Questions tagged [gas]
This tag is for questions relating to "gas", one of the four fundamental states of matter (the others being solid, liquid, and plasma). Gases follow certain laws known as the gas laws. These laws tell us about the behavior of gases i.e., the values and relations of temperature, pressure and volume etc.
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What would be the equation for calculating the total kinetic energy of a gas like nitrogen at a given temperature? [closed]
I want that we calculate the kinetic energy of gas with 3/2nRT, and I have seen in my books to use the same equation for a diatomic gas like nitrogen. Should it be 5/2 nRT , as nitrogen have a degree ...
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Evaluating Maxwell Relations with Constant Entropy for Arbitrary EOS
If you were given a Gas Equation of State, whether that be Ideal, van der Waals, Redlich-Kwong, or some more complex EOS, and you needed to evaluate a Maxwell Relation such as $\left(\frac{\partial p}{...
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Archimedes' principle for gases
https://www.toppr.com/ask/question/archimedes-principle-does-not-apply-to-gases/
https://byjus.com/question-answer/archimedes-principle-cannot-be-applied-to-gases-true-false-1/
These two pages say ...
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Enthalpy of a Van der Waals gas continuation
In my previous question Enthalpy of a Van der Waals gas, I got the expression of the enthalpy generalised, but I am still having issues finishing it since it might have some quite hard calculus...
For ...
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Enthalpy of a Van der Waals gas
I was thinking about how would one find the enthalpy in terms of $V,T$ but not on the usual ideal gas, but instead on a Van Der Waals gas with constant temperature, that is, a gas that satisfies: $$(P+...
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Does internal energy depend only on temperature?
In isothermal expansion of an ideal gas, $ \Delta U=0$ because there is no change in temperature.
But at 290K, if we compare the internal energies of Nitrogen, Neon and Ozone, Ozone has maximum ...
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Why is the thermosphere more dense than the mesosphere or stratusphere?
According to my environmental science textbook and various sources on the web, the thermosphere has the second highest density of any part of the atmosphere. It falls only behind the troposphere which ...
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Inflation of a balloon in space
Let's hypothesize there is a flat ballon in space (vacuum, no gravity and no external pressure), which is connected to a gas pump. The gas and the material of the balloon doesn't interact. At a ...
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Why aren't there shockwaves on the walls of a tube where supersonic gas flow through?
In a supersonic flow experiment, the supersonic flow is in a tube and is slowed down by friction with the tube wall, which eventually caused a normal shock to form and slow the gas back to subsonic ...
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Physics of a helium balloon
I found a helium balloon in the mountains on the ground that fell from the sky. Threw it in the back of the ATV like trash and returned home. 3 days later found it floating still attached to the ...
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How to find the internal energy of a real gas (non ideal)? [closed]
I have read my thermodynamics book and I'm unable to find where the expression for the internal energy for a real gas comes from: $$dU=C_vdT+(\frac{\partial P}{\partial T}dT-P)dV$$ If someone could ...
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Why do we count external pressure to calculate work done by gas instead of using internal pressure?
Does internal pressure remain constant while doing work on surrounding or we ignore it? And when work is done on system we still count external pressure
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Diffusion without mass conservation?
I'm looking for the physical description of a certain diffusion process, but I don't know how to precisely express it, making the search fruitless. I'd like to have some help formulating, or rather ...
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Why does the bottle create vacuum inside if left closed?
I'm not 100% it's correct but it has happened to me a lot of times, I always close down a bottle normally with not too much tightness, with no liquid inside, and after a day it always is so hard to ...
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Thermal motion at higher pressures at constant temperature
I would like to know if the thermal motion of molecules stays constant if the pressure is increased at constant temperature or not. The viscosity increases with pressure, thus the friction between the ...
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Why do the litre and cubic metre volumes of cylinder natural gas not correspond?
A $47L$ cylinder says it contains $8.4m^3$ of natural gas at $137$ bar pressure.
Could someone explain how we get from $47L$ to $8.4m^3$ ?
I’m not an expert and thought they should be different by a ...
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What exactly is the polytropic index and what definition do I use to describe gas flow when it's choked?
I'm trying to model the depressurising of a pressure vessel, and there is such thing as a choked flow equation. The equation is as follows:
$$
\dot{m}_{max}= \gamma^{\frac{1}{2}} \left ( \frac{2}{\...
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Pressure of the generated gas in experiment
Considering the usual experiment, shown in the image, what would the pressure of the produced gas be? The only information we have is the volume of gas generated and its temperature, and no, we cannot ...
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If you put some air onto the moon, is it possible to talk within the region that the air is present in?
So uhhh lets say there is some air, you've just put it onto the surface of the moon. Question being, if you are present within the mass of the air, can you listen to others and talk to them within the ...
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Measurement that takes into account air density and average kinetic energy?
I think in very thin air, high average kinetic energy of air molecules might still be perceived as cold because the number of impacts per unit time would be fewer. Is this a measure that combines ...
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When a shaken soft-drink botte is left to calm down, does it return to the same state as before being shaken?
We had a disagreement with a friend:
When a soft-drink (carbonated) bottle (e.g., 1.5l) is shaken or dropped on the floor, if opened immediately it will spill out. However, if it is left to "calm ...
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Deriving sound speed from kinetic theory
The classical derivation for the sound speed involves using the ideal gas, isentropic, and momentum conservation equations, yielding $c_{\rm s} {=} \sqrt{\gamma k_{\rm B}T/\mu}$. If the gas is ...
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Calculating upwards drift velocity of hydrogen in air, where is the error in my calculations?
I have the following problem: I'm charging a lead-acid battery in a
container. The charger could fail, producing too many amperes at too many
volts. Too many amperes I can easily handle in a fuse, so ...
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Can repulsively interacting particles form a solid?
Consider the system of itinerant classical interacting particles
$$
H = \sum_i \frac{p_i^2}{2m} + \sum_{ij} \frac{J}{r_{ij}^\alpha}
$$
in $d$-dimensions, where we assume the interactions are repulsive ...
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Generalized Lotka–Volterra equations to explore filling of energy levels in mixtures of interacting diatomic molecules
Did anyone saw any application of Generalized Lotka–Volterra equations to explore filling of energy levels in mixture of interacting diatomic molecules. The idea is to consider molecular interaction ...
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Why does the boiling water in the pot get sucked up by the jar?
In order for the jars to be sterilized for pickling tomatoes, they need to be boiled. But when one of the inverted jars was standing on the rack in the pot, it started sucking in the water that was ...
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Isobaric process: is there some missing parameter?
I'm working on a supposedly rather easy problem in thermodynamics, and yet I cannot solve it. The problem states:
"A certain quantity of Freon gas is contained in a cylinder with mobile walls. It ...
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Do some gases have short range order?
In the book "Essentials of Materials Science and Engineering" (Askeland, Fulay), it appears the following figure:
We can read in the figure's description, subsection (b,c), that vapor and ...
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Does momentum transport occur via diffusion (or random walks)?
Consider a simple gas (or fluid) within a box at thermal equilibrium. I manage to give a kick to one particle within the gas, such that it acquires some momentum. After some time, it should be ...
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How much deviation from ideal gas does the air in a 'Room' show?
First of all, I'm only concerned about air in a Room (room in our houses). Also, lets take room temperature to be $27^{\circ}$ C specifically.
My first question is, how much different is this gas (air ...
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How long does it take for gas to settle down under earth's gravity?
I was discussing about ideal gas with my colleague the other day, and these questions come up in our conversation.
Lets say we have 1 mole ideal gas in a perfectly insulating cube box of size $1m^3$,...
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Pressure rise in a container as small amount of liquid is vaporized
How would one calculate pressure rise in some closed volume as small amount of liquid is added to it? Volume is initially in vacuum. Amount of liquid is not enough to get volume saturated. Let's say 1 ...
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Why the tapered optical fiber which dipcoated with rGO didnt give significant changes of voltage inside Photodetector?
I already cut it carefully the jacket out from cladding, and then use ethanol to rub the cladding so the core can be dipcoated with PVA-rGO solution.
Now I can see higher voltage depends of how much ...
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When a volume decreases in a real gas, what is more likely: temperature decrease or pressure increase? [closed]
The ideal gas law states that when the volume is lowered, either the temperature drops or the pressure rise.
Under real-life situations, how does nature "decides" what to increase or ...
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Why is it easier to fill a chilled metal cylinder with gases? [closed]
Where I work, we chill life raft inflation cylinders before filling then with CO2, N2, and inert gases because we heard they fill easier and quicker if chilled first. Is this true?
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Work done by piston cylinder [duplicate]
If expansion in the piston cylinder take place, we get the work.
What if this expansion takes place in vacuum; will there be work done by gas?
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Why is it so hard to compress air without any machine?
I know that the particles that constitute air move freely about. There must be a significant amount of empty space between the bouncing particles. So why is it so hard to compress air without any ...
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Why does the volume of a liquid seem to increase and then rise when you release pressure too fast in a car's cooling system?
So I was pressure testing the cooling system of my car with a kit where you fix a cap, a gauge and a hand pump to the expansion tank and then pressurize the system to 1.5 bars (mostly European cars go ...
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Sealed container with half-open gas buoy
Consider a sufficiently rigid and sealed container completely filled with liquid (e.g. water), pressurized at 1 bar, at constant temperature. Inside the container there is a buoy partially filled with ...
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Why should there be a gas in a cathode ray tube?
Is it necessary to have a gas in a cathode ray tube? Why?
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Constants in entropy and volume of a real gas?
In this answer one obtains an expression of entropy of a Van der val gas:
$$S(T,V)=S_0+\int_{T_0}^T\frac{C_v(T)}{T}dT+nR \rm{ln} \left( \frac {V-nb}{V_0-nb} \right) $$
where $S$ is the entropy, $C_v$ ...
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Gas leaking out of a cylinder at constant pressure and volume [closed]
The gas is leaking out in such a way so as to maintain the cylinder at a constant pressure and volume, i.e the product of nT is constant.
If at a time t, the temperature of the gas is T and the number ...
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Holes in phase space because of collision potential?
Consider a gas. Now, we already know the particle's duration of a collision is very small and it immediately bounces away from there. Can these be thought of as topological holes in one's phase space ...
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The role of gas pressure in the life cycle of stars
As a high school student, I am curious about the significance of gas pressure in the life cycle of a star. While I have read about the radiation pressure and the pressure caused by the energy released ...
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Thermal Radiation: Can Monatomic Gases and Single-Atom Substances Emit Radiation in All Wavelengths? [duplicate]
As a high school student, I'm curious whether everything emits thermal radiation, including monatomic gases and substances composed of a single type of atom and no molecules. Can these objects emit ...
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When is a thermodynamic system isobaric?
I came across a problem where a piston and gas arrangement was present and it was heated, so if the piston is free to move we call it isobaric. But is it only true if it is quasi static (reversible ...
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Determining an adiabatic gas coefficient
Is it possible to determine the adiabatic gas coefficient of an ideal gas when measuring the pressure of the gas in an isothermal process?
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Is Brownian motion truly random?
We say that Brownian motion is caused by the random collisions of particles. But let's consider an ionized gas; in that case, there's a nonzero net charge on the atom. Doesn't this mean the ...
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Do hot gases that don't have an infrared absorption spectrum, emit infrared light, regardless of the specifics of their molecular composition?
My layperson's understanding is that, although solids and liquids usually radiate across a wide variety of wavelengths modeled by the blackbody spectrum, gases do not because the geometry of their ...
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Absorption Spectra of Atmospheric Gases
From this previous Stackexchange question:
Is a detailed absorption spectrum available for carbon dioxide from 300-1100nm?
and this paper:
https://www.osti.gov/servlets/purl/1613653
as well as this ...
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