Obtaining + Using Metals

Obtaining + Using Metals

1. Metal Ores

   • Most metals can't be found s pure lumps. You have to extract them from a compound
     • Most metals are found in Ores. 1) Metals that are un-reactive don't tend to form compounds with other elements. Unreactive metals such as gold are found uncombined-So you just have to find them and dig them up.
       • 2) However most metals do react with other elements to form compounds. These are found naturally in the Earths crust. There's a limited amount of metal ores.
         • 3) The more reactive the metal is, the harder it is to extract it from a compound.
   • Metals often have to be seperated from their oxides. Lots of common metals, like iron/alumminium react with oxygen to form their oxides. This process is called oxidation. These oxides are often the ores that the metals need to be extracted from. A reaction that seperates a metal from its oxide is called reduction reaction.
     • Formation of a metal ore: Oxidation.... Eg, magnesium is oxidised to make magenesium oxide : 2Mg + O2 = 2MgO
     • Extraction of Metal: Reduction....Eg, copper oxide is reduced to copper : 2CuO + C = 2Cu + CO2

2. Reduction of Metal Ores

   • 2 Main methods of metal extraction are reduction using carbon and electrolysis.
   • A lot of metals can be extracted from their ores using carbon. Any metal that is less reactive than carbon can be reduced from its ore using carbon. Iron is lower in the reactivity series than carbon so it can be extracted using carbon.
   • Electrolysis can be used to extract metals which are high in the reactivity series than carbon. This extraction method breaks down the ores using electricity.
     • Electrolysis removes aluminium from its ore. The main ore of aluminium is bauxite, which contains aluminium oxide - Al2O3. The aluminium oxide is melted and used as the electrolyte for the aluminium and oxygen atoms. The Aluminium atoms sink to the bottom of the tank as molten aluminium metal.
       • Electrolysis is very expensive. It will only be used if the metal can't be extracted using reduction with carbon.

3. Properties of Metals

   • Metals are all the same but slightly different. They have some basic properties in common, but each had its own specific combination of properties.
     • All metals have some typical properties. (1) Metals are strong (hard to break), but they can bent into different shapes
       • (2) They're great at conducting heat
         • (3) They conduct electricity well.
     • Their properties are useful because they can bend therefore good for the production of car bodies and bridges. They're ideal for when you need heat to pass through them so you can make things like saucepan bases.
       • And their electrical conductivity makes them great for making things like electrical wires.
     • NOt all metals are the same. For example Aluminium has a low density and is corrosion-resistant. Pure Alumin isn't very strong but it forms hard, strong alloys. It can be used for many things like window frames; electricity cables and aircraft.
       • Copper is hard, strong and has a high melting point. It is a good conductor of electricity, so its ideal for drawing out electricity. It can also be made into pipes, and as its below hydrogen in the reactivity series, it doesnt need water. This makes it good for the use in plumbing.
         • Gold is shiny and extremely easy to shape. It's used for jewellery and in situations where you want a metal that won't react with anything, such as in tooth fillings + electric currents.
   • Some metals corrode more easily than others. Some metals corrode over time. Corrosion happens because the metal is being oxidised. Metals which are high reactivity series are more likely to corrode because they react more easily with oxygen. For example, iron is less corrosion-resistant than lead : Iron + oxygen + water = hydrated iron(lll) oxide.

4. Making Metals More Useful

   • Pure metals aren't quite right for certain jobs. Scientists then mix stuff in with the metals to make them exactly how they want.
     • 1) Iron extracted in a blast furnace using carbon monoxide is only 96% iron. The other 4% is impurities, including carbon.
       • 2) This impure iron is brittle. Its used for ornamental railings but it doesnt have many other uses.
         • 3) The pure iron has a regular arrangement of identical atoms They layers of atoms can slide over each other, which makes the iron soft and easily shaped. This iron is far too bendy for most uses.
   • An alloy is a mixture od two or more metals, or a mixture of a metal and a non-metal. Most pure iron is changed into alloys called steels. Steels are formed by adding small amounts of carbons. The alloys produced are stronger and more corrosion-resistant.

5. Recycling

   • Its a chemist job to make sure we have the chemicals we need. But all these chemicals come from the Earth, and the supplies aren;t infinite.
     • Its important to recycle metals because...
       • 1) it uses less resources: Theres a finite amount of metal in the Earth. Recycling conserves the resources.
         • 2) It uses less energy. Mining and extracting metas needs lots of energy, which mostly comes from burning fossil fuels (which will run out, and which cause pollution). Recycling things like copper and aluminium takes a fraction of energy.
           • 3) It uses less money: Energy doesn't come cheap, so recycling saves money too.
             • 4) It makes less rubbish: Recycling also cuts down on the amount of rubbish that goes to landfill, which takes up space and pollutes the surroundings.