Chemistry

• Ionic bonding: oppositely charged forces are strongly attracted to each other by electrosatic forces
• covalent bonding: strong electrostatic forces between the negatively charged shared electrons and the positvely charged nuclei of the atoms involved.
• Simple molecular: atoms within a molecule have strong covalent bonds but the intermolecular forces between the molecules are weak.
• Diamond:

  • 1 carbon atom bonded to 4 others
  • not free electrons so it can't conduct electricity
  • High melting point
  • very hard due to its rigid lattice structure
• graphite

  • 1 carbon atom bonded to 3 others
  • each carbon atom has 1 free electron so it can conduct electricity
  • Layers are help weakly by intermolecular forces to they slide over eachother
• C60 fullerenes:

  • hollow sphere of 60 carbon atoms (cage-like structure)
  • It is a poor conductor because even though it has a free electron, it can't move throughout the structure
  • It is not a giant covalent structure, it just has large convalent bonds (low melting point)
  • C60 molecules are only help by intermolecular forces so they are soft and slide over each other
• Simple molecular:

  when the Mr of a molecule increases, its melting point also increases. This is because there are more intermolecular forces which require more energy to overcome.
• metallic bonding: strong electrostatic attraction between the metal cations and a sea of delocalised electrons
• Hydrocarbon - consists of hydrogen and carbons only
• Saturated hydrocarbon - it only contains single carbon bonds.
• Methanol + potassium dichromate (IV) in sulphuric acid -- (with heat)--> methanoic acid
• microbial oxidisation occurs when some microorganisms use alcohols for energy. They use oxygen in the air to oxidise alcohols, making carboxylic aicds as a by-product.
• Complete combustion of alcohols happens when the alcohol is burnt in enough oxygen. When this happens, carbon dioxide and water is produced.
• Ethanol can be made by reacting ethene with steam in the presence of steam cracking catalyst (eg. phosphoric acid). The temperature has to be 300 degrees and the pressure has to be 60-70 atmospheres.
• fermentation occurs when glucose is broken down by yeast enzymes to form ethanol and carbon dioxide. The temperature has to be 30 degrees because it is the optimum temperature.

  It must be in anaerobic conditions otherwise oxygen will convert ethanol into ethanoic acid.

  This process is renewable but the thanol isn't concentrated so it has to be distilled and also purified.
• Carboxylic acid + metal carbonate -> salt + water + carbon dioxide

  eg. methanoic acid + sodium carbonate --> sodium methanoate + water + carbon dioxide

  HCOOH (aq) + NaCo3(aq) -> HCOONa(aq) + Co2 + H2O
• Aqueous carboxylic acid + metal -> salt + hydrogen

  eg. ethanoic acid + magnesium -> magnesium ethanoate + hydrogen

  2CH3CHOOH(aq) + Mg(s) -> (CH3COO)2Mg(aq) + H2
• Isomers:

  same molecular formula but different structural formula
• A homologous series is a group of organic compounds that have similar chemical properties, due to them having the same functional group.
• An addition polymer is a long-chain molecule which formed by the joining up of many small molecules called monomers
• • sodium, potassium, ammonium, nirates --> soluble
  • chlorides - soluble (except silver and lead chloride)   
  • sulfate - soluble except lead, barium and calcium sulfate) 
  • carbonates - insoluble except sodium, potassium, ammonium
  • hydroxides - insoluble except sodium, potassium, calcium 
• longer hydrocarbons have higher boiling points, shorter hydrocarbons have lower boiling points
• Obtaining compounds using the industrial process of fractional distillation:

  • Heat crude oil vapourise
  • Pass vapours in fractionating column
  • Gases rise and cool due to the temperature gradient
  • Different fractions have different boiling points
• Ionic compounds in the solid state are non-conductors of electricity due to the absence of delocalised ions.
• in an ionic compound Ions are free to move in molten or aqueous state
• How do we call compounds which undergo electrolysis?

  Molten ionic compounds or aqueous solutions contianing mobile ions and which can conduct electricity are called electrolytes
• Substances which do not conduct electricity are called non-electrolytes. This is because they exist mostly as molecules and not ions
• Electrodes -

  • conduct electric current and is usually graphite
  • electrode which is connected to the positive side of the battery is called the anode
  • Electrode which is connected to the positive side of the battery is called the cathode
• Electrolyte -

  • molten ionic compound or aqueous solution that conducts electricity
  • Dissociates to form cations and anions
  • Ions present in the elctrolyte allow electricity to flow through it.
• Electrodes can be made of carbon, platinium and graphite. If any other metal except platinum is being used, then those electrodes will be called as reactive electrodes.
• Anions gain electrons whilst cations lose electrons
• Electrons flow from the positive terminal to the negative terminal of the battery. This is because cations require electrons at the cathode and anions lose electrons at the anode.
• Refinery gases - used in domestic heating and cooking

  Gasoline - used as fuel in cars

  Kersone - used as fuel in aircraft

  Diesel - Used as a fuel for large vehicles

  Fuel OIl - Used as a fuel for large ships and in some power stations

  Bitumen - used to surface roads and roof