1. Unit 8: Water + IMF experiencing the feel of world record swimming speed 10:30
Objectives
Define properties associated with water. (Cohesion adhesion surface tension)
Relate polarity of water to properties of water.
Define and identify the 3 intermolecular forces (IMF)
Rank the 3 IMF in terms of strength.
Words to know
Electronegativity Polar
Nonpolar Cohesion Adhesion
Surface Tension Intramolecular Intermolecular (Van der Waals)
Dipole-Dipole Hydrogen Bond London Dispersion (LD)

2. Water and some properties
Water has many properties, some of which are fairly unique to water.
The 3 properties for today are NOT unique to water. Any Polar substance should exhibit similar if not the same properties, to varying degrees.
Is water polar or nonpolar?
Why?
^ What is the significance?
Cohesion = attracts to itself
Surface Tension = Result of cohesion (tomorrow)
Adhesion = attaches to other polar molecules

5. Intermolecular Forces: Dipole-Dipole
3 Main intermolecular forces (IMF) aka Van Der Waals forces
From strongest to weakest; hydrogen bond, dipole-dipole, London dispersion (LD)
Dipole-Dipole (Medium strength)
Di = 2, the name means there are
2 poles and 2 more poles (+ and -)
ANY polar molecule will have
Dipole-dipole interactions
How can you tell if a molecule is polar?

6. IMF: Hydrogen Bond
Hydrogen bonds are the strongest IMF. (But weaker than intramolecular)
Hydrogen bond is a terrible name because….
1) They are not “chemical bonds”
2) They do involve hydrogen but not hydrogen bonded to hydrogen…
Hydrogen bonds occur when hydrogen bonds to F,O,N (3 very electronegative substances common in biology)
Copy the drawings of what are NOT Hydrogen Bonds

7. Hydrogen Bond Cont Hydrogen bonds are a type of dipole-dipole
They are some of the strongest dipole-dipoles because they use some of the most electronegative elements F,O,N
H,F,O, and N are also very common in nature and are important for our biology

9. London Dispersion (LD)
Weakest of the 3 IMF
Based off random motion of electrons
Everything with electrons has LD forces. Billionaire vs millionaire.
LD for non polar substances
Copy the Diagrams for LD and induced Dipole

10. Applications to molecules
What IMF do each of the following molecules posses?
Which molecule would have stronger IMF with itself?
Amino acid
(Part of protein)
Which molecule would have the higher boiling point?