Obtaining and Using Metals

Obtaining and Using Metals

1. Ores

   • A metals are found naturally in earth's crust. These are very unreactive metals like gold and platinum.
   • Most metals are found in ores, which are rocks which contain enough metals to be extracted for profit. Some common ores include haematite (iron), malachite (copper)
     • Removing a metal from an ore through a series of chemical reactions is called extraction. Some metals can be extracted by heating their compounds with carbon. These metals include: copper, lead, tin, iron and zinc. Others are extracted by electrolysis such as: aluminium, magnesium, calcium, sodium and potassium. The harder a metal is to extract, the more expensive it is to obtain.

2. Oxidation and Reduction

   • The extraction of metals from ores is an example of reduction. This is because the metal is removed from the oxide by heating it with carbon or through electrolysis.
   • When metals corrode (iron rusts), they are being oxidised. This is because corrosion happens when metal react with oxygen. The more reactive a metal is the more quickly it will corrode and metals with low reactivity will corrode slowly or not at all, like gold. Aluminium does not corrode as much as expected because its surface oxidises quickly to form a protective layer of aluminium oxide.

3. Recycling Metals

   • To recycle metals we melt them down and make them into something new. There are many advantages to this. Recycling metals means that reserves of metal ores will last for longer and less energy is needed to recycle most metals than is needed to extract them. Recycling also reduces the need to mine ores which creates noise and dust pollution and damage landscapes. Less pollution is produced recycling metals than in extracting metals and recycling means that less materials will go into landfill sites.
     • There are also disadvantages to recycling metals. A lot of energy is needed to sort, collect and transport metals and sometimes recycling can be more expensive than extraction.
   • The first stage of recycling is collecting. This is why it is important that we separate out our metals for recycling. Next comes sorting. Magnetic metals can be easily sorted using a magnet whereas the others need to be sorted by hand. Once sorting is done, the metals are melted down into blocks and sold onto manufacturers.

4. Properties of Metals

   • Aluminium has a low density and doesn't corrode because of the aluminium oxide layer that forms quickly. It is used with other metals to make aeroplanes due to its lightness, because the lighter an airplane is the less fuel it needs. Many cars also contain aluminium for lightness.
   • Copper is an extremely good electric conductor and so is used to make electric cables. It is also used in water pipes because it doesn't react with waters.
   • Gold is very unreactive so doesn't corrode. To add to this it is very attractive and malleable so is used to make jewellery most of the time. Gold is also one of the best electrical conductors so is used in many chips in electrical devices.
   • Iron is the most used metal because it is cheap to extract. It is made into steel with carbon and other metals to make it harder and stronger. Steel is used to make bridges, cars, electrical goods, machinery and building frames. It is also magnetic but does rust.

5. Alloys

   • Most metals are mixed with other metals to give them specific properties. These are called alloys. When metals are pure the layers can easily slide over each other, because they are all the same size, and soft, which can make them difficult to use. Mixing them with other metals makes them harder and stronger because it prevents the alloys from sliding over each other.
   • There are many different variations of alloy steels. Stainless steel does not rust at all, for example. Pure gold is too soft to be used in jewellery, so other metals like copper and silver are added to make it harder and stronger. The purity of gold is measured in carats or as a fineness- pure gold has 24 carats and a fineness of 1000 parts.
     • Nitinol is an alloy of nickel and titanium and is a shape memory allow. If it's shape is changed, it returns to its original shape when heated. One of its uses is to repair damaged arteries. Doctors can insert the nitinol into the collapsed artery, and when it is warmed by the body, it will open the artery up.