Intermolecular Forces

1. Intermolecular Forces Unit 3 Day 5

2. Do Now/Catalyst (8 min) Entrance Slip: Write your name and period at the top. • If you did not do Day 2, Day 3 or Day 4 Questions, do those now • Answer the questions under Day 5. • You may use your notes. • SHOW: • Calculation to find the number of bonds (2 pts) • Correct Lewis Structure (2 pts)

3. How are you doing?

4. Announcements Edmodo – see class codes on board ACT tutoring Sat 9am-12pm Behavior Grade every two weeks - login Office hours: Tuesday, Wednesday and Thursday New homework policy – NO late work accepted BRING YOUR NOTES PACKET EVERYDAY!

5. Objectives: Intermolecular Forces SWBAT define Van der Waals, Dispersion, Dipole-Dipole, and Hydrogen Bonding forces and compare their relative strengths.

6. Real World! Water Striders can walk on water because of hydrogen bonding and strong attractions in the water molecules!

7. Intermolecular Forces Intermolecular Forces are forces between individual atoms or compounds that hold molecules together. They are weaker than the bonds between atoms in a molecule, which are called intramolecular forces. Reminder: dipole results from differences in electronegativity, which produce small charges on atoms in a molecule.

8. Intermolecular Forces • Intermolecular forces come in three types, depending on polarity. • Dispersion Forces • Dipole-Dipole Forces • Hydrogen Bonding

9. Dispersion Forces Result from interactions between molecules, temporary charges between non-polar molecules. They are very weak.

10. Dispersion Forces: Diagram

11. Dipole-Dipole Interactions • Result from permanent partial charges. These forces are also polar, and thus slightly stronger than dispersion forces. • Note: Both Dispersion Forces and Dipole-Dipole Interactions are sometimes called van der waals forces.

12. Dipole-Dipole Interactions: Diagram

13. Hydrogen Bonding Very similar to intramolecularforces. These are strong and permanent forces (“bonds”) that result from a special type of polar attraction. Form between H and either N, O, F or Cl ONLY.

14. Hydrogen Bonding: Diagram

15. We Do: CFU #1 Order these forces from strongest to weakest: Hydrogen Bonding, Dispersion Forces, Dipole-Dipole Interactions, Covalent Bonds. Covalent bonds, hydrogen bonding, dipole-dipole interactions, dispersion forces

16. We Do: CFU #2 True or False: Intermolecular Forces hold the atoms in a molecule together False

17. We Do: CFU #3 True or False: These forces rely on differences in polarity, which produces small charges on the molecules. True

18. We Do: CFU #4 Do you think it would be harder to pull a molecule away from a compound that was held together using Hydrogen Bonds or Dipole-Dipole Interactions? Why? • Hydrogen bonds, they have stronger interactions

19. We Do: CFU #5 Do forces get stronger or weaker as differences in electronegativity increase (as polarity increases)? Stronger

20. You Do: Forces Poster (20 min) Fold paper into 3 sections, one for dipole interactions, dispersion forces and hydrogen bonding. On your posters include the following information for each force (use notes and p.250-51 of text): Definition 2 facts One real world example (except for Dipole) Drawing/diagram

21. Chemistry Interim Test Counts as a grade so do your best! Mark all answers on your answer sheet 25 questions

22. Closing Essential Question: What holds the individual molecules in a compound together?