Intermolecular Forces

1. Intermolecular Forces • Low density • Highly compressible • Fill container • Reviewing what we know • Gases • Solids • High density • Slightly compressible • Rigid (keeps its shape)

2. Intermolecular Forces • Intermolecular forces – occur between molecules • Intramolecular forces – occur inside the molecules

3. Intermolecular Forces • Dipole – dipole attraction

4. Intermolecular Forces • Hydrogen Bonding • Occurs between H and highly electronegative atom (for example N, O, F)

5. Intermolecular Forces • Affects physical properties • Boiling point • Hydrogen Bonding

6. Water and Its Phase Changes • Heating/cooling curve

7. Water and Its Phase Changes • Normal boiling point – at 1 atm = 100oC • Normal freezing point – at 1 atm = 0oC • Density • Liquid water = 1.00 g/mL • Ice = 0.917 g/mL

8. Boiling Point and Vapor Pressure

9. The Solid State: Types of Solids

10. Solids / Liquids calorie – Amount of energy required to raise the temperature of 1 gram of H2O by 1oC 1 calorie = 4.184 joules

11. Specific heat capacity (c) – The amount of energy required to change the temp. of 1 gram of a substance by 1oC.

12. H = mcDT H = heat m = mass c = specific heat constant DT (delta T) = temperature change Tf - Ti

13. c - liquid H2O = 1.0 cal/gm (4.184 j/gm) c - ice H2O = 0.5 cal/gm (2.092 j/gm) c - steam H2O = 0.5 cal/gm (2.092 j/gm)

14. H = Hf. m H = heat Hf = heat of fusion Hf for H2O = 80 cal/gm ; 334.72 J/gm m = mass

15. H = Hv. m H = heat Hv = heat of vaporization Hv for H2O = 540 cal/gm ; 2259.36 J/gm (2.3 kJ/gm) m = mass

16. Gas H=mcDT Temp (oC) Liquid H=mcDT Solid H=mcDT Time H2O Phase Change H=Hv*m Vaporize 100 Condense No temperature change occurs while: melting, freezing, vaporizing, condensing H=Hf*m Melt 0 Freeze