Metals - Extraction of Metals

In this GCSE Chemistry quiz, one of a series on metals, we look at the extraction of metals such as copper from both high grade and low grade ores.

The knowledge of how to extract metals from their ores has played an incredibly important role in every known civilisation. The ability to make coins, tools and weapons from metals has changed the way lives are lead. The first metal to be used in many areas of life is thought to be copper in around 4,000BC. This is probably because copper is an easy metal to smelt. It was used to make saws and axes but until humans learned to alloy it with tin to make bronze, these weren't particularly good tools!

The reason why it is necessary to smelt metals is that they react with other materials like oxygen, sulphur etc to form compounds. Only a small number of unreactive metals, like gold for instance, occur native (naturally as the metal itself).

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Smelting was probably an accidental discovery, perhaps a stone age human dropped a piece of jewellery into a fire and discovered a metal in the ashes. For example, in some places, the green mineral malachite can be found. This is an attractive mineral that could have been used for making simple jewellery during the stone age. This is mainly copper carbonate. If this is heated strongly, it undergoes thermal decomposition to form copper oxide, a black compound. It just so happens that when heated with carbon, copper oxide is reduced as carbon is more reactive than copper.

It is easy to see how a curious mind would experiment with other minerals, leading to the discovery and extraction of new metals. A little more imagination could lead to experimenting with mixing metals and very soon, you can see how early humans could have discovered bronze. In the same way these humans would then have learnt better methods of extraction using carbon, including producing the conditions that are needed to extract iron. It is impossible to extract the more reactive metals like magnesium and aluminium using carbon. The human race had to wait until the discovery of electricity before that became possible.

As the best grade ores are extracted and smelted, that leaves us with only the lower grade ores to satisfy demand and so the price of metals has risen. Also, some ore will have been thrown out with the mining and processing waste, so this waste is effectively a low grade ore too. As they have become more expensive, methods of obtaining metals from these lower grade ores have been developed. These new mining methods can recover metals from low grade ores and waste, for example by phytomining using plants and bioleaching using microorganisms. The big disadvantage of these methods is the speed at which they work - much more slowly than conventional 'dig the ore out of the ground' methods. This makes them relatively expensive but, as long as the price of a metal is also expensive, it makes using them worthwhile to the mining companies.

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  1. Choose the correct order of reactivity for the five metals.
    Remember 'MAZIT'
  2. Which of the following is a disadvantage of extracting copper by bioleaching?
    As always, there are advantages and disadvantages of any method of mining, in the end, it usually comes down to cost-effectiveness. If the mining company can make a profit, even from a slow method like bioleaching, they will use it
  3. Copper can be obtained from its ore by displacement using scrap iron because...
    More reactive elements will displace less reactive metals from their compounds
  4. Which of the following shows a balanced chemical equation for the reduction of iron ore in the blast furnace?
    Reduction can be defined in several ways, here, it can be defined as the removal of oxygen
  5. Metals can be extracted from low grade ores using plants. This process is called...
    Any scientific word beginning with phyto is something to do with plants (phyto is the ancient Greek word for plant)
  6. One reason for researching new methods to extract copper from low grade ores is...
    There is still some copper available in the waste heaps from copper mining but it is uneconomical to find ways to recover it until the price of copper becomes high
  7. Why is aluminium extracted using electrolysis?
    Aluminium is a very reactive metal but is protected by a tough layer of aluminium oxide, hiding its true reactivity in everyday situations
  8. If aluminium cans are not recycled, they can affect the environment by...
    There are many other benefits to recycling
  9. Ores are the starting point for extracting metals because...
    That is the definition of an ore
  10. Which of these metals is found as itself rather than in a compound?
    Gold is an extremely unreactive metal so it is found as the metal itself, rather than combined with any other element

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