# Pressure Volume and Temperature

#### V4viet

##### Member
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Can someone please explain to me the relationship between these three b/c EK is confusing me.. This is what i know of it so far..
PV=nRT

Volume and Temperature is directly related..as temp increases Volume increases and vice versa..
however...Ek saids that sometimes it's possible to decrease temp by increasing volume b/c you're transferring kinetic energy of the gases to the container to expand the container. So does that mean if you decrease volume you can increase temperature as well?

If this is possible then it makes sense that increasing the pressure you'll increase the temperature b/c volume is decrease..

however, why is that Volume and Temperature proportionally related? that's the part im confused about..is that just an exception to the rules sometimes and how would you know when it's an exception if asked on the mcat..can someone please explain to me with a better understanding of this topic..thank you

#### Jejton

##### Full Member
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Scratch that I confused the hell out of myself trying to type it out.

#### Jejton

##### Full Member
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If you increase the pressure, volume decreases and temperature increases. Try taking some snow and squeeze it in your hand. At first it becomes a hard ball of ice because you compressed the snow particles so discount this phase. If you keep pressing, you will see that you will have liquid on your hands. That is because by decreasing the volume and increasing the pressure, you have increased the temperature

#### dr.kicia

##### Senior Member
7+ Year Member
15+ Year Member
Can someone please explain to me the relationship between these three b/c EK is confusing me.. This is what i know of it so far..
PV=nRT

Volume and Temperature is directly related..as temp increases Volume increases and vice versa..
however...Ek saids that sometimes it's possible to decrease temp by increasing volume b/c you're transferring kinetic energy of the gases to the container to expand the container. So does that mean if you decrease volume you can increase temperature as well?

If this is possible then it makes sense that increasing the pressure you'll increase the temperature b/c volume is decrease..

however, why is that Volume and Temperature proportionally related? that's the part im confused about..is that just an exception to the rules sometimes and how would you know when it's an exception if asked on the mcat..can someone please explain to me with a better understanding of this topic..thank you

look at the forula again.
If V and T are on opposite sides of equasion in the same form they are proportional to each other.
The best way to see what happenes is to try to plug in numbers for both V and T and rearange the equasion to solve for P
then you can realize that P=nrT/V
so if you increase the volume the P will be smaller because you will be deviding all stuff on the right side of equasion by the larger number.
If you increase the temperature but leave V the same then your P will be higher since you will have a higher number to devide.
For instance if you increase T x2
you will have nr2T/v (bigger number then nr1T/v for instance)
Just play with the eqasion untill you know it in your sleep.

#### V4viet

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OMG THANK YOU SO MUCH..both of you guys helped me out a lot..I really appreciate it..

#### dr.kicia

##### Senior Member
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15+ Year Member
OMG THANK YOU SO MUCH..both of you guys helped me out a lot..I really appreciate it..

you are welcome
study hard

#### V4viet

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however, if Volume and Temp is indirectly related..
PV=nRT
if i move
P over to the left
V=nRT/P
Increase T while keeping P constant..wouldn't that increase Volume? and if Decreasing T while keeping P constant wouldn't that decreases volume.. I'm just confuse b/c you can play w/ the equations so many ways and will get the rules mixed up..

#### dr.kicia

##### Senior Member
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15+ Year Member
however, if Volume and Temp is indirectly related..
PV=nRT
if i move
P over to the left
V=nRT/P
Increase T while keeping P constant..wouldn't that increase Volume? and if Decreasing T while keeping P constant wouldn't that decreases volume.. I'm just confuse b/c you can play w/ the equations so many ways and will get the rules mixed up..
think what happens to a gas when temperature rises and when it is closed in some container?
Yeah a big boom!
Why because the molecules in a higher temeratures are moving faster and bauncing off of each other much more and much harder and thus expanding (increasing the volume of a gas) which makes the container explode.

#### V4viet

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hmmm... so would it safe to say that V and T are indirectly related.. and P and T are directly related but if you keep either Volume or Pressure constant..and increasing Temperature will increase either Volume or Pressure.. ? sorry I'm just trying to really understand the PV=nRT thing

#### dr.kicia

##### Senior Member
7+ Year Member
15+ Year Member
hmmm... so would it safe to say that V and T are indirectly related.. and P and T are directly related but if you keep either Volume or Pressure constant..and increasing Temperature will increase either Volume or Pressure.. ? sorry I'm just trying to really understand the PV=nRT thing

don't try to memorize ALL the relationships word for word because likely you will get mixed up or confuzed.
All you need to memorize is the equasion. ANd then just try to relate it to a passage situation or whatever question you are asked. Then all you will need is to rearange the equasion and reason out your answear.
don't try to make it more complicated LOL
remeber that MCAT tests only BASIC physics.

#### V4viet

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gotcha..thank you

#### V4viet

##### Member
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i just added you on myspace so if u get some random Phucster.. it's me..hehehe thanks a lot for your help..i really appreciate it

#### dr.kicia

##### Senior Member
7+ Year Member
15+ Year Member
no problem Whne are you taking MCAT (i am preparing for 31st of MAy )
good luck with studying.

p.s

#### V4viet

##### Member
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5+ Year Member
I think im taking it around the same time too..are you using EK books? I have a bunch of kaplan test if u want it..my sn on Aim is V4viet..it'll be great if we can exchange some information and help each other out on subjects that we are weak on

#### Bill_252001

##### B+
10+ Year Member
Volume and temperature are indirectly related - as one goes up the other goes down. If you have x amount of molecules with in a certain volume of space containing y amount of energy, and then you increase the volume without adding energy, you now have y energy spread out over a greater volume. The molecules have more freedom of motion, less likelihood of collisions and therefore can use more of that energy so the temperature decreases.

Volume and Temperature are directly related and NOT Indirectly. It's called Charles's Law.

#### V4viet

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yeah I read about Charles' Law too.. it said Temp and Volume is directly related w/ constant pressure. However it's possible to decrease temp with increase volume b/c let say you increase a volume of a container by doing work on it..the work is a transfer of energy from the gas molecule to the container..therefore will decrease the temperature.. (short for what EK gen chem said)..

#### Bill_252001

##### B+
10+ Year Member
By increasing the volume, pressure decreases which causes a decrease in temperature.

#### xucardsfan08

##### Full Member
10+ Year Member
Remember that PV=nRT is the equation for IDEAL gases. The MCAT likes to make you think, and could put a question about a real gas that deviates from the PV=nRT relationship.

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