Intermolecular Forces of Attraction, Properties and Types of Liquids and Solids, Phase Changes and Diagrams Solutions, Solution Stoichiometry, Thermochemistry, First Law of Thermodynamics, Hess' Law

• Electronegativity

  A measure of the tendency of an atom to attract a bonding pair of electrons
• The Periodic Table of Elements shows the values of electronegativity of each element and its trend across the table
• Pauling scale


  The numerical scale of electronegativities based on bond-energy joined by covalent bonds
• Polarity


  Arises from the uneven sharing of electrons between atoms in a compound or molecule, creating regions of positive and negative charge
• Types of molecules

  • Polar molecules
  • Nonpolar molecules
• If the electronegativity difference between two atoms is less than 0.5, they are NON-POLAR. If the difference is greater than 0.5, they are POLAR
• Ion-Dipole Forces


  Intermolecular attraction between charged particles (ions) and molecules with positive and negative ends (polar molecules)
• Hydrogen Bonding


  Occurs between a hydrogen atom bonded to a highly electronegative atom (such as oxygen, nitrogen, or fluorine) and another electronegative atom in a nearby molecule
• Dipole-Dipole Forces


  Attractive forces that exist between polar molecules due to the unequal sharing of electrons
• Dispersion Forces

  Induced Dipole: When a polar molecule or an ion is placed close to a nonpolar molecule, the electron distribution in the nonpolar molecule becomes distorted causing a partial change in polarity

  Ion-Induced Dipole: Interaction between an ion and an induced-dipole molecule

  Dipole-Induced Dipole: Interaction between a polar molecule and non-polar molecule that was induced to have a dipole moment
• Surface Tension


  Caused by intermolecular forces, where the liquid molecules at the outermost part of the substance or the surface are being pulled inward by the other molecules creating a film-like property to hold its shape
• Viscosity


  The property of a liquid's resistance to flow, affected by the strength of intermolecular forces and temperature
• Vapor Pressure


  The pressure exerted by the gaseous phase when a liquid and its vapor are in equilibrium, affected by temperature
• Boiling Point


  The temperature at which the vapor pressure of a liquid equals the pressure exerted by the environment (usually atmospheric pressure)
• Molar Heat of Vaporization (ΔHvap)


  The amount of energy needed to break the intermolecular forces between the liquid molecules to change their phase from liquid to gas
• Types of Solids

  • Crystalline Solids
  • Amorphous Solids
• Crystalline Solids


  • Observable highly ordered, repeating arrangement of atoms, ions, or molecules

  Often have flat faces, sharp edges, and definite geometric shapes
• Amorphous Solids


  • Lack a well-defined atomic or molecular order

  The particles are arranged randomly

  Do not have a definite geometric shape
• Phase Change


  The transformation of matter between the solid, liquid, and gas state (plasma can be included at extremely high temperatures), requiring the transfer of heat energy
• As the amount of energy increases, the particles tend to go and arrange themselves in a more disordered manner, with solids having the lowest amount of energy, followed by liquids, and then gases
• Phase Diagram


  A kind of map used in science and engineering which shows the conditions, like temperature and pressure, at which different forms, or phases, of matter exist
• Solution


  A homogenous mixture (1 phase) that is composed of at least one solute and solvent
• Types of Solutions


  • Unsaturated
  • Saturated
  • Supersaturated
• Types of Solvents

  • Aqueous
  • Non-aqueous
• Types of Solutes

  • Electrolyte
  • Non-electrolyte
• Steps to Solve a Solution Stoichiometry Problem

  1. Write the Balanced Chemical Equation

  2. Identify the Molarity (M) Values

  3. Set Up a Mole Ratio

  4. Relate Moles to Volume (if necessary)

  5. Calculate Moles of a Substance

  6. Convert Moles to Mass (if necessary)

  7. Check Your Units
• Stoichiometry

  • Applying the concepts of stoichiometry to identify the amount of reactants or products that is required or is produced in a solution
• Molarity (M)


  Concentration unit representing moles of solute per liter of solution
• Mole ratio

  Ratio between the reactants and products that reflects the stoichiometry of the reaction
• Molarity connects moles of solute to liters of solution (M = moles/liter)
• Molar mass


  Grams per mole
• Mass (g) = Moles (mol) x Molar Mass (g/mol)
• Factors Affecting Solubility


  • Temperature
  • Pressure
  • Intermolecular forces
  • Molecular size
  • Surface Area
• For most solids and liquids dissolving in liquids


  Solubility increases with temperature
• According to Henry's law


  The solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid
• Polar solutes


  Dissolve well in polar solvents
• Non-polar solutes

  Dissolve well in non-polar solvents
• Smaller solute molecules


  Tend to be more soluble than larger ones
• Materials grouped in bulk


  Dissolve slower than smaller counterparts
• Colligative properties of solutions


  Properties of a solution that depend on the amount of solute in the solution