Metals

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  • Created by: ciara
  • Created on: 30-12-13 19:58

The Reactivity Series

Potassium, sodium and lithium, calcium

With water, they fizz to give off hydrogen, leaving an alkaline solution of metal hydroxide

With dilute acid, they explode, but calcium reacts with diulte acid to fizz, giving off hydrogen and forming a salt 

Magnesium, aluminium, zinc, iron

Reacts with steam giving off hydrogen and forming the metal oxide 

Reacts with dilute acid to fizz, giving off hydrogen and forming a salt 

Copper

Has no reaction with water or dilute acid

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Displacement reactions

A more reactive metal will displace a less reactive metal from its aqueous solution.

Reactivity series: potassium, sodium, lithium, calcium, magnesium, aluminium, zinc, iron, tin, lead, copper, silver, gold

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The non-metals hydrogen and carbon are often included in the reactivity series.

This is because metal plus acid reactions lead to the the displacement of hydrogen ions. Hydrogen is placed between copper and lead. Carbon can be used in the extraction of metals from their oxides. This can only happen though if the metal is less reactive than aluminium.

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Oxidation and Reduction

The metal which loses electrons is oxidised.

The metal which gains electrons is reduced

Remember: Oxygen Is Loss Reduction Is Gain

An example of this is cheap scrap iron with copper sulfate solution. 

Fe(s) + Cu2+(aq)  -> Fe2+(s) + Cu (s)

Here, iron loses two electrons (forms a positive ion), and copper gains two electrons. Therefore, iron is reduced and copper is oxidised

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Extracting Metals

Metal ore - contains enough of the metal to make it economoic to extract the metal. Ores are mined and might need to be concentrated before the metal is extracted in purified.

Gold and other unreactive metals are found in their pure native states.

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Elements below carbon (zinc and below) can be extracted from their oxides by reducing it with carbon

Elements above carbon can be extracted by electrolysing the molten metal compound. This uses large amounts of energy in the extraction of these metals, making it expensive. 

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Extracting Copper

Copper can be extracted from copper rich ores by heating the ores in a furnace. This is called smelting. This copper can then be purified by electrolysis.

The supply of copper-rich ores is limited and is being depleted. Traditional mining and extraction have major enviromental impacts. Thereofre, new ways of extracting copper from low-grade ores are being researced to limit the environmental impact of tradition mining. 

Bioleaching - using bacteria to produce leachate solutions that contain metal compounds 

Phytomining - uses plants to absorb metal compounds and the plants are burnt to produce ash that contains the metal compounds 

Electrolyisis

Cu2+(aq) + 2e- -> Cu(s)      Negative copper electrode (cathode) - pure copper

Cu(s) -> Cu2+ (aq) +2e-      Positive copper electrode (anode) - impure copper 

Displacement

Iron + copper (II) sulfate -> iron (II) sulfate + copper (iron is oxidised, copper is reduced) 

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Recycling Metals

Benefits of recycling metals

  • Extracting them uses limited resources (non renewable)
  • Cheap - extracting is very expensive
  • Extracting has bad effects on the environment - recycling limits this
  • Saves energy
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Bonding in metals

The atoms in metals are closely packed together and arranged in regular layers. They consist of giant structures. 

Positively charged metal ions held together by electrons from the outermost shell of each metal atom. These delocalised electrons are free to move throughout the giant lattice. (http://www.bbc.co.uk/schools/gcsebitesize/science/images/gcsechem_60.gif)

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Properties of Metals

  • Metals conduct heat and electricity because of the delocalised electrons in their structures that are free to move around the metal
  • The layers of the atoms in a giant metallic structure can slide over eachother, meaning they will bend and shape
  • Alloys can be made from two or more metals to make the metal harder for everyday use. They are harder, because the regular layers in the pure metal are distorted by differently-sized atoms in an alloy. Copper, gold and aluminium are all alloyed with other metals to make them harder. 
  • Shape memory alloys can return to its original shape on heating when deformed

Transition metals are found in the central block of elements in the periodic table. They have properties that make them useful for building and making things as they are good conductors of heat and electricity and can be bent or hammered into shape

 e.g. copper is used in wiring as of high electrical conductivity, conductivity of heat, hardness to make pipes or tanks and it does not react with water. 

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Iron and Steels

We extract iron from iron ore by reducing it using carbon in a blast furnace. Iron from the blast furnace contains about 96% iron. The impurities makes it very brittle, so has limited uses. It can only be usd as cast iron as of its strength in compression. 

Pure iron, is too soft to be very useful also.

Most iron, therefore, is converted into steels. Steels are alloys with mixtures of carbon and iron. Steels may also contain other metals. They are designed to have properties for specific uses

Low carbon steels - easily shaped e.g.car bodies

High carbon steels - very hard e.g. tools

Stainless steels - resistant to corrosion 

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