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

Forces and Phases oSubstances with very little intermolecular attraction exist as gases oSubstances with strong intermolecular attraction exist as liquids oSubstances with very strong intermolecular (or ionic) attraction exist as solids

Phase Differences Solid Solid – definite volume and shape; particles packed in fixed positions; particles are not free to move Liquid Liquid – definite volume but indefinite shape; particles close together but not in fixed positions; particles are free to move Gas 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 Solids  Crystalline Solids: highly regular arrangement of their components [table salt (NaCl), pyrite (FeS 2 )].

Unit Cell The 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).