BITS Pil iBITS PilaniPilani Campus

BITS F111BITS F111Thermodynamics

BITS Pil iBITS PilaniPilani Campus

L t 1 Th l t ti dLecture 1: The language - systems, properties and equilibrium states. processes Th l ilib i d T tThermal equilibrium and Temperature

What is Thermodynamics?• Thermodynamics – Heat and Work, and Energy changes

i i l f iin material transformations

• Thermodynamics – where does a system go, and why?

Equilibrium

• Phenomenological or macroscopic thermodynamics – self-Phenomenological or macroscopic thermodynamics self

contained logical structure, independent of any assumptions

b t th d l i i i t t h iabout the underlying microscopic structure or mechanisms

• Statistical Thermodynamics – Bridges thermodynamics

with the microscopic world

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Nature of thermodynamics• Macroscopic bodies described by the values of a handful of

measurable attributes or properties

• Transformations undergone by bodies, interacting with other

bodies, described in terms of the corresponding changes in

values of propertiesp p

• Descriptions based on three laws derived from experience,

h l di t th id tifi ti f t th leach leading to the identification of a new property – thermal

equilibrium and temperature, impossibility of perpetual motion

and energy, direction of a natural process, and entropy.

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What is studied?

System, Properties, Equilibrium States, State Functions Process Cycle

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Functions, Process, Cycle

Systems – Control VolumeControl Surface

System ‐ device or a combination of many ydevices that contain aquantity of matter under considerationconsideration. 

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Systems and Surroundings• Part of the universe set apart for detailed study

• Closed System or Control Mass – One that cannot

exchange matter, but can exchange energy with the

surroundings, ie., special case of a control volume in which

matter does not cross control surface

• Open System – One that can exchange both matter and

ith th dienergy with the surroundings

• Isolated System – One that does not interact in any way

with the surroundings

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Properties and Equilibrium State• Property – measurable, macroscopic attribute of a system

( ) ( )– eg., Volume (geometric), Pressure (mechanical), and

Temperature (thermodynamic)

• Equilibrium State – “all properties unchanging with time”,

with values that do not depend on the historyp y

• Mechanical, Chemical, Thermal - Thermodynamic

• State prescribed by values of properties, and vice-versa

• Question – how many properties to specify equilibrium

state?BITSPilani, Pilani Campus

Properties• Extensive – one whose value increases in direct proportion

( ) fto the mass (extent) of the system, eg., Volume, Energy,

Mass

• Intensive – one whose value is independent of the extent

(mass) of the system, eg., Pressure, Viscosity, Density( ) y , g , , y, y

• Specific – Extensive property per unit mass, eg., Specific

V l V l /MVolume v = Volume/Mass

• Continuum approximation

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