Introduction to Physical Chemistry Chemistry 59-240 - Fall 2006 v.6 Lecturer: Dr. Rob Schurko Office: 393A Essex Hall Email: [email protected]Website: www.uwindsor.ca/schurko Teaching Assts. Lo, Hamaed, Harati & Rossini Office Hours: Anytime, but please email to schedule a time slot Lectures: MWF 12:30-1:20 51 Chrys. Hall S. Tutorials: See schedule on web, 4 sessions Labs: See schedule on web, 5 labs Assignments: No formal assignments this year ***Update: Sept. 8, 2006, new slides 6, 23, minor modifications to first seven slides
Transcript
Introduction to Physical ChemistryChemistry 59-240 - Fall 2006 v.6
Lecturer: Dr. Rob SchurkoOffice: 393A Essex HallEmail: [email protected]: www.uwindsor.ca/schurkoTeaching Assts. Lo, Hamaed, Harati & Rossini
Office Hours: Anytime, but please email to schedule atime slot
Lectures: MWF 12:30-1:20 51 Chrys. Hall S.Tutorials: See schedule on web, 4 sessionsLabs: See schedule on web, 5 labsAssignments: No formal assignments this year
***Update: Sept. 8, 2006, new slides 6, 23, minor modifications to firstseven slides
Course MaterialsChemistry 59-240
Textbooks:1. Atkins, P.W. and De Paula, J. Physical Chemistry, 8th edition,
W.H. Freeman, New York, 20062. Charles Trapp, Marshall Cady, Carmen Guinta, Peter Atkins.
Students Solution Manual for Physical Chemistry, 8th edition,W.H. Freeman, New York, 2006
3. James R. Barrante, Applied Mathematics for PhysicalChemistry, Prentice Hall, Upper Saddle, NJ, 2004, 3rd Edition.(Recommended for brushing up on math skills)
**6th & 7th editions of Atkins will also be supported!
Miscellaneous:
1. Scientific Calculator2. Web access: http://www.uwindsor.ca/schurko3. Web access: http://www.whfreeman.com/pchem8
93-100 A+ 87-92.9 A 80-86.9 A-76-79.9 B+ 73-75.9 B 70-72.9 B-66-69.9 C+ 63-65.9 C 60-62.9 C-56-59.9 D+ 53-55.9 D 50-52.9 D-36-49.9 F 0-35.9 F-
Intro WeekChemistry 59-240
Intro Week:
# Takes place in 173-6 Essex Hall at 2:30 M/T/W/R- both 2:30 and 6:00 slots should attend- if you are in a late slot and cannot make it, please emailyour TA asap (you will have to attend another section)
# Meet your TAs# Get assigned lab partners and schedules# Review safety regulations# Become familiar with the lab
# Lab manuals: available online - be sure to bring a copy ofthe manual along with you!!
Course MotivationChemistry 59-240
Physical Chemistry: Quantitative and theoretical study of theproperties and structure of matter, and their relation to theinteraction of matter with energy.
# This course serves as an introduction to chemicalthermodynamics, giving you an understanding of basicprinciples, laws and theories of physical chemistry the arenecessary for chemistry, biochemistry, pre-medical, generalscience and engineering students.
# You will develop the ability to solve quantitative problems, andlearn to use original thought and logic in the solution of problemsand derivation of equations.
# You will learn to apply mathematics in chemistry in such a waythat the equations paint a clear picture of the physicalphenomena being studied
Course OutlineChemistry 59-240
We will cover most of Chapters 1-6 of “Physical Chemistry” byP.W. Atkins (8th edition)
0. Introduction to Physical Chemistry1. The Properties of Gases.2. The First Law of Thermodynamics3. The Second Law of Thermodynamics: Concepts4. Physical Transformations of Pure Substances5. Simple Mixtures6. Phase Diagrams
Course OutlineChemistry 59-240
If you are using the 6th or 7th edition, we will cover most ofChapters 1-8 of “Physical Chemistry” by P.W. Atkins:
0. Introduction to Physical Chemistry1. The Properties of Gases.2. The First Law of Thermodynamics: Concepts3. The First Law of Thermodynamics: Machinery4. The Second Law of Thermodynamics: Concepts5. The Second Law of Thermodynamics: Machinery6. Physical Transformations of Pure Substances7. Simple Mixtures8. Phase Diagrams
Studying Physical Chemistry
Hints on how to study in physical chemistry courses# Summarize each set of notes on one page in an organized form
that helps to isolate all key points: “nerd notes”# Download all available handouts, including equation sheets# Start working on problems with the equation sheets a.s.a.p.
and do not fall behind# Physical Chemistry is not a “memory-based”, learn-by-rote
discipline, but is centred upon problem-based learning. However, you must practice solving problems, derivingequations, etc. to become proficient.
# Review assigned and in-class problems# Try the A list problems with your solutions manual# Attempt the corresponding B list problems# Attend tutorials# View animations and use other web resources# Book consultation times after you have attempted a majority of
the problems
What is Physical Chemistry?Physical chemistry includes numerous disciplines:
Thermodynamics - relationship between energy interconversionby materials, and the molecular properties
Kinetics - rates of chemical processes
Quantum Mechanics - phenomena at the molecular level
Statistical Mechanics - relationships between individualmolecules and bulk properties of matter
Spectroscopy - non-destructive interaction of light (energy) andmatter, in order to study chemical structure
Photochemistry - interaction of light and matter with the intent ofcoherently altering molecular structure
Physical Chemistry @ UWindsorWhat courses are available in Physical Chemistry?
9 59-240: Thermodynamics: Physical & Chemical Properties of Materials
Major Considerations in Phys. Chem.# Matter# Quantifying Matter
• SI vs. cgs units• SI derived units
# Energy• Types of energy• Equipartition of energy
# Quantization of Energy• Energy states and populations• Boltzmann distributions
# Light• Dual nature: wave vs. particle• Wave behaviour• Energy of radiation• Relationships between matter and light
MatterMatter: composed of electrons and nuclei (neutrons andprotons) - which can be further divided into subatomic particles
Physical Properties:
masslargely due to the nuclei; thermal properties
electric chargeatoms and molecules are bound together by electrostaticinteractions
magnetismnucleus interacts with magnetic fields;little consequence for atomic or molecular structure
spinleast “tangible” property; closest classical analogy: electronsand nuclei are spinning like little planets
Quantifying MatterSubstance: A pure form of matter
Amount of substance: Reported in terms of moles1 mol of a substance contains as many entities as exactly 12 g ofcarbon-12 (ca. 6.02 x 1023 objects)
Avogadro’s Number: NA = 6.02 x 1023 mol-1
Extensive Property: Dependent upon the amount of matter inthe substance (e.g., mass & volume)
Intensive Property: Independent of the amount of matter in asubstance (e.g., mass density, pressureand temperature)
Molar Property: Xm, an extensive property divided by theamount of substance, n: Xm = X/n
Molar Concentration:“Molarity” moles of solute dissolved inlitres of solvent: 1.0 M = 1.0 mol L-1
SI vs. Gaussian UnitsUnits: Standards for comparisonSI: Systeme Internationale (mks - the World)Gaussian: centimetres, grams and seconds (cgs, U.S.A.)
SI system: All quantities can be expressed in terms ofseven base units:
Base quantity Name Symbol length meter m mass kilogram kg time second selectric current ampere A thermodynamic temperature kelvin K amount of substance mole mol luminous intensity candela cd
for more info: http://physics.nist.gov/cuu/Units/
SI vs. Gaussian Units, 2
SI or mks unitsName Symbol meter m kilogram kg second sampere A kelvin K mole mol candela cd
Gaussian or cgs unitsName Symbol Conversioncentimeter cm 0.01 mgram g 0.001 kgsecond sbiot Bi 10 Akelvin K mole mol stilb sb 104 cd m-2
Older literature sources and many Americans still use the cgssystem of units, so it is useful to understand the relationshipbetween the SI and cgs systems.
SI Derived UnitsMany important units, some with special names and symbols,can be derived from the SI base units:
Derived quantity Name Symbol volume cubic meter m3 or L or dm3
speed, velocity meter per second m/s acceleration m. per s. squared m/s2 or m s-2
wave number reciprocal meter m-1 mass density kg per cubic m kg/m3 or kg m-3
frequency hertz Hz : s-1 force newton N : kg·m·s- 2 pressure, stress pascal Pa : N/m2 : kg·m-1·s-2
energy, work, heat joule J : N·m : kg·m2·s-2 power, radiant flux watt W : J/s : kg·m2·s-3 electric charge coulomb C : A·s electric potential, emf volt V : W/A : kg·m2·s-3·A-1
magnetic field tesla T: A/m
SI vs. Gaussian Derived UnitsMany important units, some with special names and symbols,can be derived from the SI base units:
Derived quantity Symbol Conversionerg (energy) erg 1 erg = 10-7 Jdyne (force) dyn 1 dyn = 10-5 Ngauss (magnetic field) G, Gs 1 G = 10-4 T
Other unitscalorie (energy, thermo) cal 1 cal = 4.184 Jcalorie (food energy) Cal 1 Cal = 1 kcal = 4184 Jelectron volt (energy)* eV 1 eV = 1.602 177 33 x 10-19 Jmicron (distance) µ 1 µ = 10-6 m = 1 µmAngstrom (distance) Å 1 Å = 10-10 m
* Energy acquired by an electron passing through a potential of 1 V in avacuum (commonly used unit for physicists)
dwdx
' Fx dw ' Fxdx
w ' j F(x)dx ' mx2
x1
F(x)dx ' F(x2 & x1)
for constant F
EnergyEnergy: The capacity to do work (or to heat)Work: Force causes mechanical displacement on a body
x1 x2
F
For an infinitesimal amount of work, dw, doneby a force F in the x-direction:
The amount of work for finite displacement, w, is givenby the sum of infinitesimal displacements, which isequivalent to the integral above.
Energy is conserved - it is neither created or destroyed: itcan be transferred from one location to another in the form ofmechanical work (orderly) or heat (thermal motion, random)
VE 'q1q24πε0 r
Contributions to EnergyKinetic Energy, EK: Energy an object possesses as a result ofits motion. EK = ½mv2
Potential Energy, V: Energy an object possesses as a result ofits position. Zero of potential energy is relative:
1. Gravitational Potential Energy:zero when object at surface (V = 0 when h = 0)VG = mgh, m = mass, g = 9.81 m s-2, h = height
2. Electrical Potential Energy:zero when 2 charged particles infinitely separated
qi = charge on particle i, r = distanceε0 = 8.85 x 10-12 C2 J-1 m-1
(vacuum permittivity)
Equipartition of EnergyMolecules have a certain number of degrees of freedom: theycan vibrate, rotate and translate - many properties depend onthese degrees of freedom:
Equipartition theorem: All degrees of freedom have the sameaverage energy at temperature T: total energy is partitioned overall possible degrees of freedom
Quadratic energy terms: ½mvx2 + ½mvy
2 + ½mvz2
Average energy associated with each quadratic term is ½kT,where k = 1.38 x 10-23 J K-1 (Boltzmann constant), where k isrelated to the gas constant, R = 8.314 J K-1 mol-1 by R = NAkHowever: this theorem is derived by classical physics, and canonly be applied to translational motion.
Energy QuantizationAt the start of this century, there were certainphysical anomalies which could not be explainedusing Newtonian (Classical) Mechanics - atthe atomic level matter behaves differently
A new set of mechanics, developed by Einstein,Schroedinger and others, demonstrated bothexperimentally and theoretically that at theatomic and molecular levels, the energy ofparticles is not a continuum, but rather, isquantized: Quantum Mechanics
Translational motion of molecules inmacroscopic containers can be treated in manycases by classical mechanics, but rotation,vibration and motion of electrons (electronictransitions) have quantized energy levels
NiNj
' e&(Ei & Ej) /kT
Populations of StatesAt temperatures > 0, molecules are distributed over availableenergy levels according to the Boltzmann Distribution, whichgives the ratio of particles in each energy state:
At the lowest temperature T = 0, only the lowest energy state isoccupied. At inifinte temperature, all states are equally occupied.
In real life, the population of states is described by an exponentialfunction, with the highest energy states being the least populated.
Degenerate states: States which have the same energyThese will be equally populated!
Boltzmann Distributions
Populations for (a) low& (b) high temperaturesBoltzmann predicts anexponential decrease inpopulation withincreasing temperature
At room T, only theground electronic stateis populated. However,many rotational statesare populated, since theenergy levels are soclosely spaced.
More states aresignificantly populated ifenergy level spacingsare near kT!
Spontaneity, Equilibria, Kinetics, etc.Physical chemistry is about more than just energy:
- It’s about the conversion of energy via work and heat from onesource to another
- It’s about why things happen and why things do not
- It is about the delicate balance between thermodynamically andkinetically allowed and forbidden processes
Example:# two allotropes of carbon are diamond and graphite# graphite is the more thermally stable substance# yet, we do not observe diamonds changing into graphite# diamonds are said to be “kinetically stabilized”
- It’s about understanding our entire universe
What about 59-240?Thermodynamics:
Physical behaviour of solid, liquid, gas and mixed phases
Energy interconversion via physical (e.g., compression,expansion, mixing, heating, cooling, etc.) and chemical(chemical reactions, combustion, ionization, etc.) processes
1st law: “book-keeping”, making sure energy is conserved, andknowing where energy goes or comes from
2nd law: “spontaneity”, knowing why processes actually occur,why beautiful, orderly entities are created from seeminginglyshear randomness
Practical applications: industrial processes, everydayphenomena, safe chemistry, understanding new materials
