Solids & Liquids

CA Standards

• Students know the atoms and molecules in liquids move in a random pattern relative to one another because the intermolecular forces are too weak to hold the atoms or molecules in a solid form.

Intermolecular Forces

Dipole-dipole attraction

Hydrogen bondsDispersion forces

Forces of attraction between different molecules rather than bonding forces within the same molecule.

Forces and Phases

o Substances with very little intermolecular attraction exist as gases

o Substances with strong intermolecular attraction exist as liquids

o Substances with very strong intermolecular (or ionic) attraction exist as solids

Phase Differences

Solid – definite volume and shape; particles packed in fixed positions; particles are not free to moveLiquid – definite volume but indefinite shape; particles close together but not in fixed positions; particles are free to move

Gas – neither definite volume nor definite shape; particles are at great distances from one another; particles are free to move

Three Phases of Matter

Types of SolidsCrystalline Solids: highly regular

arrangement of their components [table salt (NaCl), pyrite (FeS2)].

Unit CellThe smallest portion of a crystal lattice that shows the three-dimensional pattern of the entire lattice

Types of Solids

Amorphous solids: considerable disorder in their structures (glass and plastic).