Comparison of Properties Chapter 6

Introduction The physical properties of a substance depend on the forces between the particles of the chemical species that it is composed of The stronger the bonding and the intermolecular forces, the harder the substances, and the higher the boiling point

Continued Presence of impurities always lowers the melting point as the regular lattice is disrupted Volatility: a qualitative measure of how readily a liquid or solid is vaporized upon heating or evaporation

Metallic Structure Variable hardness, malleable rather than brittle Melting points and boiling points vary, depending on the number of valence electrons, but is generally high Good electrical and thermal conductivity as solids and liquids Insoluble, except in other metals to form alloys Electron sea model: mass of positive nuclei in a sea of electrons

Ionic Structure Hard, but brittle High melting and boiling points Do not conduct heat and electricity as solids, but do when molten or in solution More soluble in water than other solvents Examples: NaCl, CaO Metal + nonmetal

Covalent Structure Usually soft and malleable unless H-bonded Low melting and boiling points. Liquids and gases at room temperature are usually molecular covalent Do not conduct electricity or heat in any state More soluble in non-aqueous solvents, unless they can H-bond to water or react with it Examples: CO2, CH3CH2OH, I2 Nonmetal + nonmetal