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

Dipole-dipole interactions
Hydrogen Bonding- Important in Water and DNA
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,

	Intermolecular Bonds	Intramolecular Forces
Definition	Forces Between Molecules	Forces Between Atoms
Weaker or Stronger (Than Other Force	Weak	Strong
What Characteristics Do they Determine?	Physical (Heating up the substance can allow it to flow quicker, which changes its physical properties.)	Chemical (By breaking the intramolecular forces, it will split the atoms which will change the element that it is.)
Is it a Force or a Bond?	Force	Bond
Three Types	1. Dipole-dipole Interactions 2. Hydrogen Bonding3. London Dispersion Forces	1. Ionic2. Polar Covalent3. Non-Polar Covalent

Strong V.S. Weak Intermolecular Bonds

Lab Tests	Strong Intermolecular Forces	Weak Intermolecular Forces
Viscosity	High	Low
Melting Point	High	Low
Volatility (Evaporation)	Low	High
Example	Honey, Syrup	Water

Strength of Intermolecular Forces

Intermolecular Force	Occurs Between?	Relative Strength
Dipole-dipole	Polar Molecule	Medium
Hydrogen Bonding	H-F, H-O, H-N	Strong
London Dispersion	Between All Molecules	Weak

Strength of Intramolecular Forces

Intramolecular Force	How is it Formed?	Relative Strength
Ionic	Transfer of Electrons	Strong
Polar Covalent	Unequal sharing of electrons	Medium
Non-polar Covalent	Equal sharing of electrons	Weak

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Intramolecular Forces V.S. Intermolecular Forces