1.2 introduction to thermodynamics

8/11/2019 1.2 Introduction to Thermodynamics

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What is Thermodynamics?

Thermodynamics i s a branch of phys ica l

sc iences that t reats o f var ious phenomena

of energy and the re lated propert ies o f

matter , espec ia l ly of the laws of

t ransformation of heat into other formsof energy and v ice versa .

S imply put , thermodynamics i s a sc ience

of energy; the energy that has anabi l i ty to make changes.


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History of Thermodynamics

The name thermodynamics s tems f rom

the Greek words therme (heat ) and

dynamis (power) , which i s most

descr ipt ive of the ear ly e f for ts to convert

heat into pow er. Today the same name is broadly

interpreted to inc lude a l l aspects o f

energy and energy t ransformat ions ,

i n c l u d i n g p o w e r g e n e r a t i o n ,

re f r igerat ion, and re lat ionsh ips among

the prop ert ies o f matter.


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In 1712, Thomas Newcomen built an improved

steam engine, but it was expensive to build and notvery reliable.

James Watt invented the first inexpensive, reliable

steam engine in 1765. Wattssteam engine was more

than six times more efficient than Newcomens!

Watts steam engine catalyzed the industrial

revolution.

In 1798, Count Rumford noticed that canons becamehot as they were bored out. Rumsford showed that

more heat was released in the boring process than

could have been originally contained in the metal.


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He concluded that the mechanical boring process

was producing heat. This was a major departurefrom the caloric theory that was widely accepted at

the time.

In 1824, Carnot introduced ideal gas cycle analysis inhis work Reflectionon the Motive Power of Fire.

In the 1840sMayer, Joule and Helmholtz developed

the idea that energy could not be created or

destroyed. Energy is conserved. This principle is now

known as the 1st Law of Thermodynamics.


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Rudolf Clausius stated that nocycle can transfer heat

from a low temperature region to a high temperatureregion with no other interaction with its

surroundings.

This principle is known as the 2nd Law of

Thermodynamics.

The contribution of these scientists and many others

led to the development of the broad field of

thermodynamics that we know today.


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Topics in Modern Thermodynamics include:

Classical Thermodynamics

Characterize the behaviour of large groups ofmolecules based on properties of the entire group of

molecules, such as temperature and pressure.

Statistical ThermodynamicsCharacterize the behaviour of groups of molecules

based on the properties of each individual molecule

and the ways in which molecules interact.

Phase Equilibrium Thermodynamics

Characterize the behaviour of multiple phases that

exist in equilibrium with each other.

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Topics in Modern Thermodynamics include:

Chemical Reaction Equilibrium Thermodynamics

Characterize the behaviour of systems in which the

reactants and products of one or more reversible

chemical reactions are at equilibrium.

Solution Thermodynamics

Characterize the behaviour of systems that contain

more than one chemical species in a mixture.

Pure Component Thermodynamics

Characterize the behaviour of systems that contain a

pure component.


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Thermodynamics

Our s tudy wi l l be governed by two major

law: F i r s t & Second Law of Thermo-dynamics .

Thermodynamics appl ies s imple laws to a

wide range of energy systems that havemajor impact in our soc iety , for example ,

energy use in agr icu l ture , e lect r i c power

generat ion, and t ransportat ion systems.


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Thermodynamics

F i rs t Law of Thermodynamics

Th i s s tates that energy can be ne i ther

created nor destroyed. However , energy

can change forms, and energy can f low

f rom one p lace to another.

Second Law of Thermodynamics

The second law te l l s us how much

thermal energy can be converted intowork ; not a l l o f i t can be .


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Microscopic & Macroscopic

Microscopic thermodynamics we must

look at every molecu le and analyzecol lect ive molecular act ion by stat ist ica l

methods .

Macroscopic thermodynamics we look forthe overa l l e f fect o f the ind iv idual

molecu lar interact ions . Sample : The way

we l ive ; we measure the d istance in

meters and t ime in seconds . Thesemeasurements are very large compared

with the measurement of events on the

molecu lar leve l .


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Concepts & Definitions

In thermodynamics , the f i r s t

cons iderat ion i s that there must besometh ing that per forms the energy

transformat ion.

This someth ing i s ca l led substance. Say, in the fami ly automobi le engine, the

substance i s usual ly the mixture of

gasol in e and a i r.

In a steam turbine the substance i s

probably the steam. The substance may

be a so l id , l iqu id, vapor, or a mixture .


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Concepts & Definitions

SYSTEMS F ixed Mass and F ixed Space

A substance does not ex i st a lone, i t need

to be conta ined. Th is br ings us the to the

concept of a system.

A system i s def ine as any co l lect ion ofmatter or space of f i xed ident i ty and th is

concept i s one of the most important in

the s tudy of thermodynamics .


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Intensive & Extensive Properties

The state of substance complete ly

descr ibes how the substance ex ists temperature , pressure , dens i ty , and other

macroscopic propert ies and by knowing

these propert ies we can determine the

state of substance.

A property i s a character i st ic qual i ty o f

the ent i re system and depends not on how

the system changes state but only on thef ina l system states .


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Intensive & Extensive Properties

TWO TYPES OF PROPERTY

1.Extens ive depends on the s i ze on the

s ize or extent of the system (mass and

volume)

2. Intens ive independent on the s i ze of thesystem ( temperature and pressure)


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Phases of a Substance

So l id so l id i fy ing

Melt ing in t roduct ion of heat so that a

sol id substance wi l l turn into a l iquid

Vapor izat ion cont inuous addi t ion of

heat wi l l turn the l iquid substance into avapor or gas

Subl imat ion some substance in so l id

state turns into gas without pass ing

through l iqu id and vapor s tate .


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Processes and Cycles

A process i s a change i n the system state .

A thermodynamic cyc le i s a co l lect ion of

two or more processes for which the

in i t ia l and f ina l s tates are the same

Systems of Units

Newtons law states that the acce lerat ion

of a part icu lar body i s d i rect ly proport ionalto the resu l tant force act ing on i t and

inversely proport ional to i t s mass

1.2 introduction to thermodynamics

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