INTERMOLECULAR FORCES

• Kinetic Molecular Theory of Matter

  • provides an overview of the microscopic properties of molecules or atoms and their interactions.
  • microscopic properties of matter and how they translate to the state and other properties of matter.
  • It explains how these particles behave and interact with each other based on principles like motion, collisions, and temperature.
• Atoms

  • are the building blocks of matter
• Molecules

  • group of atoms bonded together
• Compounds

  • are produced when two or more atoms of different elements combine chemically.
• Intermolecular forces

  • The attractive forces between molecules
  • The stronger the interaction between two molecules, the smaller their distance will be.
• Solids

  • have particles with strong intermolecular forces such that their particles are very close to one another.
• Liquids

  • have intermediate intermolecular forces.
  • particles farther from one another compared to those in solids.
• Gases

  • have particles that are very far apart from one another due to weak intermolecular forces.
• All molecules are in constant random motion. The extent of their motion varies depending on the temperature and strength of the interaction between the particles.
• Solids

  • Due to their strong intermolecular forces, have restricted motion.
  • are only able to vibrate back and forth around a specific point or location.
• Liquid

  • having intermediate intermolecular forces, are able to move past each other.
  • Since their particles are still close to one another, the motion is restricted to small distances as they will collide with another molecule.
• Gases

  • having weak intermolecular forces, are able to move in relatively long distances before colliding with another molecule.
• Kinetic energy

  • refers to the energy of particles in motion.
  • the higher the kinetic energy, the more active the particles are.
• Temperature

  • is a measure of the average kinetic energy of molecules.
  • Increasing the temperature will result in a faster motion of the particles.
• Solid

  • is characterized by having a rigid shape and fixed volume.
  • virtually incompressible
• Liquid

  • shape depends on depends on the container
  • fixed volume
  • only slightly compressible
• Gas

  • depends on the container
  • assumes the volume of the container
  • very compressible
• Based on the kinetic molecular theory of matter, the state of a matter is determined by two factors - temperature and strength of intermolecular forces.
• At low temperatures, intermolecular forces dominate.
• At high temperatures, the molecules have higher kinetic energy and will be able to overcome the intermolecular forces present.
• Ion-ion interaction

  • is the interaction between two oppositely charged particles.
• Ions

  • charged particles are called
• Cations

  • are positively charged particles
• Anions

  • are negatively charged particles.
• Ionic Bonds

  • Ion-ion interaction is also known as
• Ion-dipole interaction

  • results from the electrostatic attraction of a molecule containing a dipole and an ion.
  • This type of interaction is responsible for the dissolution of most ionic solids in polar solvents.
  • The strength of this kind of IMFA increases as the charge of the ion increases.
• Charge Density

  • The strength of ion-dipole interaction depends on the
  • defined as the actual charge distributed over the total volume of the ion.
• Dipole-dipole

  • interactions are attractive forces that are a moderately strong type of IMFA and are present in between polar molecules.
  • are the result of the electrical interactions among dipoles on neighboring molecules.
• Hydrogen bonding

  • is a special kind of dipole-dipole force and one of the strongest types of IMFA.
  • It is an attractive force that exists when hydrogen is bonded to the most electronegative atoms, namely F, O, or N.- This relatively strong attraction explains why molecules with this type of IMFA tend to have high boiling and melting points.
• Hydrogen Bond Donor

  • is a molecule that provides the hydrogen atom participating in a hydrogen bond,
• hydrogen bond

  • acceptor is a molecule that contains the lone pair-bearing electronegative atom.
• London dispersion forces (LDFs)

  • are the weakest type of IMFA and are present in between all electrically neutral molecules ― polar and nonpolar molecules
  • This IMFA was named after the German-American physicist Fritz London
  • are caused by fluctuations in the electron distribution within atoms or molecules.
  • This happens when an atom, which is usually nonpolar, becomes polar due to the continual motion of its electrons, resulting in a temporary dipole.
  • depends on the polarizability of the molecule.
• Ionic compound

  • is composed of atoms bonded by ionic bonds.
• Ionic bonds

  • involve the transfer of an electron from a metal to a nonmetal.
• Ion-ion

  • The cations and anions in an ionic compound interact via ______ interactions.
• Coulomb's law.

  • The strength of the ion-ion interaction is governed by
• Polar covalent compounds

  • are molecules with a net dipole moment.
  • This means that the electrons are not equally shared between the atoms.
• Nonpolar covalent compounds

  • are molecules with zero dipole moment.
  • This means that the electrons in the bonds are shared equally between the atoms.
• Polarizability

  • is the measure of how easy it is to distort the electron distribution of a molecule.
• Induced dipoles

  • occur when a nonpolar atom becomes polar due to the presence of an ion or a dipole.