INTERMOLECULAR FORCES PAGE 56 IN NOTEBOOK

Intramolecular force Forces with in the molecule These would be the bonds formed between two elements Types of intramolecular forces Ionic bonds Covalent bonds Metallic bonds

INTERMOLECULAR FORCES Introduction: The physical properties of melting point, boiling point, vapor pressure, evaporation, viscosity, surface tension, and solubility are related to the strength of attractive forces between molecules. These attractive forces are called Intermolecular Forces. The amount of "stick togetherness" is important in the interpretation of the various properties listed above. There are four types of intermolecular forces. 1. Ionic forces (strongest) Van der Waals forces 2. Hydrogen bonding 3. Dipole-dipole 4. London dispersion forces (weakest)

IONIC FORCES-the strongest forces

FORCES BETWEEN MOLECULES There are 3 basic types of van der Waals interaction between molecules (in order of increasing strength): London dispersion forces (very weak) dipole-dipole interactions hydrogen bonds (strong) these secondary bonding interactions, involve the electrons (atomic glue!).

LONDON DISPERSION FORCES-very weak forces

2. DIPOLE FORCES Polar covalent molecules are sometimes described as "dipoles", meaning that the molecule has two "poles". One end (pole) of the molecule has a partial positive charge while the other end has a partial negative charge. The molecules will orientate themselves so that the opposite charges attract principle operates effectively.

DIPOLE FORCES

HYDROGEN BONDING-strong bonds Bond between a partially positively charged hydrogen and a negatively charged second element

Water as a "perfect" example of hydrogen bonding Things to know about water!!!! UNIVERSAL SOLVENT BENT MOLECULAR GEOMETRY And WATER IS POLAR!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ALL DUE TO HYDROGEN BONDING!!!!!!

Surface tension of water SKIN OR LAYER ON TOP OF WATER DUE TO HYDROGEN BONDING THIS IS WHY IT HURTS TO DO A “BELLY BUSTER” INTO A POOL OR LAKE!!!!!!

Cohesion and Adhesion

ice floats on water Because ice is less dense than water due to the arrangement of hydrogen bonds

On a separate sheet of paper IMF A layer questions What is the difference in an intermolecular force and an intramolecular force? What is the strongest IMF? What is the weakest IMF? Draw three water molecules. Then form hydrogen bonds between them. STAPLE TO YOUR UNIT SHEET AND TURN IN