drill: draw 3 possible ldds for: c4h8oc4h8o. molecular solids covalently bound molecules held...

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