Exam Notes

• There are four areas of electron density around the central c-atom. Due to electron-electron repulsion (the repulsion of like charges), these four areas move as far apart as possible to the corners of a tetrahedral. Since there are 3 bonding area, and one lone pair, the final shape is trigonal pyramidal, with a bond angle based on 109.5 degrees.
• BF3 contains polar bonds as F is more electronegative than B, resulting in bond dipoles (+ and -) . Since the shape of BF3 is trigonal planar, the electron density distribution is symmetrical and the bond dipoles cancel out. Therefore, BF3 is a non-polar molecule.
• The melting point is the temperature at enough energy has been supplied to overcome some of the attractive forces between the particles, so that they can slide past each other
• The boiling point is the temperature at which enough energy has been supplied to overcome all of the attractive forces between the particles, so that they are free to move independently of each other.
• For a substance to be conductive it must have charged particles that are free to move from one place to another and carry current.
• The hardness/ softness of a substance is determined by how easy/difficult it is to scratch -break the forces of attraction between particles using force.
• For a substance to be soluble, the solvent has to be able to form sufficiently strong enough attractions to the solute particle, and break the attractive forces between solute particles to hold it in solution.
• Endothermic requires energy/energy is absorbed/ removed heat/ +ve
• Exothermic releases energy/energy out/ adds heat/ -ve
• A process would be exothermic if heat energy is released, causing the temperature of the surroundings to increase.

  In an exothermic reaction, the energy required to form the new bonds within products is greater than the energy required to break the bonds of the reactants, so more energy is released overall
• A process would be endothermic if heat energy is absorbed, causing the temperature of the surroundings to decrease.

  In an endothermic reaction, the energy required to break the bonds within reactants is greater than the energy required to form the bonds of the products, so more energy is absorbed overall.
• For a molecule to exist as geometric isomers, it must have a double bond that restricts the rotation of the molecule, and each c-atom involved in the double bond must have two different atoms/groups of atoms bonded to it.
• For molecules of the same class, the boiling points of the molecules increases as the size of molecule/length of carbon chain increases. This is because larger/longer molecules have stronger intermolecular forces of attraction that must be overcome, so a greater amount of energy must be supplied to overcome all the attractive forces in a larger/ longer molecule
• Polar molecules (carboxylic acids, alcohols, amines) become less and less soluble as they increase in size. This is because the non-polar carbon chain gets longer, making the molecule less and less polar
• Hydrocarbons are organic compounds with only carbon and hydrogen atoms. Alkanes, alkenes, and alkynes all have only carbon and hydrogen atoms so are all classified as

  hydrocarbons.
• Saturated means that all carbon atoms in the compound are bonded to 4 other atoms/ the maximum number of atoms possible. This means that there are only single C-C bonds present. Saturated molecules are more stable as they only contain single bonds, and are fully bonded to 4 other atoms
• Addition polymerisation occurs when the double c=c bond in an alkene is broken, and the electrons involved in the double bond form new attractions to other neighbouring monomers. The reaction is know as addition polymerisation as the monomers undergo addition reactions to form a longer polymer chain
• In an addition reaction, two small molecules combine to make a larger one. In addition polymerisation a large number of small molecules known as monomers are reacted to form a long chain molecule of repeating units known as a polymer.. As a result of the reaction, the C-C

  double bonds in the monomers are broken and new single bonds are formed betweenthe monomers thus creating the long polymer chain.
• A monomer is more reactive than a polyer as it contains a double c=c bond. This will mean the monomer can undergo addition reactions, and is relatively more reactive/less stable, as it is not fully saturated. A polymer consists of only single c-c bonds and is fully saturated, therefore is relatively more stable, as it cannot undergo addition reactions (due to its lack of c=c bonds)
• A substitution reaction occurs where a a single atom or functional grouo is replaced by a different group (on the same carbon)
• organic compounds with polar functional groups have higher mp/bp than a non-polar compound of the same chain length
• Solubility decreases as length of carbon chain increases due to the non-polar nature of the carbon chain making the overall molecule increasingly non-polar
• In an addition reaction the double c=c bond is broken, and an atom/group of atoms is added to each of the c-atoms involved in that bond
• Markovnikov's rule: The c-atom of the double bond that has the most h-atoms is most likely to gain the hydrogen. This only applies when both reactant and reagent are asymmetrical
• In an elimination reaction, a functional group and an H-atom from an adjacent C-atom are removed from the compound and replaced by a double c=c bond
• Saytzeff's rule: The adjacent C-atom to the functional group that is bonded to the least H-atoms is more likely to lose an H-atom in an elimination reaction. This only applies when both reactant and reagent are asymmetrical
• Structural isomers have the same number and type of atoms - i.e the same molecular formula, but different arrangements of atoms
• Functional group priority list:

  • Carboxylic acids
  • Alcohols
  • Amines
  • Halogens
• A compound is secondary when the C-atom the functional group is bonded to is also bonded to 2 other C-atoms
• A compound is primary when the C-atom the functional group is bonded to is only bonded to 1 other C-atom
• A compound is tertiary when the C-atom the functional group is bonded to is also bonded to 3 other C-atoms