Upload
xuan-binh
View
221
Download
0
Embed Size (px)
Citation preview
7/27/2019 Chuong3 Enok Concept
http://slidepdf.com/reader/full/chuong3-enok-concept 1/24
7/27/2019 Chuong3 Enok Concept
http://slidepdf.com/reader/full/chuong3-enok-concept 2/24
Content
Thermodynamics
Thermochemistry
Chemical equilibrium
Phase equilibrium
7/27/2019 Chuong3 Enok Concept
http://slidepdf.com/reader/full/chuong3-enok-concept 3/24
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.
7/27/2019 Chuong3 Enok Concept
http://slidepdf.com/reader/full/chuong3-enok-concept 4/24
Thermodynamics & Thermochemistry
Chemical Equilibrium Phase Equilibrium
7/27/2019 Chuong3 Enok Concept
http://slidepdf.com/reader/full/chuong3-enok-concept 5/24
Concepts
7/27/2019 Chuong3 Enok Concept
http://slidepdf.com/reader/full/chuong3-enok-concept 6/24
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.
7/27/2019 Chuong3 Enok Concept
http://slidepdf.com/reader/full/chuong3-enok-concept 7/24
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.
7/27/2019 Chuong3 Enok Concept
http://slidepdf.com/reader/full/chuong3-enok-concept 8/24
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
7/27/2019 Chuong3 Enok Concept
http://slidepdf.com/reader/full/chuong3-enok-concept 9/24
Work & Heat
Work (A): product of force applied to an object over a distance.
Heat (Q): transfer of energy between two objects
7/27/2019 Chuong3 Enok Concept
http://slidepdf.com/reader/full/chuong3-enok-concept 10/24
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
7/27/2019 Chuong3 Enok Concept
http://slidepdf.com/reader/full/chuong3-enok-concept 11/24
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
7/27/2019 Chuong3 Enok Concept
http://slidepdf.com/reader/full/chuong3-enok-concept 12/24
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).
7/27/2019 Chuong3 Enok Concept
http://slidepdf.com/reader/full/chuong3-enok-concept 13/24
States of Matter
Solid Liquid
Gas Plasma
7/27/2019 Chuong3 Enok Concept
http://slidepdf.com/reader/full/chuong3-enok-concept 14/24
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.
7/27/2019 Chuong3 Enok Concept
http://slidepdf.com/reader/full/chuong3-enok-concept 15/24
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).
7/27/2019 Chuong3 Enok Concept
http://slidepdf.com/reader/full/chuong3-enok-concept 16/24
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
7/27/2019 Chuong3 Enok Concept
http://slidepdf.com/reader/full/chuong3-enok-concept 17/24
Exotherm ic process & Endo therm ic
process
Exothermic: energy released by system to surrounding.
Endothermic: energy absorbed by system from surrounding.
7/27/2019 Chuong3 Enok Concept
http://slidepdf.com/reader/full/chuong3-enok-concept 18/24
Spontaneous process:
All exothermic reactions are spontaneous. However, some
endothermic reactions are also spontaneous.
7/27/2019 Chuong3 Enok Concept
http://slidepdf.com/reader/full/chuong3-enok-concept 19/24
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
7/27/2019 Chuong3 Enok Concept
http://slidepdf.com/reader/full/chuong3-enok-concept 20/24
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.
7/27/2019 Chuong3 Enok Concept
http://slidepdf.com/reader/full/chuong3-enok-concept 21/24
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
7/27/2019 Chuong3 Enok Concept
http://slidepdf.com/reader/full/chuong3-enok-concept 22/24
Internal Energy (U)
7/27/2019 Chuong3 Enok Concept
http://slidepdf.com/reader/full/chuong3-enok-concept 23/24
Internal Energy (U)
Cannot measure absolute internal energy.
Can only measure the change in energy of the system
7/27/2019 Chuong3 Enok Concept
http://slidepdf.com/reader/full/chuong3-enok-concept 24/24
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.).