Chem 141 exam #4 study guide

Intermolecular forces Correct Answer IM forces exist among all the particles that compose matter. The state of a sample of matter- solid, liquid, or gas- depends on the magnitude of intermolecular forces among the constituent particles relative to the amount of thermal energy in the sample. Thermal energy Correct Answer When thermal energy is high relative to intermolecular forces, matter tends to be gaseous. When thermal energy is low relative to the intermolecular forces, matter tends to be liquid or solid. The three states of water: Correct Answer Gas (Steam): 100 C. Density: 5.90 x 10^-4 g/cm^3. Molar volume: 30.5L Liquid (water): 20 C. Density: 0.998 g/cm^3. Molar volume: 18.0 mL. Solid (Ice): Temperature: 0 C. Density: 0.917 g/cm^3. Molar volume: 19.6 mL. Density of solid water is less than the density of liquid water, which is atypical behavior. This is because of the unique crystal structure of ice. Properties of the states of matter: Correct Answer Gas: Density= low, shape= indefinite, volume= indefinite, strength to intermolecular forces= weak Liquid: Density=high, shape= indefinite, volume= definite, strength of intermolecular forces= moderate. Solid: Density= high, shape= definite, volume= definite, strength to intermolecular forces= strong. Molecules with partial or temporary charges are: Correct Answer Attracted to each other because their potential energy decreases as they get closer together. But even the strongest intermolecular forces are generally much weaker than bonding forces. Dispersion forces: Correct Answer An intermolecular forces exhibited by all atoms and molecules that result from fluctuations in the electron distribution. These forces occur because of fluctuations on the electron distribution within molecules or atoms. There is a fleeting charge separation called an instantaneous dipole or temporary dipole, which attract other instantaneous dipoles (positive attracts negative and vice versa). - A larger electron cloud can result in a greater dispersion forces. - Dispersion force increases with increasing molar mass.