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CHEM 121:General Chemistry II
Dr. Wanda Oehrli (Early)
Welcome back!
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“All the world is a laboratory to the inquiring mind”
• Martin H. Fischer• (1879 - 1962)• German-American physician and writer
• An education in chemistry and science can be applied to a broad variety of problems.
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Today’s Agenda• Roll sheet, please sign and note your TEAM #• Introductions• Start Chapter 11• Syllabus
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Grew up in DeKalb
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Kalamazoo College & MSU
B.A. Chemistry, 1992 Ph.D. Chemistry, 1997
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Ph.D. Research
• Optical Sensors• Funded by the Air Force• Benzene, Toluene, Zylene
(BTEX) are used to clean jet engines
• BTEX leach into ground water
• Bioremediation
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NRC Postdoctoral Research FellowCenter for Advanced Research in Biotechnology and
National Cancer Institute
1997-2004Protein FoldingGroEL GroESHow do heat shock proteins work?
Biopharmaceutical Development of drugs for cancer based on antibodies and other biomolecules
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Teaching 2005-2008 & Ball Horticultural
KishwaukeeBeloitRock ValleyElmhurstHarper
Flower seed germination
Got Married
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2009- Present
MBA – DePaulConsulting Work
Nanotechnology company in S. DakotaGreen Certification Company in CA
Investment Advisor FirmInternet Marketing
Back to teaching
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I want to get to know you!
• Please fill out the info sheet as thoroughly as possible
• This information will help me get to know you and shape the course for your needs
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Gen. Chem. Lab
• Lab begins next week! January 16!– Lab Safety and Math Review
• No class of January 20 (MLK Week) & no lab that week
• Lab resumes week following week
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Office Hours
My office is Parmer 319• M,W, F 10:30 -11:30 (meet in 310 if 319 is
occupied)• Or by appointment (e-mail me)
• Office hours will be posted on the myDU page each week
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Reading for Friday January 10:Sections 11.1-11.2
There will be a Reading Quiz at the beginning of class on Friday!
Pre-Class Reading Assignment
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Chapter 11Intermolecular Forces
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15
A Molecular Comparison of Liquids and Solids
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A Molecular Comparison of Liquids and Solids• Converting a gas into a liquid or solid requires
the molecules to get closer to each other:– cool or compress.
• Converting a solid into a liquid or gas requires the molecules to move further apart: – heat or reduce pressure.
• The forces holding solids and liquids together are called intermolecular forces.
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Intermolecular Forces
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Intermolecular Forces• The covalent bond holding a molecule together is an
intramolecular forces.• The attraction between molecules is an intermolecular force.• Intermolecular forces are much weaker than intramolecular
forces • (e.g. 16 kJ/mol vs. 431 kJ/mol for HCl).• Ex. Less energy is required to vaporize liquid HCl than
to form an HCl bond
• When a substance melts or boils the intermolecular forces are broken (not the covalent bonds). When a substance condenses intermolecular forces are formed.
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Intermolecular Forces
There are four types of intermolecular forces (IMF) for covalent molecules:
• London Dispersion Forces (LD)• Dipole-Dipole (D/D)• Hydrogen bonding (H-bond)• Ion-Dipole (I/D, only in water solutions)
We see evidence of these intermolecular forces as they affect the boiling point and melting point of compounds.– As IMF increase … bp and mp increase
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• London Dispersion Forces (LD)• Dipole-Dipole (D/D)• Ion-Dipole (I/D, only in water solutions)• Hydrogen bonding (H-bonding)
• First two are called van der Waals
Strength of IM Forces
2-10 kJ/mol
15 kJ/mol
5-25 kJ/mol
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Polarity of MoleculesDipole Moments of Polyatomic Molecules
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Induced Dipoles or Instantaneous Dipoles
Neutral molecules and atoms can induce a charge in each other
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London Dispersion Forces
The fluctuating charge distribution in an atom can give rise to an instantaneous dipole moment.
When two atoms are close, their fluctuating dipole moments are correlated, leading to attraction.
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London Dispersion Forces
• These forces are present in all molecules, whether they are polar or nonpolar.
• The tendency of an electron cloud to distort in this way is called polarizability.
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Factors Affecting London Forces
• The strength of dispersion forces tends to increase with increased molecular weight.
• Larger atoms have larger electron clouds that are easier to polarize.
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Syllabus
• Go over syllabus with your “Team”– Introduce yourselves– Take a few minutes to read the syllabus– Then, with your team, come up with at
least 3 questions you have about the class that are NOT answered on the syllabus
– Write the questions down on a 4 x 6 card (one card per team)
– I will collect the cards when you are done and put together a handout answering the questions.