Intermolecular forces and thermal interactions


  • Intermolecular forces
  • Temperature
  • Thermal energy
  • Three states of matter
  • Thermal motion
  • Average kinetic energy

Definition of Intermolecular forces and thermal interactions

Intermolecular Forces are longest-ranged (act strongly over a large distance) when they are electrostatic. Interaction of Charge Monopoles (simple charges) is the longest-ranged electrostatic force

More About Intermolecular forces and thermal interactions

  • The force between atoms within a molecule is a chemical or Intramolecular force
  • The force between molecules is a physical or intermolecular force
  • Thermal energy is the energy arising from motion of its atoms and molecules
  • It is directly proportional to the temperature of the substance
  • It is the average kinetic energy of the particles of matter and is thus responsible for movement of particles
  • The movement of particles is called thermal motion
  • The three states of matter are the result of balance between intermolecular forces and thermal energy of particles
  • When the molecular interactions are very weak, molecules do not cling together and to make liquid or solid unless thermal energy is reduced by lowering the temperature
  • Gases do not liquefy by compression only although molecules come very close to each other and intermolecular forces operate to the maximum
  • When thermal energy is lowered by lowering the temperature, gases can be liquefied easily
  • Thus, the three states of matter exist
  • There are three ways in which a water molecule moves: (1) vibration, (2) rotation, and (3) translation
  • All three modes of motion disrupt the bonds between water molecules
  • As the system becomes warmer, the thermal energy of the water molecules eventually becomes too large to allow these molecules to be locked into the rigid structure of ice. At this point, the solid melts to form a liquid in which intermolecular bonds are constantly broken and reformed as the molecules move through the liquid
  • Eventually, the thermal energy of the water molecules becomes so large that they move too rapidly to form intermolecular bonds and the liquid boils to form a gas in which each particle moves more or less randomly through space
  • The difference between solids and liquids, or liquids and gases, is therefore based on a competition between the strength of intermolecular bonds and the thermal energy of the system
  • At a given temperature, substances that contain strong intermolecular bonds are more likely to be solids. For a given intermolecular bond strength, the higher the temperature, the more likely the substance will be a gas