Solids & Liquids

NM StandardsStudents 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 attractionHydrogen bondsDispersion 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 – definite volume and shape; particles packed in fixed positions; particles are not free to move

Liquid – 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).

States of Matter

Heating/cooling curve for water

Heating curve

Cooling Curve

Heating and Cooling curves

Phase changes occur where the temperature stays flat.

After a phase change is complete and all molecules are in the same state the temperature increases to the next phase change.

Phase Diagram

Critical point: The vapor-liquid critical point denotes the

conditions above which distinct liquid and gas phases do not exist.

Triple point: Where all phases coexist in a stable equilibrium

Normal freezing and boiling points occur at 1 atm pressure read off the diagram