5-8

• Intermolecular Forces


  Electrostatic interactions between molecules
• Molecule


  Two or more atoms connected by chemical bonds
• Ion-Ion Interactions


  • Strongest intermolecular force
  • Found in large ionic solids, held together by networks of ionic bonds involving formal charges
• Ion-Dipole Interactions


  • Occur between ions and polar molecules
  • Positive ions attract the negative end of a dipole; negative ions attract the positive end
• example: Ion-Dipole InteractionsIn water (H₂O), oxygen is more electronegative, creating a polar molecule with a negative side (oxygen) and a positive side (hydrogen). Occur between ions and polar molecules. positive ions attract the negative end of the dipole. vice versa
• Dipole-Dipole Interactions


  • Occur between polar molecules
  • Positive end of one molecule's dipole attracts the negative end of another
• Dipole-Dipole Interactions?


  • form of intermolecular force that occurs when a polar molecule interacts with a non-polar molecule. . When liquid form water molecules will move, to always be making electrostatic interactions between negative end of one dipole and the positive end of another dipole
• Hydrogen Bonds


  • A special, strong type of dipole-dipole interaction
  • Occur in molecules with N-H, O-H, or F-H bonds (e.g., NH₃, H₂O, HF)
  • Strong because they involve highly electronegative elements, creating highly polarized bonds
• Nonpolar molecules


  Molecules that do not have any electrical charges or partial charges
• Polar molecule


  A molecule in which one end of the molecule is slightly positive, while the other end is slightly negative
• London dispersion force


  The weak intermolecular force that results from the motion of electrons that creates temporary dipoles in molecules
• Momentary Dipole


  • One side of an atom becomes slightly negative, and the other side slightly positive
  • Weaker than permanent dipoles
  • Can induce a dipole in a nearby atom, leading to a momentary dipole-induced dipole interaction
• Induced dipole


  Slight partial negativity repels this electron density over the sider of the atom so it will also have a slight dipole
• Melting and Boiling Points


  • Indicators of the strength of intermolecular forces
• Boiling Point


  • The temperature where the average kinetic energy balances the energy of intermolecular attractions
  • At a pressure of 1.013 x 10⁵ Pa, this is the normal boiling point
• Freezing Point


  • Below the freezing point, molecules become locked in place, and the liquid solidifies
  • At a pressure of 1.013 x 10⁵ Pa, this is the normal freezing point
• Vaporization


  Conversion of a liquid to gas
• Condensation


  Reverse of vaporization
• Stronger intermolecular forces


  Higher melting and boiling points
• London dispersion forces


  A weak intermolecular force which accounts for the attraction of non-polar molecules to each other
• London dispersion forces


  • He
  • H
  • Ne
  • pentane-pentane
• Dipole-dipole interactions


  Forces which attract the d+ (partial positive charge) with the d- (partial negative charge) of a neighbouring molecule. Intermediate strength
• Hydrogen bonding


  Special type of dipole-dipole interaction in which there is positive charge on hydrogen bound to an atom of high electronegativity and a partial negative charge on a O, N, or F of a nearby molecule. Strong Interaction.
• Solute


  The substance that gets dissolved. It can be a solid, liquid, or even a gas. eg, salt
• Solvent


  The substance that does the dissolving. It's usually present in a larger amount compared to the solute. eg, water.
• Non-polar solvents


  • Alkanes: Pentane, Hexane, Heptane, Octane
  • Alkenes: Ethene, Propene, Butene, Pentene
• Hydrocarbons are generally non-polar because they consist of carbon (C) and hydrogen (H) atoms
• 1. H Bond


  Considered non-polar covalent because the electronegativity difference between carbon (C) and hydrogen (H) is very small. It's a non-polar covalent bond since it is less than 0.5.
• • What is Miscible? If substances are soluble in one another.
• Is Hexane and Water are miscible?

  No since, hexane is non-polar, due to carbon and hydrogen bonds. And also do not form hydrogen bonds. Hexane is a week dispersion force.The strong bonds in water keep hexane from blending.
• Is Hexane and Octane are miscible?

  Yes, they are both non polar and will mix together. when you blend them they will form a homogenous mixture
• “Like Dissolves Like” Polar compounds dissolve in Polar compounds and Non-Polar compounds dissolve in Non-polar compounds
• ▪ Initial substance are reactants. ▪ New substances are products.
• How to balance Equations?

  step 1: count the atoms on each side of the equation step 2: balance any other element rather than H and O
• mole?


  M= m/n
• • M is molar mass (in grams/mol) - m is mass (in grams)- n is the number of moles (in mols).
• What is The Mole Ratio? The mole ratio allows us to convert from moles of one substance in a balanced equation to moles of a second substance in the equation
• • In Molars to Mass We can use the mole ratio to convert from moles of one substance in a balanced equation to moles of a second substance in the equation.
• How do we convert mass (m) of a sample and the number of moles (n) using the molar mass?


  n = m / M
• How to convert Moles to Mass?

  We can convert between the number of moles (n) and the mass (m) of a sample and the using the molar mass via: m = M × n