Topic 3: Metals and Alloys
- Created by: lois.michels
- Created on: 20-03-16 14:45
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- Topic 4: Metals
- Metal Extraction
- Most metals are extracted from ores found in the Earths's crust.
- Unreactive metals are found in the Earth as uncombined elements.
- Most metals are extracted from their ores by heating with carbon, such as iron is, or through electrolysis, like aluminium is.
- The method used to extract the metal is based on its place in the reactivity series.
- The more reactive a metal is, the harder it is to extract.
- The harder a metal is to extract, the more it costs to extract. Electrolysis is more expensive than carbon heating due to the cost of electricity.
- Metals up to and including Zinc are extracted by carbon heating.
- Potassium, Sodium, Calcium, Magnesium, and Aluminium all require electrolysis. Electrolysis decomposes metals into their compounds.
- Gold, silver and platinum are all found as uncombined elements.
- The more reactive a metal is, the harder it is to extract.
- The method used to extract the metal is based on its place in the reactivity series.
- Most metals are extracted from ores found in the Earths's crust.
- Redox
- Oxidation is the gain of oxygen, reduction is the loss of oxygen.
- The extraction of metals involves reduction of ores. Most ores are found as oxides.
- The oxidation of metals results in corrosion.
- A metal's resistance to corrosion is related to its position in the reactivity series.
- Iron Oxide + Carbon --> Iron + Carbon Dioxide
- Iron is obtained by the removal of oxygen from Iron Oxide through carbon heating. The iron oxide is reduced to iron.
- Aluminum Oxide --> Aluminium + Oxygen
- Recycling Metals
- Many metals can be recycled. This is when a metal is melted down and made into something new.
- Natural reserves of metal ores will last longer if metals are recycled.
- For most metals, less energy is needed to recycle than extract.
- Recycling aluminium can use just 5% of the energy needed to extract it. This also makes it cheaper.
- Recycling can reduce the need to mine ores. Mining can damage the landscape and created noise and dust pollution.
- Recycling produces less pollution.
- Sulfur Dioxide is formed when lead is extracted, and carbon dioxide is emitted when fossil fuels are used to generate the energy for electrolysis.
- More recycling means less waste metals are disposed of in landfill sites.
- Metals and Alloys
- The uses of metals are related to their properties.
- Aluminium has a low density. It does not corrode either.
- It is used to make airplanes, because the lighter the plane the less fuel it needs.
- Copper is an extremely good electrical conductor and low reactivity with water.
- Electrical cables are made using copper, and also water pipes.
- Gold is nonreactive and does not corrode. It is also very attractive.
- Its main use is jewellery because it an be worked easily into shapes and it does not tarnish.
- It is also one of the best electrical conductors and is used in printed circuit boards.
- Iron is very cheap to extract, but is not very strong so is made into steel which is stronger and harder.
- It is often a mixture of iron and carbon with other materials. It is used to make bridges, cars, electrical goods, machinery and building frames. It is also magnetic.
- Aluminium has a low density. It does not corrode either.
- Converting metals into alloys makes them stronger.
- The new particles jam up the structure of the old atoms so they cannot move and slide over each other as easily.
- Iron is alloyed with other metals to produce alloy steels with higher strenght and reistance to corrosion.
- Alloying changes the properties of metals.
- Shape memory alloys
- Nitinol is an alloy of nickel and titanium. If the shape of the alloys is changed it returns when heated.
- Some gold alloys have higher strength, including fineness and carats which indicate the percentage of pure gold.
- Shape memory alloys
- New materials are developed by chemists to fit new applications.
- The uses of metals are related to their properties.
- Metal Extraction
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