Warm up Name the following compounds: FeSeAl(NO 3 ) 3 2. Write the Lewis dot structure for the following: H 2 SPBr 3 3. How many single bonds are in each compound from #2? Agenda -Turn in Lewis Dot WS -Go over Quiz Unit 4 -Notes Unit 4-5 -Lab Hydrogen Bond Homework Oct 29 - Extra credit due Oct 30 - Online HW unit 4 Nov 4 - Test Unit 4 + Notebook

Unit 4-5 Intermolecular Forces

Remember Polarity?   Polar covalent bond: unequal sharing of electrons due to differences in electronegativity, creating a partial charge.

Intermolecular Forces  Intermolecular force: an attraction between molecules in polar compounds Much weaker than normal bonds between atoms (ionic/covalent/metallic) Much weaker than normal bonds between atoms (ionic/covalent/metallic) 3 forces 3 forces

Intermolecular Forces 1. Dipole-dipole forces: interactions between positive ends to negative ends in polar molecules.

Intermolecular Forces 2. Hydrogen bond: a dipole-dipole force between molecules with hydrogen atoms. Many biological molecules are held together by this bond. (Ex: DNA, protein, lipids) These forces are strong These forces are strong

Hydrogen Bond  Adhesion: attraction between molecules of different substances  Cohesion: attraction between molecules of the same substance Surface Tension

Hydrogen Bond  Capillary Action: the ability of a liquid to travel up the surface of a solid due to attractive forces This is what causes the meniscus This is what causes the meniscus

Intermolecular Forces 3. London Dispersion Forces: forces between nonpolar molecules that have temporary induced dipoles (weak forces)

Intermolecular Forces   Bond/force strength affects a substance’s properties Stronger bonds means more energy is required to break them

Hydrogen Bonding Lab Property of H 2 O Materials: 2 pennies, 2 beakers, 1 pipet (clean it if has bubbles) When done with the lab Rinse everything Record = 81 drops

Assignments  Notes Summary  Lab Hydrogen Bond IMF due next class  Extra Credit Due Next Class