chuong3 enok concept

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Content

Thermodynamics

Thermochemistry

Chemical equilibrium

Phase equilibrium

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Thermodynamics & Thermochemistry

Thermochemistry

how we observe,

measure andpredict energy

changes for 

physical changes

chemical

reactions

Thermodynamics

how to predict if a

chemical reaction

will occur or not.

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Thermodynamics & Thermochemistry

Chemical Equilibrium Phase Equilibrium

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Concepts

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The Nature of Energy

Energy is the capacity to do work or to

transfer heat.

Heat is the energy transferred from oneobject to another because of a difference

in temperature.

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The Nature of Energy

Kinetic Energy and

Potential Energy

Kinetic energy is the

energy of motion: KE = ½mv2 

Potential energy is the

energy an object

possesses by virtue of its position. Represents the capacity to

do work.

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Energy Units

Joule

Calorie

1 calorie is the heat

required to raise the

temperature of 1.00 g of 

H2O by 1°C.

1 cal = 4.184 J

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Work & Heat

Work (A): product of force applied to an object over a distance.

Heat (Q): transfer of energy between two objects 

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Thermodynamic system

Thermodynamicsystem is a quantity of 

matter of fixed identity,around which we candraw a boundary .

Everything outside theboundary is thesurroundings

The Universe = The System + The Surroundings

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The Sys tem and Surround ings 

The environment of a chemicalreaction is separated into twoparts, the system and the

surroundings. The system is the part of the

environment we single out for study. The system generally iscomprised only of the participants(reactants, products, solvents,etc..) in the reaction.

we divide the universe into a system and itssurroundings. The boundary between thesystem and its surroundings can be as realas the walls of a beaker that separates asolution from the rest of the universe

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Thermodynamic Systems - Def in i t ions 

OpenSystem: Freeexchangeacross

systemboundaries.

ClosedSystem: Energy canbeexchangedbut matter cannot.

IsolatedSystem: Nomatter or energycross systemboundaries. No

work can bedone on thesystem.

AdiabaticSystem: Special casewhere no heatcan beexchanged butwork can bedone on thesystem (e.g. PVwork).

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States of Matter 

Solid Liquid 

Gas Plasma 

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The thermodynam ic s tate 

The thermodynamic state of a system is defined byspecifying values of a set of measurable properties sufficient to determine all other properties .

 A thermodynamic state is the macroscopic condition of a thermodynamic system as described by its particular thermodynamic parameters.

The state of any thermodynamic system can bedescribed by a set of thermodynamic parameters, suchas temperature, pressure, density, composition,independently of its surroundings or history.

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Thermodynamic State Propert ies/Parameters  

Extensive properties: These variables or properties depend on the amount of 

material present (e.g. mass or volume).

Intensive properties: These variables or 

properties DO NOT depend on the amountof material (e.g. density, pressure, andtemperature).

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Process 

If the state of a system changes, then it is undergoing a process.The succession of states through which the system passes definesthe path of the process.

a cyclic process or a cycle: If, at the end of the process, theproperties have returned to their original values (but the state of thesurroundings may have changed)

Isochoric process : V = const

Isobaric process : P = const

Isotherma process l: T = const

 Adiabatic process : Q = 0

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Exotherm ic process & Endo therm ic 

process 

Exothermic: energy released by system to surrounding.

Endothermic: energy absorbed by system from surrounding.

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Spontaneous process:

 All exothermic reactions are spontaneous. However, some

endothermic reactions are also spontaneous.

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State function

A state function (a funct ion of state) is a property of a systemthat depends only on the current state of the system, not on theway in which the system got to that state.

A state function describes the equilibrium state of a system.

Common state function: internal energy, enthalpy and entropy.They describe quantitatively an equilibrium state of thermodynamic systems.

State functions are functions that are independent of the pathway bywhich a process occurs.

DX = Xfinal - Xinitial

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Process functions

mechanical work and heat are process quantities because they describe quantitatively the t ransi t ion  between equilibrium states of thermodynamicsystems. 

State function: depends only on the initial and final statesof system, not on how the internal energy is used. 

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Internal Energy (U)

The internal energy (U) 

of a system consists of 

the kinetic energy of allthe particles plus the

potential energy of 

interaction between the

particles and within theparticles.

U = kinet ic + po tential  

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Internal Energy (U)

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Internal Energy (U)

Cannot measure absolute internal energy.

Can only measure the change in energy of the system

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In ternal Energy 

U = U (V, T )In equilibrium:

• Intern al Energy depends on the kinetic energy of particles in a system

and their density )• Intern al Energy  of a chemical system depends on

• number of particles

• type of particles

• temperature

The internal energy is a state function  – it depends onlyon the state of a system, the method of preparation of this state (“path”) is irrelevant

(other state functions – T , P , V , etc.).