Definition

Attractive forces existing between molecules.

Dipole-Dipole Forces

• Occur between polar molecules.
• Slightly negative end of one molecule attracts slightly positive end of another.
• Applications:
  • Paints and dyes for protection and visual appeal.
  • Resins for coating materials (toughness, flexibility, adhesion, chemical resistance).
  • Synthetic resins for water resistance.

Hydrogen Bonding

Occurs when hydrogen is covalently bonded to very electronegative atoms (O, N, F).

• Interaction between electron-deficient hydrogen and lone pair on nearby electronegative atom.
• Can occur within same molecule or between nearby molecules.
• Example: Hydrogen bonding in water molecules.

Importance of Intermolecular Forces

• Determine properties of:
  • Water
  • Biological molecules (proteins, DNA)
  • Synthetic materials (glue, paints, resins)
• Crucial for adhesive action of paints and dyes.
• Enable synthetic resins to bind surfaces.

Applications in Society and Technology

• Epoxy adhesives:
  • Excellent chemical resistance
  • Good adhesion properties
  • Heat resistance
  • Used in propellers, aircraft parts, boats, cars, trucks
• Mechanism: Contains partially positively charged H-atoms and O atoms with lone pairs.
• Benefits:
  • Cost savings
  • Weight reduction in vehicles and aircraft
• Widespread use in daily life and industry.