Unit 5B: Soap
Section 5.4- 5.6
Section 5.4 Polarity of Molecules
Draw a molecule of N 2
Shows two atoms sharing electrons equally.
Each N has a EN value of 3.0. The difference in these values is zero. Therefore, the atoms pull evenly on
the electrons. This is a Non-Polar covalent bond.

All compounds that contain non-polar covalent bonds are NONPOLAR MOLECULES!
Draw a molecule of H2S
Shows unequal sharing of electrons:
EN values: Sulfur = 2.5 Hydrogen = 2.1 The difference in electronegativiy is 0.4 therefore the sulfur
pulls on the electrons slightly more, pulling them towards the sulfur atom. This is a polar covalent
bond.
Draw a molecule of CH2O
Shows unequal sharing of electrons.
EN values: Hydrogen= 2.1 Carbon = 2.5 Oxygen = 3.5
(C-O bond: EN difference of 1.0). The oxygen atom because of its higher EN value pulls significantly
harder on the electrons than the carbon does. This creates a polar covalent bond.
(C-H bond: EN difference is only 0.4 which is not strong enough to create partial charges)
*** exception*** C-H bonds are nonpolar!
Showing partial charges (polarity):
 Use δ for “partial” with a + or – to indicate the partial negative end and partial positive
end.
 Use an arrow pointing towards the partial negative atom with a “plus” tail at the partial
positive atom
 These are referred to as dipoles WHICH ARE ___________________________________
Practice: If the bond is polar, draw the polarity arrow:
C-H
O-Cl
F-F
C-Cl
Unit 5B: Soap
Section 5.4- 5.6
Polar Bonds versus Polar Molecules
 Dipoles must move in equal but opposite directions in order for the forces to cancel and
molecule to be NONPOLAR.
 Not every molecule that has a ____________bond is polar itself. If the polar bonds form
dipoles that cancel out due to geometry, then the molecule is overall
________________.
The dipoles cancel out.
No net dipole
The dipoles do not cancel out.
Net dipole
Shape is important in predicting polarity. All molecules must be drawn in the correct shape to
see proper canceling of dipoles.
Let’s Practice:
Draw the molecule for ammonia, NH3. Is it polar or non-polar? What shape is it?
Draw the molecule for dihydrogen monosulfide, H2S. Is it polar or non-polar? What shape is it?
Draw the molecule for carbon dioxide, CO2. Is it polar or non-polar? What shape is it?
Draw the molecule for carbon tetrachloride, CCl4. Is it polar or non-polar? What shape is it?
Unit 5B: Soap
Section 5.4- 5.6
Lets Make this Simple
 Nonpolar bonds= Nonpolar molecule.
 Polar bonds with a lone pair on the central atom = most likely be a polar molecule
 Polar bonds & no lone pair on central atom but all terminal atoms are the same =
nonpolar molecule. If terminal atoms are different, its polar.
Diamond & Graphite
Sketch each molecule & notice major differences.
Section 5.5 : Intermolecular Forces (IMF)
Intra-molecular forces versus inter-molecular forces-----THERE IS A DIFFERENCE!!!!!
Intramolecular forces are forces _____________the molecule (in the chemical bonds).




Breaking intramolecular forces within the molecule is a CHEMICAL CHANGE.
Bonds are broken and new bonds form to make new molecules.
Example: ___________________________________________
It requires a _______________amount of energy to break than an intermolecular force.
Intermolecular forces are forces that occur ________________separate molecules.




Breaking of intermolecular forces (between separate molecules) is a PHYSICAL CHANGE.
Example: breaking glass & Boiling water
Example: ____________________________________
Does not require as much energy to break
Types of Intermolecular Forces
London dispersion forces
 Occurs primarily in NONPOLAR molecules but are found in ALL molecules!
 “electrons” momentarily move toward one side (or gang up on one side)
 A _____________________ is created and the molecule is temporarily polar
Unit 5B: Soap
Section 5.4- 5.6
 The ______________area of one temporarily polar molecule can be attracted to the
negative of another molecule.
Draw a diagram:
 London Dispersion (LDF) are the weakest of the intermolecular forces because
molecules can’t form all the time.
 Larger molecules have _______________________London Dispersion forces than
smaller molecules. Explains why Chlorine is a gas(34 e-); Bromine is a liquid (70 e) and
Iodine is a solid (106 e)
Dipole-Dipole Forces
 Polar molecules have permanent _____________.
 The positive area of one molecule can be attracted to the ________________area of
another.
 The partial positive and partial negative “poles” are shown in a diagram as
________________.
 Dipole-dipole forces are _______________than London dispersion forces.
Draw a diagram:
Hydrogen Bonding
 A special dipole force between a hydrogen atom and _______, __________, or
____________________
 A very strong ________________forms since F, O, and N are all very small, highly
electronegative atoms.
Draw a diagram:
Hydrogen bonding is the strongest of all the intermolecular forces.
Unit 5B: Soap
Section 5.4- 5.6
Rank the forces of attraction from weakest to strongest
1. Rank the Intramolecular Forces: Ionic, Covalent, and Metallic
_______________________________________________________________
2. Rank the Intermolecular Forces: Dipole, London Dispersion, Hydrogen bonding
_______________________________________________________________
3. Rank ALL the Forces
________________________________________________________________________
________________________________________________________________________
Section 5.6: Intermolecular Forces and Properties
 The number and ____________________of IMF affects the properties of the
substances.
 ______________is required to break IMF’s.
 Energy is ______________when new IMF’s are formed.
IMF and Changes in State (melting, boiling, etc. )




From solid to liquid: some IMF’s are broken
From liquid to gas: the remainder of IMF’s are broken
This requires energy = ENDOTHERMIC PROCESS.
The ______________the IMF the more energy required to melt, boil, or evaporate.
Stronger IMF = higher melting and boiling point.
A Word or Two about Water
 Water is a small molecule and generally speaking smaller molecules have low melting
and boiling points. Water is an exception to this statement.
 Water is polar and can form ________________interactions and __________bonding.
Its boiling point is much higher as a result.
Viscosity
 ________________--to flow
 Molasses is more viscous than water.
 _______________-molecules and molecules with high IMF’s “stick” together more.
More sticking together = higher viscosity.
Unit 5B: Soap
Section 5.4- 5.6
Solubility
 Solute: _____________________________________
 Solvent: ____________________________________
 Dissolving process:
o Water breaks some IMF with other molecules to allow them to spread out.
o New IMF begin to form with solute molecules
o As these new IMF’s form, the solvent “carries off” the solute
 “like dissolves like”: polar solvents dissolve polar solutes; non-polar solvents dissolve
non-polar solutes. Polar solvents can also dissolve _____________________ because of
the charged ends.
 Example: oil and water: water is polar. Oil is non-polar. Oil will not dissolve in water.
Surface Tension
 Surface tension is the resistance of a liquid to _______________________.
 Due to _________________-IMF’s.
 Higher IMF = higher surface tension.
Soap and Water
 Soap has a _________________-head and a ______________tail.
 The polar part interacts with _________________. The non-polar part interacts
with _________________________.
 The soap surrounds the “dirt” and the outside of the micelle interacts with
__________.
 The soap disturbs the water molecules ability to _______________together to
form IMF’s.
 Soap lowers the ______________ ________________ of water to allow the
water to spread over dirty dishes.