Lesson Objectives
• Atthe end of the lesson, students should be
able to:
• • Define intermolecular forces of attraction
(IMFA).
• • Identify and describe the different types of
intermolecular forces.
• • Differentiate intermolecular and
intramolecular forces.
• • Appreciate the importance of IMFA in daily
life.
3.
Review
• Question: Whatholds atoms together within a
molecule?
• Expected answer: Chemical bonds.
• Let’s recall that while bonds hold atoms
together, INTERMOLECULAR FORCES hold
molecules together.
4.
Motivation Activity
• Observethe following phenomena:
• • Water droplets forming on a leaf
• • Perfume spreading in the air
• • Ice floating on water
• Guide Questions:
• • Why do water molecules stick together?
• • Why does perfume spread?
• • What causes ice to float?
5.
What are IntermolecularForces?
• Intermolecular forces (IMFA) are the forces of
attraction or repulsion between neighboring
particles (molecules, atoms, or ions).
• They are weaker than the forces that hold
atoms together within a molecule
(intramolecular forces).
6.
Types of IntermolecularForces
(1/2)
• 1. **London Dispersion Forces** – Weakest
IMFA; temporary attraction between nonpolar
molecules.
• Example: Interaction between O₂ or N₂
molecules.
• 2. **Dipole-Dipole Interaction** – Occurs
between polar molecules with permanent
dipoles.
• Example: HCl – molecules attract through
7.
Types of IntermolecularForces
(2/2)
• 3. **Hydrogen Bonding** – Strong dipole-
dipole force involving H bonded to N, O, or F.
• Example: H₂O, NH₃, HF.
• 4. **Ion-Dipole Interaction** – Attraction
between an ion and a polar molecule.
• Example: Na⁺ ions attracted to water
molecules in saltwater.
8.
Examples and Applications
•• Water’s high boiling point – due to hydrogen
bonding.
• • Perfume scent spreading – due to weak
dispersion forces.
• • Ice floating – caused by hydrogen bonding
structure.
• • Salt dissolving in water – ion-dipole
attraction.
9.
Activity: Identify theType of IMFA
• Identify the dominant type of intermolecular
force in each substance:
• 1. Water (H₂O)
• 2. Carbon dioxide (CO₂)
• 3. Hydrogen fluoride (HF)
• 4. Sodium chloride (NaCl) in water
• 5. Methane (CH₄)
10.
Summary
• • Intermolecularforces are attractions
between molecules.
• • Types: London dispersion, dipole-dipole,
hydrogen bonding, ion-dipole.
• • IMFA affect physical properties such as
boiling point, melting point, and solubility.
11.
Assessment
• Identify thetype of intermolecular force
present:
• 1. NH₃ molecules
• 2. CH₄ molecules
• 3. Na⁺ ions in water
• 4. HCl molecules
• 5. CO₂ molecules
12.
Reflection
• How dointermolecular forces explain the
physical properties of substances?
• In 3–5 sentences, reflect on how IMFA affect
everyday phenomena like rain, scent, or
boiling water.
