Sparks
CH301
WHY IS EVERYTHING SO
DIFFERENT?
Gas, Liquid or Solid?
UNIT 3 Day 8
What are we going to do today?
Compare intermolecular forces for different molecules.
Discuss the effect of these forces on properties of
substances.
Properties of Liquids in context of IMF
Quiz: Clicker Question
INTERMOLECULAR FORCES: fact check
Octane, C8H18, has a boiling point around 130⁰C while
water has a boiling point of 100⁰C. How is this possible?
A. Octane has more hydrogen bonding than water.
B. The London forces in octane must be stronger than the
hydrogen bonding in water.
C. This cannot be possible; octane must have a lower
boiling point than water since octane does not exhibit
hydrogen bonding.
D. Octane is more polar than water and therefore has very
strong dipole-dipole forces.
Quiz: Clicker Question
Which of the following has a higher boiling point?
A
Saturated Fatty Acid
B
Unsaturated Fatty Acid
Intermolecular Forces
IMF
Ion-Ion
Dipole-Dipole
Hydrogen Bonding
Dispersion Forces
Intermolecular Forces: Dipole-Dipole
Intermolecular Forces: Hydrogen Bonding
Intermolecular Forces: Induced DipoleInduced Dipole
Dispersion Forces
London Forces
Van der Waal’s Forces
Induced dipole-Induced dipole
Poll: Clicker Question
For these substances:
• helium
• isooctane (C8H18 in a straight chain)
• Methane, CH4
• calcium carbonate
• glycerol (possesses three OH groups, viscous liquid)
• sucrose (possesses six OH groups, solid, sugar)
• Sodium chloride
List in order of predicted increasing boiling point.
Poll: Clicker Question
Which lists these from lowest to highest boiling point?
A. He, methane, isooctane, glycerol, sucrose, NaCl, CaCO3
B. isooctane, methane, He, sucrose, glycerol, CaCO3, NaCl
C. CaCO3, NaCl , sucrose, glycerol, isooctane, methane, He
D. He, methane, isooctane, glycerol, sucrose, CaCO3, NaCl
E. glycerol, sucrose, He, methane, isooctane, NaCl, CaCO3
Complete question 5 on page 74.
Quiz: Clicker Question
The BP of Sn hydride less than the BP of the Te hydride because:
a) The Sn compound has a larger dipole
b) The Sn compound has a smaller dipole
c) The Sn compound is more polarizable (and therefore has stronger
London forces)
d) The Sn compound is less polarizable (and therefore has weaker
London forces
e) The Sn compound has more H bonding
Quiz: Clicker Question
The BP of S hydride less than the BP of the Te hydride because:
a) The S compound has a larger dipole
b) The S compound has a smaller dipole
c) The S compound is more polarizable
d) The S compound is less polarizable
e) The S compound has more hydrogen bonding
Quiz: Clicker Question
The BP of O hydride higher than the BP of the Te hydride because:
a) The O compound has a larger dipole
b) The O compound has a smaller dipole
c) The O compound is more polarizable
d) The O compound is less polarizable
e) The O compound has more hydrogen bonding
WHAT HAVE WE LEARNED TODAY?
CLASSIFY INTERMOLECULAR FORCES
ION-ION, DIPOLE-DIPOLE, INDUCED DIPOLE –
INDUCED DIPOLE
PREDICT WHAT TYPE OF IMFs EXIST FOR A
PARTICULAR COMPOUND
CONDENDSED PHASES EXIST BECAUSE OF IMFs –
ELECTROSTATIC FORCES VARY WITH
SHAPE/SIZE/COMPONENTS OF COMPOUND –
PROPERTIES OF LIQUIDS DEPEND ON IMFs
• VARIOUS PHASE TRANSITION TEMPERATURES
• VAPOR PRESSURE
Learning Outcomes
Define the three major types of intermolecular forces
(IMF) discussed in class: dipole-dipole, H-bonding, and
dispersion (London, van der Waals, induced dipoleinduced dipole)
Explain how molecular size and shape affect
the magnitude of the dispersion forces
Use a compound’s molecular structure to predict the
types of IMFs that exist in the condensed phase
Relate the IMFs to liquid properties such as boiling point,
vapor pressure, viscosity and surface tension