C1.3 Metals and their uses
Metals are very useful in our everyday lives. Ores are naturally occurring rocks that provide an economic starting point for the manufacture of metals. Iron ore is used to make iron and steel.
Copper can be easily extracted but copper-rich ores are becoming scarce so new methods of extracting copper are being developed.
Aluminium and titanium are useful metals but are expensive to produce.
Metals can be mixed together to make alloys.
Candidates should use their skills, knowledge and understanding to:
■ consider and evaluate the social, economic and environmental impacts of exploiting metal ores, of using metals and of recycling metals
■ evaluate the benefits, drawbacks and risks of using metals as structural materials.
Difference between a voltaic and an electrolytic cell - This animation addresses the common confusion students have between a voltaic (galvanic) cell and an electrolytic cell. The simulation published by Kent Chemistry, demonstrates a voltaic cell (Zn|ZnSO4 and Cu|CuSO4 half-cells that are connected together by a porous bridge) and the electrolysis of copper (II) sulfate solution using copper for both electrodes. Remember: A voltaic cell converts chemical energy into electrical energy Extracting iron - Iron ores are reduced by coke (carbon) in a blast furnace. The process is summarised in the diagram below. Hottest part of the furnace At the bottom of the furnace, adjacent to the hot air blast entry points, the temperature reaches around 1800ºC, and represents the hottest part of the furnace. Ascending vertically, the furnace temperature decreases and reaches around 300ºC Environmental impact of using metals and recycling - What are the social, economic and environmental impacts of exploiting metal ores, of using metals and of recycling metals? Metal ores are obtained by mining/quarrying and that this involved digging up and processing large amounts of rock. Most ores are mined have to be concentrated before the metal is extracted and purified. This means that metal or mineral extraction results Extracting copper - How is copper extracted from copper-rich ores? Copper can be extracted from copper-rich ores by heating the ores in a furnace (roasting and smelting). Roasting and smelting both produce poisonous sulfur dioxide (SO2). Thereafter, the impure copper formed can be purified by electrolysis. Electrolysis is summarised in the diagram below and covered in the adjacent RSC video. Properties and uses of metals - The elements in the central block of the periodic table (shown in pink by the adjacent Periodic Table) are known as transition metals. Like other metals they are good conductors of heat and electricity and can be bent or hammered into shape. They are useful as structural materials, chemical catalysts, and for making things that must allow heat or electricity Alloys - Definition of alloy A metal alloy is a mixture of metal elements. Uses of alloys Most metals in everyday use are alloys. Pure copper, gold, iron and aluminium are too soft for many uses and so are mixed with small amounts of similar metals to make them harder for everyday use. Steels are alloys since they are mixtures of iron Extracting metals: key points - Metal ore Metals are usually found in the Earth’s crust, either as the element (if the metal is unreactive) or as a metal compound (if the metal is reactive). Ores contain enough metal to make it economical to extract the metal. However, the economics of extraction may change over time. Ores are mined and may be concentrated before the metal
C1.3 AQA revision notes on ‘Metals from rocks’ from Pearson (click here for pdf)
Assessment and practical opportunities
■ comparing less reactive metals (gold, silver, copper) with more reactive metals, eg in acid
■ heating metal oxides with carbon to compare reactivity, eg CuO, PbO, Fe2O3
■ heating copper carbonate with charcoal to produce copper
■ displacement reactions, eg CuSO4(aq) + Fe (using temperature sensors to investigate differences in metal reactivity)
■ investigation of the physical properties of metals and alloys, eg density / thermal and electrical conductivity
■ electrolysis of copper sulfate solution using copper electrodes
■ ignition tube demonstration of blast furnace – potassium permanganate, mineral wool plug, iron oxide mixed with carbon
■ investigation of phytomining: growing brassica plants in compost with added copper sulfate or spraying brassica plants (eg cabbage leaves) with copper sulfate solution, ashing the plants (fume cupboard), adding sulfuric acid to the ash, filtering and obtaining the metal from the solution by displacement or electrolysis.