Structure 2.4 From models to materials 
Structure 2.4.1
Understandings:
  • Bonding is best described as a continuum between the ionic, covalent and metallic models, and can be represented by a bonding triangle.
Learning outcomes:
  • Use bonding models to explain the properties of a material.
Additional notes:
  • A triangular bonding diagram is provided in the data booklet.
Linking questions:
  • Structure 3.1 How do the trends in properties of period 3 oxides reflect the trend in their bonding?
  • Structures 2.1, 2.2 What are the limitations of discrete bonding categories?
This video covers how to use the bond triangle. 
Structure 2.4.2
Understandings:
  • The position of a compound in the bonding triangle is determined by the relative contributions of the three bonding types to the overall bond.
Learning outcomes:
  • Determine the position of a compound in the bonding triangle from electronegativity data.
  • Predict the properties of a compound based on its position in the bonding triangle.
Additional notes:
  • To illustrate the relationship between bonding type and properties, include example materials of varying percentage bonding character. Only binary compounds need to be considered.
  • Calculations of percentage ionic character are not required.
  • Electronegativity data are given in the data booklet.
Linking questions:
  • Structure 2.1, 2.2, 2.3 Why do composites like reinforced concretes, which are made from ionic and covalently bonded components and steel bars, have unique properties?
Video coming soon
Structure 2.4.3
Understandings:
  • Alloys are mixtures of a metal and other metals or non-metals. They have enhanced properties.
Learning outcomes:
  • Explain the properties of alloys in terms of non-directional bonding.
Additional notes:
  • Illustrate with common examples such as bronze, brass and stainless steel. Specific examples of alloys do not have to be learned.
Linking questions:
  • Structure 1.1 Why are alloys more correctly described as mixtures rather than as compounds?
This video covers alloys and their properties. 
Structure 2.4.4
Understandings:
  • Polymers are large molecules, or macromolecules, made from repeating subunits called monomers.
Learning outcomes:
  • Describe the common properties of plastics in terms of their structure.
Additional notes:
  • Examples of natural and synthetic polymers should be discussed.
Linking questions:
  • Structure 3.2 What are the structural features of some plastics that make them biodegradable?
This video covers LDPE and HDPE. 
This video covers polystyrene. 
This video covers butyl rubber. 
This video covers thermoplastic and thermosetting polymers. 
Structure 2.4.5
Understandings:
  • Addition polymers form by the breaking of a double bond in each monomer.
Learning outcomes:
  • Represent the repeating unit of an addition polymer from given monomer structures.
Additional notes:
  • Examples should include polymerisation reactions of alkenes.
  • Structures of monomers do not have to be learned but will be provided or will need to be deduced from the polymer.
Linking questions:
  • Structure 3.2 What functional groups in molecules can enable them to act as monomers for addition reactions?
  • Reactivity 2.1 Why is the atom economy 100% for an addition polymerisation reaction?
This video covers addition polymers. 
HL content (2.4.6 only)
Structure 2.4.6
Understandings:
  • Condensation polymers form by the reaction between functional groups in each monomer with the release of a small molecule.
Learning outcomes:
  • Represent the repeating unit of polyamides and polyesters from given monomer structures.
Additional notes:
  • All biological macromolecules form by condensation reactions and break down by hydrolysis.
Linking questions:
  • Structure 3.2 What functional groups in molecules can enable them to act as monomers for condensation reactions?
This video covers condensation polymers. 
This video covers condensation polymers. 
This video coves the formation of kevlar.