General Chemistry

• The word "kinetic" comes from the Greek word "kinein" which means "to move".
• Kinetic Molecular Theory explains the properties of solids and liquids in terms of intermolecular forces of attraction and the kinetic energy of the individual particles.
• Liquid

  • The particles are slightly far from one another. This amount of space enables liquids to flow and take the shape of their containers.
  • They have no definite sizes and shapes.
• Solid

  • The particles are closely packed together. Because of their compact arrangement, solids have definite sizes and shapes.
  • This particle arrangement is also responsible for their malleability and ductility.
• Gas

  • The particles move freely and are very far from one another.
  • They have no definite sizes and shapes.
• The Kinetic Molecular Theory

  1. All matter is made up of tiny particles.
  2. These particles are in constant motion.
  3. The speed of particle is proportional to temperature.
  4. Solids, liquids, and gases differ in distances between particles, in the freedom of motion of particles and in the extent to which the particles interact.
• Temperature affects the amount of kinetic energy of the molecules, therefore affecting their movement. This means that the particles of matter expand upon heating and contract upon cooling.
• Freezing - liquid to solid

  Melting - solid to liquid

  Evaporation - liquid to gas

  Condensation - gas to liquid

  Sublimation - solid to gas

  Deposition - gas to solid
• Ionic Bonds

  • metal and non-metal
  • one atom transfers electrons to the other.
• Covalent Bonds

  • formed between non-metals and non-metals.
  • two atoms share electrons
• Intramolecular Forces of Attraction

  • are those responsible for interactions within a molecule, such as covalent and ionic bonds.
  • stronger than intermolecular attractions.
• Intermolecular Forces of Attraction

  • are attractive forces between molecules or particles in the solid or liquid states.
  • pertain to forces that hold individual particles such as atoms, molecules. or ions together.
• Types of Intermolecular Forces of Attraction

  1. London Dispersion Force
• Types of Intermolecular Forces of Attraction

  1. London Dispersion Force (Vander Waals forces)
  2. Dipole-Dipole Interaction
  3. Ion-Dipole Interaction
  4. Hydrogen Bond
• London Dispersion Force

  • also known as vander waals forces named after the Dutch scientist Johannes Diderik vander Waals.
  • the weakest type of intermolecular forces of attraction.
  • when two non-polar molecules approach each other, an instantaneous dipole moment forms.
• Dipole-Dipole Interaction

  • exist between polar molecules
  • one end of a dipole attracts the oppositely charged end of the other dipole.
• Ion-Dipole Interaction

  • acts between an ion (either positive or negative) and a polar molecule.
  • this explains the solubility of ionic compounds in water, which is polar molecule.
• Hydrogen Bond

  • it is a special and very strong type of force that exist between a hydrogen atom bound to a small and highly electronegative non-metal atom.
  • occur in polar molecules containing H and any of highly electronegative elements (Nitrogen, Fluorine, and Oxygen).
  • e.g. Ammonia (NH3)
• Properties of Liquids and Intermolecular Force

  1. Surface Tension
  2. Viscosity
  3. Vapor Pressure
  4. Boiling Point
  5. Molar heat of Vaporization
• Surface Tension

  • refers to the force that causes the molecules on the surface of a liquid to be pushed together and form a layer.
  • the surface molecules lock into a thin layer of elastic membrane because they are all attracted with each other and are being pulled by the molecules at the center.
  • explains why a drop of liquid is spherical in shape.
  • also explains why a water strider can walk on the surface of the water.
• The stronger the intermolecular force of attraction, the greater the surface tension.
• Viscosity

  • the resistance of fluids to flow
  • a substance that flows readily has low viscosity.
• • If the IMFA is strong, the liquid will have a high viscosity because it will have a high resistance against flowing.
  • The greater the IMFA, the higher the viscosity, and the less readily the liquid flows.
• Temperature also affect viscosity. The higher the temperature, the lower the liquid's viscosity.
• Vapor Pressure

  • is the pressure of the vapor resulting from evaporation of a liquid above a sample of the liquid in a closed container.
• If a liquid has weak IMFA, the escaping tendency of the molecule is high. This causes a high vapor pressure for a liquid.
• If the escaping tendency of the molecules is low, evaporation is slow, and this produces a low vapor pressure for the liquid. Liquids have different vapor pressures at different temperatures.
• Boiling Point

  • the boiling point of a liquid is the temperature at which the vapor pressure of the liquid is equal to the atmospheric pressure.
• Liquids that have high vapor pressure have low boiling points. The higher the vapor pressure of a liquid, the lower its boiling point.
• Molar Heat of Vaporization

  • Heat of vaporization is the amount of heat needed to vaporize a given amount of substance as its boiling point.
  • Since heat is supplied, the process is endothermic but temperature remains constant during the process.
• Substances with high heat of vaporization have strong IMFA. The stronger the IMFA, the higher the heat of vaporization.