All Questions
Tagged with thermodynamics pressure
786 questions
75
votes
5
answers
66k
views
Why does a candle blow out when we blow on it? Our breath is 16% oxygen and only 4% CO2
Don't say that a layer of carbon dioxide covers the flame, because our breath has more oxygen than carbon dioxide.
Also, our breath does not extinguish the flame by cooling it as it is itself warmer ...
- 2,366
60
votes
2
answers
7k
views
Why does pressure in a thermos increase after shaking up hot water and soap?
Whenever I wash my thermos, I put hot water and then some soap in; then I seal the one end with my hand or use the lid. After shaking it up, if I slowly remove the lid or my hand, it expels a little ...
- 581
51
votes
6
answers
14k
views
Why do gases have weight?
I know that a gas is made of atoms or molecules moving freely in space.
When these particles hit the walls of where they're kept in they cause something called pressure.
But these particles never ...
- 647
46
votes
2
answers
54k
views
What happens when you put water under intense pressure?
Pretend you have an indestructible tube that cannot leak, inside which is water. Imagine that in each side of the tube, you have very powerful pistons
What would happen if you compress the water ...
- 515
39
votes
4
answers
18k
views
Should a soda bottle be stored horizontally or vertically?
I am having an argument with my friend about how a nearly-full soda bottle should be stored in the fridge, with the goal of keeping the soda from going flat (i.e. keeping as much of the gas dissolved ...
- 520
37
votes
19
answers
162k
views
Why does the gas get cold when I spray it?
When you spray gas from a compressed spray, the gas gets very cold, even though, the compressed spray is in the room temperature.
I think, when it goes from high pressure to lower one, it gets cold, ...
- 481
36
votes
7
answers
10k
views
Is it possible to "cook" pasta at room temperature with low enough pressure?
It is known fact, that boiling point of water decreases by decreasing of pressure. So there is a pressure at which water boils at room temperature.
Would it be possible to cook e.g. pasta at room ...
- 505
25
votes
1
answer
4k
views
Why is it so much more energy intensive to compress hydrogen than methane?
Why do you need 13.8 MJ/kg (9% of energy content) to compress hydrogen to 200 bar, but only 1.4 MJ/kg (2.5% of energy content) for methane?
I looked into compressibility factors and the ...
20
votes
4
answers
10k
views
Does the amount of oxygen in air, actually get lower as you go to higher altitudes?
I have heard that there is less oxygen as you go higher (that's what my teacher told me). A reason that supports that is, as you go to higher altitudes, it becomes more and more difficult to breathe. ...
- 837
20
votes
7
answers
7k
views
What would actually happen to a person jettisoned into space?
Alright, so we have all seen the movies where someone gets blasted out of the airlock on their starship, or their suit decompresses while on a space walk. The poor schmoe usually either decompresses ...
- 323
18
votes
5
answers
64k
views
If I take a bottle of air into space, and open it, where does it go?
It seems to me that space doesn't have any/much air, and if my bottle is full of air, when I open it, where does the air go?
- 939
18
votes
5
answers
24k
views
What is the difference between mechanical and thermodynamic pressure?
To start with I know thermodynamics deals with processes at equilibrium. Hence the thermodynamic pressure should most likely be the pressure of a fluid at equilibrium.
I'm not sure if a fluid flow (...
- 478
18
votes
5
answers
33k
views
Why is the internal energy of a real gas a function of pressure and temperature only?
While studying thermodynamics, I read that the internal energy of an ideal gas is a function of temperature only. On searching the internet, i found an article which stated that the internal energy of ...
- 597
17
votes
3
answers
1k
views
Fluids with critical point at ordinary temperature and pressure
Are there any fluids with critical point near STP or that are supercritical at STP?
If not would it be feasible to design a molecule for a substance with critical point near STP using theoretical/...
- 3,540
15
votes
8
answers
6k
views
Why (does/we assume) gas exert same pressure everywhere in a closed container?
I was reading about the gaseous state when this question struck my mind: What made us assume that, at every point inside the container, a gas exerts equal pressure? When one brings a barometer, is it ...
- 522
14
votes
6
answers
7k
views
Why does my fireplace shoot flames out the front until I open my backdoor?
I have a natural gas fireplace with fake logs in it. I open the flue, turn on the gas for a couple seconds, and throw a match in. The flames kind of go up and out of the flue, but most of the flames ...
- 279
14
votes
4
answers
5k
views
Why does pressure increase with water depth?
Let's say I took a tiny metal sphere that when put under water has the surface area to allow, at any point in time, to be surrounded by up to 1000 water molecules. Now lets say we put this sphere ...
- 1,288
14
votes
8
answers
20k
views
Work done by a gas
In the expression for work done by a gas,
$$W=\int P \,\mathrm{d}V,$$
aren't we supposed to use internal pressure?
Moreover work done by gas is the work done by the force exerted by the gas, but ...
- 157
14
votes
8
answers
1k
views
Is there a pressure gradient in a stationary gas with a temperature gradient?
Consider a gas with ideal equation of state $P = n k_{\rm B} T$, in a fixed rectangular container with two opposite walls maintained at different temperatures, under conditions where there are no ...
- 61.8k
14
votes
3
answers
3k
views
Can you drink a glass of lemonade on the moon with a straw?
I don't think it's possible but want to be sure and the exact reason.
I don't think it is possible because the atmosphere on the moon is less than one hundred trillionth ($10^{−14} $) of Earth's ...
- 3,368
14
votes
2
answers
582
views
Definition of stress at the microscale
Take, for simplicity, a Lennard-Jones fluid below the critical temperature, which is to say that there is a phase separation into fluid and gas and thus an interface is formed. The macroscale picture ...
- 2,483
13
votes
5
answers
118k
views
What happens to the temperature when an ideal gas is compressed?
I am rather confused about this. I know from Charles' law that under constant pressure, the volume of a gas is directly proportional to its absolute temperature i.e.
$$\frac{V_1}{T_1} = \frac{V_2}{...
user36790
13
votes
3
answers
7k
views
Inflating a balloon (expansion resistance)
I am doing a quick calculation on how to calculate the pressure needed to inflate a perfectly spherical balloon to a certain volume, however I have difficulties with the fact that the balloon (rubber) ...
- 333
12
votes
7
answers
22k
views
Why does air pressure decrease with altitude?
I am looking to find the reason: why air pressure decreases with altitude? Has it to do with the fact that gravitational force is less at higher altitude due to the greater distance between the masses?...
- 279
12
votes
4
answers
9k
views
Calculating Atmospheric Pressure on an Imaginary Planet
I am planning a series of science fiction novels that take place on an imaginary binary planet system. Both planets have a lower surface gravity than the Earth and one has slightly more mass than the ...
- 361
11
votes
7
answers
5k
views
Does a cube under high pressure transform into a ball?
Will a material in the shape of a cube, under high pressure, crumble into the shape of a ball?
One would expect that there will develop strains and stresses, after which the corners crumble and ...
- 137
11
votes
2
answers
4k
views
When we pour cold water on a closed jar containing only hot water and water vapour, why does the hot water in jar start boiling?
Here is a video link for the experiment.
In the experiment, cold water is being poured on a closed jar containing hot water and water vapour and we observe that the hot water inside jar starts boiling....
- 261
11
votes
3
answers
4k
views
Why does the air pressure at the surface of the earth exactly equal the weight of the entire air column above it
Why does the air pressure at the surface of the earth (resulting from collisions of molecules on the surface of the earth which has to do with the velocity of the particles) exactly equal the weight ...
- 113
11
votes
1
answer
828
views
What pressure or tension occurs in a glass jar when I pour boiling water inside?
Sometimes it happens that when you pour a boiling water into a glass jar, it cracks. Since glass is very hard material and resilient to pressure, the tension must be very high. Is it possible to ...
- 3,109
10
votes
3
answers
6k
views
How much pressure would it take to compress a block of solid steel into one-tenth the original volume?
We all know to compress objects into smaller volumes, you would need to apply pressure to them. The required pressure depends on how strong the material is and which form is it (gas, liquid, solid).
I ...
- 129
10
votes
3
answers
13k
views
Can ice melt in a perfectly closed container?
If I have an ice cube of, let's say, for example (15$\times$15$\times$15 cm), it was put inside a container of internal dimensions (15$\times$15$\times$15 cm), and the container is strong so ...
- 111
10
votes
1
answer
57k
views
How much work is needed to compress a certain volume of gas?
I want to know the formula (and what does the symbols stand for) for how much work is needed to compress a certain volume of gas?
10
votes
2
answers
2k
views
What is the pressure of a charged gas?
I have $N$ ${\rm H}^+$ gas molecules in a sealed, electrically insulated container. What equation can I use to accurately calculate the pressure of the gas?
It seems to me that $PV = nRT$ will not ...
- 153
10
votes
6
answers
79k
views
What is the effect of an increase in pressure on latent heat of vaporization?
What is latent heat of vaporization ($L_v$) in the first place? Wikipedia seems to indicate that it is the energy used in overcoming intermolecular interactions, without taking into account at all any ...
- 203
9
votes
7
answers
15k
views
What is gravity's relationship with atmospheric pressure?
I'm asking for clarification here. If Earth had the same atmospheric mass per square unit of ground but the Earth had suddenly gained mass so it had twice the gravity at the surface, would the Earth ...
- 226
9
votes
1
answer
1k
views
How did Torricelli know that he created a vacuum?
I have read about the experiment of Torricelli, he filled a tube with mercury and placed it standing in a basin filled with mercury, then mercury poured out into the basin from the tube. He concluded ...
- 91
8
votes
1
answer
43k
views
Why did my frozen water bottle explode when I opened it after it defrosted a bit?
Last night I filled a 20 fl oz bottle (http://www.thenibble.com/reviews/main/beverages/soft-drinks/boylans-mash.asp) with lukewarm water from my tap. I filled the bottle pretty much to the brim, ...
- 183
8
votes
2
answers
8k
views
Difference between pressure and temperature
If I am given the average kinetic energy of the molecules of a gas or a liquid, how can I tell if the fluid will burn me/crush me/both if I immerse my hand in it?
Equivalently, what is the difference ...
- 181
8
votes
3
answers
19k
views
Why does deodorant always feel cold?
We all use deodorant and they always feel cold, why is that?
Is it because it is liquid inside the bottle and a gas when it is released?
- 863
7
votes
6
answers
3k
views
Why is pressure in the outermost layer of a star lower than at its center?
I have done the math and I have obtained the hydrostatic pressure in a star is lower at the outermost layer of a star than in its center, where the pressure is actually maximum. Although the equations ...
- 1,870
7
votes
1
answer
2k
views
What would happen to an unprotected human body on the surface of Venus?
In the tremendous heat and pressure on the surface of Venus what would happen to an exposed human body?
Would it burn up, dissolve, mummify or something else? Presumably the water and fats would boil ...
7
votes
1
answer
1k
views
How much pressure would be needed to contain a 1 gigaton nuclear bomb explosion within a sphere of one meter radius?
How much pressure would be needed to contain the largest human exploitable nuclear bomb within a sphere of one radius?
Also would it be possible to create a magnetic field that controlled some ...
- 215
7
votes
2
answers
3k
views
Microscopic interpretation of pressure in liquids
Pressure can be explained at microscopic level for a gas with kinetic theory of gases. From that the pressure $p$ is linked to the velocity of molecules (and it is caused by the high amount of ...
- 2,637
7
votes
2
answers
3k
views
How is pressure an intensive coordinate?
Most textbooks explain intensive coordinates by asking us to consider a system and divide it into two parts. The properties which remain the same will be called intensive and the properties that ...
- 1,053
7
votes
2
answers
12k
views
What is the meaning of pressure of a solid?
Currently I'm taking an introductory course on thermodynamics. I've got a problem with understanding what is the meaning of pressure of a solid body. The question arose when I looked at phase diagram ...
- 173
7
votes
3
answers
2k
views
Do objects sink in ice?
The title explains it all. Do objects suspended in ice sink over time? You may remember the story of World War 2 planes that were found 260 ft under the ice which would be anachronistic with seasonal ...
- 303
7
votes
2
answers
523
views
Proof of pressure of ideal gas from first principles
Here's a question aimed at a deeper intuitive understanding of statistical physics and the theory of ideal gases, which has bothered me for quite a while.
Assume a billiard table 2D. The table has ...
- 211
7
votes
1
answer
476
views
Is Pressure isotropic in an Ideal Gas in QM?
I have made some calculations which to my surprise show that the pressure is anisotropic in an ideal gas. I don't know if it is correct.
The calculation goes as follows:
Basically I modelled the ...
- 289
7
votes
3
answers
703
views
Could Dust Equation of State have some negative pressure?
Traditionally the cosmological equation of state of cold matter (so-called dust) is simply:
$$p = 0.$$
But, in Newtonian terms, each particle is gravitationally attracting every other particle.
...
- 5,991
6
votes
3
answers
2k
views
What keeps a gas giant from falling in on itself?
There is not enough gravity at the center to start nuclear fusion, but it seems that there would be plenty enough to collapse the planet.
- 227