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

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Can a point particle experience deformation?

One of the assumptions in an ideal gas is that the particles are small hard spheres. Another assumption is "All collisions between gas molecules are elastic and all motion is frictionless". Assuming ...
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55 views

When deriving pressure, why do we take rebound time to be travelling time?

The derivation of the ideal gas law runs along the following lines. Imagining a container filled with some particles, by definition: $P = F/A$ $F = dp/dt$ $F_{avg} = \Delta P/ \Delta t$ If we ...
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58 views

What percentage of the energy in a dust cloud must be lost before it can collapse into a star?

With reference to this previous question about how dust clouds can collapse to form stars: How is hydrostatic pressure overcome when a star is formed? The answer given is that they must radiate away ...
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144 views

Derivation of ideal gas law

I looked up on the ideal gas law which our high school textbook derives with the empirical Combined Gas Law. However, the textbook did give a good explanation for this equation $$pV = \frac{N}{3}m\bar{...
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78 views

What is the difference between the Method of Characteristics being formulated in terms of theta & alpha and theta & nu?

So I'm doing an MSc thesis involving the method of characteristics in rocket nozzles. My lecture notes have the MoC formulated such that the positive characteristics are defined as: C+ = Tan ( $\...
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26 views

Find initial temperature of ideal gas when heated by 400K and volume doubles [closed]

An ideal gas in a flask is heated by $400K$ and expands its volume by the factor $2$. The final pressure equals the initial pressure. I want to calculate the initial temperature $T_0$. As the gas is ...
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2answers
304 views

Behavior of two gases in a closed container

If two ideal gases with different molecular weights (i.e. nitrogen and argon) are injected into a closed container (of any given size, but assume ~1L), what will happen over time, assuming all ...
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44 views

Density profile in the atmosphere, which equations to use…? [closed]

I came across the following density profile in the atmosphere: ...
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39 views

Gas equation problem

I have been trying to solve this for hours without success. This is a problem: iron bottle (volume is equal $3\,\mathrm{dm^3}$) is filled with oxygen at the temperature of $310\,\mathrm{K}$ and with a ...
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44 views

Does shaking a carbonated soda warm it up?

I had an odd situation where i left a soda near the fridge exhaust and it developed some ice crystals (i could hear it sloshing). When i took it out i instinctively shook up the closed soda can with ...
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1answer
52 views

Struggling with a conversion. Showing number of atoms per cubic meter using pressure in Torr

I have been trying to show that the following is true: N = 9.65 x 10^24 x (P/T) Where N is the number of atoms per cubic meter of an ideal gas at pressure P (in Torr) and temperature T (in Kelvin). ...
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79 views

Finding $U(S,V,N)$ for ideal gas, given $pV=NkT$ and $U(T)=N c_V T$

Given the experimental results for the ideal gas, I want to recover the internal energy expressed in its natural variables as: $$U(S,V,N) = \alpha e^{\frac{S}{N c_V}} V^{\frac{c_V-c_p}{c_V}} N^{\frac{...
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42 views

How much carbon dioxide do we actually ingest from a can of coke?

On this most trustworthy page it states that a 355 mL can of coke contains on average about 2.2 grams of carbon dioxide. As far as I know, this carbon dioxide can exist in solution as carbonic acid, ...
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2answers
161 views

Kinetic energy and momentum of an expanding gas

Let's take the simplest case of an ideal gas undergoing adiabatic expansion against a vacuum of finite volume, without any heat and work transfer into or out of the system. The gas moves in bulk to ...
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3answers
81 views

Is there a dynamic prelude to the state equation?

If I'm not mistaken, the state equation $$PV=nRT$$ also known as the 'ideal gas law' serves as a mathematical model relating pressure-volume-mass-temperature states of an assumed ideal gas. In other ...
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194 views

What is the closest gas to ideal at STP?

I assume it is probably one of the noble gases eg Helium or Argon, but is this true?
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105 views

Is the reason why water in a cup rises if a solid is placed within it the ideal gas law?

Let's say you have a cylinder with water that takes up volume V and has temperature T. When a solid mass is placed within the cylinder, the water momentarily takes up a smaller volume within the ...
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1answer
62 views

Can Kinetic Theory obtain fluids behavior?

My understanding is that it can't. But when presenting it here I received comments that contradict this. So, as suggested, I am asking the question to be able to receive concrete approaches on this ...
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51 views

sudden volume increase piston

I am wondering what happens in the following situation. I have a piston filled with an ideal gas for which I suddenly/instantaneaouly iscrease the volume. In particular I want to know what happens to ...
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89 views

Calculating volume of tank by measuring airflow and pressure raise

I have been doing some pneumatics recently, and it came to my mind that volume of some tank could be calculated by measuring airflow ($\mathrm m^3/\mathrm s$) and the speed of pressure raise ($\mathrm ...
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21 views

Temperature and air flow - are they related?

If I open a window, does the air "changes" (e.g. the $O_2$ concentration) in the room more quickly if there was a temperature difference between inside and outside?
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61 views

Change of temperature in liquid when it is pressurized fast to high pressure

Here's one question I've been thinking for some time: Let's assume that certain volume of water (or any other normal liquid, I'm just thinking how these kind of things should be calculated) is ...
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63 views

Difficulty in understanding Maxwell Boltzmann distribution in case on ions in a field

I learned that the velocity of molecules obey Maxwell Boltzmann (MB) distribution at a Temperature T. If I have ions of mass 'M' accelerated to 2eV in a specific region. As the ions are not "...
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318 views

What is the pressure of a charged gas?

I have $N$ ${\rm H}^+$ gas molecules in a sealed, electrically insulated container. What equation can I use to accurately calculate the pressure of the gas? It seems to me that $PV = nRT$ will not ...
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1answer
45 views

Do siphons work for gasses?

There are videos of sulfur hexafluoride which show it is so dense (6.17 kg/m^3), an aluminum foil boat will float on it like water. I'm curious if gasses can be used in a siphon. I'm particularly ...
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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,...
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731 views

Simpler derivation of Sackur-Tetrode equation

Is there a reason the following derivation for the Sackur-Tetrode equation is not common? I am teaching a lower undergraduate level class and would like to derive it with simpler terms of only using ...
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53 views

Can a flowing gas create a static charge?

On the Static Electricity page of Wikipedia the claim is made that "The flowing movement of gases in pipes alone creates little, if any, static electricity" with a cited reference [ref 19] being made ...
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77 views

Pressure profile and output of a coil heated burner

In a hot air balloon burner (and probably lots of other burners) liquid gas is passing through a heating coil before it exits at a hose. I realize that the point of having a heating coil is to ...
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1k views

How do I keep the temperature constant in a Boyle's Law experiment?

I'm trying to get a head start on our lab experiment next week about Boyle's Law. The set-up is we have an air chamber can immersed in a pot of boiling water (which is kept boiling over an electric ...
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1answer
458 views

Calculate pressure from partition function with separated volume geometric parameters?

How does one calculate the pressure from the partition function if it is specified in terms of three parameters defining the space of which the gas occupies, but all three parameters are not always ...
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53 views

Constant RPM of Gas Compressor

I would like to improve my understanding of gas compressors. If the compressor is moving at constant RPM, does it mean that it can only allow the same volumetric flow rate at all times? So the power ...
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1answer
310 views

Is average kinetic energy equal to the total thermal energy of a gas?

"Average KE" as in this equation: $$K_{average} = \frac{3}{2} kT$$ Since potential energy in ideal gas model is eliminated, I guess this equation is also for the total thermal energy of a gas/a ...
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128 views

Efficiency of a compressed air engine

I am doing some personal research on the efficiency of compressed air cars. I am currently trying to come up with an 'ideal' cycle to use as a reference for efficiency (c.f. Otto Cycle for petrol cars)...
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1answer
178 views

What does chemical potential $\mu = 0$ mean?

First off, just to be clear, the chemical potential being equal to zero is different from not having a chemical potential at all (e.g. a photon gas)? Now: physically, what does having chemical ...
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3answers
267 views

Does a gas in a container lose kinetic energy?

When a gas is in a container, it frequently collides with the container wall, exerting pressure. However, with a collision, kinetic energy ought to be transferred from the gas molecule to the ...
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6answers
489 views

Why it is colder in mountains, at high altitudes?

The conventional answer is to say that "lower temperature follows from lower pressure because temperature is average molecular energy (average speed)". For instance "Temperature is a measure of ...
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1answer
39 views

Mono-atomic gas particles coupled by spring forces don't care how many particles are involved?

I calculated the partition function of $N$ classical atoms of identical mass $m$ who all experience a mutual spring forces with identical spring constant $k$. The Hamilton is \begin{align} H = \dfrac{...
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123 views

7/2 versus 9/2 for diatomic heat capacity

Question I calculated the classical heat capacity of a diatomic gas as $C_V = (9/2)Nk_B$, however the accepted value is $C_V = (7/2)Nk_B$. I assumed the classical Hamiltonian of two identical atoms ...
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253 views

Calculate pressure with the ideal gas law or $\rho gh$?

In a container the pressure on the walls due to a gas can be calculated using the ideal gas law $\bigl(pV=NRT\bigr)$. However, for a column of water, or the pressure at earth's surface due to a ...
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1answer
879 views

Why do we ignore rotational energy in monatomic gases? [duplicate]

I understand that the average energy of each degree of freedom in a thermodynamic system is $\frac12kT$. And so, for an ideal monatomic gas, there are three degrees of freedom associated with the ...
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185 views

Rapid/ Slow Expansion in Gases

How is rapid expansion of gases different from slow expansion?
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313 views

Can the Sun's core be treated as an ideal gas?

I know that a gas behaves more like an ideal gas at higher temperature, and that is very well achieved in the Sun's core. But also low pressure is needed for a gas to behave like an ideal gas, and the ...
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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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52 views

Can I interpret Avogadro's principle of gases from the state equation (ideal gas law)?

Considering the molar form of the ideal gas law I can solve for the ratio of some gas volume, $V$ divided by the number of gas particles, $n$ in mols $$\frac{V}{n}=\frac{RT}{P}$$ And $R$ is the ...
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1k views

Why is it difficult to mix helium and nitrogen gases?

I recently learned an interesting fact: That it's difficult to mix helium and nitrogen gases in a compressed gas cylinder. Gas suppliers that need to mix the two gases have to rotate the cylinders for ...
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1answer
188 views

Monatomic gas work

Recently I was trying to solve the following problem: monatomic gas expanded from 0.2 to 0.5 m^3 and pressure increased from 404 to 808 kPa. Find work done by gas, heat gained and change in internal ...
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20 views

How abruptly would you have to brake to form an almost complete vacuum in the back seat? [duplicate]

Suppose you brake with a car (or any other moving object). As the air inside will rush forward, won't there be a relative dearth of air molecules in the back? So, how strong does the acceleration have ...
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191 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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1answer
57 views

Isothermal Atmosphere

I was taught that for isothermal atmosphere: $\frac{dP}{dz}=-\rho g$ How come the equation is only true for isothermal atmosphere? I suppose $dP$ can be caused by changed in temperature as well?