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

Intermolecular Forces Intermolecular forces – occur between molecules Intramolecular forces – occur inside the molecules

Intermolecular Forces Dipole – dipole attraction

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

Intermolecular Forces Hydrogen Bonding Affects physical properties Boiling point

Water and Its Phase Changes Heating/cooling curve

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

Boiling Point and Vapor Pressure

The Solid State: Types of Solids

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

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

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

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)

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

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

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