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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Thermodynamic Problem: Heating of House with Open Windows

I recently ran into the following interesting problem I am now stuck on: $$S = \frac{n}{2}(\sigma+5R\ln\frac{U}{n} +2R \ln\frac{V}{n}) $$ The air inside a house with open windows is initially in ...
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Demonstrating the average dot-product of relative incident velocity with CM velocity of colliding pairs of ideal gas atoms is zero

In The Feynman Lectures on Physics Vol. I Ch. 39: The Kinetic Theory of Gases an argument is given in 39–4 Temperature and kinetic energy, showing that the average value of the dot-product of the ...
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Understanding Feynman's development of the ideal gas law: Vol I 39-2 of The Feynman Lectures on Physics

In The Feynman Lectures on Physics, Volume I 39-2 The pressure of a gas, the following is presented: If $v$ is the velocity of an atom, and $v_{x}$ is the $x$-component of $v$, then $mv_{x}$ is ...
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Air coming out of balloon

I have discovered recently that when we have a balloon in a room filled with air, with temperature $T_1$, and then this balloon gets a hole and air is let out, the temperature of the air that comes ...
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215 views

Adiabatic expansion of ideal gas

I am considering a system with initial pressure $P_{A}$ and volume $V_{A}$. The internal energy $U_{A}$ should be zero. Then I have the following law for an ideal mono atomic gas $P^{3}V^{5}=const$. ...
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Thermodynamics and gaseous state combination question

A water vapour filling the space under the piston of a cylinder is compressed (or expanded) so that it remain saturated all the time,being just on the verge of condensation. Find the molar heat ...
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Wave equation on Air- Solid interaction

Suppose that there is, due to an explosion $h$ meters above the ground, a wave in the air with high density, velocity and pressure, capable of inducing an elastic wave on the earth's surface. How does ...
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Why do aneroid barometers have error with temperature?

Altimeters use slightly evacuated (compared to atmospheric pressure at sea level) metal aneroid wafers. The wafers have a reference pressure outside the aircraft referred to as the "static port". ...
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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 ...
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Isothermal compression without a heat reservoir

I have devised a method to isothermally compress a gas without the use of a heat reservoir. Consider a container of gas. To compress the gas normally, one would simply move one of the walls of the ...
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Degeneracy in Maxwell Boltzmann distribution

While deriving Maxwell-Boltzmann distribution function we consider particles having degeneracy. But in classical mechanics how the concept of degeneracy of particle comes within?
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Will the discrete emission of Green House Gases (GHG) increase the global temperature by an infinitesimal amount?

Suppose you take a trip with a gas-guzzling car on a Sunday. Will your action increase the global temperature by an infinitesimal amount?
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Why are compressed air tanks cold? [duplicate]

Why is a compressed air tank cold to the touch when it’s in a compressed state before use?
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Perfect gases and gravitational field

I have made this reasoning, thinking about it for a time but it's time to ask to you for comments / opinions and solider advices. Let's take a perfect gas: we know the temperature is related to the ...
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Would a plane get lighter if dry ice is inside and it sublimes during the flight?

During a series of comments here, it was suggested that taking dry ice into an airplane, the airplane gets lighter as the ice sublimes. This was supported by the idea that when the dry-ice sublimes ...
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Internal energy of an ideal gas?

From my past studies I have had the presumption that for an ideal gas the equation: $du=c_v dT$ ( where $du$ is the density of internal energy, $c_v$ is the specific heat capacity at constant ...
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Why in an ideal gas as the volume increases, both the pressure and the temperature drop?

I was reading Fundamentals of Physics(Halliday, 10th ed.), chapter 19, when I saw a statement "Figure 19-15a shows our usual insulated cylinder, now containing an ideal gas and resting on an ...
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Example of reversible isochoric process for an ideal gas

I’ve seen many books considering reversible isochoric processes performed by an ideal gas. But is that possible? Suppose I’ve a general isochoric process going from A to B, suppose I’m having a ...
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Speed of Bubble in Coke

I was trying to solve the following problem, but my results seem illogical when I graph my solution. Assuming we have a bubble at the end of a coke glass, I want to solve for the speed of the bubble ...
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Relating the maximum entropy with the pressure given in terms of volume

For a monoatomic ideal gas let the pressure of gas in a container be given as $p=p_0- \alpha V$ Where $p_0$ and $\alpha$ are constants and $V$ is the volume of gas. Then find the volume at which ...
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608 views

Ratio of specific heats of mixture of gases

Suppose I have $1$ mole of a monoatomic gas and $1$ mole of a diatomic gas. If I mix them, the ratio of their specific heats at constant pressure to that constant volume becomes:$$\gamma = \frac{3}{2}$...
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Is the thermal energy of the an ideal gas equal to the sum of the kinetic energies of the individual particles?

I have been wondering about it all day as I heard that particles of bodies at absolute zero have no kinetic energy. So, is it true that the total kinetic energy of an ideal gas is equal to its thermal ...
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How do we choose the path when deriving the ideal gas law?

So, my textbook details the derivation of ideal gas law in this way: $$m_0v -(-m_0v)=2m_0v \tag{1}$$ $$F=\frac{2m_0v} {\Delta t} \tag{2}$$ $$\Delta t = \frac {a} v \tag{3}$$ $$F=\frac{2m_0v^...
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Why is the work done by the system equal P external x (V final - V initial)?

Please See this video https://www.youtube.com/watch?v=j_6JxoL8qD4 Firstly, at 1:13 in the video, is the work done here by the system or on the system? Secondly, are V final(s) in both cases equal? ...
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$h^3$ term in probability density function of ideal gas

Other than that we need the $h^3$ to 1) make the units correct and to 2) account for the normalization of the probability distribution, what interpretation can we give to this $h^3$ term in \begin{...
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What value does $\Phi$ take in this formula for ideal gas entropy?

In Wikipedia's ideal gas article there is a derivation for the thermodynamic entropy that results in $$S = Nk\ln\left[\frac{V}{N} \left(\frac{U}{\hat{c}_V Nk}\right)^{\hat{c}_V} \frac{1}{\Phi}\right],$...
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Chemical potential for ideal fermi gas with single particle energies $\epsilon_k^{\pm}=\pm \hbar c |\mathbf k|$

I came across the following question in some example problems for my graduate statistical mechanics course final exam: Consider an ideal gas of fermions of density $n$ in three dimensions with the ...
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In a gravitational field, will the temperature of an ideal gas will be lower at higher altitude?

I know there are similar questions, but I have some arguments which seem to explain that temperature of an ideal gas in a gravitational field will be lower at higher altitudes. I am assuming that: 1....
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Determining volume of gas evolved when a specimen is heated

I have a question regarding ideal gasses and pressures. The end goal is to determine the amount of gas (volume) evolved when a specimen within the vessel has been introducted to heat. The specimen ...
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What law or formula discusses the relationship between pressure and dew point?

A lot of times, dew point is focused primarily upon temperature and relative humidity. However, that same point of saturation is affected by the pressure, but I can't find a formula, or law even, that ...
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How long does it take for a balloon to deflate?

Since gas flows from an area of high pressure to low pressure, upon opening an aperture on say a balloon one would expect the contents to diffuse out until both the inside and outside reach a pressure ...
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Ideal gas going though an adiabatic process

Adiabatic process is a process in which there is no heat exchange between the surrounding and the gas. So for example if an expansion happens really fast this process is adiabatic because there is no ...
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In the Ideal Gas Law, why is the variable for Gas Constant labeled as an R?

The formula is written as PV=nRT. Seems like they had a logical progression going on in regards to labeling for the most part: Pressure being a P, Volume being a V, and Temperature being a T. ...
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Is vapor pressure affected by dissolved gasses in the liquid?

If I take a half full bottle of water, seal it with a pressure gauge, and wait a few days then it will be at equilibrium. If I observe the pressure, that would be the water vapor's pressure. However, ...
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Derive Charles's Law from ideal gas equation

For a thermodynamics experiment I had to determine the ratio of the volumes of two tanks. The process used was isothermal. I pressurized up one tank and slowly opened the valve between the two tanks ...
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Relation between particle numbers and collisions between gas molecules inside a closed container

I'm not a physicist, nor studying physics, so this may be a dumb or a very hard question, I don’t know. I'm not sure if I used correct tags, feel free to correct them if you feel like it is necesary. ...
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Is there a way to derive the ideal gas law from statistical mechanics?

If notions of thermodynamics emerge from statistical mechanics, is there a way to derive the ideal gas law? And this derivation would be more "fundamental"?
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How can I calculate the efficiency of an air-powered car?

An air-powered car is powered using high pressure compressed air stored in a tank. The pressurized tank is connected to an air-powered engine. The volume of the tank is 0.3 m3, and the initial ...
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Gas Laws: Why is PV directly proportional to mT?

My book mentions that the three informal gas laws (Boyle's, Charles', and Gay-Lussac's) can be combined into a more general relation PV ∝ mT (the precursor to the Ideal Gas Law). Where: P is ...
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Gas expansion and temperature

A piston is freed and the gas inside is expanded, volume will increase therefore temperature will increase too according to charles law, right? But at the same time pressure will decrease and so ...
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Immediate pressure change after compressing a gas

I'm confused with some of the pressure and temperature implications of compressing gases with minute, incremental changes and doing it suddenly. Below is an exercise I've been attempting: Here is my ...
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p vs V graph - dependence question

Context: I'm reading Fermi's Thermodynamics. On page 6, he states that the work done transforming a system from state $A$ to state $B$ (with the accompanying graph below) is given by $$W=\int_{V_A}^{...
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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 ...
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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 ...
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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?
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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 ...
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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 ...
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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 ...
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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 ...
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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?