Liquids and Solids Zumdahl, Ch. 10

Try to remember - KMT Volume of the particle is negligible Particles are in constant random motion Particles exert no forces between each other

Intermolecular Forces (IMF) Also known as Van der Waals forces Dipole-Dipole Force Hydrogen Bonding London Dispersion

Intramolecular Forces Also known as bonds Ionic bond: 400 - 4000 kJ/mol Covalent bond: 150 – 1000 kJ/mol Intermolecular forces significantly less Importance of Intermolecular Forces (IMF) Freezing point and boiling point Vapor pressure

Dipole – Dipole Force Polar molecules attract each other 5 – 25 kJ/mol (decrease with distance)

Hydrogen “Bonding” Special case of dipole-dipole: 10-40 kJ/mol H atom and N, O, F, (Cl) Role in DNA structure THE example: H2O

London Dispersion Force Any molecule with positive nuclei and negative electrons has LDF. So, EVERYTHING HAS LDF! 0.05 – 40 kJ/mol Why such a huge range? As molar mass increases, LDF increases

LDF = Atomic-Sized Dipole

Summary of IMFs London Dispersion Dipole-Dipole Force Hydrogen Bonding Typically weakest IMF Dominates for large molecules Dipole-Dipole Force Found in polar molecules Dominates as EN differences increase Hydrogen Bonding H and N, O, F, (Cl) Typically the strongest IMF

IMFs Impact on Liquids As IMF increases, boiling point increases As IMF increases, vapor pressure decreases As IMF increases, surface tension increases As IMF increase, viscosity increases Capillary action