Presentation on theme: "Metals. Elements found in the Earths crust Oxygen Silicon Aluminium Iron Calcium Sodium Magnesium Potassium Titanium Hydrogen All other elements 46% 28%"— Presentation transcript:
Elements found in the Earths crust Oxygen Silicon Aluminium Iron Calcium Sodium Magnesium Potassium Titanium Hydrogen All other elements 46% 28% 8% 5% 4% 3% 2% 0.5% 1% 2% Metals make up a relatively small proportion of the Earths crust and are normally found in rocks as ores
Most metals are found as ores In ores, the metal or metal compound is concentrated enough to make it economic to extract the metal. Bauxite – aluminium oxide (Al 2 O 3 ) Haematite – iron oxide (Fe 2 O 3 ) Some unreactive metals such as gold can be found as the metal itself – chemical separation is not needed. Malachite – copper carbonate (CuCO 3 )
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 Least reactive Sometimes non-metals are included for reference. C H Unreactive metals – little or no extraction needed More reactive metals – usually extracted by reduction – heating with carbon to remove oxygen Very reactive metals – extracted using electrolysis
Iron sword Silver bracelet Gold ring Using the reactivity series, decide which items would be most corroded. Copper pin
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 I_______ C____ L________ ron ore (haematite) oke imestone hot air iron oxide + carbon (coke) iron + carbon dioxide 1500 o C molten iron molten slag hot waste gases a reduction (loss of oxygen) – the iron oxide is reduced to iron metal
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. Iron from the blast furnace being converted into steel 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.
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 doesnt rust.
Metals are malleable 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 They can be hammered or bent into shape
Alloys are harder than pure metals The different sized atoms of other metals stop the layers sliding over one another Alloys are mixtures of metals (or in the case of some steels iron mixed with carbon). They are stronger than pure metals.
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 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 doesnt corrode easily.
Titanium Like aluminium, titanium is an extremely useful metal because it is light, strong and resists corrosion. It was used in the manufacture of Concorde ….. and is used in artificial hip joints Titanium ore
The transition metals These are found in the middle block of the Periodic Table They are useful metals and have typical metallic properties: Good conductors of heat and electricity Malleable High melting point Strong ScVZnNiMnFeCrCuCoTi
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 Dental braces After they are bent or deformed, these alloys regain their original shape – they have a shape memory. They have many uses e.g. 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.