1. Intermolecular Forces

2. What are IMF’s?
INTERmolecular forces—attractions between molecules that can vary from strong to weak.
IMF’s are always weaker than INTRA molecular forces, the forces that hold atoms together in a compound (Ionic, Polar Covalent, Nonpolar Covalent).

3. What properties do IMF’s affect & WHY?
High Melting Points/ High Boiling Points
High Viscosity
High Surface Tension
Low Vapor Pressure = Strong IMF’s like Hydrogen Bonding
WHY?
Strong IMF’s mean molecules like to stay close. So they won’t melt or boil easily; liquids will be thick and “sticky”; liquids will NOT turn into vapors/gases easily.

4. Types of IMF’s Bond IMF Characteristics Results in Ionic
Strongest. Holds ionic crystals together.
High MP/BP.
Solid
Covalent
Hydrogen Bonding
polar
2nd strongest. Special D-D that happens only when H is on one end of a polar molecule and F, O, or N are on the other end.
High MP/BP, surface tension, etc.
Liquid, Solid
Dipole-Dipole
Weaker. Occur between – and + ends of polar molecules.
Medium MP/BP
Liquid, Gas
London
Dispersion
Forces
nonpolar
Weakest. Occur between ALL atoms and nonpolar molecules.
Low MP/BP
Gas usually

5. Types of IMF’s Bond IMF Characteristics Examples Ionic
Strongest. Holds ionic crystals together.
Covalent
Hydrogen Bonding
polar
2nd strongest. Special D-D that happens only when H is on one end of a polar molecule and F, O, or N are on the other end.
Dipole-Dipole
Weaker. Occur between – and + ends of polar molecules.
London
Dispersion
Forces
nonpolar
Weakest. Occur between ALL atoms and nonpolar molecules.