Solids Molecular Solids Covalently bound molecules held together by intermolecular forces Molecular Solids Non-conductors Insoluble in water mostly Low MP & BP Held by intermolecular F Intermolecular Forces Instantaneous weak forces that hold one molecule to another or to another part of itself Intermolecular Forces H-bond Dipole-dipole Dipole-induced dipole London dispersion Network Molecular Solids Bound by a continuous network of covalent bonds High MP, insoluble, non- conductor Ionic Solids Ions or ionic compounds held together by electrostatic charge F attraction = Kq 1 q 2 /d 2 Ionic Solids Non-conductors as solids Conductors in solution Soluble in water mostly Very high MP & BP Brittle Metallic Solids Conductors, insoluble in water mostly, high MP & BP, held by gravitational type force F attraction = Gm 1 m 2 /d 2 Crystal Solid Any substance that has a well defined crystal structure Crystal Lattice The three dimensional arrangement of unit cells in a crystal structure Unit Cell The smallest repeating unit that a crystal structure can be divided into Crystal Structures CubicMonoclinic TetragonalTriclinic Orthorhombic Hexagonal Rhombohedral Cubic All angles = 90 o All sides are = All faces are squares Tetragonal All angles = 90 o 2 side sets are =, third 1 set of opposing squares 2 sets opposing rectangles Orthorhombic All angles = 90 o all 3 side sets are 3 unequal sets opposing rectangles Hexagonal All angles = 90 o or 120 o 1 set of opposing hexagons 3 sets opposing rectangles Monoclinic 2 sets of angles = 90 o third set 90 o 1 set of opposing parallel 2 sets opposing rectangles Triclinic No angles = 90 o 3 unequal sets of opposing parallelograms Rhombohedral No angles = 90 o All sides = 3 sets of opposing congruent rhombuses Simple Cube Unit cell with one atom at each vertex 1 atom/cell Body Centered Cube BCC Unit cell with one atom at each vertex & one atom in the center of the cube 2 atoms/cell Face Centered Cube FCC or CCP Unit cell with one atom at each vertex & one atom on each face of the cube 4 atoms/cell The density of iron in its normal state of BCC is 7.86 g/mL. Calculate its density in the FCC state Drill: List & describe the 7 crystal structures Hydrated Crystal A solid with water in the crystal CuSO 4 *5H 2 O Anhydrous Solid A crystal without water Hygroscopic Crystals that absorb moisture from the air Deliquescent Crystals that absorb enough moisture from the air to liquify Efflorescent Crystals that give up water to the surroundings Polymorphous When a single substance can have multiple crystal structures Isomorphous When different substances have the same crystal structure Amorphous Solid A solid w/o a well defined crystal structure Super-cooled liquid Liquid Crystals Part solid & part liquid Has a well defined crystal structure in 1 or 2 but not all 3 dimensions Smectic Liquid crystal that have a well defined crystal structure in 2 dimensions Nematic Liquid crystals that have a well defined crystal structure in only 1 dimension Liquid A substance that holds together loosely, but has no structure in any dimension Solid Definite size & shape Particles vibrate about fixed points Liquid Definite size but no shape Particles vibrate about moving points Gas No definite size or shape Particles move at random Melting Point Temperature at which the solid phase & liquid phase are at equilibrium MP & FP are equal Melting Point Temperature at which the vapor pressure of a solid = the vapor pressure of its liquid phase Boiling Point Temperature at which the liquid phase & gaseous phase are at equilibrium Boiling Point Temperature at which the vapor pressure of a liquid = the vapor pressure of its gaseous phase or atmospheric P Adhesion The attraction of particles from different substances to each other Cohesion The attraction of particles of the same substance towards each other Capillarity The movement of a liquid up a thin tube due to adhesion & cohesion Surface Tension Pressure on the surface of a liquid caused by the uneven forces acting on the surface molecules Vapor Pressure The pressure caused by the evaporated particles in the vapor above a liquid Intermolecular Forces Weak temporary attractions between atoms from one molecule to another or another part of a larger molecule Intermolecular Forces Hydrogen-bond Dipole-dipole Dipole-induced dipole London dispersion forces Hydrogen Bond Strongest of the intermolecular forces Occurs when H is bound to one highly EN element & connects to another Dipole-Dipole When two polar molecules connect Dipole-Induced Dipole When a polar molecule gets near a non-polar one, it induces the non-polar one to become polar; thus, they connect London Dispersion Instantaneous attraction for fractions of seconds in which non-polar molecules connect Very weak force Predict & explain the MP trends of: 1) Li, Na, K, & Rb 2) F 2, Cl 2, Br 2, & I 2 3) LiF, NaCl, KBr, & RbI Phase Diagram Graphic representation of all the phases of a substance with respect to temperature & pressure 1 atm 100 K400 K Approximate MP & BP: Phase Diagrams Describe conditions at each number Define solids, liquids, gases, melting & Boiling points Determine the phase changes for the 3 arrows: PHASE DIAGRAM