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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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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 ...
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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 ...
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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 ?
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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.
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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 ...
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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. ...
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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 ...
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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 ...
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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( ...
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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 ...
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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 ...
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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?
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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?
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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. ...
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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, $PV= nRT$?
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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 $P$,...
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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, ...
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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 ...
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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},...
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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 ...
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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 ...
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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 ...
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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?
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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1answer
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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, $n$ ...
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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' ...
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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-\...
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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 ...
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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 ...
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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?
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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? ...
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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 ...
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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 ...
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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 ...
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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 ...
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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-...
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3answers
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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/...
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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 ...
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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{ \...
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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 ...
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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....
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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 ...
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3answers
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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 ...
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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?
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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 ...
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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 ...