Metals and their Uses

Metals and their Uses

1. Extracting Metals

   • Rock that contains enough metal or a metal compound to make it worth extracting the metal is called an ore
   • Mining ores often involves digging up large amounts of rock
   • The ore may need to be concentrated before the metal is extracted
   • These processes can produce large amounts of waste and may have major impacts on the environment
   • A few unreactive metals, low in the Reactivity Series, such as gold are found in the Earth as the metal
   • Gold can be separated from rocks through physical methods
   • Most metals are found as compounds - so they have to be extracted by chemical reactions
   • Metals can be extracted from compounds by displacement using a more reactive element
   • Metals which are less reactive than Carbon can be extracted from oxides by heating with Carbon
   • A reduction reaction takes place as carbon removes the oxygen from the oxide to produce the metal

2. Iron and Steels

   • Many of the ores used to produce iron contain Iron (III) Oxide
   • Iron (III) Oxide is reduced at high temperatures in a blast furnace using Carbon
   • The Iron produced contains 96% Iron
     • Cast Iron
   • The impurities in the Iron produced make it hard and brittle so it only has a few uses as a Cast Iron
   • Removing all of the impurities makes pure iron, which is too soft for many uses
   • Most Iron is used to make Steels
   • Steels are alloys of Iron, because they are mixtures of Iron with Carbon and other elements
   • Alloys can be made so that they have properties for specific uses
   • The amounts of Carbon and other elements are carefully adjusted when making steels
   • Low-carbon steels are easily shaped and high-carbon stills are hard
   • Some steels, e.g. stainless steels, contain larger quantities of other materials
     • They resist corrosion

3. Aluminium and Titanium

   • Aluminium has a low density, and although it is quite high in the reactivity series, it is resistant to corrosion
   • Aluminium is more reactive than Carbon and so its oxide cannot be reduced using Carbon
   • It has to be extracted by electrolysis of molten Aluminium Oxide
   • The process requires high temperatures and a lot of electricity making it expensive to extract
   • Pure aluminium is not very strong, but aluminium alloys are stronger and harder - so have many uses
   • Titanium is resistant to corrosion and is very strong - has a low density compared to other metals
   • Titanium Oxide can be reduced by Carbon , but the metal reacts with Carbon making it brittle
   • Titanium is extracted from its ore by a process that involves several stages and large amounts of energy - so a very expensive process

4. Extracting Copper

   • Copper can be extracted from copper-rich ores by smelting
     • Smelting = heating the ore strongly in a furnace
   • Smelting produces impure copper - purified by electrolysis
   • Smelting and purifying copper ore require huge amounts of heating and electricity
   • Copper-rich ores are limited resources
   • Scientists are developing new ways of extracting copper from low-grade ores...
     • Phytomining uses plants to absorb copper compounds from the ground - The plants are burned and produce ash from which copper can be extracted
       • Phytomining
     • Bioleaching uses bacteris to produce solutions containing copper compounds
       • Bioleaching
   • Solutions of copper compound can be reacted with a metal that is more reactive than copper, such as scrap iron, to displace the copper
   • Copper can also be extracted from solutions of copper compounds by electrolysis

5. Useful Metals

   • Elements from the central block of the periodic table are known as the transition metals
   • They are all metals and have similar products
   • They are all good conductors of heat and electricity
   • Many of the Transition Metals are strong, but can be bent or hammered into shape
   • These properties make them useful materials for buildings, vehicles, containers, pipes and wires
   • Copper is a very good conductor of heat and does not react with water - it can be bent but it is hard enough to keep its shape
   • These properties make it useful for making pipes and tanks in water and heating systems - conducts electricity so used for wires
   • Pure iron, copper, gold and aluminium are soft and easily bent - they are often mixed with different elements to make alloys to make them harder and keep their shape better
   • Iron is made into steels
   • Gold used for jewellery is usually an alloy
   • Most aluminium in buildings and aircrafts are alloys
   • Copper alloys include bronze and brass

6. Metallic Issues

   • Mining for metal ores involves digging up and processing large amounts of rock
   • - This can produce large amounts of waste material and effect large areas of environment
   • Recycling metals saves the energy needed to extract the metal
   • + Recycling saves resources because less ore needs to be mined and less fossil fuel is needed to provide the energy for the extraction
   • Advantages and Disadvantages of using metals in construction
     • - Obtaining metals from ores causes pollution and uses up limited resources
     • - Metals are more expensive than other materials such as concrete
     • - Iron and steel can rust
     • + They are strong
     • + They can be bent into shape
     • + They can be made into flexible wires
     • + They are good electrical conductors

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