Chem Ch 8&9

Evaporation

When molecules escape the surface of a liquid

Equilibrium

When rate of evaporation = rate of condensation

Vapor pressure

The pressure of a container at equilibrium; the max amount of gas a container can hold.

volatile liquid

High vapor pressure and weak forces keeping it together

nonvolatile liquid

Low vapor pressure, strong forces keeping it together

Boiling Point

point at which the vapor pressure is equal to the surrounding pressure. The lower the external pressure, the lower the boiling point

Critical temperature

The temp above which the liquid phase cannot exist.

Critical pressure

The pressure that must be applied to cause condensation at the critical temp.

Triple Point

When all phases are in equilibrium

Sublimation point

When a substance goes from solid to gas

Four types of Solids

• molecular

• ionic

• network covalent

• metals

intermolecular forces

Holds molecules together with much less strength than bonds

Hydrogen Bonding

Strongest intermolecular force, between H and N,O, or F

Dipole

between polar molecules, strength is dependent on polarity

Dispersion(London) forces

Between nonpolar molecules, very weak, and reliant on random electron motion

What strength of force results in a low melting point and high vapor pressure?

Weak forces

Ionic Solids

• Made of ions

• strong w/ high melting point

• conducts when dissolved in water

Lattice Energy

A measure of the strength of an ionic bond. The smaller the ions, the closer they approach one another, and the stronger the bond is

Network covalent bonds

• Chemically bonded

• Strongest w/ very high melting point

• nonconductive

• C, Si, SiO

Metals

Uses the Electron Sea Model, very conductive

Electron Sea Model

Positive Ions are held together in a mobile sea of electrons

Two types of Alloys

• Substitutional Alloys

• Interstitial Alloys

Substitutional Alloys

Formed through atom substitution when metals being mixed have the same sized atom and substitute for one another in the crystal lattice structure.

Interstitial Alloys

Formed when small atoms fill in the interstitial spaces of larger metal atoms in the crystal lattice

Exothermic

Gives off energy

Endothermic

Requires energy input

Specific heat

The amount of energy required to change the state of 1g of a substance 1degree C

Enthalpy

The heat content w/i a reaction

Hess’s Law

Change in energy for a reaction is the same whether or not it occurs directly or in a series.

Enthalpy of formations

Sum of products - sum of reactants

Bond energies

The energy required to break bonds

Break - make