91Ó°ÊÓ

Why does liquid water spread out when poured on a flat glass plate, while liquid mercury forms spherical drops?

Arrange the following substances in order of increasing melting points: \(\mathrm{CH}_{4}, \mathrm{GeH}_{4}, \mathrm{SiH}_{4}\), and \(\mathrm{SnH}_{4}\).

Indicate whether or not each of the following solids is an ionic solid. (a) glass, \(\mathrm{SiO}_{2}\) (d) \(\mathrm{Fe}\) (b) ice, \(\mathrm{H}_{2} \mathrm{O}\) (e) dry ice, \(\mathrm{CO}_{2}\) (c) \(\mathrm{CaCl}_{2}\)

Explain how an increase in the strength of intermolecular forces affects each of the following properties of a substance. (a) vapor pressure of a solid (b) hardness of a molecular solid (c) boiling point of a liquid (d) viscosity of a liquid (e) melting point of a molecular solid

Which substance in each pair has the higher vapor pressure at the same temperature? (a) \(\mathrm{Cl}_{2}\) or \(\mathrm{I}_{2}\) (c) \(\mathrm{PF}_{3}\) or \(\mathrm{NF}_{3}\) (b) \(\mathrm{CH}_{3} \mathrm{OH}\) or \(\mathrm{CH}_{3} \mathrm{SH}\)

Explain why diamond is a good insulator, while graphite is a good conductor of electricity.

Compare the following substances with respect to electrical conductivity, hardness, melting point, and vapor pressure at room temperature: \(\mathrm{NaCl}, \mathrm{SiC}, \mathrm{SiCl}_{4}\), and \(\mathrm{Fe}\).

Which characteristic of molecules changes in magnitude from one state to another and is largely responsible for whether a substance is a gas, a liquid, or a solid?

List the names for all possible phase changes.