Liquids & Solids I. 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

II. 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)

Ch Liquids & Solids III. 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

Heating Curves

A. Heating Curves Melting - PE  Solid - KE  Liquid - KE  Boiling - PE  Gas - KE 

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 “Volcano” clip - water has a very high heat capacity

A. Heating Curves  Phase Change change in PE (molecular arrangement) temp remains constant  Heat of Fusion (  H fus ) energy required to melt 1 gram of a substance at its m.p.

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

B. Phase Diagrams  Show the phases of a substance at different temps and pressures.