Physics Stack Exchange
Physics Stack Exchange

Questions tagged [ideal-gas]

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

An ideal gas is a theoretical gas composed of many randomly moving point particles (also called Brownian motion) that are not subject to interparticle interactions.

Learn more about this topic from Wikipedia.

1302 questions
26
votes
4 answers

Why is the ideal gas law only valid for hydrogen?

I got this question in school: Explain, based on the properties of an ideal gas, why the ideal gas law only gives good results for hydrogen. We know that the ideal gas law is $$P\cdot V=n\cdot R\cdot T$$ with $P$ being the pressure, $V$ the…
jng224
  • 3,796
22
votes
4 answers

How slow is a reversible adiabatic expansion of an ideal gas?

A truly reversible thermodynamic process needs to be infinitesimally displaced from equilibrium at all times and therefore takes infinite time to complete. However, if I execute the process slowly, I should be able to get close to reversibility. …
Mark Eichenlaub
  • 53,961
20
votes
5 answers

Would the temperature of a gas change when accelerated in a train?

I was thinking about a situation where some gas is enclosed inside a container and kept in a train at rest. The train accelerates, gains a maximum speed and then suddenly stops. Would the temperature of the gas change during this process? I know…
Rajath Radhakrishnan
  • 3,935
20
votes
2 answers

How does a gas of particles with uniform speed reach the Maxwell-Boltzmann distribution?

Take an empty container and fill it with $N$ gas particles (ideally a monoatomic gas), each having the same kinetic energy $E$, then isolate the container. Since initially the speeds don't follow the Maxwell-Boltzmann distribution, such a system…
suissidle
  • 407
19
votes
4 answers

Is entropy real or just a consequence of the way we choose to examine a physical system?

Let's take an ideal gas as an example. Usually, the gas is parameterized in two different ways - by the position and momentum of each of its particles (in the kinetic-molecular model) and by its volume $V$, pressure $p$ and temperature $T$ in…
mdkovachev
  • 547
18
votes
5 answers

Why is the internal energy of a real gas a function of pressure and temperature only?

While studying thermodynamics, I read that the internal energy of an ideal gas is a function of temperature only. On searching the internet, i found an article which stated that the internal energy of a real gas is a function of temperature and…
MrAP
  • 607
17
votes
7 answers

Why is there a maximum humidity?

Recently I've been browsing humidifiers for my room. Everyone "knows" that humidity is measured in percentages, and 100% humidity is the maximum humidity that the air "can hold" - that's how people seem to explain it. But, why should there be a…
spinachflakes
  • 7,318
16
votes
7 answers

How to deduce $E=(3/2)kT$?

It says in my course notes for undergraduate environmental physics that a particle has so-called "kinetic energy" $$E=\frac{3}{2}kT=\frac{1}{2}mv^{2}$$ Where does this formula come from? What is $k$?
Niklas Rosencrantz
  • 1,073
14
votes
4 answers

Deriving combined gas law from Boyle's and Charles' laws

I know that the combined gas law, $$\frac{PV}{T}=k$$ should be derivable from Boyle's Law and Charles' Law. Since these are very basic equations, I presumed that it would be a simple matter, so I tried it myself. Charles' Law is $$\frac{V}{T}=k_1$$…
stett
  • 243
14
votes
8 answers

Is there a pressure gradient in a stationary gas with a temperature gradient?

Consider a gas with ideal equation of state $P = n k_{\rm B} T$, in a fixed rectangular container with two opposite walls maintained at different temperatures, under conditions where there are no convection cells and a steady state has been…
Andrew Steane
  • 65,285
13
votes
4 answers

Why does this perpetuum mobile not work?(Gases and Densities)

I recently came up with the following concept. It is very simple, and may have been thought of before. A picture says more than a thousand words, so here is it explained in a picture: Note that water was used to make the example easier to…
Qqwy
  • 480
13
votes
4 answers

How can the combined gas law be derived from the other three, if none of the variables remain constant?

In Boyles, Charles and Gay-Lussac's Gas Laws, one of the variables has to remain constant in order for them to be true. Therefore, how is it possible that the Combined Gas Law is true, if NONE of the variables are held constant?
suse
  • 1,298
13
votes
2 answers

Does the term "diatomic ideal gas" make any sense?

As per the kinetic theory of ideal gases, ideal gases are considered to behave as point particles that occupy negligible volume, and exert no intermolecular attractions. At the same time, diatomic ideal gas molecules, by definition, must be extended…
Pritt Balagopal
  • 3,237
13
votes
2 answers

Internal energy of an ideal gas as a function of volume

Okay so I've been reading a bit on Thermodynamics and I found something that I couldn't wrap around my head. For an ideal gas, the change in internal energy is equal to $$\Delta U = Q + W$$ And also, if the internal energy is a function of volume…
Vinsen
  • 133
  • 1
  • 1
  • 4
13
votes
5 answers

What happens to the temperature when an ideal gas is compressed?

I am rather confused about this. I know from Charles' law that under constant pressure, the volume of a gas is directly proportional to its absolute temperature i.e. $$\frac{V_1}{T_1} = \frac{V_2}{T_2}$$ Thus accordingly, during compression,…
user36790
1
2 3
…
86 87