideal conditions.
According to Bernoulli's equation, as pressure ...
1
vote
0answers
26 views
Boltzmann transport equation for granular gases
I am researching about granular gases and their collisions, and have come across this Boltzmann transport equation:
$$\frac { \partial f ( v ) } { \partial t } = \iint d u _ { 1 } d u _ { 2 } f \left( ...
0
votes
2answers
44 views
Deriving pressure from particle velocity: missing 1/3 factor
Let us assume we have a perfect gas, isotropic, homogeneous, inside a cube of side a.
We want to calculate the pressure as a function of the velocities of the particles inside.
We must find the ...
1
vote
2answers
36 views
What is the criteria of trapped ideal gas to form Bose-Einstein condensate (BEC)?
If we have ideal gas of bosons in a trapped harmonic potential, is the only necessary thing for BEC is a temperature less than the transition temperature? Or is there any other things we should keep ...
-3
votes
2answers
60 views
Compression of gas [closed]
What happens when a gas kept in a metallic container is suddenly compressed via a piston and left for some time? Does the pressure increase or decrease?
0
votes
1answer
44 views
How was Maxwell able to derive velocity distribution? [closed]
Did he assume that their velocities follow some kind of statistical distribution and fit the parameters accordingly. Or did he mathematically prove it?
2
votes
2answers
121 views
Thermodynamic Entropy seems to be contradictory
For an ideal gas the entropy change with energy is inversely proportional to temperature:
This must yield:
$$S=\frac 3 2 k_B \ N ln(T)$$
For various reasons, this equation is hard to find.
...
4
votes
2answers
91 views
Does quantum gases obey ideal gas equation $ PV= nRT$?
At extremely low temperature, does an ideal gas of bosons or fermions obey the ideal gas equation, $PV= nRT$?
1
vote
2answers
43 views
Are forces of gases intensive or extensive?
What am I wrong at in here:
I read that pressure is an intensive property.
According to this and to $P=\frac{nRT}{V}$, can this be true:
$(1)$: When $V$ is constant, increasing $n$ won't increase $P$,...
0
votes
2answers
47 views
Definition of volume of a gas and Amagat's law
How would you define the volume of an (ideal) gas?
I would say it is the volume of the container holding the gas (whether it is a fixed container or a flexible one like a balloon).
However, ...
0
votes
0answers
27 views
How to find Volumetric Expansion if not given the volumetric coefficient?
I'm doing a few practice questions on thermodynamics to prepare for my exams next year and I have been stuck with this question ever since. I tried to move on to answer other questions and came back ...
1
vote
1answer
29 views
Proportionality between pressure, volume, and number of microstates for an ideal gas?
I'm pretty new to Thermodynamics, but I've been playing around with some different computations to reinforce my understanding. I came across the result $$\Omega \propto \left( PV^\gamma \right)^{fN/2},...
0
votes
1answer
25 views
What would be the total pressure in this container in accordance to the Ideal Gas Law?
If I had an apparatus such as the one below:
where each of the four blue lines represents a valve, and then I was to open the three lower valves such that the pipes connecting the three containers ...
0
votes
1answer
37 views
Does the amount/speed a balloon rises vary with the temperature of the gas inside, given a constant type and amount of gas?
I'm attempting to conduct an experiment with a balloon. I fill it up with some amount of helium. If I cool the balloon down (say with liquid nitrogen), the balloon's volume will decrease (because of ...
0
votes
1answer
45 views
Joule expansion and center of mass
This question comes from a doubt resulting from some physics forums. Similar to and related to this question, I have a doubt on Joule expansion raised by reading too much bad faith arguments.
I'm not ...
0
votes
2answers
61 views
Does Avogadro's law only apply to ideal gases?
I know the ideal gas law may change a little when for real gases or diatomic ones does Avogadro's law change too or does it stay the same?
0
votes
1answer
45 views
Limitations of converting pressure into kinetic energy
Bernoulli's principle states that an increase in the kinetic energy of a fluid occurs simultaneously with a decrease in pressure for isentropic processes. What then limits us from converting all of ...
1
vote
3answers
100 views
Ideal gas and moveable pistons
Suppose there is an ideal, monatomic gas contained in a cylinder with a moveable piston and you bring that system (system = gas only) through some process. If that process changes the volume (or ...
0
votes
3answers
51 views
How does a gas spring work?
I read Wikipedia and do not understand the following.
If you create pressure on the gas (or any spring) it gives pressure against.
Why is the gas spring holding mass when pulled out, and while ...
0
votes
2answers
48 views
What kind of ideal gas process a positively sloped line in a $pV$-diagram represents?
I've come across an ideal gas process which can be represented by a positively sloped line in the $pV$ diagram. I found something about this on KhanAcademy, but it's simply a worked example on how to ...
0
votes
1answer
33 views
Finding the internal energy change of an ideal monoatomic gas using a graph
Here's what the text says (in the graph, $V$ is in cubic meters and $P$ is in atm):
A sample of an ideal monoatomic gas goes trough the process shown in the figure below. From $A$ to $B$, the ...
1
vote
1answer
33 views
Modelling Oxygen Diffusion [closed]
I am creating a system of differential equations to model oxygen diffusion in tissue.
I have:
$\frac{dP}{dt}=D_o\nabla^2P-qn$
where $q$ represents the sink rate at positions occupied by cells, $n$ ...
0
votes
1answer
24 views
Kelvin and kinetic theory of gases
I know that the degree of freedom increase by 2 when the temperature is high and decrease by 2 when the temperature is low. A dumb question here, what temperature is considered as 'high temperature' ...
0
votes
1answer
44 views
Energy Equation of an ideal gas in expanding space-time
Short question:
If the energy equation of an ideal plasma is written as follows:
$\begin{equation}
\frac{\mathrm{d}p}{\mathrm{d}t}=-\Gamma p\nabla\cdot v-\left(\Gamma-1\right)\left( \nabla\cdot q-\...
0
votes
1answer
42 views
How does an ideal gas radiate?
Recently I've been reading a lot about blackbody radiation, Rayleigh-Jeans law, Planck's law and the UV catastrophe.
In deriving the Rayleigh-Jeans and Planck's laws, we are examining a perfectly ...
0
votes
1answer
53 views
Carnot cycle with isometric processes
Consider the following slightly modified Carnot cycle with two extra isochoric processes for an ideal gas of adiabatic constant $\gamma$ working between temperatures $T_H>T_C$. A pV diagram is ...
4
votes
5answers
169 views
What would happen to a room full of neutrons?
Suppose you had a room full of neutrons at standard pressure and temperature. Would it be just like a room full of hydrogen?
0
votes
2answers
49 views
Combined gas equation in adiabatic process
We know that $PV^{\gamma}=constant $. There are also 2 more equations which relates $P$ & $T$ and $V$ & $R$. Is there any equation which relates all these 3 things like ideal gas equation?
...
4
votes
0answers
80 views
Weird and unintuitive results from thermodynamics/hydrostatics for an isothermal atmosphere and possible explanation(?)
It is known from hydrostatics that for a fluid in equilibrium in a gravitational field,
$$\frac{dP}{dz} = -ρg$$
Let us from now on suppose the atmosphere is isothermal and has temperature $T$.
We ...
1
vote
1answer
37 views
Is it possible to estimate the average time until entropy decreases a certain amount?
We all know the classical Joule free expansion experiment for an ideal gas: we trap an ideal gas inside half of a cylinder. Then, we open the door and the gas expands to the whole cylinder. After ...
0
votes
3answers
239 views
What is the meaning of $PV^\gamma=$ constant in an adiabatic process?
In an adiabatic process, heat transfer doesn't occur and hence $\Delta U=-W$ (an increase in internal energy due to work done on the system or a decrease in internal energy due to work done on the ...
0
votes
0answers
22 views
Difficulty in calculating effusion rate using the kinetic theory of gases and statistical mechanics
I have tried multiple sources and methods, but my attempts at a proof of the number of particles leaving a gas using statistical mechanics keep finding the same wrong result. I have tried to read ...
1
vote
1answer
37 views
Confusion while deriving kinetic-molecular theory of gases
How many of the molecules will collide within a given area A of the
wall normal to the x-direction in some fixed time interval Δt ? On average half the molecules have a positive x-...
2
votes
3answers
106 views
Atmospheric pressure, density and temperature variation with altitude
I'm trying to understand how one can calculate pressure, density and temperature of the atmosphere as a function of altitude.
My assumptions are mostly sourced from https://en.wikipedia.org/wiki/...
0
votes
1answer
29 views
Ideal gas law in combustion engine analysis
I'm studying this derivation of the Diesel engine theoretical efficiency:
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/diesel.html
Here the ideal gas law is used in many occasions. Why is it ...
0
votes
1answer
58 views
Why is potential energy zero in this calculation of partition function?
In section 7.2 of Rief's "Fundamentals of Statistical and Thermal physics". While calculating the partition function for ideal gas he writes:
$$
\begin{array}{l}
\displaystyle{Z'
= \int{
\...
5
votes
1answer
344 views
As I inflate a balloon at a constant temperature does the pressure of gases inside it on the balloon increase?
I know it's a dumb question but I am having a little misunderstanding with Boyle's Law.
Shouldn't pressure be inversely proportional with Volume , or this is meant for the pressure outside of gases ...
1
vote
0answers
45 views
Temperature increase of a gas in a period of time [closed]
Pardon my simple question for you physics geniuses but:
I'm attempting to simulate hot air balloons for a game. I have a gas of known volume, temperature, pressure and density inside a confined space....
0
votes
1answer
30 views
Is translational/rotational KE conserved when diatomic molecules collide?
When two diatomic molecules of a gas collide, is the collision elastic or inelastic? Is rotational KE also conserved/not conserved?
My guess is that translational KE is conserved while rotational KE ...
1
vote
3answers
93 views
If we push a syringe with gas in it In space , would its temperature increase permanently , Violating Boyles Law?
On Earth
If we push a gas syringe very fast Inwards , work is done on the gas by
W = PV
which increases the Kinetic energy of molecules in it and since Temperature is Average Kinetic Energy ...
1
vote
2answers
35 views
Does Temperature decrease on increasing No of mol of a gas in container ?
ideal gas Law says that
PV/T = nR
So does lets say you increase n
and you Keep P and V constant
should'nt the temperature decrease?
0
votes
1answer
46 views
Confusion between molar gas constant and boltzmann constant?
So after reading reading through internet I came to the conclusion that :
For gas of any element
PV/T = Constant of proportionality
and that constant of proportionality can be expressed in ...
0
votes
1answer
63 views
In ideal gas $\partial_V(PdV)_T=P$
First $\partial_V(PdV)_T=\partial_V(PV)_T=P$
However, if write it by chain rule and $P=nRT/V$
$\partial_V(PdV)_T=P\partial_V(dV)_T+\partial_V(P)_TdV=P\cdot 1+\partial_V(P)_TdV=P+P=2P$.
What's wrong ...
