# 0.22 Entropy and the second law of thermodynamics

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## Introduction

We have spent much of the previous concept studies finding that chemical and physical processes come to equilibrium. We have observed this in phase equilibrium of pure substances, solution equilibrium, solubility equilibrium, chemical reactions in the gas phase, and acid-base equilibrium. In each case, we have been able to understand equilibrium as a dynamic process. At equilibrium, there are competing processes, forward and reverse, which come to equilibrium when the rates of the competing processes are equal. For example, when liquid and vapor are at equilibrium at the vapor pressure of the liquid, the rate of evaporation of the liquid is equal to the rate of condensation of the vapor.

However, our dynamic equilibrium model does not tell us the conditions at equilibrium. For each liquid, we know that there is one pressure for each temperature at which the liquid can be in equilibrium with its vapor. But we cannot predict or calculate what that pressure is for each temperature for each liquid. We can only make qualitative predictions. Thermodynamics will give us the means to make these predictions and will give us a new physical insight into the nature of equilibrium.

We will begin by developing a means to predict what processes will happen “spontaneously.” This is a term chemists use to refer to processes that are not at equilibrium. It is easiest to explain with an example. We know that, if the pressure of water vapor is 1 atm at 25 ºC, the water vapor will spontaneously condense. On the other hand, we have also seen that, if the pressure of water vapor is below 23 torr at 25 ºC, the liquid water will spontaneously evaporate. These are both examples of spontaneous processes. Note that these are opposite processes. This means that the spontaneity of a process depends on the conditions, in this case, the pressure and the temperature. Any process not at equilibrium is a process occurring spontaneously. One way to understand equilibrium, then, is to understand spontaneity. We will see that the Second Law of Thermodynamics provides us the ability to predict spontaneous processes.

## Foundation

We have come a long way to reach this point, so we have a substantial foundation to build on. We know all the elements of the Atomic Molecular Theory, including the models for molecular structure and bonding. We have developed the postulates of the Kinetic Molecular Theory. We have observed and defined phase transitions and phase equilibrium. We have also observed equilibrium in a variety of reaction systems, including acids and bases. We will assume an understanding of the energetics of chemical reactions, including the idea of a “state function” and the concept of Hess’ Law.

## Observation 1: spontaneous mixing

We begin by examining common characteristics of spontaneous processes, and for simplicity, we focus on processes not involving phase transitions or chemical reactions. A very clear example of such a process is mixing. Imagine adding a drop of blue ink into a glass of water. At first, the blue dye in the ink is highly concentrated. Therefore, the molecules of the dye are closely congregated. Slowly but steadily, the dye begins to diffuse throughout the entire glass of water, so that eventually the water appears as a uniform blue color. This occurs more readily with agitation or stirring but occurs spontaneously even without such effort. Careful measurements show that this process occurs without a change in temperature, so there is no energy input or released during the mixing.

do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
it is a goid question and i want to know the answer as well
Maciej
Abigail
Do somebody tell me a best nano engineering book for beginners?
what is fullerene does it is used to make bukky balls
are you nano engineer ?
s.
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.
Tarell
what is the actual application of fullerenes nowadays?
Damian
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.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
so some one know about replacing silicon atom with phosphorous in semiconductors device?
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.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
for screen printed electrodes ?
SUYASH
What is lattice structure?
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
what's the easiest and fastest way to the synthesize AgNP?
China
Cied
types of nano material
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
what is nano technology
what is system testing?
preparation of nanomaterial
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
what is system testing
what is the application of nanotechnology?
Stotaw
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
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
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
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
Hello
Uday
I'm interested in Nanotube
Uday
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
Prasenjit
how did you get the value of 2000N.What calculations are needed to arrive at it
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Good
Berger describes sociologists as concerned with
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