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is still not a complete phase diagram, because we have not includedthe combinations of temperature and pressure at which solid and liquid are at equilibrium. As a starting point for theseobservations, we look more carefully at the conditions near 0°C. Very careful measurements reveal that the solid-gasline and the liquid-gas line intersect in where the temperature is 0.01°C. Under these conditions, we observe inside thecontainer that solid, liquid, and gas are all three at equilibrium inside the container. As such, this unique temperature-pressurecombination is called the triple point . At this point, the liquid and the solid have the same vapor pressure,so all three phases can be at equilibrium. If we raise the applied pressure slightly above the triple point, the vapor must disappear.We can observe that, by very slightly varying the temperature, the solid and liquid remain in equilibrium. We can further observe thatthe temperature at which the solid and liquid are in equilibrium varies almost imperceptibly as we increase the pressure. If weinclude the solid-liquid equilibrium conditions on the previous phase diagram, we get this , where the solid-liquid line is very nearly vertical.

Phase diagram of water

Each substance has its own unique phase diagram, corresponding to the diagram in for water.

Observation 4: dynamic equilibrium

There are several questions raised by our observations of phase equilibrium and vapor pressure. The first wewill consider is why the pressure of a vapor in equilibrium with its liquid does not depend on the volume of the container intowhich the liquid evaporates, or on the amount of liquid in the container, or on the amount of vapor in the container. Why do weget the same pressure for the same temperature, regardless of other conditions? To address this question, we need to understand thecoexistence of vapor and liquid in equilibrium. How is this equilibrium achieved?

To approach these questions, let us look again at the situation in . We begin with a container with a fixed volume containing some liquid,and equilibrium is achieved at the vapor pressure of the liquid at the fixed temperature given. When we adjust the volume to a largerfixed volume, the pressure adjusts to equilibrium at exactly the same vapor pressure.

Clearly, there are more molecules in the vapor after the volume is increased and equilibrium is reestablished,because the vapor exerts the same pressure in a larger container at the same temperature. Also clearly, more liquid must haveevaporated to achieve this equilibrium. A very interesting question to pose here is how the liquid responded to the increase in volume, which presumably only affected the space in which the gas moleculesmove. How did the liquid "know" to evaporate when the volume was increased? The molecules in the liquid could not detectthe increase in volume for the gas, and thus could not possibly be responding to that increase.

The only reasonable conclusion is that the molecules in the liquid were always evaporating, even before thevolume of the container was increased. There must be a constant movement of molecules from the liquid phase into the gas phase.Since the pressure of the gas above the liquid remains constant when the volume is constant, then there must be a constant numberof molecules in the gas. If evaporation is constantly occurring, then condensation must also be occurring constantly, and moleculesin the gas must constantly be entering the liquid phase. Since the pressure remains constant in a fixed volume, then the number ofmolecules entering the gas from the liquid must be exactly offset by the number of molecules entering the liquid from the gas.

Questions & Answers

How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
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
characteristics of micro business
for teaching engĺish at school how nano technology help us
How can I make nanorobot?
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
how can I make nanorobot?
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?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
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Source:  OpenStax, General chemistry ii. OpenStax CNX. Mar 25, 2005 Download for free at http://cnx.org/content/col10262/1.2
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