Notes

Outline

Liquids and Solids Part 2-Solids

Vapor Pressure Vapor Pressure- The pressure of a vapor in equilibrium with the liquid state Factors Influencing Vapor Pressure Increasing molecular mass (size) decreases vapor pressure (Increased molecular forces) Increasing Temperature increases vapor pressure(Increased Kinetic Energy overcoming molecular forces)

Boiling Point of Liquids Boiling Point-Temperature at which the vapor pressure of a liquid becomes equal to the external pressure

T-102 Vapor Pressure vs Temperature

Factors Affecting the Boiling Point of a substance External Pressure-Increasing the pressure increases Boiling Point Example-Reduced Pressure  Distillation Impurities-Increases Boiling Point

Factors Affecting Boiling Point Between Substances Molecular Size-Increases the molecular forces between molecules leads to higher Boiling Point Structure- Branching reduces molecular forces and decreases Boiling Point Molecular Forces-Graeter the forces the higher the Boiling Point

Estimating Boiling Points Using Vapor Pressure Curves Do Problem

T-102 Vapor Pressure Curve

Phase Diagrams Boiling Point Curve (boundary) Melting Point Curve Sublimation Point Curve Triple Point Critical Points

T-103 General Phase Diagram

Specific Phase Diagrams Water Carbon Dioxide

T-104 Phase Diagrams of Water and Carbon Dioxide

Particle Organization of Solids Crystalline- solid with a pattern of particle arrangement in solid matrix Crystalline solids do not exhibit softening upon heating before they melt Amorphous-solid with no discernable pattern of particle arrangement in its solid matrix Amorphic solids will soften when heated and then eventually melt

Crystal Lattice and Unit Cell of Crystalline Solids Crystal Lattice-A solid matrix with a repeating pattern of particle arrangement Unit Cell-Repeating geometrical pattern that repeats itself in making the lattice Examples of Unit Cells Cubic Monoclinic Rhombic Orthorhobic Triclinic

Cubic Unit Cell Construction Primitive(simple) cubic Involves one particle per unit cell(1/8 in each corner) Body Centered Cubic(bcc) Involves two particles per unit cell(1/8 in each corner plus whole particle in center Face Centered Cubic (fcc) Involves four particles per unit cell (1/8 in each corner plus ½ in each face plus 1 particle in center

T-105 Cubic Unit Cells

T-108 Space Filled Models of Cubic Unit Cells

T-11.38 Unit Cell Construction of CsCl

Principle of X-Ray Diffraction Inspired by Professor Max Von Laue Procedure of Structural Determination 1. Crystal carefully grown (minimal imperfections) 2. X-Rays generated 3. Aimed at continually  rotating crystal 4. X-Rays Diffract through spacings of crystal 5. Scattered X-Rays expose photographic film producing “powder patterns” 6. Patterns analyzed using Braggs Law for identifying unit cell construction

T-11.47 Schematic Diagram of X-Ray Diffractor

Types of Crystalline Solids Ionic Molecular Covalent Networked Metallic

Ionic Crystalline Solids High M.P High electrical conductivity in molten state Hard crystalline Principle bonding forces = Ionic Examples All ionic salts

Molecular Crystalline Solids Soft Brittle Low M.P. Low electrical conductivity Principle Bonding forces = Intermolecular forces Examples Ice Organic solids

Covalent Networked Crystalline Solids Very high M.P. Extremely low electrical conductivity Very Hard Principle Bonding forces = co-valent bonding Examples Carbon

Structures of Carbon Diamond Graphite Fullerenes Amorphic

Co-valent Networked Structures of Carbon-Diamond Diamond- Tetrahedrally arranged Carbon atoms of high density and index of refraction Non-Conductor Extremely hard Extremely Dense Highly reactive and reflective

Co-Valent Networked Structure of Carbon-Graphite Hexagonally Close Packed Platlet layered arrangement of Carbon Atoms Soft and spongy High Conductivity Dark Grey or black Good Lubricant Low density

T-109 Structures of Diamond and Graphite

Co-Valent Networked Structure of Carbon-Fullerenes C60 or C70 dodecahedron shaped Carbon matrix Attracts cations within its “bucky ball” Super-conductive properties has potential

Amorphic Carbon Lamp black

Metallic Crystalline Solids Variable M.P. range High electrical and thermal conductivity Variable Hardness Principal Bonding forces = metallic bonding Metallic bond-bond between metallic atoms involving the positive nucleii and loosely held valence electrons

Isomorphism Isomorphic solids-Crystalline solids of the same unit cell construction Examples NaCl and KCl Seven forms of ice Many crystalline metals

Polymorphism Polymorphic solids- a crystalline solid that exhibits two or more unit cell construction Examples Carbon Sulfur (monoclinic, Rhombic, Orthorhombic, Triclinic) Calcium Carbonate (marble and chalk)