Properties of Metals and Alloys

Metals are strong and bendy and they are great conductors
1. Most of the elements are metals
2. All metals have fairly similar properties
  1. Metals are strong (hard to break) but can be bent or hammered into different shapes
  2. Great at conducting heat
  3. Conduct electricity well
3. Metals (especially transition metals which are found in the centre block of the periodic table) have loads of everyday uses because of these properties..
  1. Their strength and bendability makes them handy for making into things like bridges and car bodies
  2. Metals are ideal if you want to make something that heat needs to travel through like a saucepan base
  3. And their conductivity makes them great for making things like electrical wires
Metals are good but not perfect
1. Metals are very useful structural materials but some corrode when exposed to air and water so they need to be protected e.g. painting. If metal corrodes they lose their strength and hardness
2. Metals can get "tired" when stresses and strains are repeatedly put on them over time. This is known as metal fatigue and leads to metals breaking which can be dangerous
A metals properties decide on how its best used
1. Not all metals are the same
  1. Copper is a good conductor of electricity so its ideal for drawing out into electrical wires. Its hard and strong but can be bent. It also doesnt react with water
  2. Aluminium is corrosion resistant and has a low density. Pure aluminium isnt particularly strong but it forms hard strong alloys
  3. Titanium is another low density metal. Unlike aluminium its very strong. Its also corrosion resistant
2. Different metals are chosen for different uses because of their specific properties
  1. If you were doing plumbing youd pick a metal that could be bent to make pipes and tanks and is below hydrogen in the reactivity seiries so it doesnt react with water e.g. copper
  2. If you wanted to make an aeroplane youd probably use metal as its strong and can be bent into shape but it would need to be light e.g. aluminium
  3. If your making replacement hips youd pick a metal that wouldnt corrode when it comes in contact with water. Itd also have to be light and not that bendy e.g. titanium
Alloys are a mix of two metals
Pure iron tend to be a bit too bendy
1. 1. Iron straight from the blast furnace is only 96% iron. 4% is impurities such as carbon
  1. 2. This impure iron is used as cast iron. Its handy for making ornamental railing but it doesnt have many uses because its to brittle
    1. 3. So all the impurities are removed from most of the blast furnace iron. This pure iron has a regular arrangement of identical atoms. The layers of atoms can slide over each other which makes the iron soft and easily shaped however it is very bendy
2. Most iron is converted into steel an alloy
  1. Most of the pure iron is changed into alloys called steels. Steels are formed by adding small amounts of carbon and sometimes other metals to the iron
    1. Low carbon steel (0.1% carbon) properties are: easily shaped, used for car bodies
    2. High carbon steel (1.5% carbon) properties are: very hard, inflexible, used for blades for cutting tools and bridges
    3. Stainless steel (chrominum added and sometimes nickel) properties are: corrosion resistant, used for cutlery, containers for corrosive substances
Alloys are harder than pure metals
1. Different elements have different size atoms. So when an element such as carbon is added to pure iron the smaller carbon atom will upset the layers of pure iron atoms making it more difficult for them to slide over each other
2. Metals that are actually alloys
  1. Bronze = copper + tin
    1. Bronze is harder than copper. Good for making medals and statues
  2. Cupronickel = copper + nickel
    1. This is hard and corrosion resistant used to make silver coins
  3. Gold alloys are used to make jewellery
    1. Pure gold is too soft. Metals like zinc and silver are used to harden the gold
  4. Aluminium alloys are used to make aircraft
    1. Aluminium has a low density but its alloyed with small amounts of other metals to make it stronger

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