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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Acceleration needed to make a solid turn into gas? [closed]

There's a joke in a show in France where it is said speaking of a human that he would turn into gas if accelerated enough. My questions : Is this possible without friction ? What would be this ...
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12answers
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Why does hot air rise in a column instead of cold air pressing down?

Ok, this looks like a dumb question or even near trolling, but I really don't understand it. When air is heated over an oven plate, it rises. Obviously, I can check by blowing some smoke in. The ...
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1answer
949 views

Why do expanding gases lower temperatures around them?

I want to give you an example to my question: When you spray some pressured gas on a surface, liquid water for example, the surface could freeze. but why.. As far as I know molecules close to each ...
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2answers
153 views

Identifying an ideal gas

I'm pretty confused. So I've been told that the equation of state for $n$ moles of some type of gas is $P(V-b) = nRT$. That's not quite like an ideal gas. But then the relations $C_p - C_v = R$, and $\...
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1answer
83 views

A thermometer in the wind

Consider two cases, Situation 1: a thermometer is stationary and air is blowing past it. Situation 2: the thermometer is moving with the wind, say on a car or something. Assuming now friction ...
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0answers
842 views

Calculate Liters Remaining in a CO2 gas cylinder/bottle [closed]

I know: The gas is CO2 (very close to 100% CO2) V - The Volume of the Cylinder (constant) P - The pressure of the Cylinder (from a sensor) T - The temperature of the Cylinder (from a sensor) I ...
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1answer
645 views

Can the helium from a gas bottle lift the bottle?

Does a gas bottle full of helium contain so much helium that, if the helium can expand into a baloon, can lift the empty gas bottle? And input on this question highly appreciated...
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1answer
264 views

Gauge Pressure and Bar Pressure [closed]

I ran into a problem trying to calculate the absolute pressure of an isolated system. I was given that the gauge pressure in a tire is 200kPa or 2 bars. To get the absolute pressure I would have to ...
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1answer
29 views

Injected gas versus pressure rise

Very simple concept for some, but quite honestly I’m striving to grasp: Premises: You have a $20 \text{ m}^3$ pressure vessel. You start filling it with gas. You see a rise in the gauge pressure ...
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1answer
1k views

How does speed of gas molecules change with pressure? [closed]

A thought experiment. I have a box of fixed dimensions, inside this box I have molecules of $H_2$ at constant temperature. I'll be gradually increasing pressure inside the box and the temperature ...
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0answers
20 views

Reactor opening and total time to reach a specific temperature

Let's say I have a reactor (we assume that its shape can be approximated by a horizontal cylinder) in which there is air at the temperature of 1000K and at pressure of 1.5 bar. Now, I want to open it ...
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2answers
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Behaviour of gases in a vacuum

I have a doubt related to the behaviour of gases in a vacuum. In the following figure: The grey part is the vacuum and the green part is the gas, let the gas be Carbon Monoxide. The following are ...
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1answer
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Why is the excluded volume 4 times the volume of the gas molecule in van der Waal's Volume Correction Of Ideal Gas Equation? [closed]

Why there is a factor of 4 in van der Waal's Volume Correction?
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0answers
476 views

Difference Value of the Specific heats at constant Pressure and Temperature of Real Gases

As in ideal gases, we can have the equation of $C_p=C_v+R$, or to be precise, the difference of the Specific heats of ideal gases at constant pressure and volume is the universal gas constant. But, we ...
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1answer
338 views

How to determine rotational energy of gas molecules

For an arbitrary polyatomic molecular gas, what is the expected behavior of $U_{rot}(T)$, the rotational kinetic energy of the atoms, in the two limits T high and T low? So far, I have written an ...
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1answer
1k views

Methane under pressure [closed]

A tank is filled with liquid methane. Then it is closed. It sits in an infinite room at STP (standard temperature and pressure). (Initial temperature is not important; assume density of liquid ...
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2answers
4k views

Why do helium balloons rise and fall?

I understand why a regular party balloon filled with helium falls over time due to leakage of the helium. However I've also noticed that recently filled helium balloons put outside rise and fall. At ...
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2answers
3k views

Confusion with Fluid pressure

I have studied on the internet that gases exert equal pressure in all directions in a container but liquids do not. In liquids pressure exerted on the wall of a container increases with depth. Why is ...
2
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1answer
62 views

Suffocation in a granular medium

I read of a recent accident in Alberta in which three girls fell into an open bed truck carrying canola seeds and suffocated. In that situation would it have been possible to keep breathing by using ...
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1answer
584 views

How to calculate gas flow/permeation through solid metal membrane

Given the absolute pressures of air on both sides of a titanium membrane of known thickness (0.1mm) and diameter (3mm), how would one calculate the rate of gas exchange/escape through the titanium ...
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2answers
76 views

What is the smallest possible packing of earth air inside a box?

It is often stated that all the air in a room could suddenly rush into one corner but that there is simply a very low probability that it would do so. One possible way this could in fact happen is via ...
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1answer
368 views

Putting an open can of soda into a loose plastic bag to preserve its fizz?

A friend insists that, to preserve the fizz in an open can of soda, you just put it in the refrigerator inside an unsealed plastic bag. The theory is not that the bag preserves the pressure in the can,...
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1answer
843 views

Flow rate of gas down a pipe at low pressures

I'm trying to understand an 'approximate derivation' of the flow rate of gas down a pipe at low pressure from my book (an example problem). It uses the result that the flux of a gas is given by $\...
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5answers
8k views

Is it possible to trap smoke or a smoke like gas inside a glass bubble?

I am a glassblower, and I would like to trap smoke in a glass bubble, my hope is to create an infinitely lingering smoke inside. Is this possible?
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3answers
5k views

Does gas spread out equally everywhere?

An excerpt from this page: Gases can fill a container of any size or shape. It doesn't even matter how big the container is. The molecules still spread out to fill the whole space equally. That is ...
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4answers
4k views

Why are coke bottles that much fizzier if you shake them?

We've all been there: you drop your bottle of soda at some point and when you try to open it, it bursts into foam. My question is, then: why does shaking a carbonated drink make the dissolved gas ...
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2answers
27k views

How does smoke move in the air and how can one direct it?

Let us assume there is a closed room with two people in it and only one of them is smoking a cigarette. Which equation describes the behavior of the smoke from the cigarette spreading? Is it “...
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3answers
369 views

Is there a number that describes a gas's departure from the ideal gas law?

When judging if relativity is important in a given phenomenon, we might examine the number $v/c$, with $v$ a typical velocity of the object. If this number is near one, relativity is important. In ...

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