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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6answers
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Why can’t you feel the collision of each air molecule?

The molecules in a gas move very fast because of its thermal motion. But why can’t we feel the hit of each of the fast gas molecules?
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2answers
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Principle of how refrigerator works: how is temperature dropping but pressure is not?

I'm taking "Physics of the everyday" on Brilliant. Here is the diagram of how refrigerators work: Regarding the cooling step: After exiting the compressor, this gas cools to room ...
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0answers
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How does Gravity compare to the Van der Waals Forces?

Van der Waals forces' is a general term used to define the attraction of intermolecular forces between molecules. There are two kinds of Van der Waals forces: weak London Dispersion Forces and ...
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1answer
39 views

Is steam just a combination of small waterdrops and air?

I have seen a question here about steam. It made me unsure about the nature of steam. Isn't steam a hot white cloud of water vapor? Is it just water in a gas state, so that its temperature can be ...
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1answer
33 views

Question about “suction” , and overall physics, in this Whoosh Bottle Experiment

https://www.chemedx.org/blog/there-more-whoosh-bottle So this is a pretty standard "Whoosh Bottle" experiment, but with a twist, in that he covers his hand (palm) on the bottle after the ...
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2answers
30 views

Non-popping bubbles

I used a compressed air can to clean my laptop's keyboard and speakers. After that procedure I noticed there're small bubbles in the holes of the speakers. I've tried to pop them with a thin brush and ...
2
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1answer
40 views

What is the meaning of grain opacity and why does it affect the formation time of gas giants?

While doing research for my presentation on the formation of gas giants, more specifically the "core-accretion model", I have been stumbling across the term "grain opacity" and don'...
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3answers
65 views

How many water molecules should I put together before I can tell If it's liquid, gas or Solid?

How many water molecules should I put together before I can tell If it's liquid, gas, or Solid? I know, there isn't any clear boundary that says that you have to put $50$ molecules or $100$ ...
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1answer
19 views

Doubt about the idea of pressure exerted by a gas’ visualisation

In an educational video on derivation of the formula (3/2)PV=Kinetic energy of the gas, it was assumed that 1/3 of the particles are linearly translating along the three axes of the coordinate plane ...
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2answers
94 views

How does gravitational potential energy pertain to a single gas particle escaping the atmosphere?

What's the effective difference between a helium molecule moving at 11.18 km/s and one moving at 11.2 km/s at the edge of the atmosphere? Is the idea that, with a particle moving just below the ...
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2answers
23 views

Is there a gas present in the Martian atmosphere similar to hydrogen?

is there a gas present in the Martian atmosphere which could be extracted to inflate a balloon with sufficient lift to support an instrument platform for low altitude reconnaissance.
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0answers
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Is there any problem in this task? (molecular formula of a gas inside a cylinder) [closed]

I got this task: A cylinder of volume V₁ = 2 L filled with gas of mass m = 7.48 g at T = 10 °C and under pressure P₁ = 2 bar Calculate the amount of gas substance in the cylinder. Infer the molecular ...
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1answer
19 views

How do turbine engines improve compression ratio?

As I have learnt from the Venturi tube that Pressure is inversely proportional to velocity. When a general aircraft is flying at say Mach 0.8 and at the same time there is a pressure decrease with ...
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1answer
41 views

What is meant by “is driven by collisions between its atoms and molecules”?" in NASA's statement?

"The behavior of a dense atmosphere is driven by collisions between its atoms and molecules." says https://www.nasa.gov/content/goddard/ladee-lunar-neon. It seems to me that a gas's behavior ...
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3answers
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What does “rarely” mean in NASA's statement: “technically referred to as an exosphere because it’s so thin, its atoms rarely collide.”?

The following statement is from this article: The behavior of a dense atmosphere is driven by collisions between its atoms and molecules. However, the moon's atmosphere is technically referred to as ...
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0answers
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What is the state of the art gas concentration measurement technics, especialy for $\rm CO_2$?

Reviewing different sensors, I could find: NDIR (Nondispersive infrared sensor) is a simple spectroscopic sensor often used as a gas detector. It is non-dispersive in the fact that no dispersive ...
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1answer
50 views

Graphs of thermodynamic transformations

I received a question from one of my students of a high school (17 years old) with reference to a graph of a Clayperon-plane. Suppose that it is the one shown in the figure. From state $A \to B$ is ...
2
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1answer
43 views

Deformation of a sphere

I am currently building a computational model for a simulation of a rover landing on the surface of mars. As part of the assignment I need to model airbags being used to cushion the fall. (Assuming ...
0
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1answer
54 views

I am having difficulty understanting this question from thermodynamics [closed]

According to above question the process is isothermal. Hence the product PV is always constant. Since Volume is decreasing, hence Pressure must increase. Hence Work done by gas is calculated by ...
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1answer
60 views

Relighting a candle from its smoke, and being burned?

Having been extinguished, a candle can be relit from the resulting trail of smoke, even from meters away. However despite this apparently high level of heat, paper, bystanders, etc… are never ...
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2answers
62 views

Why is volume of gas independent of its molecule size?

According to the ideal gas law: $pv = nRt $ My question is, why is the volume $v$ independent of the volume of individual components of the gas, i.e. molecules? As the sizes of individual molecules ...
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1answer
29 views

Pressure on the walls of a balloon

Is the atmospheric pressure the only pressure acting on the exterior walls of a balloon keep the air/gas inside the ballon at equilibrium? Or the walls of balloon being elastic, do exert pressure on ...
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3answers
53 views

Why change in entropy in reversible adiabatic process is zero?

In the adiabatic expansion step of carnot cycle, adiabatic change is carried out in an insulated system. In this process volume gets increased but entropy remains constant. Now if we look at the ...
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1answer
28 views

Barometric formula with variable gravity

Recently, I have wondered about what would be the atmospheric pressure as a function of altitude in a planet that only consists of gas. The equation that does just that is the barometric formula (see ...
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1answer
30 views

How Joule-Thomson coefficient is measured experimentally?

I am reading about Joule-Thomson effect but I can't understand how the respective coefficient $μ$ can be measured experimentally. The Joule-Thomson coefficient is defined as: $$μ=\left(\frac{\partial ...
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1answer
47 views

Is underproved bread dough an example of the Young–Laplace equation?

I was watching minuteEarth's video on Young-Laplace with regards to RDS in premature babies when I made the connection that bread dough, as a foam with many curved pockets of gas, would necessarily be ...
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2answers
28 views

How Do Accelerated Electrons Between Electrodes Cause Ionization of Gas Molecules?

Due to small number of free electrons in gases these electrons are accelerated in electric field which creates collisions with gas molecules causing an ionization of molecules. I am not sure how do ...
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1answer
29 views

Gas regulator pressure

When I open the gas regulator, it pushes the pin and depress the valve in the cylinder which releases the gas out (am I right on this?). If that is the case, is gas released even when there is no hose ...
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1answer
23 views

Is there any website or method to calculate the refractive index of gases like $\rm CO_2$ in the mid IR?

I want to know the complex refractive index of some gases like CO2, CH4, C2H6 .. etc in the mid infrared. Is there any website, software or a method to know them?
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1answer
22 views

Liquid nitrous oxide released from gas cylinder

Say you have liquid nitrous oxide in a standard gas cylinder (about 55 bar) at room temperature. Normally the cylinder sits upright and gas is released via valve. Now let's assume you released liquid ...
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1answer
15 views

What pressure does liquid nitrous oxide need at -45°C?

What pressure does liquid nitrous oxide need at -45°C to remain liquid? How can I calculate it's pressure required for other temperatures?
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1answer
43 views

Is it possible to visualize water vapour with a low-cost instrument or setup in a lab? [closed]

Would infrared or laser be of any help? In a lab setting.
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0answers
18 views

Examples of Flows with Constant Velocity and Pressure

I am looking through a paper and there is a section where they derive field quantities (temperature and heat flux) for a gas flow which has vanishing (or at least constant) velocity and pressure ...
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1answer
27 views

How fast do very small particles diffuse through still air?

I have been trying without success to find the rate at which small particles, on the order of $3\cdot10^{-10}\mathrm{g}$, diffuse in air at room temperature $-$ say 20 to 25 degrees C. The purpose of ...
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0answers
23 views

Gas pressure along the axis in effusion

I'm trying to approximate the pressure P along the axis x, i.e. P(x), for the following setup. At one end of a cylinder a gas is inserted (at some pressure, let's call it P0). At the other end of the ...
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1answer
36 views

Why smoke particles go down? [closed]

Let's say in an apartment the upstairs neighbor smokes but the smoke goes down to the below neighbors. Is it a difference in temperature that causes the smoke to flow down instead of going up through ...
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0answers
22 views

How to calculate the velocity of an ionised gas when a field of 100 Tesla is applied?

Say I have an ionised gas, oxygen/hydrogen and I am creating a magnetic field with a strength of 100 Tesla by inducing a voltage of 100 V/S in a magnetic material (the charge becoming 100, this gas is ...
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1answer
14 views

Quantifying how fast gases reach equilibrium again when opening a window

When opening a window in a typical room with higher CO2 and lower O2 concentrations compared to the outside, how fast does it equilibrate again? Assuming no wind, just diffusion, the answer still ...
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2answers
59 views

If the earth constantly exerts a force on air molecules downwards, then why do they not fall to the ground?

I'm sorry if this seems like a really stupid question but it has really puzzled me... The earth exerts gravitational force on all objects with mass, and gas has mass. I know that this force results in ...
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1answer
15 views

Derivation of pressure of a gas from mean sqaured speed of molecules

I understand that the pressure exerted by a molecule on the walls of a container, in the $x$ direction is given by $P=n m v_x^2$ Where $v_x$ is the mean $x$ component of velocity, $m$ is mass and $n$ ...
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1answer
35 views

In kinetic theory of gases, how do we figure out the forces exerted by walls on molecules?

This is a cube with each side having a length of $l$ containing a certain amount of molecules in it. Let's say a molecule of mass m is traveling in the $y$-direction with the velocity $v$ and hits the ...
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2answers
102 views

Why does gas not do work when expanding in a vacuum?

Why does a gas do no work when expanding in a vacuum? I know it is true that there is no opposing force from other air molecules for the gas to overcome in a vacuum, so that gas molecules won't do ...
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1answer
25 views

A strange consequence of Isotropy in Phase Space

In Goodstein, States of Matter, page 66 the following is stated: For a single particle the number of states in a region $d^3pd^3r$ of its phase space is: $$\frac{d^3pd^3r}{(2 \pi \hbar)^2} \tag{1.3....
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0answers
24 views

Fixed volume air flow to vacuum

I have a work project and am trying to wrap my head around the foundational aspects of the fluid dynamics before I attempt to take measurements. I want to have an idea of what to expect compared with ...
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0answers
25 views

Thermal velocity vs speed of sound

Is it possible that for a gas, speed of sound$>$thermal velocity? I cannot imagine it since, for the ideal gas limit, the interactions solely rely on the bouncing back of molecules
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1answer
22 views

Vapor pressure in a closed box

If there is a closed box at room temperature with water inside after a certain point there will be an equilibrium condition where some water is liquid and some is vapor. So there will be a certain ...
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2answers
65 views

What is this atmospheric escape chart actually showing?

The wikipedia article on atmospheric escape has this chart: It all seems plausible enough... for a body to retain an atmosphere of a gas, the velocity of gas molecules in its exosphere must be mostly ...
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3answers
747 views

Why are spectrums of incandescent light bulbs continuous despite the presence of Argon around them?

Incandescent bulbs emit light by heating a filament using electricity, this would lead to a continuous spectrum according to Kirchoff's first law. However, the glass casing around the filament is ...
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0answers
15 views

Steam in boiler from evaporation not boiling

Vapor pressure inside a closed container keeps building up and the boiling point of water become higher. What if the steam is required to reach say , 30psi, and the pressure in the boiler is that ...
4
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2answers
64 views

Does a gas move from a region of high to low pressure according to it's own partial pressure rather than the total gas pressure?

I have a plastic bottle that is impermeable to ${\rm CO}_2$ but slightly permeable to $\rm O_2$. If I fill up the bottle with pure $\rm CO_2$ at $3$ atmospheres and expose it to $\rm O_2$ at $1$ ...

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