Metals, Reactivity and Extraction: notes

Properties and Alloys

• Properties of metals: shiny, good conductors of heat and electricity, malleable and ductile. Copper is used for electric wires because it conducts well.
• Alloys: a mixture of a metal with other elements. Brass is copper mixed with zinc. Stainless steel is iron mixed with chromium and nickel.

Reactivity

• Reactivity series: metals ranked from most to least reactive: potassium, sodium, calcium, magnesium, aluminium, zinc, iron, lead, copper, silver, gold.
• Reaction with water: sodium reacts strongly with cold water to give sodium hydroxide and hydrogen. Copper does not react with water.
• Reaction with acid: zinc plus H2SO4 gives zinc sulphate and hydrogen. Copper does not react with dilute acid.
• Reaction with oxygen: magnesium plus oxygen gives magnesium oxide. Gold does not react with oxygen.
• Displacement: a more reactive metal pushes a less reactive metal out of its compound. Zinc plus copper sulphate gives zinc sulphate and copper.

Extraction

• Ore: a rock containing a metal compound worth extracting. Iron ore is mainly iron(III) oxide.
• Iron: heated in a blast furnace with coke and limestone. Carbon monoxide from the coke reduces the ore: iron(III) oxide plus carbon monoxide gives iron plus carbon dioxide.
• Aluminium: aluminium oxide is dissolved in molten cryolite and split by electrolysis. Carbon cannot reduce it because aluminium is too reactive.
• Zinc: zinc oxide is heated with carbon, which removes the oxygen: zinc oxide plus carbon gives zinc plus carbon monoxide.

Rusting and Mining

• Rusting: iron reacts with oxygen and water to form rust. Rust needs both air and water.
• Prevention: painting, oiling, greasing, and galvanising (coating with zinc). A galvanised roof in Harare resists rust for years.
• Mining in Zimbabwe: chrome, gold, platinum and nickel are mined along the Great Dyke. Coal is mined at Hwange.