Intermolecular forces Definition The forces of attraction between

Intermolecular forces • Definition: The forces of attraction between neighboring molecules are called intermolecular forces. • These attractions are much weaker than either an ionic or a covalent bond. • These forces hold polar and non polar covalent molecules together so that liquids and solids can form

Forces of Attraction determine the phase at Room Temperature • According to the kinetic-molecular theory, the state of a substance at room temperature depends on the strength of the attractions between its particles.

The stronger the intermolecular forces, the higher the boiling point of a liquid 1. Weak Intermolecular forces are found in the gas phase of matter at room temperature and pressure. 2. Moderate Intermolecular forces are found in the liquid phase of matter at room temperature and pressure. 3. Strong Intermolecular forces are found in the solid phase of matter at STP. 4. Molecules with stronger intermolecular forces will have higher boiling points.

3 Types of Intermolecular Forces • Van der Waals forces (also called London Dispersion forces) • Dipole-dipole forces • Hydrogen bonding

Dipoles… - Temporary Dipole forms when electrons momentarily shift to one side of an atom at random. Very Temporary. - Induced Dipoles occur when a neighboring molecule moves past one with a temporary dipole. - Permanent dipoles is the result of a polar bond in the molecular structure.

Van der Waals Forces • Weakest Intermolecular Force • Caused by temporary dipoles • Present in both nonpolar and polar molecules • The larger the molecule the greater the Van der Waals forces.

Dipole Forces • Stronger than Van der Waals forces • Form due to Permanent dipoles in Polar Molecules only. • Opposite charged ends of the molecules attract.

Hydrogen Bond • Not really a bond just a very super strong attraction! • Occur only in molecules that have hydrogen bonded to F, O or N. • The strongest Intermolecular bond!