Chemistry

• Polymers


  Very long, carbon-based, covalently bonded, intricate chains of smaller units called monomers joined together
• Polymerisation


  Monomers join together to form polymers
• Polymerisation


  • Requires high pressure and a catalyst
• Types of polymerisation


  • Addition polymerisation
  • Condensation polymerisation
• Addition polymers


  Monomers have a carbon-carbon double bond. The monomers "open up" the double bond and join together with adjacent monomers to form a polymer chain
• Addition polymer


  • Polyethylene
• Condensation polymers


  Monomers need to have two functional groups (e.g. alcohol and carboxylic acid). The monomers react together and bonds form between them, making polymer chains
• Condensation polymer


  • Polyester
• Formation of polyester


  Condensation reaction between a diol (contains two alcohol groups) and a dicarboxylic acid (contains two carboxylic acid groups) to form ester links
• Difference between addition and condensation polymerisation: addition has 1 product, condensation has 2 products (polymer and a small molecule)
• The minimum number of functional groups a molecule must have in order to be able to form part of a condensation polymer chain is 2
• Properties of polymers


  • Non-biodegradable
  • Synthetic plastics or natural polymers (e.g. DNA, carbohydrates, proteins)
• Monomers


  Smaller units that join together to make much bigger polymer chains
• Structure of polymer chains


  • Can consist of various different arrangements, e.g. linear, branched, tangled web
• Factors affecting polymer properties

  • Monomers used
  • Reaction conditions
• Different plastics formed by different monomers

  • Polyethylene
  • Polypropylene
• Monomers that form polymers with very different properties depending on the reaction conditions are high density polyethylene (HDPE) and low density polyethylene (LDPE)
• LDPE


  Polymer chains are loosely packed, not closely together
• HDPE

  Polymer chains are packed closely together
• LDPE requires very high pressures and a catalyst, HDPE does not
• Carbohydrates or sugar molecules are compounds consisting of carbon, hydrogen, and oxygen atoms
• Monosaccharide


  A single sugar unit, e.g. glucose, fructose
• Polysaccharide


  Made up of many monosaccharide units joined by condensation polymerisation
• Polysaccharides


  • Starch, cellulose
• Amino acids


  The building blocks for proteins and polypeptides
• Amino acid molecule


  Has a basic (amine group, -NH2) and an acidic (carboxylic group, -COOH) functional group
• Peptide bond formation


  Between amino acids to form polypeptides and proteins
• Isotopes are atoms of the same element with different mass numbers (different number of neutrons)
• Relative atomic mass


  Calculated using the abundance and mass of each isotope
• Isotopes of boron


  • Boron-10, Boron-11
• The atomic number of each isotope is always the same