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The "phase" of a substance is the particular physical state it is in. The most common phases are solid, liquid,and gas, each easily distinguishable by their significantly different physical properties. A given substance can exist indifferent phases under different conditions: water can exist as solid ice, liquid, or steam, but water molecules are H 2 O regardless of the phase. Furthermore, a substance changes phase without undergoing any chemical transformation: the evaporation ofwater or the melting of ice occur without decomposition or modification of the water molecules. In describing the differingstates of matter changes between them, we will also assume an understanding of the principles of the Atomic Molecular Theory and the Kinetic Molecular Theory . We will also assume an understanding of the bonding, structure, and properties of individual molecules.


We have developed a very clear molecular picture of the gas phase, via the Kinetic Molecular Theory. The gasparticles (atoms or molecules) are very distant from one another, sufficiently so that there are no interactions between theparticles. The path of each particle is independent of the paths of all other particles. We can determine many of the properties of thegas from this description; for example, the pressure can be determined by calculating the average force exerted by collisionsof the gas particles with the walls of the container.

To discuss liquids and solids, though, we will be forced to abandon the most fundamental pieces of the KineticMolecular Theory of Gases. First, it is clear that the particles in the liquid or solid phases are very much closer together than theyare in the gas phase, because the densities of these "condensed" phases are of the order of a thousand timesgreater than the typical density of a gas. In fact, we should expect that the particles in the liquid or solid phases areessentially in contact with each other constantly. Second, since the particles in liquid or solid are in close contact, it is notreasonable to imagine that the particles do no interact with one another. Our assumption that the gas particles do not interact isbased, in part, on the concept that the particles are too far apart to interact. Moreover, particles in a liquid or solid mustinteract, for without attractions between these particles, random motion would require that the solid or liquid dissipate or fallapart.

In this study, we will pursue a model to describe the differences between condensed phases and gases and todescribe the transitions which occur between the solid, liquid, and gas phases. We will find that intermolecular interactions play themost important role in governing phase transitions, and we will pursue an understanding of the variations of these intermolecularinteractions for different substances.

Observation 1: gas-liquid phase transitions

We begin by returning to our observations of Charles' Law . Recall that we trap an amount of gas in a cylinder fitted with a piston, and we apply afixed pressure to the piston. We vary the temperature of the gas, and since the pressure applied to the piston is constant, thepiston moves to maintain a constant pressure of the trapped gas. At each temperature, we then measure the volume of the gas. From ourprevious observations, we know that the volume of the gas is proportional to the absolute temperature in degrees Kelvin. Thus agraph of volume versus absolute temperature is a straight line, which can be extrapolated to zero volume at 0K.

Questions & Answers

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
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
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
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.
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Concept development studies in chemistry. OpenStax CNX. Dec 06, 2007 Download for free at http://cnx.org/content/col10264/1.5
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