Liquids and Solids

Flashcards about Liquids and Solids

Intermolecular forces

Attractive forces between ions and molecules in the liquid and solid states, weaker than ionic and covalent bonds.

Ion-dipole attractions

Form between ions and polar molecules; strongest of the temporary attractions between particles.

Dipole-dipole attractions

Attractions between two polar molecules.

Hydrogen bonding

A particularly strong type of dipole-dipole attraction requiring a hydrogen bond donor (H bonded to N, O, or F) and a hydrogen bond acceptor (N, O, or F with lone pair electrons).

Dispersion forces

Occur between all molecules but are most notable between nonpolar molecules; short-lived attractions between instantaneous dipoles and induced dipoles.

Polarizability

The ability of an electron cloud to become asymmetric, affecting the strength of dispersion forces.

Viscosity

The resistance to flow, determined by the strength of intermolecular attractions and temperature. Decreases as temperature increases.

Surface tension

The tendency of a liquid to minimize its surface, affected by intermolecular forces.

Cohesion

Attraction between like particles.

Adhesion

Attraction between different particles.

Capillary action

The ability of a liquid to flow against gravity up a narrow tube, involving cohesion and adhesion.

Melting (Fusion)

The transition from solid to liquid.

Freezing

The transition from liquid to solid.

Evaporation (Vaporization)

The transition from liquid to gas.

Condensation

The transition from gas to liquid.

Sublimation

The transition from solid to gas.

Deposition

The transition from gas to solid.

Enthalpy of Vaporization (ΔHvap)

The energy change for the vaporization of 1 mole of a liquid.

Enthalpy of Fusion (ΔHfus)

The energy change associated with the melting of one mole of a substance.

Enthalpy of Sublimation (ΔHsub)

The energy changes associated with the sublimation of one mole of a substance.

Heating Curve

A graph that shows how the temperature changes as a pure substance is heated.

Volatile

Substances that vaporize easily.

Nonvolatile

Substances that do not easily vaporize.

Vapor Pressure

Affected by strength of intermolecular forces and temperature; volatile substances have more gas phase molecules above the surface of the liquid.

Heat of Vaporization

The amount of energy needed to vaporize one mole of a substance.

Clausius-Clapeyron Equation

ln(Pvap) = −(ΔHvap/R)(1/T) + β

ln(P2/P1) = −(ΔHvap/R)((1/T2) - (1/T1))

Boiling Point

Boiling

Occurs when the vapor pressure of the liquid equals the pressure of the surroundings.

Normal Boiling Point

The boiling point of a liquid at a pressure of 1.00 atm.

Distillation

Volatile substances can be separated from a liquid-phase mixture via this process.

Vapor Pressure Equilibrium

When the rate of evaporation of liquid molecules equals the rate of condensation of gas molecules.

Phase Diagram

This shows the phase of a specific substance under all possible pressure-temperature combinations.

Triple Point

Represents the P and T at which all three phases of the substance are in equilibrium.

Critical Point

Occurs at the pressure and temperature conditions above which the substance no longer exists as either a liquid or gas.

Supercritical Fluid

Exists at T and P above the critical pressure and critical temperature, has properties common to both liquids and gases.

Crystalline Solids

Have definite melting points, abruptly forming a liquid once the melting point is reached.

Amorphous Solids

Get softer as their temperature is raised, gradually forming a liquid.

Molecular Solids

Contain molecules held to each other by intermolecular forces and have relatively low melting points.

Ionic Solids

Composed of ions held together by ionic bonds and have quite high melting points.

Covalent-Network Solids

Composed of atoms connected by covalent bonds throughout the solid and have extremely high melting points.

Metallic Solids

Composed of metal ions loosely held together by their valence electrons and have a broad range of melting points.

Electron-Sea Model

Each metal atom contributes its valence electrons and forms a cation with the valence electrons free to move throughout the structure.

Malleable

Can be hammered or bent into different shapes without breaking.

Ductile

Can be drawn into long, thin wires.

Unit Cell

Simplest repeating unit of a crystal structure.

Simple Cubic Uniti Cell

Simplest way is for the particles to align on top of one another.

Packing of Atom's

How the layers are arranged in the three-dimensional structure

Cubic Unit Cells

Have 90 degree angles and edges of equal length

Simple Cubic Unit Cell and Body-Centered Cubic Unit Cell

Unit cell; includes a great deal of empty space between the atoms.

Hexagonal Close-Packing (hcp)

Involves a two-layer repeat and forms a hexagonal unit cell.

Cubic Close-Packing (ccp)

Results in the formation of a face-centered unit cell.

Packing Efficiency

The fraction of the unit cell volume occupied by atoms.

Coordination Number

The number of nearest neighbors for each atom in the structure.

Nitinol

Alloy of nickel and titanium; when warm, it forms a body-centered cubic unit cell, and when cooled, it changes shape to a hexagonal unit cell.

Ionic Solid Cations and Anions

Consist of cations and anions of very different sizes, typically large anions and small cations.