Metals

You will be able to

• Describe the structure of a pure metal and an alloy using diagrams of the ions.
• Explain why alloys are harder and stronger than the pure metals they are made from.
• State the uses of brass, stainless steel, mild steel and aluminium alloys and relate each use to its properties.

You will be able to

• Describe the reactions, if any, of metals with cold water, steam and dilute hydrochloric acid.
• Deduce an order of reactivity from displacement reactions of metals with aqueous salt solutions and from the reduction of metal oxides.
• Write symbol and ionic equations for displacement reactions and explain why aluminium appears unreactive.

You will be able to

• State that both water and oxygen are needed for iron to rust, and that salt water speeds rusting up.
• Describe barrier methods (painting, greasing, plastic coating) and explain why they stop working where the coating is scratched.
• Explain galvanising and sacrificial protection in terms of the reactivity series: the more reactive metal is oxidised and loses electrons instead of the iron.

You will be able to

• Describe the extraction of iron from hematite in the blast furnace: the raw materials, the reactions in each zone and the products tapped off.
• State the equations for each zone and identify carbon monoxide as the reducing agent and iron(III) oxide as the substance reduced.
• Explain how limestone removes the acidic impurity silicon(IV) oxide as slag, and how blowing oxygen through molten iron turns it into steel.

You will be able to

• Describe the extraction of aluminium from purified bauxite (aluminium oxide) dissolved in molten cryolite, naming the electrodes and the products.
• Write the ionic half-equations at the cathode (Al³⁺ + 3e⁻ → Al) and at the anode (2O²⁻ → O₂ + 4e⁻) and explain why the carbon anodes must be replaced.
• Explain why cryolite is used and why aluminium cannot be extracted by reduction with carbon.