1. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 1 Figure 10.1 Schematic Representations of the Three States of Matter

2. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 2 Intermolecular Forces Forces between (rather than within) molecules.  dipole-dipole attraction: molecules with dipoles orient themselves so that “+” and “  ” ends of the dipoles are close to each other. Ô hydrogen bonds: dipole-dipole attraction in which hydrogen is bound to a highly electronegative atom. (F, O, N)

3. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 3 Figure 10.2 Dipole- Dipole Attractions

4. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 4 Figure 10.3 A Water Molecule

5. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 5 London Dispersion Forces 4 relatively weak forces that exist among noble gas atoms and nonpolar molecules. (Ar, C 8 H 18 ) 4 caused by instantaneous dipole, in which electron distribution becomes asymmetrical. 4 the ease with which electron “cloud” of an atom can be distorted is called polarizability.

6. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 6 Figure 10.5 London Dispersion Forces

7. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 7 Some Properties of a Liquid Surface Tension: The resistance to an increase in its surface area (polar molecules). Capillary Action: Spontaneous rising of a liquid in a narrow tube. Viscosity: Resistance to flow (molecules with large intermolecular forces).

8. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 8 Types of Solids Crystalline Solids: highly regular arrangement of their components [table salt (NaCl), pyrite (FeS 2 )]. Amorphous solids: considerable disorder in their structures (glass).

9. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 9 Representation of Components in a Crystalline Solid Lattice: A 3-dimensional system of points designating the centers of components (atoms, ions, or molecules) that make up the substance.

10. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 10 Figure 10.9 Three Cubic Unit Cells and the Correspond ing Lattices

11. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 11 Representation of Components in a Crystalline Solid Unit Cell: The smallest repeating unit of the lattice. 4 simple cubic 4 body-centered cubic 4 face-centered cubic

12. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 12 Bragg Equation Used for analysis of crystal structures and in conjunction with X-ray diffraction- n = 2d sin  d = distance between atoms n = an integer = wavelength of the x-rays

13. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 13 Types of Crystalline Solids Ionic Solid: contains ions at the points of the lattice that describe the structure of the solid (NaCl). Molecular Solid: discrete covalently bonded molecules at each of its lattice points (sucrose, ice).

14. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 14 Figure 10.12 Examples of Three Types of Crystalline Solids

15. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 15 Packing in Metals Model: Packing uniform, hard spheres to best use available space. This is called closest packing. Each atom has 12 nearest neighbors. 4 hexagonal closest packed (“aba”) 4 cubic closest packed (“abc”)

16. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 16 Figure 10.13 The Closest Packing Arrangem ent of Uniform Spheres

17. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 17 Bonding Models for Metals Electron Sea Model: A regular array of metals in a “sea” of electrons. Band (Molecular Orbital) Model: Electrons assumed to travel around metal crystal in MOs formed from valence atomic orbitals of metal atoms.

18. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 18 Metal Alloys 1. Substitutional Alloy: some metal atoms replaced by others of similar size. brass = Cu/Zn Sterling Silver/Pewter/Solder Are all sub alloys Substances that have a mixture of elements and metallic properties.

19. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 19 Metal Alloys (continued) 2.Interstitial Alloy: Interstices (holes) in closest packed metal structure are occupied by small atoms. steel = iron + carbon 3.Both types: Alloy steels contain a mix of substitutional (carbon) and interstitial (Cr, Mo) alloys.

20. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 20 Figure 10.21 Two Types of Alloys

21. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 21 Network Solids Composed of strong directional covalent bonds that are best viewed as a “giant molecule”. 4 brittle 4 do not conduct heat or electricity 4 carbon, silicon-based graphite, diamond, ceramics, glass

22. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 22

23. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 23 Silica versus Carbon Silicon and Carbon are are right next to each in Group 4A Carbon-based life forms-Biology-Carbon Hydrogen Chains Silicon rich rock and soil-Geology-Silicon Oxygen chains

24. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 24 Silica SiO 4 -4 (silicate) or SiO 2 (silica) But why isn’t SiO 2 like CO 2 Silicates are interconnected silicate ions- tetrahedral shape –usually a metal cation mixed with the polyatomic anion to form neutral compounds- other than that- they simply combine with themselves in SiO 4 instead of SiO 2

25. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 25

26. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 26 Structure of Quartz

27. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 27 Glass When you melt silicates-an amorphous solid results-like obsidian-or glass. However if you add Na 2 CO 3 to the silicate mix and melt-common glass forms- Or you can add B 2 O 3 to the mix and get borosilicate glass that expands and contracts very little under varying temps which is good for labware

28. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 28 Ceramics Ceramics- even though made of clay which is primarily silicates- it is also made up of a mineral called Kaolinite which has aluminum, carbon and sodium and potassium desposits as well as bits and pieces of carbon in it. So once you melt and fire the clay-it cannot be remelted and reshaped-however-silicates can.

29. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 29 Firing Clay-to make Ceramics A glass is homogeneous Clay is heterogeneous-when water is present-its platelets of silica and other mixtures slide over each other but when fired and water removed- the “other bits’ get LOCKED into the silica glass matrix.

30. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 30 Semiconductors 4 Conductivity is enhanced by doping with group 3a or group 5a elements. A substance in which some electrons can cross the band gap.

31. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 31 N-TYPE Dope a Si crystal with Arsenic which has 1 more valence e- to jump across the small gaps thus creating electricity or neg charge.

32. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 32 Figure 10.29 Silicon Crystal Doped with (a) Arsenic and (b) Boron

33. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 33 P-Type Dope the Si Crystal with Boron which has 1 less valence e- than Si and creates holes for e-s to jump into and out of –kind of like Chinese Checkers-thus creating positive structure –P-

34. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 34 P-N-Junction Produces direct current from alternating current-look at the image to see how could this be. These small micro rectifiers have revolutionized electronics

35. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 35 Figure 10.31 The p- n Junctio n

36. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 36 Molecular Solids Like H 2 0, CO 2, S STRONG intramolecular force WEAK INTERmolecular force Some molecules have no dipole dipole moment-Only Inter forces are London Dispreson Forces some due-dependant upon polarity

37. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 37 Ionic Solids P. 480-we’re saving this one until last

38. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 38 Vaporization Molecules escaping from the surface of a liquid require energy to break the strong intermolec forces. These energy feeds into an endothermic system- which when the molecule vapoirzes-causes cooling to occur Most of the sun’s energy is used to vaporize water which in turn cools the Earth-not heat it. Delta Hvap of water=40.7kJ/mol

39. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 39 Vapor Pressure... is the pressure of the vapor present at equilibrium.... is determined principally by the size of the intermolecular forces in the liquid.... increases significantly with temperature. Volatile liquids have high vapor pressures.

40. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 40 Figure 10.36 Behavio r of a Liquid in a Closed Contain er

41. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 41 Condensation So at equilibrium- condensation and evaporation happen at an equal rate Liquids with high vapor pressures-volatile Low vapor pressures=high intermolec forces Vapor pressure increases with temp- DUH

42. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 42

43. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 43

44. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 44 Sublimation Solids have vapor pressures as well Some solids sublime –Which means-they go from solid to gas –Like CO 2 and I 2

45. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 45 Change of state With addition of heat-normal Solid-liquid-gas Represented by a heating curve –Plot of temp versus time

46. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 46 Figur e 10.42 Heatin g Curve for Water

47. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 47 Melting Point Molecules break loose from lattice points and solid changes to liquid. (Temperature is constant as melting occurs.) heat of fusion or enthalpy of fusion vapor pressure of solid = vapor pressure of liquid

48. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 48

49. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 49 Figure 10.47 The Phase Diagram for Water

50. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 50

51. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 51 What state What would happen if at a certain temp-the vapor pressure of a solid was less than that of the liquid- what would be the state? What would happen if the reverse was true? What would be the state? What if they were equal-what state? So which is melting-which is freezing ?

52. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 52 Normal Melting point When both solid and liq vapor pressures summed equal to 1atm

53. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 53 Boiling Point Constant temperature when added energy is used to vaporize the liquid. vapor pressure of liquid = pressure of surrounding atmosphere If vap pressure is less- than NO BUBBLES can escape

54. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 54 Supercooled Cooled below 0 and at 1atm and still remain a liquid

55. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 55 Superheated Allowed to boil at temps above the bp

56. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 56 Phase Diagram Represents phases as a function of temperature and pressure. critical temperature: temperature above which the vapor can not be liquefied. critical pressure: pressure required to liquefy AT the critical temperature. critical point: critical temperature and pressure (for water, T c = 374°C and 218 atm).

57. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 57 Okay At 1atm from -20 to 0C-what state At 2.0 torr from -20 to- 10 what state At 4.58 torr from -20 to 0.01 what state At 225atm from 300C What is critical point of water and what does it rep?

58. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 58