Molecular Forces

Intramolecular Forces- Forces between atoms that hold molecules together and determine the chemical behavior or substances

• Ionic

• Covalent

Intermolecular Forces- Forces between molecules

• Dipole-dipole interactions

• Hydrogen Bonding

• London Dispersion Forces

Intermolecular Forces

• Much weaker than intramolecular bonds but they are important because they determine physical properties of the molecules :

  -Melting Point

  -Boiling Point

  -Density

  -Viscosity

  -Volatility

• There are three types of intermolecular forces

1. Dipole-dipole interactions

2. Hydrogen Bonding- Important in Water and DNA

3. London Dispersion Forces

• More polarized bonds in a molecule results in greater intermolecular attractions

• Greater intermolecular attractions have higher melting and boiling points, greater viscosities, and lower volatiles than non-polar covalent compounds.

Examples: Honey and Syrup

Scenario: If I wanted to pour honey into a container, it would flow very slow. To quicken the process, I would need to heat up the honey to break/ weaken the intermolecular forces to make it flow quicker,

Strong V.S. Weak Intermolecular Bonds

Strength of Intermolecular Forces

Strength of Intramolecular Forces