3. Learning
Objectives
• At the end of the
lesson, you are
expected to:
1. Identify the common types of
intermolecular forces of
attraction (IMFA) using
diagrams.
2. Differentiate Dipole-dipole
forces, London dispersion
forces, ion-dipole forces, and
hydrogen bonding in terms of
relative strength; and
3. Illustrate what type of IMFA
is/are present in a molecule.
5. Intermolecular
Forces
• attractive forces present
in between molecules
4 common types of
intermolecular forces of
attraction (IMFA)
London dispersion forces
dipole-dipole forces
ion-dipole forces
hydrogen bonding forces.
collectively known as van der
Waals forces of attraction,
named after the Dutch scientist
Johannes van der Waals.
6. London Dispersion
Forces (LDFs)
• weakest type of IMFA and are
present in between all
electrically neutral molecules ―
polar and nonpolar molecules.
• named after the German-
American physicist Fritz
London who proposed the
origin of these intermolecular
attractions.
• when an atom, which is usually
nonpolar, becomes polar due to
the continual motion of its
electrons resulting in a temporary
dipole or instantaneous dipole
• The temporary dipole of a
molecule induces instantaneous
dipoles to neighbor molecules.
7. London Dispersion
Forces (LDFs)
• When more electrons are
present in a molecule, the
stronger the LDFs are
because larger molecules
are more polarizable.
• Polarizability is the
measure of how easy it
is to distort the electron
distribution of a
molecule.
8. Ion-Dipole Forces
• This results from the
electrostatic attraction of a
molecule containing a dipole
and an ion.
• Electrostatic attraction is the
phenomena of opposite
charges being pulled to one
another. The negative charge
of electrons is attracted to the
positive charge contained
within a nucleus.
When NaCl dissolves in water, it
exists as Na+ and Cl- . The
cation Na+ is attracted to the
partially negative O atom of water
while the anion Cl- is attracted to
the partially positive H atom of
water.
9. Hydrogen
Bonding
• It is a special kind of dipole-
dipole force and one of the
strongest types of IMFA.
• Hydrogen bonding is an
attractive force that exists
when hydrogen is bonded to
F, O, or N.
10. Hydrogen
Bonding
• In such cases, the partially
positive hydrogen of one
molecule interacts with the
partially negative F, O, or N
atoms in another molecule
• This relatively strong attraction
explains why molecules with this
type of IMFA tend to have high
boiling and melting points.
11. Hydrogen
Bonding
• Some molecules may also
interact with water even
though they cannot form
hydrogen bonds themselves.
• Take the case of
formaldehyde and
water
Water Formaldehyde
Formaldehyde does not
exhibit hydrogen bonding
on its own.
12. Water Formaldehyde
Formaldehyde does not
exhibit hydrogen bonding
on its own.
• However, in the presence of
water, the O atom of
formaldehyde can form hydrogen
bonds with the H atoms of water.
13. Dipole-Dipole
Forces
• These are attractive forces
that are a moderately strong
type of IMFA and are present
in between polar molecules.
• Dipole-dipole forces are the
result of the electrical
interactions among dipoles
on neighboring molecules.
• This means that the partially
positive end of one molecule
interacts with the partially negative
end of a neighboring molecule.
14. • Formaldehyde becomes a
hydrogen bond acceptor
while water is the hydrogen
bond donor.
A hydrogen bond donor is
a molecule that provides the
hydrogen atom participating
in a hydrogen bond while a
hydrogen bond acceptor is
a molecule that contains the
lone pair-bearing
electronegative atom.
15.
16. This refers to the measure of the degree of inequality in
the attraction of electrons between atoms in a
molecule.
Question
Challenge: Sing your answer.
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POLARITY
17. If the electronegativity difference range of a certain
molecule is 0.2 then what type of bond exist in that
molecule?
Question
Challenge: Sing your answer.
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NON POLAR COVALENT BOND
18. The maximum amount of solute that dissolves in a
given quantity of solvent.
Question
Challenge: Cry out your answer.
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SOLUBILITY
19. TRUE OR FALSE. “ Like dissolves like”
Question
Challenge: Open your camera and dance
while saying your answer
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TRUE
20. Question
Challenge: Say your answer 20 times in just 5 seconds.
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TRUE OR FALSE. Polar molecules have lower
boiling point than non polar ones.
FALSE
21. Question
Challenge:
Open your camera and dance “otso-otso”
while saying your answer.
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This is a molecule that has a polar and non-
polar end.
EMULSIFIER
22. Polar: Asymmetrical; Nonpolar: ________.
Question
Challenge: Say your answer with a goat
sound
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SYMMETRICAL
23. Question
Challenge:
Open your camera and dance “otso-otso”
while saying your answer.
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Hydrophobic : water-fearing;
Hydrophilic : _____________
Water-Loving
24. Question
Challenge: Laugh out your answer.
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The temperature at which a solid turns
into liquid.
MELTING POINT
25. Question
Challenge: Read the statement without including letter “O”
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JUST READ. Polar molecules have relatively
stronger forces of attraction compared with
nonpolar ones, a greater amount of heat must be
applied to break these forces, thereby it has higher
melting point.
