1. Notes: 13.2 OBJECTIVES: Students will be able to (SWBAT)
Predict the type of intermolecular forces that will affect molecules
QUESTIONS TO PONDER:
What is the difference between intermolecular and intramolecular attractions?
What are some examples of different type of IMFs?
What factors affect the types of IMFs molecules experience?
What are some properties affected by IMFs?

2. Forces of Attraction (13.2)
Intermolecular forces (IMF)
the forces between molecules or particles.
Intramolecular forces
the forces within molecules or particles.
Intramolecular force
Intermolecular force

3. Intramolecular Forces
Intramolecular forces are the forces within the compound itself  the bonds between atoms in a compound or molecule
Ionic
Covalent
Metallic
ionic
metallic
covalent

4. 4 Types of Intermolecular Forces
dispersion or London Forces (weakest)
Dipole-induced interactions (stronger)
Dipole-dipole interactions (even stronger)
Hydrogen-bonding (strongest)

5. London Dispersion Forces
dispersion or London Forces (weakest)
between 2 or more nonpolar molecules
When the electron cloud of one nonpolar molecule nears another nonpolar molecule, electrons will temporarily shift or disperse
When close enough, the dispersed electrons to one end will be more negative and attract to the more positive side of another nonpolar molecule (side with less disperse electrons)

6. London Dispersion Forces

7. Dipole-dipole interactions
Dipole-dipole (stronger)
between 2 or more polar molecules
Positive end of one molecule is attracted to the negative end of another molecule

8. Dipole-induced interactions
When a polar molecule causes a nonpolar molecule to temporarily have a dipole by dispersing its electron cloud
Attraction strength is between dispersion and dipole-dipole
POLAR
NONPOLAR
TEMPORARY DIPOLE

9. Hydrogen Bonds (H-bonds)
Type of dipole-dipole force
Occurs when molecules have H attached to F, O, or N (high EN)
Ex H2O
Strongest attraction out of the intermolecular forces

10. Factors that affect IMF Strength
Type of IMF (London, dipole-dipole, H-bond)
Molecular Weight (big vs small, long vs short)

11. Hydrocarbons
Hydrocarbons are molecules that contain mostly C’s and H’s (sometimes O’s and N’s and others)
They can be very big because C can link together in a long chain
They can form rings as well
Hydrocarbons that are only C’s and H’s and are symmetrical are generally nonpolar
Straight-chained hydrocarbon
Ringed hydrocarbon

12. Nonpolar hydrocarbon – more “even” areas
Polar hydrocarbon – an area that is more positive or negative than the rest

13. Molecular Weight
Larger mass  stronger interactions between atoms  more “cloud” to move around
CH4 is a gas at room temperature
C8H18 is a liquid at room temperature
Most likely a gas at room temperature
Most likely a liquid or solid at room temperature

14. Boiling and Melting Point
Melting point (mp)  when a solid becomes liquid
Boiling point (bp)  when a liquid becomes a gas
Stronger interactions  harder to pull apart  more likely a liquid or a solid
Higher mp or bp  more heat/energy to pull apart molecules because stronger IMFs
Polar: higher mp/bp than nonpolar
Heavier nonpolar: higher mp/bp than lighter nonpolar

15. Bond type
Covalent
Nonpolar
Small
Polar
Ionic

16. Forces: weakest to strongest
Hydrogen bond
Dipole-dipole
london
intramolecular