Classification of Matter - Wilkes Universitymencer/pdf_docs/Class_Matter.pdfClassification of Matter...
Transcript of Classification of Matter - Wilkes Universitymencer/pdf_docs/Class_Matter.pdfClassification of Matter...
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.