10. Metals Flashcards
Properties of all metals
(a) thermal conductivity
(b) electrical conductivity
(c) malleability and ductility
(d) high MP and BP
Metal reactions with
(a) dilute acids
(b) cold water and steam
(c) oxygen
(a) dilute acids- salt and water
(b) cold water and steam- hydroxide + hydrogen
(c) oxygen- oxide
Uses of metals in terms of their
physical properties
(a) aluminium in the manufacture of aircraft because of its low density
(b) aluminium in the manufacture of overhead electrical cables because of its low density and good electrical conductivity
(c) aluminium in food containers because of its resistance to corrosion
(d) copper in electrical wiring because of its good electrical conductivity and ductility
Alloys definition and examples
a mixture of a metal with other elements, including:
(a) brass as a mixture of copper and zinc
(b) stainless steel as a mixture of iron and other elements such as chromium, nickel and carbon
property and uses of alloys
alloys can be harder and stronger than the pure metals because the different sized atoms in alloys mean the layers can no longer slide over each other. more useful
stainless steel in cutlery because of its hardness and resistance to rusting
relative reactivities of metals
the most reactive metal is the one that has the highest tendency to lose outer shell electrons to form a positive ion. better reducing agents- oxidised- readily lose e-.
Explain the apparent unreactivity of aluminium
Aluminium reacts so readily with the oxygen in air, a protective oxide layer is formed on its surface which prevents any further reaction so it behaves as it is unreactive.
Potassium and Sodium conditions and uses
very reactive- stored under oil to prevent contact with water or air.
good conductors of heat and low MP so are used as coolants for nuclear reactors.
conditions required for the rusting of iron and steel to form hydrated iron(III) oxide.
common barrier methods
how barrier methods prevent rusting
both water and oxygen
painting, greasing and coating with plastic
prevent contact with air and moisture.
Use of zinc in galvanising as an
example of a barrier method AND sacrificial protection
A more reactive metal (zinc) is attached to a less reactive one (Fe). it will oxidise first- more easily lose e- form ion more readily, protecting Fe.
Describe the ease in obtaining metals from their ores
before carbon (group 1,2,3)- electrolysis
between carbon and copper (zinc, iron, lead, hydrogen)- carbon/ carbon monoxide as a reducing agent in blast furnace
after copper- unreactive so purify
Extraction of Iron from hematite
(a) the burning of carbon (coke) to provide heat and produce carbon dioxide
(b) the reduction of carbon dioxide to carbon monoxide
(c) the reduction of iron(III) oxide by carbon monoxide
(d) the thermal decomposition of calcium carbonate /limestone to produce calcium oxide
(e) the formation of slag
(a) C + O2 → CO2
(b) C + CO2 → 2CO
(c) Fe2O3 + 3CO → 2Fe + 3CO2
(d) CaCO3 → CaO + CO2
(e) CaO + SiO2 → CaSiO3
Extraction of Aluminium from bauxite
the role of cryolite
why the carbon anodes need to be regularly replaced
the reactions at the electrodes,
bauxite is purified to produce AL2O3 and then aluminium is extracted by electrolysis
dissolved in molten cryolite- reduces melting point.
carbon anodes react with oxygen produces at high temperatures so they burn away.
Al 3+ (aq) + 3e-→ Al (s)
O2- (aq) → O2 (g) + 4e-
2Al2O3 → 4Al (l) + 3O2 (g)
