Grade 11 PhySci

3. PICTURE ANALYSIS

4. INTERMOLECULAR
FORCES

5. OBJECTIVES
 describe the types of intermolecular
forces present in substances, and
 identify the types of intermolecular
forces present between and among
substances

6. Intramolecular forces are forces that affect the
binding of atoms in a molecule. Intermolecular
forces are those that affect the binding of molecules
with other molecules.

7. They also include the forces of repulsion
or attraction between a molecule and
neighboring particles like atoms or ions.
We shall present three classes of
intermolecular forces.

9. Three general types of
intermolecular forces
(imf)

10. Three general types of intermolecular forces
• Van der Waals Forces
 dipole-dipole interaction
 dipole-induced dipole interaction
 dispersion forces
• Ion-dipole Interaction
• H-bonding

11. VAN DER WAALS FORCES
Johannes Diderik van der Waals was a
Dutch physicist and thermodynamicist
born on November 23, 1837, in Leiden,
Netherlands, and died on March 8, 1923,
in Amsterdam. He made significant
contributions to the fields of
thermodynamics and molecular sciences,
particularly in understanding the behavior
of gases and liquids.

12. VAN DER WAALS FORCES
-a general term used to define the attraction of
intermolecular forces between molecules.
 There are three kinds of Van der Waals
forces: weak London Dispersion Forces,
dipole induced dipole attraction and
stronger dipole-dipole forces.

13.  Dipole-Dipole Interaction
 Occurs between molecules that have permanent dipoles.
 A molecule with a permanent dipole has a partial positive
charge on one end and a partial negative charge on the other
due to differences in electronegativity between its
constituent atoms.
 The positive end of one polar molecule is attracted to the
negative end of another polar molecule, resulting in dipole-
dipole interactions.
 These forces tend to be stronger than dispersion forces but
weaker than hydrogen bonding.

14.  Dipole-Dipole Interaction
 Forces of attraction between oppositely charged ends of
polar molecules.
 The strength of the dipole-dipole force is dependent on the
polarity of the molecules

15.  A polar molecule induces a temporary dipole in a
neighboring non-polar molecule by reorienting its electron
cloud.
 This induced dipole induces a partial opposite charge in the
non-polar molecule, leading to an attraction between the
two molecules.
 While weaker than dipole-dipole interactions, dipole-
induced dipole interactions are still significant in
determining the properties of substances.
 Dipole-induced dipole interaction

17.  The weakest type of intermolecular force and are present in
all molecules, whether polar or non-polar.
 These temporary dipoles induce similar temporary dipoles
in neighboring molecules, resulting in an attractive force
between them.
 Dispersion forces increase with increasing molecular size
and surface area because larger molecules have more
electrons, leading to stronger temporary dipoles and hence
stronger dispersion forces.
 DISPERSION FORCES (London dispersion forces)

19. It occurs between an ion (either positively or
negatively charged) and the partial charges on the polar
molecules. Polar molecules have regions of partial
positive and negative charge due to differences in
electronegativity between their constituent atoms.
ION-DIPOLE INTERACTION

20. Ion-dipole interactions tend to be relatively strong
compared to other intermolecular forces such as London
dispersion forces or dipole-dipole interactions. The
strength of the interaction depends on the magnitude of
the charges involved and the distance between the ion and
the dipole.

23. Hydrogen bonding
It is a specific type of dipole-dipole interaction that
occurs between a hydrogen atom covalently bonded to a
highly electronegative atom (usually nitrogen, oxygen, or
fluorine) and a lone pair of electrons on another
electronegative atom in a different molecule.

24. Hydrogen bonds are typically stronger than
typical dipole-dipole interactions but weaker than
covalent or ionic bonds. However, they are stronger
than van der Waals interactions.

27. TYPES OF IMFA PRESENT IN… RELATIVE
STRENGTH
London Dispersion Forces All molecules WEAK
(increases with the size of the molecule)
Dipole-dipole Forces Polar molecules MODERATE
(increases with increasing polarity)
Ion-dipole Forces Solution of ionic compounds
dissolved in polar solvent
STRONG
(increases with increasing ionic charge)
Hydrogen Bonding Molecules with H-F,H,O,H-N
bonds
STRONG

29. ACTIVITY 5
Create a triple venn diagram and
state the similarities and differences of
Van der Waals forces, ion-dipole
interaction, and Hydrogen bonding.

30. PERFORMANCE TASK 2
Have you ever been attracted to someone? Now,
make a poem about how this someone (you are
attracted with) turns you into another version of you.
Just like how water turned into salt water after the
attraction with salt substance.

31. ASSESSMENT

32. TRUE OR FALSE
1.There are two types of forces.
2. Dipole-dipole interaction is the
attraction of the same charges of dipoles of
a molecule.
3. London dispersion forces is the
strongest type of intermolecular forces.
4. Water is an example of H-bonding.
5. Water is dissolved in salt.

33. ASSIGNMENT
This part will test whether you fully understood what intermolecular forces
are present between and among molecules. You can answer this by recalling
the strategies discussed earlier in this module. Remember also that there
may be more than one IMF present in the among molecules of the given
substances.
Identify the intermolecular forces present in the following substances.
1) Silicon tetrafluoride, SiF4
2) Acetone, CH2O
3) Methyl alcohol, CH3OH
4) Methane, CH4
5) Phosphorus trichloride, PCl3