1. Intermolecular Forces

2. Kinetic Molecular Theory  Describes the behavior of subatomic particles Liquids, solids, and gases are composed of small particles that have mass. Particles are in constant, random, rapid motion. Particles have collisions. Particles have an avg. KE directly related to temperature. The state of a substance at room temperature depends on the strength of the attractions between its particles.

3. Definition of IMF  Attractive forces between molecules.  Much weaker than chemical bonds within molecules.

4. Definition of IMF  Intramolecular forces: Covalent Bonding  Much stronger than chemical bonds between atoms.  Examples : nonpolar, polar sharing

5. Definition of IMF  Intermolecular Forces  Attractive forces between molecules.  Much weaker than chemical bonds within molecules.

6. Intermolecular Forces  Attractive forces between molecules or particles (ions, metal atoms, etc…)  Examples:  dispersion, (London /Vander Waals);  dipole-dipole,  dipole-ion,  hydrogen “bonding”,  metallic bonding,  ion-ion

7. Intermolecular Forces  Relative Strength:  Examples:  dispersion, (London /Vander Waals);  dipole-dipole,  dipole-ion,  hydrogen “bonding”,  metallic bonding,  ion-ion Weakest Strongest

8. Types of IMF

9.  London Dispersion Forces View animation online.animation

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

11. Types of IMF  Hydrogen Bonding

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

13. Physical Properties Liquids & Solids

14. 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

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

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

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

18. Types of Solids Ionic (NaCl) Metallic

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

20. Liquids & Solids Changes of State

21. Phase Changes

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

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

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

25. 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.

26. 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

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

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

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

30. 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

31. 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.

32. 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

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