# 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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### 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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### What is force and area which is being talked about in the following case? And explain the relation between area and n(collisions) [closed]

In order to confine a gas we must apply a pressure. A standard vessel for holding gases is used in all textbooks, a cylinder with a piston in it. Now, it makes no difference what the shapes of water ...
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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 ...
1 vote
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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 ...
1 vote
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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 ...
1 vote
60 views

### 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 ...
1 vote
41 views

### 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 ...
95 views

### 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 ...
1 vote
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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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### What is the average time period ratio for a gas?

Background So I saw the following trick in an amazing set of lecture notes (Section 2.5 pdf) If $$U(\lambda r_1, \lambda r_2, \dots,\lambda r_n) = \lambda^k U(r_1,r_2,\dots,r_n)$$ Then we can play ...
29 views

### 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 ...
1 vote
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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 ...
1 vote
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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?
3k views

### 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 ...
1 vote
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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 ...
1 vote
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### Is it only thermal energy that contributes to entropy of a system, or it is also chemical one and others?

(Here, by ”thermal energy” I mean the energy associated with chaotic motion of molecules.) Preface In a textbook “Principles & Practice of Physics” by Eric Mazur, I came across two things, which ...
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### Molecular Gas flow as function of Pressure, Density and Temperature gradients

In all the flow dynamics textbook I have consulted the gas flow is driven by pressure gradients. Is there a way to analyse a molecular gas flow when also temperature and density gradients exist?
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### How would you measure the pressure on a plate in flow?

I want to figure out how much pressure is being imparted on a plate perpendicular to flow in a pipe. Similar to this setup, Some initial thinking is that I could just measure the static pressure ...
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### Why does high temperature result in lower pressure?

I took this picture from wikipedia. As you can see the higher pressure the higher temperature. However, As I read the article from this site they said that, At higher temperatures, the molecules ...
1 vote
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### Is natural gas transported as a liquid or supercritical fluid? [closed]

is natural gas transported as a liquid or supercritical fluid? I am curious as to what phase natural gas is in when being transported in pipelines over long distances. Both liquid and supercritical ...
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### In a polytropic process, how can I prove the validity of this equation: $v_1 = v_2 (\frac{T_2}{T_1})\exp{\frac{1}{1.1-1}}$?

in this exercise, I have hydrogen and it follows this thermodynamics cycle, 1-2 } --> polytropic process with exponent $n = 1.1$, 2-3 } --> adiabatic process, 3-1 } --> isobaric process, my ...
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### What is the force exreted by gas particles per unit area on the walls of the container? [closed]

It must not be pressure because it is a energy.
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### Kinetic theory of gases and its derivation

In the kinetic theory of gases, the time taken for a change in momentum is $2l/v(x)$, where $l$ is the length of a cube and $v(x)$ is the velocity in the $x$ direction. Shouldn't the time correspond ...
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### A gas absorbs heat $Q$ isobarically

I encountered a question asking "When gas absorbs heat $Q$ isobarically, what will be its work done, change in internal energy and temperature?" The work done is obviously positive, but I ...
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### Partial Derivatives - BWRS Equation of State [closed]

I require the following two partial derivatives from the BWRS Equation of State (BWR modified by Starling). $\left (\frac{\partial V}{\partial P} \right )_{T}$ \$\left (\frac{\partial V}{\partial T} \...