Chapter 12: Intermolecular Forces, Liquids, Solids, and Phase Changes Flashcards

These flashcards provide definitions for key terms related to intermolecular forces, phase changes, liquid properties, solid structures, and advanced materials as covered in Chemistry Chapter 12.

Intramolecular forces

Bonding forces found within a molecule.

Intermolecular forces

Nonbonding forces found between molecules.

Van der Waals radius

One-half the closest distance between the nuclei of two nonbonded atoms in adjacent molecules.

Ion-dipole forces

Attractive forces that result when an ion and a nearby polar molecule attract each other.

Dipole-dipole forces

The attractive forces between the positive pole of one polar molecule and the negative pole of another polar molecule.

Hydrogen bond

The attraction between an H atom covalently bonded to a small, highly electronegative atom (N, O, or F) and a lone pair of the N, O, or F atom of another molecule.

Dispersion (London) forces

Intermolecular forces that arise when an instantaneous dipole in one particle induces a dipole in another.

Polarizability

The ease with which the electron cloud of a particle is distorted; it correlates closely with molar mass.

Phase

A physically distinct, homogeneous part of a system.

Fusion (Melting)

The process where particles in a solid gain kinetic energy and move out of their fixed positions to become a liquid.

Vaporization

The process where molecules in the liquid phase gain sufficient kinetic energy to separate from each other completely and form a gas.

Sublimation

The process where particles in a solid move directly into the gas phase.

Deposition

The process where gas particles move directly into the solid phase.

Vapor pressure

The pressure exerted by a vapor on a liquid when the system reaches a state of dynamic equilibrium in a closed flask.

Clausius-Clapeyron equation

An equation that relates vapor pressure ($P$) to temperature ($T$).

Boiling point

The temperature at which the vapor pressure of a liquid equals the external pressure.

Normal boiling point

The boiling point of a substance observed at standard atmospheric pressure or $760\,torr$.

Triple point

The temperature and pressure condition at which solid, liquid, and gas phases coexist in equilibrium.

Critical point

The temperature and pressure above which the liquid and gas phases of a substance become indistinguishable.

Surface tension

The energy required to increase the surface area of a liquid; it decreases with increasing temperature.

Capillarity

The rising of a liquid through a narrow space against the pull of gravity.

Viscosity

The resistance of a fluid to flow, resulting from intermolecular attractions that impede the movement of molecules.

Crystalline solids

Solids that have well-defined shapes due to the orderly arrangement of their particles.

Amorphous solids

Solids that lack an orderly arrangement and have poorly defined shapes.

Crystal lattice

An orderly three-dimensional array of particles composing a crystal.

Unit cell

The smallest portion of a crystal lattice that yields the crystal if it is repeated in all directions.

Coordination number

The number of nearest neighbors of a particle in a crystal.

Simple cubic unit cell

A unit cell type with atoms at 8 corners, a coordination number of 6, and a total of 1 atom per unit cell.

Body-centered cubic unit cell

A unit cell with atoms at 8 corners and 1 atom at the center, a coordination number of 8, and a total of 2 atoms per unit cell.

Face-centered cubic unit cell

A unit cell with atoms at 8 corners and 1 atom at each of the 6 faces, a coordination number of 12, and a total of 4 atoms per unit cell.

Band theory

A model for metallic bonding where atomic orbitals combine to form a continuum (band) of molecular orbitals (MOs).

Valence band

The lower portion of the molecular orbital band that is filled with valence electrons.

Conduction band

The empty, higher energy portion of the molecular orbital band in a metal.

Polymer

An extremely large molecule (macromolecule) consisting of a covalently linked chain of smaller molecules called monomers.

Degree of polymerization ($n$)

The number of repeat units in a polymer chain.

Radius of gyration ($R_g$)

The average distance from the center of mass of a polymer molecule to the outer edge of the random coil.

Elastomers

Polymers that can be stretched and immediately spring back to their initial shapes when released.

Quantum dots

Nanoparticles of semiconducting materials smaller than $10\,nm$.