Intermolecular Forces, Phase Changes, and Crystalline Solids Study Guide

Vocabulary-style flashcards covering intermolecular forces, heat associated with phase changes, types of crystalline solids, and the unique properties of water based on lecture notes.

Intermolecular Forces

The attractive forces between molecules that determine physical states and are weaker than chemical bonds.

London Dispersion Forces

The weakest intermolecular force, caused by temporary shifts in electron distribution around atoms or molecules; found in all molecules.

Dipole-Dipole Forces

Attractive forces between polar molecules where the positive end of one molecule attracts the negative end of another.

Hydrogen Bonding

A strong type of dipole-dipole force occurring when hydrogen is bonded to nitrogen, oxygen, or fluorine and is attracted to these atoms in nearby molecules.

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

The energy required to change a substance from a solid to a liquid at its melting point; for water, this is $334\,J/g$.

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

The energy required to change a substance from a liquid to a gas at its boiling point; for water, this is $2,260\,J/g$.

Crystalline Solids

Solids characterized by atoms, ions, or molecules arranged in a repeating, orderly pattern.

Ionic Solids

Hard, brittle solids made of cations and anions held by ionic bonds; they conduct electricity when melted or dissolved in water.

Covalent Network Solids

Extremely hard solids with very high melting points, consisting of atoms bonded in a continuous network of covalent bonds (e.g., diamond).

Molecular Solids

Soft solids with low melting points, composed of molecules held together by intermolecular forces like London dispersion or hydrogen bonds.

Metallic Solids

Lustrous, malleable, and ductile solids composed of metal atoms and delocalized electrons that move freely throughout the structure.

Solid Less Dense Than Liquid (Water)

The property where ice floats because hydrogen bonding creates a crystalline structure with more space between molecules than in liquid water.

Specific Heat Capacity

The energy required to raise the temperature of a substance by $1\,^\circ\text{C}$; water has a high capacity of $4.18\,J/(g \cdot ^\circ\text{C})$.

Surface Tension

A property where a liquid's surface acts like a thin elastic sheet due to hydrogen bonding pulling molecules together strongly.

Cohesion

The property of water molecules sticking to each other due to hydrogen bonding.

Adhesion

The property of water molecules sticking to other polar surfaces.

Capillary Action

The movement of water up plant stems against gravity, enabled by the combination of cohesion and adhesion.