Intermolecular Forces, Liquids, and Solids Lecture Flashcards

Vocabulary flashcards covering intermolecular forces, phase changes, vapor pressure, and solid-state structures including unit cells.

High-Pressure Liquid Chromatography (HPLC)

An instrumental technique that uses a liquid mobile phase and separates substances based on their polarity.

Solid

A state of matter characterized by a definite shape and volume; particles are close together and held in a fixed place.

Liquid

A state of matter with a definite volume that adopts the shape of its container; particles are close together but can move past each other.

Gas

A state of matter that adopts the shape and volume of its container; particles are far apart and have very little interaction.

Intermolecular forces

The forces that occur between molecules; examples include dipole-dipole interactions, hydrogen bonds, and London dispersion forces.

Dipole-Dipole interactions

Attractions between polar covalent molecules.

Hydrogen bond

A strong intermolecular force between molecules containing $H-F$, $H-O$, or $H-N$ bonds.

Surface tension

The tendency of some liquids to minimize surface area.

London dispersion forces

Weak intermolecular forces that result from instantaneous dipoles; they are present in all covalent molecules.

Ion-dipole interaction

The electrostatic interaction between an ion and a polar molecule.

Miscible

A term describing liquids that are completely soluble in each other, such as ethanol and water.

Immiscible

A term describing liquids that do not mix with each other, such as water and oil.

Micelle

A spherical assembly of molecules or polyatomic ions containing polar heads and nonpolar tails.

Phase change

A transition from one state of matter to another.

Enthalpy of fusion ($\Delta H_{fus}$)

The heat required to convert a solid to a liquid at constant pressure.

Enthalpy of vaporization ($\Delta H_{vap}$)

The heat required to convert a liquid to a gas at constant pressure.

Vapor pressure

The pressure of the gas above the liquid when the liquid and gas are in dynamic equilibrium.

Boiling point

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

Volatile

A property of a substance tending to evaporate quickly; characterized by higher vapor pressure.

Boltzmann distribution

The distribution of energies for particles in a substance.

Clausius-Clapeyron Equation

An equation relating vapor pressure and temperature: $\ln(P) = -\frac{\Delta H_{vap}}{R} \times \frac{1}{T} + \ln(\beta)$.

Lattice energy

A measure of how tightly the ions stick together in an ionic compound.

Covalent networks

Lattices of covalent bonds that form giant molecules.

Polymers

Substances that contain long chains of covalently bonded atoms.

Crystalline solids

Solids that contain atoms, molecules, or ions in ordered, repeating units.

Amorphous solids

Solids that do not have a rigid, repeating order.

X-Ray Crystallography

An analytical technique used to determine the structure of crystalline solids based on how X-rays diffract when they encounter electrons.

Bragg's law

The mathematical relationship for constructive interference in X-ray diffraction: $n\lambda = 2d \sin(\theta)$.

Unit cell

The simplest repeating pattern within a crystal.

Packing efficiency

The percentage of the unit cell volume that is occupied by atoms.

Simple cubic cell

A cubic unit cell with 1 atom per unit cell and an edge length of $2r$, where $r$ is the atomic radius.

Face-centered cubic (FCC) cell

A cubic unit cell with 4 atoms per unit cell and an edge length of $2r\sqrt{2}$; it has a packing efficiency of $74.0\%$.

Body-centered cubic (BCC) cell

A cubic unit cell with 2 atoms per unit cell and an edge length of $\frac{4r}{\sqrt{3}}$; it has a packing efficiency of $68.0\%$.