Properties and Uses

Properties and Uses

1. Properties

   • Metals are strong and they can be bent or hammered into different shapes (e.g. car bodies or bridges).
   • They are great at conducting heat and electricity (e.g. saucepans or electrical wires).
   • Aluminium has a low density and is corrosion-resistant. Pure aluminium isn't particularly strong but it forms strong alloys which make it a useful structural material (e.g. window frames. electricity cables or aircraft).
   • Copper is hard, strong and has a high melting point. It is a good conductor of electricity so is ideal for drawing out electrical wires. It can also be used for pipes as it is below hydrogen in the reactivity series so it doesn't react with water.
   • Gold is shiny and very mallable so it is used for jewellery and in situation where you want something that wont react with anything (e.g. tooth fillings and electrical circuits).
   • Some metals corrode easily as a result of oxidisation. Metals high in the reactivity series are more likely to react as they react more easily with oxygen (e.g. iron is less corrosion-resistant than lead)

2. Uses

   • Iron
     • Iron extracted from a blast furnace using carbon monoxide and is only 96% iron and 4% impurities including carbon. This makes it brittle so it can be used for ornamental railings but that is about it.
     • When all the impurities are removed, the pure iron has a regular arrangement of identical atoms meaning the layers can slide over one another making it soft and easily shaped. This iron is far too bendy for most uses.
     • Steel is formed by adding small amounts of carbon to pure iron producing strong and corrosion-resistant alloys.
       • Low carbon steel (0.1% carbon) is easily shaped and used in car bodies. High carbon steel (1.5% carbon) is very hard and inflexible used in blades for cutting tools and bridges. Stainless steel (with chromium and sometimes nickle too) is rust resistant so is used for cutlery and containers for corrosive substances.
   • Alloys
     • An alloy is a mixture of 2 or more metals or a metal and a non-metal. Different elements have different sized alloys so, for example, when carbon is added to pure iron, the smaller carbon atom will disrupt the layers of the pure iron atoms making it more difficult for them to slide over one another causing them to be harder.
     • As we understand properties of metals, alloys can be designed for specific uses.
   • Gold
     • Gold alloys are sued to make jewellery as pure gold is too soft. Metals such as zinc, nickle and copper are used to harden it. Proportions of gold in an alloy are described by carats or fineness. Pure gold is 24 carats so 18 carats is 18/24 parts of the alloy are gold (75%). Fineness refers to the parts of pure gold per 1000 so 750 fineness is roughly the same as 18 carats.

3. Recycling

   • Recycling is important as it uses less resources as there is a finite amount of metal in the earth. It also uses less energy as mining and extraction needs lots of energy which mostly comes from burning fossil fuels (causing pollution) recycling copper and aluminium takes a fraction of the energy. It is cheaper and it makes less waste too reducing the amount of rubbish that goes into landfill that takes up space and pollutes the surroundings.
   • It isn't free as there are costs involved in collecting, transporting, sorting and processing it but it is cheaper than mining and extracting. (e.e. for every 1kg of aluminium cans you save 95% of the energy needed to extract fresh aluminium, 4kg of aluminium ore and a lot of waste. In fact, aluminium is one of the most cost-effective metals to recycle).
   • Mining makes a mess of the landscape and you need to mine 4 tonnes of every 1 tonne of aluminium needed.