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STATES OF MATTER

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  1. STATES OF MATTER

  2. Intermolecular Forces of Attraction

  3. Kinetic Molecular Theory • All matter is composed of atoms that are in constant motion

  4. Kinetic Theory Facts • All phases of matter express the degree that they reflect the kinetic theory through their kinetic energy • kinetic energy is measured by temperature • phase changes involve changes in temperature due to the existence threshold temperature of each phase (i.e. ice naturally is found at cold not hot temperatures)

  5. While gases have a great deal of random motion, solids and liquids exist at lower temperatures, thus allowing other forces of attraction to act upon them • these forces are the van der Waals forces

  6. Definitions • Bonds are intramolecular forces of attraction • Forces of attraction between molecules are called intermolecular forces of attraction • intermolecular forces of attraction are commonly called van der Waals forces

  7. The Condensed Phases • Solids and Liquids • Physical properties of the condensed phases reflect the degree of intermolecular forces (i.e. boiling point)

  8. Dipole-dipole forces • Exist between neutral polar molecules • work best the closer the molecules are to each other • the greater the polarity of the molecules, the greater the force of attraction

  9. H bonding • Special case of dipole-dipole interaction specifically between H of one polar molecule with N, O or F and an unshared electron pair of another nearby small electronegative ion (usually N, O, or F on another molecule) • VERY STRONG

  10. London dispersion forces • Induced dipoles • not really dipoles on the AVERAGE, but instantaneously dipole conditions can exist thus allowing for pseudopolar regions to occur

  11. No matter how strong the van der Waal force of attraction is, it is still not stronger than attractions involving ions

  12. Ion-dipole forces • Attraction between ions and the partial charge on the end of a polar molecule • ex. NaCl in water solution

  13. INTRAMOLECULAR: INTERMOLECULAR: FORCES WITHIN A MOLECULE FORCES FORCES BETWEEN MOLECULES STRONG INTRAMOLECULMR FORCES O = O VERY WEMK INTERMOLECULAR FORCES MUCH WEAKER THAN EITHER IONIC OR COVALENT BONDS ELECTROSTATIC DICTATE WHETHER MOLEULAR SUBTANCE IS GAS, LIQUID OR SOLID AT ROOM CONDITIONS GAS: NEGLIGIBLE LIQUID: WEAK TO MODERATE SOLID: MODERATE TO STRONG

  14. HELP DEFINE STANDARD STATE OF A SUBSTANCE INTERMOLECULAR FORCES: HELP DEFINE COMMON PHYSICAL PROPERTIESOF A SUBSTANCE ARE MUCH WEAKER THAN BONDS (INTRA MOLECULAR FORCES) BOILING/MELTING POINTS SURFACE TENSION CAPILLARY ACTION VISCOSITY IONIC BONDS: ~300 - 1000’S kJ/MOL COVALENT BONDS: ~150 - ~800 kJ/MOL INTERMOLCULAR FORCES: ~1 - 40 kJ/MOL STRENGTH DIMINISHES WITH INCREASING DISTANCE

  15. d+ d- d+ d- d- d+ d- d+ d- d+ IONIC COMPOUNDS: MOLECULAR COMPOUNDS: MOLECULAR DIPOLE “INDUCED” TEMPORARY DIPOLE DISPERSION FORCES PRESENT IN ALL MOLECULAR SUBSTANCES! INCREASES WITH MOLECULAR MASS F2 Cl2 I2 -188 oC 58.8 184

  16. Cl Cl C Cl O H H O C O Cl F d+ d+ DIPOLE-DIPOLE FORCES PERMANENT DIPOLE NATURAL ASSYMETRIC CHAGE DISTRIBUTION POLAR MOLECULE OCCURS IF CENTERS OF CHARGES DO NOT COINCIDE 2d- THE MORE POLAR THE MOLECULE, THE STRONGER THEINTERMOLECULAR FORCE CH3 - CH2 - CH3 CH3CN 44 = MASS = 41 0.1 = DIPOLE MOMENT = 3.9 231 = BOILING POINT (K) = 355

  17. SPECIAL CASE OF DIPOLE FORCES HYDROGEN BOND H ATOM ATTACHED TO F, O, N LARGE ELECTRONEGATIVITY DIFFERENCE SMALL SIZE ALLOWS H TO GET CLOSE H2O H2S H2Se H2Te 18 34 81 130 ~ - 73 oC - 60.7 -41.5 -2 100 THIS PROPERTY AFFECTS LIFE AND MANY OTHER PROPERTIES

  18. DIFFUSION: MOLECULES MOVING THRU MOLECULES VISCOSITY: RESISTANCE TO FLOW SURFACE TENSION:

  19. GAS (VAPOR) LIQUID SYSTEM ENERGY SYSTEM ENERGY SOLID CONDENSATION VAPORIZATION SUBLIMATION DEPOSITION MELTING (FUSION) FREEZING

  20. MELTING POINT DHf = HEAT REQUIRED TO MELT SUBSTANCEAT ITS MELTING POINT HEAT REQUIRED TO BREAK DOWN INTERMOLECULAR FORCES > 0 J/g OR J/mol VAPOR LIQUID + VAPOR LIQUID ENTHALPY TEMPERATURE LIQUID + SOLID SOLID FREEZING POINT TIME

  21. bar Patm /A = PRESSURE F Dh 14.7 lb/in2 = 1 ATM = 760 mm Hg torr GAS P = Patm - Dh

  22. 1 atm 760 mm Hg 535 mm Hg x 760 mm Hg 1 atm 0.645 atm x 1 atm 760 torr 480 torr x WHAT IS THE PRESSURE OF A GAS (ATM) IF IT SUPPORTS A COLUMN OF MERCURY TO A HEIGHT OF 535 mm? = 0.704 atm IF THE ATMOSPHERIC PRESSURE DROPS TO 0.645 atm, HOW HIGH IS THE COLUMN OF MERCURY SUPPORTED? = 490 OR 4.9 x 102 mm Hg IF THE BAROMETRIC PRESSURE IS 755 mm Hg AND A GAS CREATES A Dh OF 275 mm IN A MANOMETER, WHAT IS THE PRESSURE OF THE GAS? P = Patm - Dh = 755 - 275 = 480 mm Hg = 480 torr = 0.632 atm

  23. P x V = k (n, T) OR P a 1/V BOYLE’S LAW VOLUME PRESSURE

  24. VOLUME CONSTANT PRESSURE!!! CHARLES’ LAW V = k(n, P) x T OR V a T TEMPERATURE

  25. n = 4 n = 2 VOLUME TEMPERATURE 0 oC ABSOLUTE OR KELVIN SCALE K = oC + 273 -273.15 oC n = 1.0 n = 0.5 USE IN ALL CALCULATIONS!!!

  26. AVOGADRO: EQUAL VOLUMES OF GASES AT SAME T & P CONTAIN EQUAL NUMBER OF MOLECULES! V = k(n, T) x n P x V = k (n, T) V = k(n, P) x T IDEAL GAS LAW PV = nRT PV = nkT R = 0.0821 L.atm.mol-1.K-1

  27. 1.5 atm x 1473 K 298 K 1 mol x 0.0821 L.atm.mol-1.K-1 x 273 K 1.0 atm nRT P THE PRESSURE IN AN AEROSOL CAN AT 25 oC IS 1.5 atm. A FIRE CAN REACH 1200 oC. WHAT IS THE PRESSURE OF THE CAN AT THAT TEMPERATURE? P V = n R T INIT FINAL 1.5 Vi n 0.0821 25 + 273 X Vi n 0.0821 1200 + 273 Pf / Tf = R= Pi / Ti Pi / Ti STP Pf = 7.4 atm WHAT IS THE V OF 1.0 MOL GAS AT 1.0 atm AND 0 oC? = 22.4 L V =

  28. IDEAL VS. REAL GAS MOLECULES FAR APART FAR APART NO COLLISIONS SOME COLLISIONS LOW INTERACTIONS NO INTERACTIONS OCCUPY NO SPACE & HAVE NO VOLUME MATTER; MUST OCCUPY SPACE & HAVE VOLUME PV/RT = 1 PV/RT > 1 SINCE GASES ARE REAL: • CAN NEVER ACHIEVE ABSOLUTE 0 • APPROACH IDEAL GAS AT HIGH VOLUMES LOW P, HIGH T

  29. KINETIC MOLECULAR THEORY 1. THE VOLUME OF GAS MOLECULES IS NEGLIBLE COMPARED TO THE VOLUME OF THE CONTAINER 2. PARTICLES UNDERGO CONSTANT RANDOM MOTION AND DO NOT INTERACT WITH ONE ANOTHER 3. AVERAGE KINETIC ENERGY OF THE PARTICLES IS PROPORTIONAL TO ABSOLUTE TEMPERATURE TEMPERATURE IS THE MEASURE OF THE AVG. KINETIC ENERGY OF THE PARTICLES IN THE SYSTEM E ~ RT R = 8.314 J.mol-1.K-1

  30. LIQUID VAPOR EQUILIBRIA DYNAMIC EQUILIBRIUM! EVAPORATION VAPOR PRESSURE ALL NON-GASEOUS MATERIALS EXERT A VAPOR PRESSURE. FOR SOLIDS: VERY LOW ASSUMED TO BE 0

  31. 760 VAPOR PRESSURE (mm Hg) VOLATILE NON-VOLATILE DHVAP AMOUNT OF HEAT REQUIRED TO VAPORIZE SOME AMOUNT OF LIQUID T, oC NORMAL BOILING POINT VS BOILING POINT

  32. 1.0 P, a t m T, oC BOILING POINT LIQUID MELTING POINT SOLID VAPOR (GAS) TRIPLE POINT

  33. INTERMOLECULAR > < CAPILLARY ACTION ADHESIVE VS COHESIVE FORCES ADHESIVE COHESIVE

  34. IONIC DISPERSION, DIPOLE & H-BONDING DISPERSION + DIPOLE OR ANY OF THE PHYSICAL PROPERTIES DISPERSION ONLY X BOILING POINT DISPERSION: INCREASING MASS DIPOLE-DIPOLE: INCREASING POLARITY HYDROGEN BOND: INCREASING “NUMBER” X X X INTERMOLECULAR FORCES

  35. WHAT FORCES ARE PRESENT IN: A) NaBr B) NF3 C) CH2OHCH2CH2OH D) Ar IONIC DISPERSION + DIPOLE-DIPOLE DISPERSION + DIPOLE + H-BOND DISPERSION WHICH OF THE FOLLOWING HAVE THE HIGHER BP? A) C6H14 C10H22 C2H6 B) C6H14 C6H13OH C6H12(OH)2 C) CCl4 CCl3F CF4 D) HCl HF F2

  36. UNIT CELLS THE REPEATING PATTERN IN A THREE DIMENSIONAL ARRAY CRYSTAL LATTICE: A A A A A A A A A A A A A A A A A A A A A A A A A A A NOTE: THIS ATOM IS SHARED BY MORE THAN ONE UNIT CELL NOT 5 ATOMS PER CELL IS 1 + 1/4(4) = 2 FULL ATOMS CONSIDER FACES, EDGES, CORNERS AND THOSE TOTALLY WITHIN CELL

  37. CRYSTALLINE SOLIDS AMORPHOUS SOLIDS WELL DEFINED POSTIONS FOR EMCH ATOM ORDERED REPETITION OF PATTERN LONG RANGE ORDER! ILL DEFINED POSTIONS ORDER EXTENDS OVER SHORT RANGE LOCAL ORDER!

  38. 6 FACES 12 EDGES EIGHT CORNERS UNIT CELL STOICHIOMETRY ATOM LOCATED ENTIRELY WITHIN CELL CONTRIBUTES 1 FULL ATOM TO CELL STOICHIOMETRY 2 CELLS 4 CELLS 8 CELLS FACE ATOM CONTRIBUTES 1/2 x 6 = 3 ATOMS TO UNIT CELL EDGE ATOM CONTRIBUTES 1/4 x 12 = 3 ATOMS TO UNIT CELL CORNER ATOM CONTRIBUTES 1/8 x 8 = 1 ATOM TO UNIT CELL WHAT ARE THESE UNIT CELLS?

  39. c g b a b a SIMPLE CUBIC (SC) a = b = c a = b = c = 90o SC = 1 ATOM/UNIT CELL BODY CENTERED CUBIC (bcc) CONTAINED WITHIN CELL BCC = 2 ATOMS/UNIT CELL FACE CENTERED CUBIC (fcc) FCC = 4 ATOMS/UNIT CELL

  40. 52% 68% 74% ATOMS/UNIT CELL x MASS ATOM SIDE3 MASS OF SUBSTANCE VOLUME OF SUBSTANCE COORDINATION NUMBER (CN) OR GEOMETRY 4 PARTICLES CONNECTED TO CENTRAL ATOM = TETRAHEDRON CN = 4 CN = 8 CN = 6 CN = 12 PACKING EFFICIENCY: % OF UNIT CELL OCCUPIED BY ATOMS, IONS OR MOLECULES DENSITY IS DETERMINED BY HOW CLOSE (EFFICIENCY) PARTICLES ARE PACKED INTO A UNIT CELL DENSITY IS A MEASURE OF HOW CONCENTRATED IS THE MASS OF A PURE SUBSTANCE ....OR HOW TIGHTLY PACKED d =

  41. METALLIC IONIC COVALENT MOLECULAR FOUR TYPES OF CRYSTALLINE SOLIDS: COVALENT TYPE BOND IN METALS METALLIC: DELOCALIZED “SEA” OF ELECTRONS ENERGY BAND 2 MOLECULAR ORBITALS 2 ATOMIC ORBITALS 16 6 x 1023 4 8

  42. ENERGY EMPTY ORBITALS FERMI LEVEL BAND GAP FILLED ORBITALS NON- CONDUCTOR SEMI- CONDUCTOR METAL

  43. EXTENDED SOLIDS IONIC CRYSTALS HIGH MELTING & BOILING POINTS IONIC COMPOUNDS LARGE NETWORKS COVALENT SOLIDS HIGH MELTING, HARD SOLIDS DIAMOND, MOST SEMICONDUCTORS, SiO2 MOLECULAR SOLIDS INDIVIDUAL MOLECULES IN A LATTICE LOW MELTING, SOFT ICE, SUGAR, IODINE, SOLID HYDROGEN

  44. GASES

  45. Importance of Gases • Airbags fill with N2 gas in an accident. • Gas is generated by the decomposition of sodium azide, NaN3. • 2 NaN3 ---> 2 Na + 3 N2

  46. THREE STATES OF MATTER

  47. General Properties of Gases • There is a lot of “free” space in a gas. • Gases can be expanded infinitely. • Gases fill containers uniformly and completely. • Gases diffuse and mix rapidly.