<< Chapter < Page Chapter >> Page >

Vapor-liquid phase transition

Consider, then, trying to measure the volume for lower and lower temperatures to follow the graph . To be specific, we take exactly 1.00 mol of butane C 4 H 10 at 1 atm pressure. As we lower the temperature from 400K to 300K, we observe the expected proportional decrease in the volume from32.8L to 24.6L and this proportionality works very well for temperatures just slightly above 272.6K, where the volume is 22.4L.However, when we reach 272.6K, the volume of the butane drops very abruptly, falling to about 0.097L at temperatures just slightlybelow 272.6K. This is less than one-half of one percent of the previous volume! The striking change in volume is shown in the graph as a vertical line at 272.6K.

This dramatic change in physical properties at one temperature is referred to as a phase transition . When cooling butane through the temperature 272.6K, the butane is abruptly converted at thattemperature from one phase, gas, to another phase, liquid, with very different physical properties. If we reverse the process,starting with liquid butane at 1 atm pressure and temperature below 272.6K and then heating, we find that the butane remains entirelyliquid for temperatures below 272.6K and then becomes entirely gas for temperatures above 272.6K. We refer to the temperature of thephase transition as the boiling point temperature. (We will discuss the phases present at the boiling point, rather than above and below that temperature, in another section .)

We now consider how the phase transition depends on a variety of factors. First, we consider capturing 2.00mol of butane in the cylinder initially, still at 1 atm pressure. The volume of 2.00 mol is twice that of 1.00 mol, by Avogadro's hypothesis . The proportional decrease in the volume of 2.00 mol of gas is shown in along with the previous result for 1.00 mol. Note that the phase transition is observed tooccur at exactly the same temperature, 272.6K, even though there is double the mass of butane.

Variation of phase transition with pressure

Consider instead then varying the applied pressure. The result for cooling 1.00 molof butane at a constant 2.00 atm pressure is also shown in . We observe the now familiar phase transition with a similar dramatic drop in volume. However, in thiscase, we find that the phase transition occurs at 293.2K, over 20K higher than at the lower pressure. Therefore, the temperature ofthe phase transition depends on the pressure applied. We can measure the boiling point temperature of butane as a function ofthe applied pressure, and this result is plotted here .

Boiling point versus pressure

Finally, we consider varying the substance which we trap in the cylinder. In each case, we discover that theboiling point temperature depends on both what the substance is and on the applied pressure, but does not depend on the amount of thesubstance we trap. In , we have also plotted the boiling point as a function of the pressurefor several substances. It is very clear that the boiling points for different substances can be very different from one another,although the variation of the boiling point with pressure looks similar from one substance to the next.

Questions & Answers

how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Do somebody tell me a best nano engineering book for beginners?
s. Reply
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
I'm interested in nanotube
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
what is system testing
what is the application of nanotechnology?
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
anybody can imagine what will be happen after 100 years from now in nano tech world
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
silver nanoparticles could handle the job?
not now but maybe in future only AgNP maybe any other nanomaterials
I'm interested in Nanotube
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
can nanotechnology change the direction of the face of the world
Prasenjit Reply
Got questions? Join the online conversation and get instant answers!
QuizOver.com Reply

Get the best Algebra and trigonometry course in your pocket!

Source:  OpenStax, Concept development studies in chemistry. OpenStax CNX. Dec 06, 2007 Download for free at http://cnx.org/content/col10264/1.5
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Concept development studies in chemistry' conversation and receive update notifications?