Option E : Chemical Industries

Chemical industries have a major place in the world economy. The industrial revolution, which commenced in the 18 century, was also a materials revolution that started with the large-scale extraction of iron. This continues to the present day with the extraction of other metals, the production of bulk chemicals such as fertilisers, the oil and plastics industries, and the speciality chemicals industry producing medicines, enzymes, catalysts and additives. When teaching this option, emphasise chemical reactions and their relevant equations.

E.1         Initial Overview (2h)

 
E.1.1  

Outline the abundance, occurrence and availability of sources of materials.
A qualitative picture only is intended. Include minerals (especially metals and their ores), petroleum and biotechnology.

 

E.1.2   

Identify the factors that influence the establishment of a chemical industry in a particular location. Include sources of suitable raw materials, energy supply, transport to and from the site, availability ofinvestment, skills and labour and existence of markets for the product.

E.1.3   

Outline the division of the industry into both intermediates and consumer products.

 

E.1.4   

State the increasing importance of biotechnology in chemical manufacture.
Examples can be found in the manufacture of insulin and vitamins.

E.2         Principles of Extraction and Production of Metals (2h)

 
E.2.1  

Outline the principles used in the physical separation of materials.

 

E.2.2   

Discuss the chemical principles involved in the extraction of metals from their ores.
Relate this to chemical reactions based on the reactivity series (see 10.2), but also include factors such as chemical conversion (iron), electrolytic conversion (aluminium) and energy requirements.

E.3         Iron and Aluminium (4h)

 
E.3.1  

State the main sources of iron.
Include iron ores and scrap (recycled) iron.

 

E.3.2   

Explain the reactions that occur in the blast furnace. Include the role of coke, limestone and the formation of slag. The relevant equations should be considered.

 

E.3.3   

Explain the conversion of iron into steel using the basic oxygen converter.

 

E.3.4   

Describe the properties and uses of steel as an alloy of iron.
Consider carbon steels and alloy steels (including stainless steel).

 

E.3.5     

Discuss the production of aluminium by electrolysis of alumina in molten cryolite.
Explain the need for cryolite as a solvent because of the very high melting point of Al2O3. Account for the materials used in the construction of the cell and the choice of electrodes.

 

E.3.6    

Describe the main properties and uses of aluminium.
Include the properties of the aluminium oxide coating and the resulting resistance to corrosion. Compare with the properties and uses of iron and steel.

 

E.3.7   

Discuss the environmental impact of iron and aluminium production.
Include the effects of mining the ore, siting the plant, energy costs and recycling the metals.

E.4         The Oil Industry (4h)

 
E.4.1  

Outline the importance of oil as a source of chemical feedstock.
Although only about 10% of the refined products of crude oil are used as chemical feedstock, it is still the most significant source of organic chemicals. Compare the use of oil as an energy source and as a chemical feedstock.

 

E.4.2   

Outline the removal of sulphur from crude oil.
Refer to the need for this removal and the use of sulphur in the manufacture of sulphuric acid.

 

E.4.3   

Describe the fractional distillation of oil.
Compare simple distillation with fractional distillation. Students should understand that the vapour phase is always richer in the more volatile component. No calculations using Raoult's law or Dalton's law are required.

 

E.4.4   

Describe cracking and its products.
Include thermal cracking (both steam and catalytic) and hydrocracking.

 

E.4.5     

Describe reforming processes and their products.
Include isomerization, cyclization and aromatization. Reforming is important in some countries as a source of hydrogen for the Haber process (see 8.2.5).

 

E.4.6    

State the uses of refinery products as feedstock for the organic chemical industry.
Refinery products are used as raw materials in the manufacture of solvents, plastics, pesticides, food additives, pharmaceuticals, detergents, cosmetics and dyes.

 

E.5           Polymers (3h)

Cross reference with 11.3

 
E.5.1  

Describe how the properties of polymers depend on their structural features.
Include the :

  • different amounts of branching in low- and high-density polyethene

  • different positions of the methyl groups in isotactic and atactic polypropene

  • formation of cross-links in phenol-methanal plastics (compare thermoplastics and thermosets)

E.5.2   

Describe ways of modifying the properties of polymers.
Include the use of :

  • plasticizers in polyvinyl chloride.

  • volatile hydrocarbons in the formation of expanded polystyrene

  • air in the manufacture of polyurethane foams.

E.5.3   

Discuss the advantages and disadvantages of polymer use.
Consider strength, density, insulation, lack of reactivity, use of natural resources, disposal and
biodegradability. Use polyethene, polyurethane foams, polyvinyl chloride and phenol-methanal plastics as examples.

 

E.6         Silicon (1.5h)

 
E.6.1  

Describe the extraction and purification of silicon.
Include zone refining.

E.6.2   

Compare the electrical conductivity of a semiconductor with that of metals and non-metals.
Relate this to the ionisation energies of semiconductors compared to metals and non-metals.

E.6.3   

Explain the doping of silicon to produce n-type and p-type semiconductors.
In p-type semiconductors, electron holes in the crystal are created by introducing a small percentage of a group 3 element eg In, Ga). In n-type semiconductors inclusion of a group 5 element (eg As) provides extra electrons.

 

E.7       Ellingham Diagrams (1.5 h)

 
E.7.1  

Analyse Ellingham diagrams to predict the feasibility of reducing metal oxides.
Refer also to the Ellingham diagram in the data booklet.

E.8         Mechanisms in the Organic Chemicals Industry (2h)

 
E.8.1  

Compare and discuss the mechanisms of thermal and catalytic cracking.
Thermal cracking involves a free-radical mechanism whereas catalytic cracking has an anionic mechanism.

E.8.2   

Describe the mechanism involved in the manufacture of low-density polyethene.
This is a free-radical mechanism.

E.8.3   

Outline the use of Ziegler-Natta catalysts in the manufacture of high-density polyethene.
The mechanism is ionic but details are not required.

E.9         The Chlor-alkali Industry (2h)

 
E.9.1  

Discuss the production of chlorine by the electrolysis of sodium chloride.
Explain why an electrolytic process is required and why the diaphragm cell is preferable to the mercury cathode cell.

 

E.9.2   

Outline the importance of the products of this process.
The process produces sodium hydroxide with chlorine and hydrogen as by-products.

E.9.3   

Discuss the environmental impact of this process.
Include reasons why the diaphragm cell has replaced the mercury-cathode cell in many parts of the world, and that knowledge of the effect on the ozone layer has led to reservations about the use of chlorine-containing solvents.