Solids, Liquids, and Intermolecular Forces ❮ 179HF exhibits an especially strong form of dipole–dipole force known as hydrogen bonding.
Since hydrogen bonding is stronger than normal dipole–dipole forces, HF has a higher
viscosity.
Give yourself 1 point for this answer.
(d) Glass is a liquid with very high viscosity (amorphous solid). Heating any liquid gives
the molecules more kinetic energy, which lowers the viscosity. In the case of glass, the
decrease in viscosity begins with the material becoming softer and softer until it flows
freely.
Give yourself 1 point for this answer.
Total your points. There are 4 points possible.❯ Rapid Review
● The state of matter in which a substance exists depends on the competition between
the kinetic energy of the particles (proportional to temperature) and the strength of the
intermolecular forces between the particles.
● The melting point is the temperature at which a substance goes from the solid to the
liquid state and is the same as the freezing point.
● The boiling point is the temperature at which a substance goes from the liquid to the
gaseous state. This takes place within the body of the liquid, unlike evaporation, which
takes place only at the surface of the liquid.
● Sublimation is the conversion of a solid to a gas without ever having become a liquid.
Deposition is the reverse process.
● Phase changes are changes of state.
● Intermolecular forces are the attractive or repulsive forces between atoms, molecules, or
ions due to full or partial charges. Be careful not to confuse intermolecular forces with
intramolecular forces, the forces within the molecule.
● Ion–dipole intermolecular forces occur between ions and polar molecules.
● Dipole–dipole intermolecular forces occur between polar molecules.
● Hydrogen bonds are intermolecular forces between dipoles in which there is a hydrogen
atom attached to an N, O, or F atom.
● Ion-induced dipole intermolecular forces occur between an ion and a nonpolar molecule.
● London (dispersion) forces are intermolecular forces between nonpolar molecules.
● Liquids possess surface tension (liquids behaving as if they had a thin “skin” on their
surface, due to unequal attraction of molecules at the surface of the liquid), viscosity
(resistance to flow), and capillary action (flow up a small tube).
● Amorphous solids have very little structure in the solid state.
● Crystalline solids have a great deal of structure in the solid state.
● The crystal lattice of a crystalline solid is the regular ordering of the unit cells.
● Know the five types of crystalline solid: atomic, molecular, ionic, metallic, and network.
● Phase changes can be related to the strength of intermolecular forces.