Properties of Metals

Physical Properties

• they are malleable -can be bent and beaten into different shapes
• they can be stretched to form wires -ductile
• good conductors of electricity and heat (thermal conductivity)
• high melting and boiling points
• high density (except sodium) (except sodium and mercury)
• they are shiny
• they are strong

Extraction of Metals

Metals are usually found in nature as ores, which mainly consist of metal oxides. The extraction of a metal from its ore depends on its reactivity. A more reactive metal usually requires tougher methods of extraction compared to a less reactive metal. Zinc and metals lying below it in the reactivity series can be extracted from their oxides through heating with carbon. Aluminium and other metals above it in the reactivity series form very stable oxides that are not easily reduced. They can only be extracted from their ores through electrolysis of their molten oxides.

Reactivity series

Thermal Stability of Metal Carbonates

Reactive metals form very stable carbonates which do not decompose easily upon heating. On the other hand, the carbonates of metals which are less reactive are easily decomposed by heat.

Carbonates of potassium and sodium are thermally stable since these metals are found high in the reactivity series. Carbonates of calcium, magnesium, zinc, iron, lead and copper decompose upon heating to form metal oxide and carbon dioxide.

Silver carbonate is the least stable since silver metal is the least reactive. It decomposes completely into silver metal and carbon dioxide.

Extraction of metals

Extraction method of Potassium, sodium, calcium, magnesium and aluminun is reduction via electrolysis. Extraction method of zinc, iron and lead is reduction by heating carbon or carbon monoxide. Copper, silver and gold are extracted naturally.

Extraction of Iron

Iron is extracted from its ore, haematite (contains iron(III) oxide, Fe₂O₃), by heating with carbon. Haematite, coke (mainly carbon) and limestone (calcium carbonate, CaCO₃) are loaded at the top of the blast furnace while hot air is introduced at the bottom of the furnace. haematite, coke and limestone

Raw Materials

• Iron Ore eg haematite ore [iron(III) oxide]
• coke (carbon, C)
• hot air (with O₂ )
• limestone (calcium carbonate, CaCO₃)

Blast furnace

carbon + oxygen → carbon dioxide

C(s) + O₂(g) → CO₂(g)

Carbon dioxide then further reacts with carbon to produce carbon monoxide.

carbon dioxide + carbon → carbon monoxide

CO₂(g) + C(s) → 2CO(g)

iron(III) oxide + carbon monoxide → molten iron + carbon dioxide

Fe₂O₃(s) + 3CO(g) → 2Fe(l) + 3CO₂(g)

3. Limestone undergoes thermal decomposition.

calcium carbonate → calcium oxide + carbon dioxide

CaCO₃(s) → CaO(s) + CO₂(g)

Silicon dioxide, an acidic impurity, is removed by reacting with calcium oxide, which is basic in nature.

calcium oxide + silicon dioxide → calcium silicate (slag)

CaO(s) + SiO₂(s) → CaSiO₃(l)

The molten slag forms a layer above the denser molten iron, and they can be both separately, and regularly, drained away from the bottom of the furnace. It is used to make cement and roads.  The iron whilst molten is poured into Moulds and left to solidify (cast iron) and is used to make railings and storage tanks. The rest of the iron is used to make steel

Uses of quiklime

• to neutralise acidity in soil
• making steel from iron
• as drying agent in industry

Uses of slaked lime

• neutralising acidic industrial waste products
• neutralize acidity in soil

Uses of limestone

• making cement
• making iron from iron ore

Lime in agriculture and construction

Calcium oxide (lime)

Basic oxide used to neutralize acidic soil and used as a drying agent for drying ammonia. Limestone is decomposed to form quiklime which them reacts with water to form lime.

Calcium carbonate (limestone)

Used as building material (cement, concrete) etc., for extraction of iron, glass industry, neutralize soil or chemical wastes

Extraction of Gold

It is very unreactive metal. It involves the treatment of ore (reduced to fine powder) with sodium cyanide. Zinc is then added to displace other metals. The pure metal is obtained by electrolysis. Gold is used to make jewelry as it is resistant to corrosion

Uses of metals