I. Kinetic Molecular Theory KMT

Assumptions of KMT All matter is composed of tiny particles These particles are in constant, random motion. Some particles are moving fast, some are moving slowly. Temperature is a measure of the average Kinetic Energy and is proportional to the average speed of the molecules.

KMT Model  op_KMT_frames.htm op_KMT_frames.htm  Click on the link above to see how particles of matter behave according to the KMT.

Liquids & Solids II. Intermolecular Forces

A. Definition of IMF  Attractive forces between molecules.  Much weaker than chemical bonds within molecules.  a.k.a. van der Waals forces

B. Types of IMF

 London Dispersion Forces View animation online.animation

B. Types of IMF  Dipole-Dipole Forces + + - - View animation online.animation

B. Types of IMF  Hydrogen Bonding

C. Determining IMF  NCl 3 polar = dispersion, dipole-dipole  CH 4 nonpolar = dispersion  HF H-F bond = dispersion, dipole- dipole, hydrogen bonding

III. Physical Properties Liquids & Solids

A. Liquids vs. Solids LIQUIDS Stronger than in gases Y high N slower than in gases SOLIDS Very strong N high N extremely slow IMF Strength Fluid Density Compressible Diffusion

B. Liquid Properties  Surface Tension attractive force between particles in a liquid that minimizes surface area

B. Liquid Properties  Capillary Action attractive force between the surface of a liquid and the surface of a solid watermercury

C. Types of Solids  Crystalline - repeating geometric pattern covalent network metallic ionic covalent molecular  Amorphous - no geometric pattern decreasing m.p.

C. Types of Solids Ionic (NaCl) Metallic

C. Types of Solids Covalent Molecular (H 2 O) Covalent Network (SiO 2 - quartz) Amorphous (SiO 2 - glass)

Liquids & Solids IV. Changes of State

A. Phase Changes

 Evaporation molecules at the surface gain enough energy to overcome IMF  Volatility measure of evaporation rate depends on temp & IMF

A. Phase Changes Kinetic Energy # of Particles p. 477 Boltzmann Distribution tempvolatilityIMFvolatility

A. Phase Changes  Equilibrium trapped molecules reach a balance between evaporation & condensation

A. Phase Changes  Vapor Pressure pressure of vapor above a liquid at equilibrium IMFv.p.tempv.p. depends on temp & IMF directly related to volatility p.478 temp v.p.

A. Phase Changes  Boiling Point temp at which v.p. of liquid equals external pressure IMFb.p.P atm b.p. depends on P atm & IMF Normal B.P. - b.p. at 1 atm

 Which has a higher m.p.? polar or nonpolar? covalent or ionic? A. Phase Changes  Melting Point equal to freezing point polar ionic IMFm.p.

A. Phase Changes  Sublimation solid  gas v.p. of solid equals external pressure  EX: dry ice, mothballs, solid air fresheners

A. Phase Changes Energy RequiredEnergy Released Solid  Liquid Melting or fusion Liquid  Solid freezing Liquid  Gas Vaporization, evaporation or boiling Gas  Liquid condensation Solid  Gas sublimation Gas  Solid deposition

Heating Curves

A. Heating Curves Kinetic Energy Changes – Heat Energy speeds up the molecules. Potential Energy Changes – Heat energy separates the molecules from solid to liquid, liquid to gas.

A. Heating Curves  Temperature Change change in KE (molecular motion) depends on heat capacity  Heat Capacity energy required to raise the temp of 1 gram of a substance by 1°C

A. Heating Curves  Phase Change change in PE (molecular arrangement) temp remains constant Phase Change Diagrams Show the phases of a substance at different temperatures and pressures.

 The energy involved in a phase change is calculated using:  Heat of Fusion (  H fus )  Heat of Vaporization (  H vap )

Heat of Fusion  Heat of Fusion is the energy required to change 1 gram of a substance from the solid to the liquid state without changing its temperature.  This energy breaks down the solid bonds, but it leaves a significant amount of energy associated with the intermolecular forces of the liquid state. Heat of Fusion is used for calculations involving the phase changes of solid  liquid or liquid  solid

A. Heating Curves  Heat of Vaporization (  H vap ) energy required to boil 1 gram of a substance at its b.p.  EX: sweating, steam burns, the drinking bird