Materials and Metal Extraction (Optional topic)

This is Option 2 on the syllabus. Either this, or Industrial & Atmospheric Chemistry, is to be studied, but not both. Apart from a bit about polymers and crystal structure, the subject matter is mainly metal chemistry – the comparison of metals and non-metals, the difference between transition elements and d-block elements, the characteristic of d-block elements, the extraction of metals (Na and Al) by the electrolysis of molten salts, and the manufacture and recycling of iron and steel.

The metals listed below are listed on the syllabus, and this chart shows their ores, the metal compound in the ore, and the method of extraction

Metal

Ore
Formula of compound in ore
Method of extraction
Sodium
Aluminium
Iron
Rock salt
Bauxite
Haematite
NaCl
Al2O3
Fe2O3
Electrolysis
Electrolysis
Reduction with carbon

Definitions

The following definitions and explanations to be known:

Metals and Non-metals

The formal distinction is that a metal is an element which on ionisation gives positive ions, whereas a non-metal gives negative ions. As a general rule, metals are hard, have metallic lustre, have good electrical and thermal conductivity, are malleable and ductile, but there are many exceptions to these properties.


Transition Elements and D-block Elements

Transition elements and d-block elements are not exactly the same. In period 4, the d-block elements run from scandium (At. No. 21) to zinc (At. No. 30). Zinc, however, does not have the characteristic properties of transition elements (i.e., variable valency, coloured compounds, catalytic activity) and so is not classed as a transition element; this is because its d orbital is full, with 10 electrons.


Crystal Structure

It is necessary to know:

  • What a crystal is
  • What are the building blocks of each of the three types of crystal
  • What holds these building blocks together
  • What are the properties of each type of crystal.


Plastics & Polymers

A polymer is a substance made by the combining together of large numbers of small molecules.

A plastic is a material which can be softened and moulded by heat and pressure. Most plastics consist of polymers and are made by polymerisation.

Polymerisation is a process in which many small and simple molecules (called monomers) join together to form a much larger molecule, called the polymer. Most polymers are made by a process called addition polymerisation. Some important addition polymers are poly(et)hene, PVC, (polyvinyl chloride), polystyrene and Teflon.

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