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.

Filter by
Sorted by
Tagged with
-1
votes
0answers
16 views

Calculations for filling gas into a container

So, I need to fill a container of $500ml$ volume with $99\%$ oxygen gas. And I need to know what calculations should be made for the pressure and amount of gas to put in the container. I just know the ...
1
vote
1answer
46 views

Hit rate of molecules on a wall

Reviewing my final from last semester to prep for comps: Question: A piston of mass M can move freely in a tube with cross-section area A filled with ideal monoatomic gas with molecular mass m ≪ M and ...
0
votes
1answer
29 views

The internal energy of a real gas

I apologise in advance, but I am asking for clarification. I learnt from a first year undergraduate physics book that in the case of ideal monatomic gases, the internal energy is given by $E_{int} = n ...
0
votes
2answers
67 views

Free Expansion - Isothermal vs Adiabatic

By free expansion, I am referring to gas kept in a piston-cylinder arrangement freely allowed to expand against vacuum. It is clear to me that free expansion is an irreversible process because if it ...
0
votes
0answers
12 views

Volume correction of Van der Waal's equation

A simple derivation of the ideal gas law by assuming all gas molecules to be perfect spheres is as follows: Considering some area of the wall of a container A, the pressure exerted by all molecules ...
2
votes
2answers
82 views

How is the Pressure defined in the Van der Waals' equation?

I have some doubts regarding the Van der Waals' equation which relates the Pressure, volume and temperature of real gases. It is given by : $$(P_{real}+\frac{an^2}{V^2})(V-nb) = nRT$$ I also read that ...
0
votes
1answer
25 views

Form of Energy in Compressed Gas

What would be the best way to categorize the energy stored in a compressed gas? Should I call elastic potential energy? Maybe mechanical? It's not that exotic a way to store energy but it doesn't ...
-1
votes
1answer
22 views

Why do lighter gases float?

Why do lighter gases float? What makes them float? Is there a force pushing them upward or are they less affected by gravity.
0
votes
4answers
45 views

Why is there atmospheric pressure?

Why is there atmospheric pressure? Gas molecules have empty spaces between them right (intermolecular space). But to have atmospheric pressure all the gas pressure will have to line up without any ...
0
votes
1answer
37 views

How to simulate mixing of gases with different compositions?

Let's assume that we have the following apparatus in which volumes A and B are separated by a magical, impermeable, adiabatic barrier labelled S. (Let's also assume that the volumes are cubes, and ...
0
votes
1answer
38 views

Explaining $\beta_p$ curve for Van der waals gas

Given the Van der waals gas $$\left(p+\frac{a}{V^2}\right)\left(V-b\right)=RT$$ in standard notations. I tried finding isobaric expansivity $\beta_p$ which is defined as $$\beta_p\equiv\frac{1}{V}\...
1
vote
1answer
37 views

How to dilute 5000 ppmvol of $\mathrm{CO}_2$ to obtain 250 ppm with a fluxmeter?

My problem is that I have a tank, containing $\mathrm{CO}_2$ at 5000 ppmvol, Oxygen $21\%$ vol and Nitrogen the rest, connected with a mass flow controller (flux max at $150$ ml/min). And I have a ...
1
vote
1answer
29 views

How does the kinetic-molecular theory explain why atmospheric pressure is greater at lower altitudes than at higher altitudes?

It is believed that pressure exerted by a gas is caused by "momentum exchanges by colliding molecules". Also it is a fact that the atmospheric pressure on a body is greater at lower ...
0
votes
0answers
12 views

How much pressure does it take to start an underwater gas fire?

It's recommended for underwater use of acetylene torches that you set the oxygen pressure to 90 psi, so that it creates an air bubble which allows the fire to get started. This made me wonder... do ...
0
votes
1answer
18 views

Could you survive on hydrox in at 10 atmospheres?

I was told that hydrox is incredibly dangerous, that pure oxygen will combust without any source of ignition at 3 to 4 atmospheres of pressure, and that because humans are hydrocarbons they will act ...
0
votes
1answer
34 views

The effect of hand fans for better breathing in emergencies

Suppose I am in a room or system with a lot of smoke and it is difficult to breathe. If I put a hand fan in front of my face, does the wind from the fan blow the smoke away from my face, making it a ...
0
votes
2answers
44 views

How many Degrees of Freedom do Linear Triatomic Gas Molecules Have and Why?

I read this in one of my textbooks that stated Linear Triatomic Gas Molecules like CO2, HCN, CS2 in which all the atoms are linear, the total number of degrees of freedom are Nf = NT + NR + NV where ...
1
vote
2answers
76 views

A simple way to make liquid oxygen at home

I have an idea to make liquid oxygen at home, but without any calculations, I am not sure whether it will work at all. The idea is based on the fact that gases tend to liquefy easily in higher ...
1
vote
1answer
31 views

Thermodynamics - Superheated vapor expanding into vacuum

When I have a gas in one vessel which is expanding into another vessel in vacuum, I know the work done will be $0$. My question is, what if that gas is not ideal, and it's a superheated vapor, is ...
0
votes
1answer
9 views

Diffusing pressurized gas with minimum noise

Problem: I need to diffuse pressurized dry air (about 4-6 bar) in to a room, while creating minimal noise. The inner diameter of the tube is about 8 mm. Without a proper nozzle, there are bond to be ...
2
votes
1answer
61 views

Air's considerable resistance to compression

My conception of air has been that, as a gas, its molecules are loosely situated. When placing food items in a plastic, sealable storage bag, to avoid a major air pocket one has to squeeze much of the ...
1
vote
1answer
71 views

Definition of $PV$ work

A balloon contains gas with pressure $P_1$, volume $V_1$. It is connected to a container with vacuum with volume $V_2$, and the gas is released into the vacuum. What is the work done by the gas and ...
1
vote
0answers
12 views

What is the most common method used to cool hydrogen below its boiling point?

I would like to know what methods companies/organizations/scientists use to cool gaseous hydrogen below its boiling point of ~250 degrees Celsius. I am a new student to thermochemistry and am not ...
0
votes
3answers
73 views

Why are there two states of matter in a bottle of gas?

Say a bottle of natural gas used for heating or cooking. There is a liquid phase, which I believe is the densest part, at the bottom of the bottle. And on top of it, there is presumably gas in a ...
0
votes
1answer
18 views

Does electric current through gases emit light?

Not electric spark or electric arc, just normal current through gases created by heating the air between cathode and anode as shown in the following video at 1:25. https://www.youtube.com/watch?v=pg0-...
0
votes
2answers
38 views

Why liquids evaporate completely when heated at their boiling points?

I'm confused about why the boiling of liquids happen. The boiling point of a liquid is defined as the temperature in which it's vapor pressure is equal to the pressure of the gas above the liquid( for ...
0
votes
0answers
22 views

Doppler cooling Ethanol

Is it possible to use laser cooling to cool Ethanol in it's gas phase? I've seen research on IR diode cooling when you reverse the electrodes but laser cooling was/has always been limited to atoms and ...
1
vote
1answer
31 views

Why does lighter air goes up? [duplicate]

If we increase the temperature of a volume of air it will rise up but if we look from molecular level, there kinetic energy has just changed but not thier weight so why they rise up and do not go in ...
0
votes
2answers
66 views

Density of ideal gas molecules

From Boyle's Law, in very low pressure ($P \rightarrow 0$), it is a good approximation for real gases to behave as ideal gases. (refer to the graph) Boyle's Law stated that $ P \propto \frac{1}{V} $ ...
0
votes
1answer
22 views

Airtightness of a plastic-on-rubber seal

I want to make a pressure container out of this food container The seal is rubber that is pushed into plastic edges. However, I don't know if it's going to work until after i've attached an air valve ...
0
votes
1answer
29 views

Engines principle overview [closed]

In engines we have air and a hydrocarbon. Once we want to go forward we open the box containing it and the oxygen reacts with the hydrocarbon giving some gases. Due to the fact it is an exothermic ...
1
vote
1answer
23 views

Number of Ionization event estimation

First of all, I am new in this field and therefore if I ask a silly question please forgive me. I have a gas-cell (say 3$\times$3$\times$3 mm$^3$ volume) filled with a N$_2$ gas. The number density is ...
0
votes
2answers
36 views

Orthogonality of two randomly chosen velocity vectors in the kinetic theory of gas and the relative velocity

I was looking for the average value of the relative velocity of ideal gas molecules in the kinetic theory. The following is from this article. The vector notation is not mathematically rigorous, just ...
9
votes
4answers
2k views

Could evaporation of a liquid into a gas be thought of as dissolving the liquid in a gas?

As I understand it, evaporation is thought of as a phase transition from a liquid into a gas. Individual molecules get enough energy to break surface tension, and flung up into the gas. A gas that's ...
0
votes
2answers
53 views

$P$, $V$, $T$ in case of pressure cookers?

In a pressure cooker, when T increases -P increases which means that the K.E of molecules increases. But According to equation PV/Tinc so T inc P inc and V dec. If they less volume I.e gas molecules ...
1
vote
0answers
32 views

First-Order Phase Transition

When the density/volume abruptly changes (isobar/isothermal) while providing a sufficient latent heat to the system, is this variation related to a high compression/expansion as it is illustrated to ...
0
votes
2answers
43 views

Why do some gases have fewer degrees of freedom at same temperature?

I am trying to understand the degres of freedom for gases. Air has 5 degrees of freedom at room temperature but why does Argon, $Ar$ have 3 degrees of freedom while $O_2$ has 5 at the same temperature ...
2
votes
3answers
148 views

Temperature of a gas: Is it velocity only?

I've been going through Feynman's lectures. One thing he said, unless I misunderstood, is that the temperature of a gas molecule is determined by its velocity, but not its vibration or rotation. Did I ...
-2
votes
3answers
98 views

Can helium gas lift the bottle itself?

I came up with this argument: it’s possible that in the right circumstance helium would weigh more than the empty bottle. If I were to fill empty bottle full of helium can it lift the bottle in the ...
0
votes
0answers
13 views

The question is about kinetic theory of gases regarding mean free path

In the derivation we have stated that the molecule moves only in a particular cylinder ( due to assumption that molecules of gas’s travel in straight line ) and travels through the cylinder even after ...
23
votes
4answers
5k views

Is there any way for a gas to pass through a solid metal?

Let's say that we have a gaseous or liquidus compound (I don't know if elements or compounds make a difference, take this as a thought experiment), and we have a tungsten or steel block that's 5cm (or ...
0
votes
1answer
24 views

Calculating Temperature of boiling water using constant volume gas thermometer

Why different gases give slightly different temperature at same pressure in a constant volume gas thermometer? My book says we should lower the amount of gas in the thermometer to get perfect result
2
votes
5answers
372 views

Why is there a special connection between entropy and heat?

As I understand it: $dS = \frac{1}{T}dU + \frac{p}{T}dV$ (for a thermodynamic system where $dN=0$) and since for an ideal gas $pV=Nk_BT$ and $U=C_VT$ we can say $dS = \frac{C_V}{U}dU + \frac{Nk_B}{V}...
0
votes
1answer
47 views

Does the ideal gas law apply to gases which consist of more than one atom?

In the derivation of the ideal gas law, one sets for the average kinetical energy $f = 3$ degrees of freedom. This refers to the transition in x,y,z axes. This is true for gases, which consist of only ...
0
votes
1answer
32 views

The Hindenburg's max alt was a function of its gas cell volume. Is there an equation to determine how much volume a gas fills at different altitudes?

I'm trying to determine the maximum altitude that an airship can safely reach. According to this paper the answer can be determined in a straightforward manner. Development of an Aerodynamic Model and ...
2
votes
1answer
36 views

Pressure Exerted by Piston on Gas

I’m currently doing a lab where we are measuring the work done by weights on a gas, where the weights are added on top of a piston. Now, what I don’t understand is that work is equal to net force ...
0
votes
0answers
17 views

How do we explain No change in Entropy in an Adiabatic Quasi-Static Expansion from the perspective of Boltzman's Idea of Entropy?

I understand from the formula of Clausius idea of Entropy that the change in entropy in an adiabatic quasi-static process is zero. I do not understand, how we can explain the same idea from the ...
3
votes
7answers
187 views

Why can't a particle rotate about its axis? [duplicate]

When treating an atom as a point partcle, it is usually assumed that it cannot rotate about its axis. Is it that anything considered as a point particle cannot rotate about its own axis? If so, why is ...

1
2 3 4 5
9