# 0.12 Phase equilibrium and intermolecular interactions

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## Foundation

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.

## Goals

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.

how can chip be made from sand
are nano particles real
yeah
Joseph
Hello, if I study Physics teacher in bachelor, can I study Nanotechnology in master?
no can't
Lohitha
where we get a research paper on Nano chemistry....?
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
Ali
what are the products of Nano chemistry?
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
hey
Giriraj
Preparation and Applications of Nanomaterial for Drug Delivery
revolt
da
Application of nanotechnology in medicine
has a lot of application modern world
Kamaluddeen
yes
narayan
what is variations in raman spectra for nanomaterials
ya I also want to know the raman spectra
Bhagvanji
I only see partial conversation and what's the question here!
what about nanotechnology for water purification
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
how did you get the value of 2000N.What calculations are needed to arrive at it
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