Classification of Matter

There are exceptions to everything when we try to over-simplify (ex. Hg(l)).

Properties are Used to Classify   Physical Appearance

  dull vs. shiny   liquid vs. solid at RT

  Conductivity of Pure Material   Insulators vs. conductors

  Solubility   in water, acetone, and hexane

  Conductivity of Solids that dissolve in H2O   Electrolytes (strong / weak) vs. Non-electrolytes

Dislikes do not mix

Some of the forces involved . .

Network Forces

Sea of electrons around cations

Lattice of anions and cations

Localized, shared electrons

METALLIC

IONIC

NETWORK COVALENT

Ion-Dipole Forces:

Highly polar solvents can dissolve ionic compounds.

Networks . . . one more category

Metallic networks (shiny / conduct)

Covalent networks (less clear cut)

Ionic-covalent

Ionic “salts” (water soluble /

Solutions conduct)

The molecular categories . . .

Polar substances (may include H-bonders)

Non-polar substances (ex. N2 or C6H14)

Intermolecular Forces

  London Dispersion . . . 0.5 kJ mol-1 to 5 kJ mol-1   H-bonding . . . ~20 kJ mol-1   Covalent . . . ~150 kJ mol-1 to 1,000 kJ mol-1

Intra- vs. Inter-molecular Forces

Conductivity testers (kits, DVM, etc.)

Solute (aqueous) conductivity

Molecular shape and overall dipoles

Some molecules possess regions that are polar and regions that are non-polar.

Some molecules possess a single overall polar or non-polar nature.

There will be borderline cases . . .

  Solubility . . . three simple categories of soluble, slightly soluble, and insoluble (not really).   ex. a LIQUID substance could be slightly soluble in water,

acetone, AND hexane. That substance is weakly polar (which represents the best “average” behavior of the substance).

  Some metals undergo reactions and appear to dissolve. However, these processes differ from simple dissolution.

  There are a fairly large number of notable exceptions to the water solubility of ionic compounds (ex. AgCl, BaSO4, etc.).

  Conductivity also varies across a wide continuum of behavior.   Note that there are some highly polar molecular substances that

are capable of imparting high conductivity to water.