Tagged Questions
0
votes
0answers
44 views
Air pressure in balloon
I have to calculate the air pressure inside of an hot air balloon. After some searching I found out that I can use the ideal gas law: PV = nRT (from Wikipedia)
So to get the pressure in the balloon I ...
2
votes
1answer
47 views
Thermodynamics, PV diagrams?
My teacher told me that the total amount of work done on or by a gas can be represented by the area enclosed in the process in a PV diagram. This is only valid for non isothermic processes, right?
2
votes
2answers
31 views
Gas Circulation Using Pressure Difference
Dear all, see attached picture
Please, is it possible to have the gas recirculated from the gas phase to the liquid as described in the diagram assuming the gas is not soluble in the water.
These ...
0
votes
0answers
14 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 ...
0
votes
1answer
41 views
If a balloon is continuously filled with air and stays at a constant shape and size will there be any empty space in the balloon?
If a container like a balloon but with constant volume is filled, is it possible to pack air molecules so closely together that they don't have any empty space between them? If so, what would this ...
-3
votes
0answers
51 views
When do we have $p = -\frac{\partial F}{\partial V}$? [closed]
In what context can we say that :
$$p = -\frac{\partial F}{\partial V}$$
?
0
votes
2answers
76 views
Temperature change inside pressure chamber
Let's say there is a pressure chamber with some sort of sample / specimen (e.g. protein crystal) in it. Now I apply a certain amount of gas pressure, e.g. 10 or 20 atm. Let's say I use xenon as a gas. ...
2
votes
2answers
122 views
Have negative pressures any physical meaning?
Some cubic thermodynamical equations of state predict negative pressures, have negative pressures any physical meaning? Could they be related to negative mass?
3
votes
1answer
74 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 ...
1
vote
0answers
43 views
How to solve state parameters using these givens for an ideal gas?
In a thermodynamic turbine using air as an ideal gas, given that you have a known inlet temperature value $T_i$, a known exit pressure value $P_e$, a known inlet and exit velocity $V_i$ and $V_e$, a ...
3
votes
2answers
135 views
With ideal gases, varying quantity of moles, and having a constant volume how do temperature and pressure behave?
I'm trying to build a simulation of gases so I ended-up trying to use law of ideal gases ($PV = nRT$).
In my scenario:
volume is constant ($V=1\rm{m}^3$);
a known quantity of moles are being added ...
3
votes
1answer
414 views
Area under a $pV$ diagram
What does the area under a Pressure volume diagram equal?
I read in my textbook it equals 'external' work done, but why is this?
First of all, what exactly is external work?
Can you get it ...
0
votes
1answer
998 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?
1
vote
3answers
132 views
Water, can it break through temperature?
If water is heaten up to ridicilously high temperatures, is it possible for the atoms in the molecules to lose their bonds?
And if it is possible, isn't this some kind of chain-reaction?
Like you ...
2
votes
1answer
698 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, ...
2
votes
1answer
595 views
Heat of vaporization of water - dependence on relative humidity?
Does the heat of vaporization of water depend strongly on the relative humidity of the gas into which it evaporates?
Some context: If we want to calculate the dew point of water, we find the ...
4
votes
1answer
251 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 ...
2
votes
4answers
6k views
Why are volume and pressure inversely proportional to each other?
It makes sense, that if you have a balloon and press it down with your hands, the volume will decrease and the pressure will increase. This confirms Boyle's Law, $ pV=k=nRT $.
But what if the ...
8
votes
5answers
2k 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?
-2
votes
1answer
183 views
For how long can we make an air balloon stay flying via remotely controlled heat system?
I wonder how a function $$f=f(h, m_{\mathrm empty}, V_{max}, T_{h}), $$ with the top height $h$, the empty mass $m$, the maximum volume $V_{max}$, and the temperature of the heater $T_{h}$ would look ...
0
votes
2answers
349 views
What is the physical or mathematical meaning of the Gibbs-Duhem equation?
The Gibbs-Duhem equation states
$$0~=~SdT-VdP+\sum(N_i d\mu_i),$$
where $\mu$ is the chemical potential. Does it have any mathematical (about intensive parameters) or physical meaning?
4
votes
2answers
160 views
What's the classical limit of the pressure of the ultrarelativistic Bose gas
The pressure for the ultrarelativistic Bose gas is
$$p~=~U/(3V) ~\propto~ (kT)^4/(hc)^3.$$
It looks to me like it diverges for $h \to 0$. Looking at the derivation, it diverges because $h$ is the ...
3
votes
1answer
123 views
In a Sterling Engine, does heat from the hot side transfer to the cold side?
A Sterling Engine is a closed system. The "hot" side oscillates between higher temperature with higher pressure and lower temperature with lower pressure. Does Nature switch back and forth between ...
1
vote
1answer
2k views
1
vote
3answers
643 views
When a gas expands against an external pressure of 0, must the stopper on the cylinder be massless?
Basically, I need to conceptually understand why the work a gas does is the integral of pressure external * dv and is 0 when pressure external is 0. I understand why dw = - p external * dv and so ...
1
vote
1answer
271 views
Given two boiling temperatures and pressures, how can I find the latent heat?
I am given the fact that at a certain pressure a liquid boils at a corresponding temperature, at a different pressure it boils at a different temperature, and then I am asked to find the latent heat ...
4
votes
1answer
173 views
Can i use coils with compressed air to make a superconductor?
What im saying is inside pipes i am going to use compressing so that that in the places with low pressure they cool the superconducotor. is this possible? Can i use this concept to make ...
1
vote
1answer
213 views
simulations at constant pressure-volume and constant volume-temperature
I have read some papers where the authors perform simulations at constant pressure
and constant volumen or sometimes constant volume constant temperature. My question
is when is it better to use one ...
2
votes
1answer
2k views
Best way to solve P-V-T Question
Typically in an exam or problem set we have a problem that's like this:
Determine the specified property at the indicated state of water. Locate the state on a sketch of the T-v and P-v diagram.
p= 3 ...
2
votes
7answers
3k 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, ...
4
votes
0answers
775 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) ...
1
vote
3answers
400 views
Why isn't pressure a measure of energy?
Hey guys, I'm having a problem in understanding the 1st Law of Thermodynamics.
If i would increase the pressure of a closed system by compressing a gas in a cylinder isothermal, the 1.Law states, ...
