Download - Thermodynamics & Kinetics

AMMSI A

CSIR National Metallurgical Laboratory

Jamshedpure,India.

[email protected] & [email protected]

12/30/2013 AMMASI A CSIR -NML India
mailto:[email protected]:[email protected]

Thermodynamics is the science of flow of heat

Thermodynamics is the study of the effects of work, heat, and energy on a system.

Thermodynamics is only concerned with macroscopic changes and observations. Not only

Heat transfers until thermal equilibrium is established. Nothing happening.

observation ,No one are violating so for

Why is it so ????


Derived from Greek word & is the science of flow of heat

Developed in 19th and early 20th century

(i) Invention of stream engine in 18th century

and issue of the relation between heat and work .

(ii) Count Rumford observed that qg

(iii) In 1840 Joules experiment proved the count Rumford observation.

This was led to First law of thermodynamics .

(iv) In mid 19th Entropy as the thermo parameter

(v) In 1904 W Nerst and Max Planck absolute entropy value - Third law of thermodynamics

C and S tHER.pptxC and S tHER.pptxSecond law of thermodynamics.pptxThird law of thermodynamics.pptx

Entirely empirical ,observation and common sense

Developed before people knew about atom and molecules so science based on macroscopic properties of matter.


A thermodynamic system is said to be at equilibrium when it is at mechanical, thermal and chemical equilibrium.

The word equilibrium means a state of balance.

In a state of thermodynamic equilibrium, there are no net flows of matter or of energy, no phase changes, and no unbalanced potentials (or driving forces), within the system.

For a thermodynamic system thermal equilibrium is achieved when temperature is constant, mechanical equilibrium is attained when pressure or volume is constant and chemical equilibrium is attained when the chemical potentials are constant.

Nothing is happening


Alternately, at equilibrium the total energy is minimum or

equilibrium corresponds to a minimum energy state.

It was already mentioned that at complete equilibrium dG=0 and that a system is in mechanical, thermal and chemical equilibrium.

At mechanical and thermal equilibrium in a heterogeneous system, the pressure and temperature is equal in all the phases. The concept of chemical equilibrium can be understood in terms of the chemical potential.

Nothing is happening and Absence of driving potential & ??


Quasi equilibrium

Para equilibrium

Metastable equilibrium

Unstable equilibrium


Thermodynamics terminology


Describing systems requires:

Variable or parameter which can quantitatively

Intensive & Extensive properties

System is Homogeneous or Heterogeneous

System is in Equilibrium State

The number of components


Extensive properties Intensive properties

Those properties of system that vary with its size or mass

These properties of system are additive Total volume of a system is sum of all the volume of the component part V T = V2

Ex : M,V ,E ,H ,S and G etc of a substance

Those properties of system that are independent of its size or mass

These properties of system are not additive. Hence a value may be assigned at each point in system.

Ex : P,T , , and molar energy etc of substance

Note : Ratio of any extensive properties is independent of the total mass

All specific and molar properties are intensive properties


Classical thermodynamics concerns the relationships between bulk properties of matter. Nothing is examined at the atomic or molecular level.

Statistical thermodynamics seeks to explain those bulk properties in terms of constituent atoms. The statistical part treats the aggregation of atoms, not the behavior of any individual atom.

C & S

C AND THERMO.pptx

Thermal equilibrium: Two systems are said to be in thermal equilibrium if there is no net flow of heat between them when they are brought into thermal contact.

Temperature is the indicator of thermal equilibrium in the sense that there is no net flow of heat between two systems in thermal contact that have the same temperature.

THE ZEROTH LAW OF THERMODYNAMICS

Two systems individually in thermal equilibrium with a third system are in thermal equilibrium with each other.


Common sense law : Concept of temperature and heat flow

A B TA=TC

TB=TC

C

Then TA=TB

Temperature.pptx

Temperature is the indicator of thermal equilibrium in the sense that there is no net flow of heat between two systems in thermal contact that have the same temperature.

THE ZEROTH LAW OF THERMODYNAMICS

Two systems individually in thermal equilibrium with a third system are in thermal equilibrium with each other.


Temperature is a measure of average kinetic energy of particle in a substance.

Temperature really tells us how fast atom /molecules moving in the system .


Empirical law

PV

T(

PV=0= f(T)

0 100

-273.15


Boyle's &Charles' law


1.First law of thermodynamics that energy cannot be created nor destroyed although it can be converted from one form to another or transferred from a system to the surroundings or vice versa

2.The total energy of the universe is a constant.

3.The energy of a system which isolated from surrounding is constant

Simply the law of conservation of energy

Energy is conserved!

NO THEORETICAL PROOFF 12/30/2013 AMMASI A CSIR -NML India

1. It is not possible to construct a perpetual machine which can do work without the expenditure of energy .if the were not true ,it would have been possible to construct such a machine .

2. James joule (1850) conducted large no of Experiments regarding the conversion of work into heat energy . He concluded that for every 4.183 J of work done on system, one calorie of heat produced .

3. Energy is conserved in chemical reaction also


internal energy increases

If a system does work on the external world, and no heat is added, its internal energy decreases.


The total energy which includes the energy of creation of the system or matter (U) and the energy to displace the systems surroundings in the absence of external force fields so that the system can be created is given by enthalpy

In thermodynamics, the internal energy is the total energy contained by a thermodynamic system. It is the energy needed to create the system. It excludes the energy to displace the system's surroundings, or any energy introduced due to external force fields.


Internal energy has two major components,

(i) Kinetic energy and

(ii) Potential energy.

The kinetic energy is due to the motion of the system's particles whether it be the motion of atoms, molecules, atomic nuclei, electrons, or other particles (translations, rotations, vibrations).

The potential energy includes all energies given by the mass of particles, by the chemical composition, i.e. the chemical energy stored in chemical bonds, the nuclear energy stored by the configuration of protons, neutrons, and other elementary particles in atomic nuclei.

U is function of state


--Amount of heat required to raise its temperature by one degree Specific heat , atomic heat and molar heat

Heat capacity at Volume (Cv) U = f(V,T) dE= q-P dV

Specific heat.pptx

Amount of heat required to raise the temperature of 1 g of a substance by 1 C or 1 K

Amount of heat (J)

Substance Specific heat (c) J/g C

Water 4.184

Ice 2.03

Steam 2.01

Al (s) 0.897

Fe (s) 0.449


Heat capacity at constant pressure (Cp)

U = f ( T,P) dE= q-P dV

Relation between Cv and Cp

For an ideal gas and isothermal process


H change when substance is heated from T1 to T2 @ constant P

(a) Without phase transformation

(b) with phase transformation ( melting, vaporization or other phase transformation .

H 298 for pure element is assumed to be zero at standard state


Heat of formation of compound

3 Fe2 O3 + CO =2Fe3O2 +CO2 r = -2.67 kJ/mole

Heat of reaction

2 Al +3/2 O2 = Al2O3 -1700kJ/mole

Heat of combustion

C +O2= CO2 -393.5kJ/mole

Heat of transformation

Zn s Zn l @ 963K Lf,Zn =+7.28 kJ/mole

Heat of solution


The first law of thermodynamics provides no information regarding the feasibility of such transformation

First law does not provide any information regarding the direction a processes will take whether it is a spontaneous or a non spontaneous process


i) In electric machines efficiency of the conversion of electrical energy to mechanical and vice versa can occurs as high as 90%

ii ) While , in heat engine efficiency of the conversion of heat energy into work is quite low ,10 to 40 %

Note : Irreversible nature of flow of heat & heat cant be transferred from low to high temperature without aid of external energy .


Kelvin-Planck statement Clausius statement

There exists a property called entropy which is a thermodynamic property of a system.

Naturally occurring processes are directional & irreversible

Entropy 12/30/2013 AMMASI A CSIR -NML India

Melting of solid is a accompanied by moderate S increase while vaporization involves really large S increase

solidification and condensation ???

SsurrHsys

T


Let us ask a question as to whether it would be possible to convert all the energy supplied to a system into useful work?

Although the first law indicates that out of the total energy input to the system, part of it is usefully converted to work and some of it is stored in the system, the first law is unable to quantify the non -recoverable losses of energy such as friction and dissipation.

Entropy is a thermodynamic property that is a measure of the energy not available for work in a thermodynamic process, such as in energy conversion devices, engines, or machines.

an energy TS is not available to do useful work


Classical thermodynamics .

A microstate specifies all molecular details about the system including the position and velocity of every molecule. In statistical mechanics, entropy is given as:

is the number of microstates. In statistical mechanics, entropy is a measure of the number of ways in which a system may be arranged, often taken to be a measure of "disorder"


Free energy is the energy available to do work It is the total energy available in the system minus the energy not available for useful conversion to work. We already said enthalpy and TS. Therefore, in common metallurgical systems that operate at constant pressure, the energy available from a system to convert to useful work is the Gibbs free energy that is defined as G= H-T S According to II law , To predict the spontaneity of a process entropy

most of the physical & chemical processes. Therefore a thermodynamic function which reformulates the spontaneity criterion considering only the system under study is required


Most of chemical and metallurgical reaction are performed at constant T & P Gibbs Free Energy (G) Interest at System under constant T & Volume Helmholtz Free Energy (A) or Isothermal work content A = E - TS dA =-S dT P dV System under these condition is called closed system

Free energy.pptx

Our ultimate object to express first & second law explicitly in terms of T and P which experimentally most easily controlled

G = E + PV TS or G = H TS

Also called as thermodynamics Potential

Combined statement of first and second law

d G = dE +P dV +V dP -T dS- S dT

= -P dV +T dS +P dV +V dP -T dS- S dT

= V dP-S dT

Generally we always interest in P V type work So

d G = V dP-S dT

Maxwell Relations.pptx

Thermodynamic conditions for spontaneity and equilibrium

for closed system.

Spontaneous Equilibrium Non spontaneous

GS < 0 GS = 0 GS > 0

SU > 0 SU = 0 SU < 0


We know If z= f (x,y) ; dz= Mdx +Ndy

( M / y )x = ( N / x) ----- Eq (a)

Following forms of combined Eq of first & second law of thermodynamics all of which apply to a system of constant composition and mass at equilibrium.

d E = T dS PdV

dH = T dS + V dP

dA = -S dT P dV

d G = V dP-S dT


Apply relation to Eq (a)

( T/ V)S = -( P/ S) V

( T/ P)S = ( V/ S )P

Maxwell Relation

( P/ T)V= ( S/ V)T

( V/ T)P= -( S/ P)T

These Equations are used to calculate thermodynamic parameter.


First and second law of thermodynamics state that the energy and entropy of system are function of its state . Since these law deal only with changes in energy and entropy respectively.

absolute value of energy and entropy ???


In 1902, T.W. Richard researched that

relationship of T with H, which were measured by some battery reaction. low temperature.

Nernst heat theorem state that for all reaction involving substances

3

, H G0KT


Planck state that Entropy of any homogeneous substance which is in complete internal equilibrium may be taken as zero at 0K

S = 0 at absolute zero

Assignment of zero value to entropy of crystalline elements is zero purely a convention and that assignment of a zero value to entropy of most compound is a consequence of convection as well as third law .

Chemical reaction A + B = AB

SAB SA-SB = 0

The temperature of the substance can not drop to 0 K by finite ways

.


In actual practice it may and frequently does , happen that a phase cooled to vicinity of absolute temperature , more random atomic arrangement characteristic of higher temperature is frozen

Ex when solid CO is cooled to a near absolute zero ,there is very strong presumption that molecules do not arrange themselves in most orderly fashion .

instead of -C-O-C-O-C-C- people found that C-O-C-O-O-

Third law applicable to solution , pure crystalline which are in complete internal equilibrium .


-w

(ii) Isochoric process ,W = 0

(iii)Isobaric process W=P(V2-V1)

(iv) Isothermal process ..

Transition from

one state to another state


Zero th law :Common sense

Temperature

1st law of thermodynamics : you can break even

Internal energy and Enthalpy

2nd law of thermodynamics : you can break even at 0K Entropy and Free energy

3rd law of thermodynamics : you cant get to 0K Absolute value ..


Fugacity indicates the escaping tendency of the matter or substance or component.

High fugacity would indicate a greater tendency of a compound to escape out of system, dissolve , intermix or react.

dG =V dP-S dT

At constant T and for one mole of ideal gas

dG = RT d(lnP) f = P @ all pressure


Fugacity for real or non ideal gas

dG= RT d (lnf)

Real gases approach ideal behavior as pressure is decreased

Hence, P

As consequence of lower /decrease in pressure of an real gas f=P

Only at very high level of pressure and for an real gas we use FUGACITY instead of PRESSURE.

i.e. P


Thermodynamic variable (H,S & G etc ) of the substance in pure state are different from those in state of solution.

There fore H,S & G changes with change in composition besides T & P .

Index to measure these changes in H ,S & G when pure substance goes into a state of solution.

a = f /f Activity is a measure of free concentration.

Concentration available for reaction.


dG= RT d (lnf)

= RT d (f a) = RT(dln f + dln a)

Activity of a substance in its standard state is to be unity .

Integrating eqn (a) from standard to actual state at constant T

G-G -

General form : partial free energy of I th species

G I = GI +RT (ln a1 )

Standard State.pptx

Chemical reaction under isothermal isobaric condition

+RT ln( aDd.aE

e / aAa .aB

b )

+ RT ln Q

0 = + RT ln K

= -RT ln K where K= (Q )eq

Thermodynamics equilibrium.pptxThermodynamics equilibrium.pptx

1) When K is greater than Unity ,Equilibrium lies well to right

Product predominate in Eq mixture.

2) When K is less than unity ,Equilibrium lies to left

Reactant predominate


dP- dT

= - dT

Gibbs Helmholz Eq

Integrating and divided by T 2


It is for the chemical reaction involving the gases species

Partial pressure ,total pressure and vacuum


Free energy of single phase at internal phase at equilibrium as a function of T,P and Composition .

We assumed that there is no electric ,magnetic, gravitational and surface fields ,etc effect on our system.

1) dn1

+ ( 2


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