Melting point, solubility, and conductivity depend on bonding type.
| Structure Type | Melting/Boiling Point | Solubility (Water) | Conductivity |
|---|---|---|---|
| Giant Covalent | Very High | Insoluble | No (except Graphite) |
| Ionic | High | Soluble (mostly) | Only when molten/aq |
| Polar Covalent | Medium | Soluble ("Like dissolves like") | No |
| Non-Polar Covalent | Low | Insoluble | No |
Polar solvents (water) dissolve polar/ionic solutes. Non-polar solvents (hexane) dissolve non-polar solutes. This is because the solvent–solute intermolecular forces must be comparable in strength to the forces being broken.
Ethanol (C₂H₅OH) is miscible with water, but hexanol (C₆H₁₃OH) barely dissolves. Both have an –OH group. Why the difference?
In ethanol, the polar –OH group dominates, enabling hydrogen bonding with water. In hexanol, the long non-polar hydrocarbon chain dominates — the molecule is predominantly non-polar. "Like dissolves like" — hexanol behaves more like a non-polar substance.