Metals

Elements found in the Earth’s crust Metals make up a relatively small proportion of the Earth’s crust and are normally found in rocks as ores 46% Oxygen 28% Silicon Aluminium 8% 5% Iron 4% Calcium 3% Sodium Magnesium 2% Potassium 2% Titanium 0.5% Hydrogen 0.5% All other elements 1%

Most metals are found as ores Bauxite – aluminium oxide (Al2O3) Haematite – iron oxide (Fe2O3) Malachite – copper carbonate (CuCO3) In ores, the metal or metal compound is concentrated enough to make it economic to extract the metal. Some unreactive metals such as gold can be found as the metal itself – chemical separation is not needed.

The method used to extract a metal from its ore depends on the reactivity of the metal. K Na Ca Mg Al Zn Fe Sn Pb Cu Ag Au Pt Most reactive Very reactive metals – extracted using electrolysis C More reactive metals – usually extracted by reduction – heating with carbon to remove oxygen H Unreactive metals – little or no extraction needed Least reactive Sometimes non-metals are included for reference.

Using the reactivity series, decide which items would be most corroded. Gold ring Iron sword Copper pin Silver bracelet

Match the material to the use given the property. Steel Cast iron Pure Iron

The extraction of iron – reduction in the blast furnace Raw materials ron ore (haematite) I_______ C____ oke hot waste gases L________ imestone iron oxide + carbon (coke) iron + carbon dioxide a reduction (loss of oxygen) – the iron oxide is reduced to iron metal 1500oC hot air hot air molten slag molten iron

Blast furnaces (for extracting iron) at Port Talbot

Steel Iron from the blast furnace (cast iron) is brittle since it contains about 4% carbon. It therefore has limited uses. Similarly pure iron (wrought iron) is too soft for many uses. Therefore most iron is converted into steel. Steel is basically iron with up to 1.5% carbon. Many other metals can be added to make alloy steels with a wide range of properties. Iron from the blast furnace being converted into steel

Low carbon steel (mild steel) is easily shaped

The Angel of the North is made of a steel alloy – iron combined with a small amount of copper

Stainless steel (iron with about 15% chromium) is perfect for cutlery and razor blades etc. Stainless steel doesn’t rust.

Metals are malleable They can be hammered or bent into shape Most pure metals have their atoms arranged in a regular pattern and the layers of atoms can easily slide over one another when a force is applied. Force causes layers of atoms to slide over one another

Alloys are harder than pure metals Alloys are mixtures of metals (or in the case of some steels iron mixed with carbon). They are stronger than pure metals. The different sized atoms of other metals stop the layers sliding over one another

Copper Malachite – copper ore Polished malachite Copper is a good heat and electrical conductor and used for saucepans and electrical wire. Since it is an unreactive metal it is also used for water pipes and coinage.

The outside of the Statue of Liberty is made from copper. Over time, the colour has changed as the copper has weathered.

Why are aluminium alloys used for the following?

Aluminium is extracted from the ore bauxite Aluminium is the most common metal in the Earth's crust. Aluminium is extracted from the ore bauxite However it is a reactive metal (high in the reactivity series) and has to be extracted using electrolysis (passing electricity through the molten ore). Because lots of energy is needed and there are several stages to the process, aluminium is relatively expensive despite being a common metal.

Open cast mining of bauxite in Australia

Open cast mining for metal ores What effect does this have on the environment?

Uses of aluminium Like most metals, pure aluminium is not used very much – it is usually made into alloys. Alloys of aluminium have low density and high strength, vital for the aerospace industry. Aluminium alloys were used to make the external fuel tanks of the space shuttle.

Because of its low density and good electrical conductivity, aluminium is used in overhead power cables. Although aluminium is a reactive metal it is normally covered with a protective oxide layer and doesn’t corrode easily.

Titanium Like aluminium, titanium is an extremely useful metal because it is light, strong and resists corrosion. Titanium ore It was used in the manufacture of Concorde ….. and is used in artificial hip joints

Good conductors of heat and electricity The transition metals These are found in the middle block of the Periodic Table   Sc Ti V Cr Mn Fe Co Ni Cu Zn They are useful metals and have typical metallic properties: Good conductors of heat and electricity Strong Malleable High melting point

Recycling metals Six billion aluminium cans are made each year – this is enough to reach to the moon and back! It takes the same amount of energy to make one new aluminium can as it does to make twenty recycled cans! So recycling metals such as aluminium: Saves energy Protects the environment – less rain forest has to be cut down to dig out metal ores Conserves the limited supplies of metal ores Reduces the amount of waste sent to landfill sites

Smart alloys After they are bent or deformed, these alloys regain their original shape – they have a shape memory. They have many uses e.g. Dental braces The dental brace pulls the teeth into the right position as it warms up!

Opening up collapsed arteries

Spectacle frames Spectacle frames made of ‘smart alloys’ return quickly to their original shape after being bent.