drill: draw 3 possible ldds for: c4h8oc4h8o. molecular solids covalently bound molecules held...
TRANSCRIPT
Drill: Draw 3 possible LDDs for:
C4H8O
Molecular Solids•Covalently bound molecules held together by intermolecular forces (asphalt or ice)
Solids
Solid or Crystal•Any substance that has a well defined crystal structure
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
Importance of H-bonding
• Hydrogen bonding will have a profound effect on the strength of the bond; thus, will cause a tremendous increase of the BP or MP.
Network Molecular Solids or Macromolecules
•Bound by a continuous network of covalent bonds
•High MP, insoluble, non-conductor
Ionic Solids•Ions or ionic compounds held together by electrostatic charge
•Fattraction = Kq1q2/d2
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
•Fattraction = Gm1m2/d2
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
Drill:•Describe unit cells & crystal lattice
Simple Cube•Unit cell with one atom at each vertex
•1 atom/cell
http://departments.kings.edu/chemlab/animation/index.html
Great website
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
Hydrated Crystal•A solid with water in the crystal
•CuSO4*5H2O
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
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
Drill:•Name & describe each of the 7 crystal structures
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•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-Dipole
+ + + - + - + - - -
- - - + - + - + + +
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
Dipole-Induced Dipole
+ + + - + + - - + - - -
- + - + - + + - + - + -
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, & Rb2) F2, Cl2, Br2, & I2
3) LiF, NaCl, KBr, & RbI
Phase Diagram•Graphic representation of all the phases of a substance with respect to temperature & pressure
1 atm
100 K 400 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
0
50
100
150
200
250
300
350
400
450
500
0 100 200 300 400 500 600Temperature (K)
Pre
ssur
e (k
Pa)
A
B
C
D
H
K
M
P