Chapter 9 Sections 1-3 Student Notes PHW

Chapter 9 Sections 1-3 Student Notes PHW - Chapter 9...

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Unformatted text preview: Chapter 9 Objectives 9.1 Describe the differences between intermolecular and intramolecular forces with an emphasis on the relative energies of each type of attraction. 9.2 Discuss the influence of these forces on physical properties such as freezing point and boiling point. 9.3 Provide real-life applications with biological systems such as DNA or proteins, and other systems as appropriate. On Exam 2, students will only be responsible for sections 9.1 − 9.3, pp. 391 − 404 in textbook 10/2/2009 Zumdahl Chapter 16 1 Intermolecular Forces: Why Condensed Phases Exist • Intramolecular Forces, Intramolecular i.e., Chemical bonds • • • Densities of H2O at 1 atm & 0 oC in g/cm3 ~ 0.0008 1.000 0.917 Strong Directional Short Range (relative) • Intermolecular Forces Intermolecular • Weaker than chemical bonds, usually much weaker • Less directional than covalent bonds, more directional than ionic bonds ionic • Longer range than covalent bonds but at shorter range than ionic bonds • Condensed Phases ● ● Solids and Liquids Intermolecular forces: Mutual attractions hold the molecules closer Intermolecular forces: together than gases 10/2/2009 Zumdahl Chapter 16 2 1 Types of Intermolecular (Non-bonding) Interactions 10/2/2009 Zumdahl Chapter 16 3 Dipole − Dipole Interactions and Hydrogen Bonding What is a hydrogen bond? A particularly strong dipole−dipole interaction where hydrogen is dipole− “bound” to a highly electronegative second row atom, i.e., N, O, or bound” F. The strength of the interaction results from the great polarity of polarity the bond and the closer than normal approach of the dipoles. 10/2/2009 Zumdahl Chapter 16 4 2 The Boiling Points of the Covalent Hydrides of Elements in Groups 4A, 5A, 6A, and 7A. 10/2/2009 Note Importance of Hydrogen Bonding Zumdahl Chapter 16 5 Ion − Dipole Interactions 10/2/2009 Zumdahl Chapter 16 6 3 Ion − Induced Dipole Interactions Ar Ar 10/2/2009 Zumdahl Chapter 16 7 London Dispersion Forces 10/2/2009 Zumdahl Chapter 16 8 4 r→ Typical 10/2/2009 hydrogen bond: BondChapter 16 ~ well depth ~ 25 kJ/mol Zumdahl strength 9 Kinetic Theory of Liquids and Solids • Intermolecular distances Intermolecular – – – – Solids about 3 X 10 -10 m = Liquids about 5 X 10 -10 m = Gases: much larger than liquids unless P > 100 atm Intramolecular bonds Intramolecular 10/2/2009 Zumdahl Chapter 16 10 5 The Liquid State Characteristics of the Liquid State Low compressibility High density, relative to gases Surface tension Exhibit capillary action • Cohesive forces • Adhesive forces – Viscosity – – – – • water is "thin", having a lower viscosity • vegetable oil is "thick" having a higher viscosity. 10/2/2009 Zumdahl Chapter 16 11 A molecule in the interior of a liquid is attracted to the molecules molecules surrounding it, whereas a molecule at the surface of liquid is attracted only by molecules below it and on each side of it. bind molecules of the same type together bind a substance to a surface 10/2/2009 Zumdahl Chapter 16 12 6 Adhesive Forces and Capillary Action X X Concave Meniscus X Convex Meniscus X Example: X X Example: X x 10/2/2009 Zumdahl Chapter 16 13 Introduction to Structures and Types of Solids – Highly regular arrangement – “Lattice”: 3D arrangement, with unit cell structures Lattice” • • • Simple cubic (Po metal) Body-centered cubic (Ur metal) BodyFace-centered cubic (Au metal) Face- – Disordered structures – Non-crystalline Non– E.g., window glass 10/2/2009 Zumdahl Chapter 16 14 7 Three cubic unit cells and the corresponding lattices 10/2/2009 Zumdahl Chapter 16 15 X-rays scattered from two different atoms may reinforce (constructive interference) or (constructive interference) cancel (destructive interference) one another destructive interference) ( d = distance between atoms λ = wavelength 10/2/2009 Zumdahl Chapter 16 16 8 Reflection of X rays Bragg Equation n λ = 2 d sin θ 10/2/2009 See textZumdahl Chapter 16 for details pp. 399−402 399− 17 Examples of Three Types of Crystalline Solids Atomic Solids 10/2/2009 Ionic Solids Zumdahl Chapter 16 Molecular Solids 18 9 In te r a c tin g m o le c u le s o r io n s P le a s e a ls o re v ie w C h a p te r 1 3 s u c h c o n c e p ts a s io n s , io n ic , c o v a le n t b o n d in g a n d d ip o le m o m e n ts C o n s id e r th e c o m p o s itio n , e lc e tr o n e g a tiv ie s a n d s tr u c tu re o f th e s p e c ie s NO A r e p o la r m o le c u le s in v o lv e d ? NO YES A re io n s in v o lv e d ? A re p o la r m o le c u le s a n d io n s p r e s e n t? NO Y E S (D ip o le - D ip o le in te r a c tio n s ) A re h y d ro g e n a to m s b o n d e d to N , O , o r F a to m s ? YES YES NO D is p e rs io n fo r c e s o n ly (in d u c e d d ip o le s ) E x a m p le s : A r ( l) , I2 (s ) D ip o le -D ip o le fo rc e s E x a m p le s : H 2S , C H 3C l H y d r o g e n B o n d in g (s p e c ia liz e d ty p e o f d ip o le -d ip o le ) E x a m p le s : liq u id a n d s o lid H 2 O , N H 3, H F Io n -D ip o le fo rc e s Io n ic B o n d in g E x a m p le s : K B r in w a te r E x a m p le s : N a C l, N H 4 N O 3 V a n d e r W a a ls fo r c e s h ig h e s t S t r e n g t h o f In te r s p e c ie s F o r c e s G e n e r a lly In c r e a s e s fr o m L e f t t o R ig h t N o te s 1 . D is p e rs iv e fo rc e s a r e fo u n d in a ll s u b s ta n c e s . T h e s tre n g th o f d is p e r s iv e fo r c e s in c r e a s e s w ith M o la r M a s s . 2 . D ip o le -D ip o le fo r c e s a d d to th e e ffe c t o f d is p e rs iv e fo rc e s a n d a r e fo u n d in p o la r m o le c u le s . 3 . H y d r o g e n b o n d s , w h ic h re q u ire H a to m s b o n d e d to F , O , o r N , a ls o a d d to th e e ffe c t o f d is p e r s io n fo r c e s . H y d r o g e n b o n d s te n d to b e th e s tr o n g e s t ty p e o f in te r m o le c u la r fo r c e s . 4 . O rd in a r y Io n ic (a n d c o v a le n t) b o n d in g fo r c e s a r e th e s tro n g e s t. 10/2/2009 Zumdahl Chapter 16 19 Chapter 9 Liquids and Solids 9.1 Intermolecular Forces 9.2 The Liquid State 9.3 An Introduction to Structures and Types of Solids 9.4 Structure and Bonding in Metals 9.5 Carbon and Silicon: Network Atomic Solids 9.6 Molecular Solids 9.7 Ionic Solids 9.8 Structures of Actual Ionic Solids 9.9 Lattice Defects 9.10 Vapor Pressure and Changes of State 9.11 Phase Diagrams 10/2/2009 Zumdahl Chapter 16 20 10 ...
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This note was uploaded on 10/06/2009 for the course CHEM 1101 taught by Professor Bottomley during the Fall '08 term at Georgia Tech.

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