Grab a small whiteboard Drill Grab a small whiteboard What is the formal charge on each atom in the following structure? What is the overall charge on the molecule?

Drill – Part 2 What is the Lewis structure of PO4-3?

Check HW and Review of some concepts IMF Lab More IMF practice Agenda Registration Stuff Check HW and Review of some concepts IMF Lab More IMF practice

Let’s Discuss… What is the difference between intramolecular and intermolecular forces?

Intra – within a molecule Inter – exist between molecules

Ionic Polar covalent Nonpolar covalent When referring to intramolecular forces, which one of these is the strongest? Ionic Polar covalent Nonpolar covalent

3 Types of Intermolecular Forces (IMF) London Dispersion (weakest) Dipole-dipole Hydrogen

Chart = Important

T or F? All molecules have dipole-dipole interactions?

False – all compounds have London Dispersion forces NOTE: The more electrons a molecule has, the stronger the Dispersion forces

The stronger the intermolecular forces of attraction, the more energy is required to break those forces.

What type of IMF is involved? SiCl4 1. Dispersion 2. Dipole-Dipole 3. Hydrogen

Dispersion forces Nonpolar molecule

What type of IMF is involved AsCl3 and H2S bond together?

Both are polar molecules – so dipole

Lab Time!

Molecular Weight Mass of a molecule As the weight increases, IMF increases

Surface Tension The stronger the intermolecular forces in the liquid, the greater the surface tension

Strong odor indicates weak IMF because of lower vapor pressure compound can have an odor only when its vapor pressure is sufficient to supply a noticeable amount of vapor to the nose. If intermolecular forces are strong, vapor pressure is low, because molecules have less free energy in the solid or liquid than as vapor.

Evaporation Rate The stronger the intermolecular forces in a liquid, the slower the evaporation rate because the molecules are held together by stronger attractions. You should note that a liquid doesn't necessarily have to reach boiling point before evaporation can occur. Evaporation takes place all the time. 

Safety Goggles! Place bookbags on table/away from lab stations You will have 4 minutes at each station Make sure cap is back on the bottle ASAP!!

When you are done… Answer analysis questions Place lab in the bin Start IMF Practice – You will get an answer key Use your own notes to help you!  Start Review Packet

Next Week Monday: Finish IMF and Review Wednesday: Unit 3 Test