AQA GCSE CHEMISTRY: EXTRACTING METALS

AQA GCSE CHEMISTRY: EXTRACTING METALS

1. EXTRACTING METALS (reduction)

   • A few unreactive metals like gold are found in the Earth as the metal itself, rather than as a compound. The rest of the metals we get by extracting them from rocks.
   • A metal ore is a rock which contains enough metal to worthwile extracting the metal from it.
   • In many cases the ore is an oxideof the metal. For example, the main aluminium ore is called bauxite - it's main aluminium oxide (AL2O3).
   • Most metals need to be extracted from their ores using a chemical reaction.
   • The profitability of metal extraction can change over time.
   • A metal can be extracted from it's ore chemically by reduction, or by electrolysis.
   • Some ores may have to be concentrated before the metal is extracted, this involves getting rid of the unwanted rocky material.
   • Electrolysis can also be used to purify the extracted metal.
   • A metal can extracted from it's ore chemically by reduction using carbon.
   • When an ore is reduced, oxygen is removed from it.
   • The position of the metal in the reactivity series determines wether it can be extracted by reduction with carbon.

2. EXTRACTING METALS (ELECTROLYSIS)

   • Metals that are more reactive than carbon have to be extracted using electrolysis of molten compounds.
   • An example of a metal that has to be extracted this way is aluminium.
   • This process is much more expensive than reduction with carbon, because it uses a lot of energy (high temperature).
   • Copper produced by reduction with carbon is impure - and impure copper doesn't conduct electricity very well. This isn't very useful, because a lot of copper is used to make electrical wiring.
   • Electrolysis is used to purify it even though it is quite expensive, but this produces very pure copper, which is a much better conductor.
   • Electrolysis is the breaking down of a substance using electricity.
   • It requires a liquid to conduct the electricity, called the electrolyte.
   • Electrolytes are often metal salt solutions made from the ore or molten metal oxides.
   • The electrolyte has free ions these conduct the electricity and allow the whole thing to work.
   • Electrons are taken away by the (positive) anode and given away by the (negative) cathode. As ions gain or lose electrons, they become atoms or molecules and are released.

3. DISPLACEMENT REACTION

   • More reactive metals react more vigorously than less reactive metals.
   • If you put a reactive metal into a solution of a dissolved metal compound, the reactive metal will replace the less reactive metal in the compound.
   • The more reactive metal bonds more strongly to the non-metal bit of the compound, and pushes out the less reactive metal.

4. BIOLEACHING AND PHYTOMINING

   • Bioleaching uses bacteria to separate copper from copper sulphide. The bacteria get energy from the bond between copper and sulphur, separating out the copper from the ore in the process. The leachate (the solution produced by the process) contains copper, which can be extracted by filtering.
   • Phytomining involves growing plants in soil that contains copper. The plants can't use or get rid of the copper, so it gradually builds up in the leaves. The plants can be harvested, dried and burned in a furnace. The copper can be collected from the ash left in the furnace.

5. IMPACTS OF EXTRACTING METALS

   • Mining metal ores is good: jobs; products; money; improve area.
   • Mining ores is bad for the environment: noise; destroys landscape; loss of habitat; dangerous.

6. RECYCLING METALS

   • Mining and extracting metals takes lots of energy, most of which comes from burning fossil fuels.
   • Fossil fuels are running out so it's important to converse them. Burning them contributes to acid rain, global dimming, and climate change.
   • Recycling metals only uses a small fraction of the energy needed to mine and extract new metal. It saves money too.
   • There is a finite amount of each metal in the earth. Recycling converses these resources.
   • Recycling metal cuts down on the amount of rubbish that gets sent to the landfill. Landfill takes up space, and pollutes the surroundings. if all the aluminium cans in the UK were recycled, there'd be 14 million fewer dustbins to empty each year.