chemistry 451 - pennsylvania state universitycourses.chem.psu.edu/chem451/lecture1final.pdf ·...

Prof. Mueller/Sykes Chemistry 451 – Spring 2004 Lecture 1 - 1

Chemistry 451

CHEM 451 PHYSICAL CHEMISTRY ( 3 credits) Introduction to chemical principles, including properties of matter and fundamentals of chemical thermodynamics.

Prerequisites: CHEM 013, MATH 141, PHYS 202 or PHYS 212


Chemistry 451

Physical Chemistry: Quantitative and theoretical study of the properties and structure of matter and their relation to the interaction of matter and energy.

This course serves as am introduction to chemical thermodynamics, giving you an understanding of basic principles, laws, and theories of physical chemistry that are necessary for chemistry, biochemistry, pre-medical, general science, and engineering students.


Chemistry 451

By performing well in this course you should:

• gain abilities in quantitative problem solving

• develop the ability to use original thought (and logic) in the solution of problems and the derivation of equations.

What about the mathematics ?

• Equations should not obfuscate the science !

• Mathematics should paint a clear picture of the physical phenomena being studied.


Administrative Details

Meets M, W, and F from 1:25 PM until 2:15 PM

During class, you must silence or turn off all cell phones, pagers, etc. Any disruption of class will result in being asked to leave.

Office Hours: Monday, Tuesday, Thursday, Friday: 11:00 AM - 12:00 PM


Office Location

331 Whitmore Lab

Whitmore


Class Web Page

http://courses.chem.psu.edu/chem451/index.html

On-line now: syllabus, book web linkStill to come: syllabus updates (if any)

lecture notes (abridged)schedule of classes (reading)homework assignmentsexam schedules and answersadditional fun links


Grading

2 mid-term exams 20% each 40%

Lecture problems (~12) and quizzes (5 - 7)

25% prob10% quiz

35%

Final exam 25% 25%

Total 100%


Exams and Assignments (1)

Two Midterms: all at 6:30 – 7:45 PM

Wed., 18 February 2004

Mon., 5 April 2004

Final Exam: as scheduled by university



You MUST let me know by Wednesday 21 January 2004 of any conflicts with these exams. After that time, only university-sanctioned events (exams, etc.) will be considered as valid excuses.



Lecture Problems: assigned on Monday, due on Wednesday before 1:30 PM. You must work independently on these short problems.

Homework: assigned but not collected

Quizzes: 5 - 9 ten-minute quizzes will occur on Wednesdays (no advance warning)


“Physical Chemistry”

Thermodynamics - relationship between energy interconversion by materials and the molecular properties

Kinetics - rates of chemical processes

Quantum Mechanics - phenomena at the atomic and molecular scale

Statistical Mechanics - relationship between individual molecules and the bulk properties of matter.

Spectroscopy - non-destructive interaction of light (energy) and matter, used to study chemical structure.

Photochemistry - interaction of light and matter with the intent of altering molecular structure.


Course Outline

http://www.whfreeman.com/pchem7/

We will approach this first course in Physical Chemistry following along the lines of Chap. 1-10 (Part 1: Equilibrium) in Atkins and de Paula, Physical Chemistry, with one or two small excusions…


Course Outline1 - The properties of gases

24.1 - The kinetic theory of gases

2 - The First Law: the concepts

3 - The First Law: the machinery

4 - The Second Law: the concepts

5 - The Second Law: the machinery

6 - Physical transformations of pure substances

7 - Simple mixtures

8 - Phase diagrams

9 - Chemical equilibrium

10 - Equilibrium electrochemistry


The Structure of Physical Chemistry

http://www.whfreeman.com/pchem7/content/chapter0.htm

All in-class links should appear on class web page

Matter and Energy

Quantification

Partitioning

Equivalence


Matter

Composed of electrons and nuclei (neutrons and protons) which can be further divided (but not here) into subatomic particles. Matter has the following physical properties:

• Mass - largely due to nuclei

• Electronic moments - monopole (charge) is most important

• Magnetic moments - dipole is most important

• Spin - least tangible of properties (some useful classical analogies)


Quantification of Matter

Substance: a pure form of matter

Amount of substance (n): reported in terms of moles. 1 mol of a substance contains as many entities as exactly 12 g of carbon-12 (around 6.02 x 1023 entities).

Avogadro’s constant: NA = 6.0221 x 1023 mol-1

Extensive property: dependent upon the amount of matter in the substance (e.g. mass, volume)

Intensive property: independent upon the amount of matter in the substance (e.g. pressure, temperature)

Molar property: Xm, an extensive property divided by the amount of substance. Xm = X/n (now an intensive property)


Units - SI(see http://physics.nist.gov/cuu/Units/)

Systeme Internationale (mks) has seven base units:

Base quantity Name Symbol

Length meter m

Mass kilogram kg

Time second s

Electric current ampere A

Thermodynamic temperature kelvin K

Amount of substance mole mol

Luminous intensity candela cd


SI Derived UnitsDerived quantity Name Symbol

Volume cubic meter m3

Speed (velocity) meter per second m/s or m s-1

Acceleration meter per second squared m/s2 or m s-2

Wave number reciprocal meter m-1

Mass density kg per cubic meter 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 watt W: J/s: kg m2 s-3

Electric charge coulomb C: A s

Electric potential volt V: W/A: kg m2 s-3 A-1


Energy

Energy: the capacity to do work

Work: motion against an opposing force

Conservation of energy: the total energy of an isolated system is unchanged by any process.

Energy is neither created nor destroyed - it can be transferred from one location to another in the form of mechanical work or heat.


Work

Fz = −dwdz

dw = −FzdzSign convention to be explained w = − Fzdz

z1

z2∫ = −Fz z2 − z1( )

Fz

z2z1


Contributions to Energy

Kinetic Energy, Ek: Energy an object possesses as a result of its motion

Potential Energy, V: Energy an object possesses as a result of its position

Gravitational potential energy

Electrical potential energy

Ek = 12 mv 2

VG = mghq qVE =

1 2

4πε0r


Energy: Units

SI unit of energy - the joule (1 J = N m = 1 kg m2 s-2)

Molar energy - J mol-1 or (more useful) kJ mol-1

Other useful units of energy:

Electronvolt: 1 eV = 1.6602176 x 10-19 J

Calorie: 1 cal = 4.184 J (exactly)


Energy: Partitioning

Molecules have a certain number of degrees of freedom: they can rotate, vibrate, and translate - many properties depend upon these degrees of freedom.

Equipartition theorem: All degrees of freedom have the same average energy at temperature T; total energy is partitioned over all possible degrees of freedom.

Quadratic energy terms:

Average energy associated with each quadratic term is 1/2 kT where k = 1.38 x 10-23 J K-1 (the Boltzmann constant). However, this is a classical result so care must be taken in its application to atomic and molecular systems.

12 mvx

2 + 12 mvy

2 + 12 mvz

2


Energy: QuantizationAt the atomic level, not all physical properties are explained by Newtonian (classical) mechanics.

Einstein, Schrödinger, Heisenberg, Planck, and others developed and demonstrated that at atomic and molecular levels a quantum mechanics was needed where energy of particles is not a continuum, but rather is quantized.

At the molecular level rotations, vibrations, and the motions of electrons (electronic transitions) must have quantized energy levels.


How are Energy and Matter Related ?

1. Dual nature of light

Wave nature of light

interference - two light waves produced near to one another will interfere constructively and destructively

Particle nature of light

light has been shown (Einstein) to behave in particle-like packets called photons



1. Dual nature of light



2. Dual nature of matter ?

Particle nature of matter

central to our understanding of the classical world

Wave nature of matter

the De Broglie relation: λ = h/p



2. Dual nature of matter - electrons diffract !


Mathematics Preparation

• Concepts you must already know– Basic algebra, trigonometry, and geometry– Differentiation in one variable– Integration

• Concepts we will help you with– Partial differentiation – More difficult integration (line integrals,

etc.)

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