Chemistry Chapter 11: Solids and Liquids

intermolecular forces

the electrostatic attractions between molecules

dipole-dipole force

attraction in which positive areas of one molecule attracts the negative areas of other molecules; strengthened by increased polar difference between molecules; molecules align themselves so that the positive end of one molecule is facing the negative end of another molecule

hydrogen bonds

attraction in which one of the participating atoms is hydrogen and the other element is either fluorine, oxygen, or nitrogen. strongest intermolecular force

Dispersion forces

attraction caused by the random concentrations of electrons around molecules. More common and intense between larger molecules due to the higher electron count

crystalline solids

solids that when shattered form smaller shapes with similar edges and angles

amorphous solids

solids that, when shattered or split, result in irregular fragments

sublimation

the direct change from the solid to the gaseous state

crystal lattice

a three-dimensional pattern that makes up every crystal. The shape thereof depends on the number and kinds of particles involved

deposition

when a substance changes directly from a gas to a solid

polymorphous

when elements or compounds for more than one type of crystal lattice

allotropic elements

pure elements that are polymorphous

allotropes

different forms of allotropic elements

lattice energy

energy released when gaseous particles form crystals. Equal and opposite to separation energy

atomic crystals

crystals that only form when noble gases freeze. Particles in these solids are individual atoms; soft and poor conductors of electricity

Covalent molecular crystals

crystals made of covalently bonded atoms held together by any combination of dipole-dipole forces

Covalent Network Crystals

crystals made of tightly-bound networks of atoms that act as giant molecules, hence the high melting points

ionic crystals

crystals made of a repeating network of ions defined by a unit cell. Fracture easily, high melting points.

metallic crystals

crystals that have a repeating network of ions surrounded by a sea of valence electrons. vary greatly in physical properties. Conduct electricity well

cohesion

attraction of particles in liquids

adhesion

attraction between particles of the liquid and particles of other materials

surface tension

the elastic skin that forms the surface of liquids

surfactants

agents that break down surface tension of liquids

viscosity

a liquid’s ability to resist flowing

meniscus

a concave surface resulting from a difference in force between adhesion and cohesion

capillary action

in which water rises up narrow capillary tubes easily because of its meniscus

evaporation

when vaporization occurs in a non-boiling liquid

vapor pressure

pressure exerted by evaporated water molecules in a gas

dynamic equilibrium

a situation that occurs when the two process of condensation and evaporation balance each other out so that no net effect can be observed

normal boiling point

the temperature at which vapor pressure in a liquid equals 1 atm or 760 torr

distillation

the process of vaporization and condensation to separate mixtures

phase diagram

a graphical way to summarize the temperature and pressure conditions in which a substance exists as a solid, liquid, or gas

triple point

the conditions at which matter can exist in all three states

critical temperature

highest temperature at which a gas can be liquefied

Critical pressure

pressure required to liquefy a gas at its critical temperature