Chemistry paper 2

• Addition polymerisation


  1. 1 monomer (alkene) repeated

  2. 1 functional group

  3. 1 product
• Things to remember when drawing polymers

  • Break the double bond
  • Brackets and an n
  • Bonds extending out of the brackets
• Condensation polymerisation


  1. 2 monomer types each containing 2 of the same functional group OR 1 monomer with 2 different functional groups

  2. 2 products, the condensation polymer and water
• Naturally occurring polymers


  • DNA - nucleotides - encodes genetic information
  • Protein - amino acids - enzymes, haemoglobin, antibodies, make body tissue
  • Starch - sugars - chemical store of energy
  • Cellulose - sugars - in plant cell walls
• DNA


  Two polymer chains made of 4 monomers called nucleotides twisted into a double helix
• Polymers


  • Monomers they are made from
  • Conditions they are under (temperature, pressure, and catalyst)
• Low density poly(ethene) (LDPE)


  Made from ethene at moderate temperatures and high pressure
• High density poly(ethene) (HDPE)


  Made from ethene at lower temperature and pressure with a catalyst
• Thermosoftening polymers


  • Melt when heated
  • No cross links between chains, so can move over each other when heated
• Thermosetting polymers


  • Do not melt
  • Cross links made of strong covalent bonds which do not break even when heated to high temperatures
• Corrosion


  • Only iron rusts - water and oxygen are needed
  • Iron flames away as it rusts, exposing the next layer. This continues to happen, and the metal gets worn away
  • In other metals, the substance formed from corrosion forms a protective layer on the surface of the metal - they will not wear away
• Preventing corrosion


  • Barriers - stops oxygen and water reaching the metal e.g. paint, oil or grease and electroplating (coat with a metal that won't corrode)
  • Sacrificial - coat with a more reactive metal that oxygen and water will react with instead of the iron e.g. magnesium on ships
  • Galvanising - combined both methods. Iron is coated with zinc which acts as a barrier but if it gets scratched then the zinc reacts (as a sacrificial metal) with oxygen/water to form a protective coating
• Making potable water from ground water

  1. Choose appropriate water source (river, lake or reservoir)

  2. Filter through filter beds (remove undissolved solids)

  3. Sterilise (kill harmful microbes) using chlorine, ozone or UV
• Making potable water from seawater

  1. Desalination (removing the salt from seawater)

  2. 2 methods: reverse osmosis, distillation (evaporation and condensation)

  3. This uses a lot of energy
• Waste water treatment


  1. Screening

  2. Sedimentation

  3. Aerobic digestion of effluent

  4. Anaerobic digestion of sludge
• Evolution of the atmosphere

  1. Atmosphere is mostly CO2

  2. Intense volcanic activity releases nitrogen, water vapour and small amounts of methane and ammonia

  3. Water vapour cooled and condensed to form oceans

  4. CO2 dissolved into the oceans forming carbonate precipitates (would lead to formation of sedimentary rocks and fossil fuels)

  5. Plants and algae evolved which absorbed CO2 for photosynthesis and related O2

  6. Atmosphere is 80% N2 and 20% O2
• Pollutants from burning fuels

  • Carbon monoxide - formed by incomplete combustion - toxic
  • Particulates - formed by incomplete combustion - global dimming and respiratory issues
  • Nitrogen oxides - heat from combustion engines make N2 and O2 react - acid rain and respiratory issues
  • Sulfur dioxide - sulfur impurities in coal react with oxygen - acid rain and respiratory problems
• Formulation


  Mixture designed as a useful product e.g. fuel, fertilisers, and medicines
• Pure substance


  Single element or compound, melt and boil at one specific temperature
• Flame tests for metals

  • Lithium - crimson
  • Calcium - orange-red
  • Potassium - lilac
  • Sodium - yellow
  • Copper - green
• Flame test procedure


  Dip platinum wire loop in dilute HCL, heat in a blue flame until it burns with no colour. Dip into sample then put into blue flame and identify metal from colour
• Sodium hydroxide tests for metals

  • Magnesium - white precipitate
  • Calcium - white precipitate
  • Aluminium (redissolves in excess sodium hydroxide to form a colourless solution) - white precipitate
  • Copper - blue precipitate
  • Iron ll - green precipitate
  • Iron lll - brown precipitate
• Chemical tests for non-metals

  • Sulfates - add dilute hydrochloric acid, add barium chloride solution, result = white precipitate
  • Halides - add dilute nitric acid, add silver nitrate, result = chlorine (white precipitate), bromine (cream precipitate), iodine (yellow precipitate)
  • Carbonates - add dilute acid, bubble gas through limewater, result = limewater goes cloudy
• Gas tests


  • Hydrogen = lit splint, squeaky pop
  • Oxygen = glowing splint, relights
  • Chlorine = damp blue litmus paper, bleaches white
  • Carbon dioxide = limewater, goes cloudy
• Cracking


  • Crude oil is a mixture of different length hydrocarbons
  • Short chain hydrocarbons are more flammable so are higher in demand for fuels
  • To meet demand we break long chain hydrocarbons down
  • Conditions: high temperature, catalyst or steam
  • Products: shorter alkane and alkene
• Homologous series


  • Alkanes: C-C, methane, ethane, propane, butane, CnH2n+2
  • Alkene: C=C, ethene, propene, butene, pentene, CnH2n
  • Alcohols: -OH,methanol, ethanol, propanol, butanol
  • Carboxylic acids: -COOH, methanoic acid, ethanoic acid, propanoic acid, butanoic acid
  • Esters: -COO, ethyl ethanoate
• Fermentation


  1. Glucose ➡️ ethanol + carbon dioxide

  2. Carried out by yeast at 37°C, in a slightly acidic solution under anaerobic conditions

  3. If conditions change, the enzymes can denature

  4. Uses: making alcohol and bread
• Catalyst


  • Catalysts speed up chemical reactions
  • They do this by providing an alternative route for the reaction to happen that requires less activation energy
  • They are also not used up in reactions