When a gas cools, its volume _______?

[erikiksaz]

I answered decrease to the question, but my TA (teacher's assistant) told me that it's increase. She gave us the equation PV=T, pressure, volume, temp. Anyways, i tried holding pressure constant, so V and T both vary proportionally. But, after asking her about this, she said that holding pressure constant was impossible, and that P and V were functions.

Anyways, could someone clear this up? I thought it was relatively simple, but i guess not!

 

[Heisenberg]

Assuming constant pressure, yes, the volume will decrease (for ideal gases...). Constant pressure is indeed possible - it's called an isobaric process. Is there more to the question that might explain what she said?

 

[TuxDave]

You're correct, your TA is wrong.

 

[jamesave]

in general, the volume will decrease as temperature decrease. Again, pressure is assumed to be the equal.. wouldn't it be possible to hold pressure equal.

I think this is what they do in the Prius with the gas tank. If I am not mistaken their tank is collapsible, which try to make the gas liquefied (and, thus, help the environment)

 

[white]

ask another TA or the professor. if the only information given is that fill-in-the-blank statement, then you have to assume that pressure is held constant. otherwise it would be "when a gas cools, its volume may increase or decrease depending on how pressure and volume vary." it is possible that your TA messed up and tried to cover up his or her mistake instead of owning up to it.

 

[jagec]

Not enough info. Obviously if the container is open to atmosphere (or flexible), pressure = 1 atm = constant.

And explain to me how your TA thinks that V is always a "function". Sometimes it is, but if I've got a rigid metal container, V is a NUMBER, no more, no less.

 

[habib89]

as said before, if that's the only information you got, then you're right.. cause you always assume everything being equal, the only variables in that situation woudl be volume and temperature.. in which case, they are proportional.. so your'e right..

 

[Chronoshock]

pv/nt=r, P and V is related by Boyles law (where do you get boils? Your P____ or V_____) Since both are in the numerator, if one goes up the other goes down. Tada!

 

[George P Burdell]

if the question didn't state "pressure not constant", you can assume a constant pressure due to absence of data pointing to the contrary.

 

[simms]

decrease

 

[WhiteKnight]

Originally posted by: Chronoshock
pv/nt=r, P and V is related by Boyles law (where do you get boils? Your P____ or V_____) Since both are in the numerator, if one goes up the other goes down. Tada!

I learned it as Puss Vacuole.

 

[Demon-Xanth]

When a gas's volume increases, it cools. When a gas cools, it's volume decreases.