Metals

found on the left of the periodic table

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  • Created by: Harri
  • Created on: 16-06-11 18:16

properties of metals

metals are:

  • hard
  • strong
  • dense - heavy
  • shiny
  • ductile - can be drawn into a wire
  • malleable - can be hammered without cracking
  • good conductors - of heat and electricity
  • sonorous - sounds when struck (e.g. bell)
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Occurance of Metals in Earth's Crust

  • some metals are found as uncombined metalic elements in the earth's crust ie. ans native metals such as gold and copper
  • most metals are found as compounds such as copper sulphate (CuSO₄) and magnesium cholride (MgCl₂)
  • some metals are more reactive and will have already reacted with the elements in the earth.
  • the elements are most likely to be combined with oxgen because it is common and quite reactive.
  • an ore is a substance that contains enough of the metal to make extraction worth while
  • to extract a metal from its ore, when it is at the top of the periodic table, it needs elecrolisis, if its in the middle, it needs a reduction reaction and if its at the bottom it doesnt need anything
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reactivity series with water

metals show similar physical properties but can differ in their chemical properties. some metals are very reactive eg. potassium while others are extremely unreactive eg. gold

the reactivity series stays in the same order but the reactions change with acid water etc.

  • potassium (K)
  • sodium (Na)         hissing, exothermic, effevesance, hydrogen and metal hydroxie produced
  • lithium (Li)
  • calcium (Ca)        fast but not vigerous  
  • magnesium (Mg)  slow reaction
  • aluminium (Al)      only reacts with warm water
  • zinc (Zn)             
  • iron (Fe)              dont react with water unless its steam
  • tin (Sn)
  • lead (Pb)
  • copper (Cu)
  • silver (Ag)            dont react at all
  • gold (Au)
  • platinum (Pt)
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reactivity series with hyrocholric acid

  • the metals where mixed, the gas produces was lit. when hydrogen is lit it pops.
  • calcium (Ca)        effervessence exothermic  
  • magnesium (Mg) quite squeeky pop, exothermic
  • zinc (Zn)             loud squeeky pop
  • iron (Fe)              squeeky pop
  • copper (Cu)         no effervessence
  • metal + acid → salt + hydrogen eg. zinc + sulphuric acid → zinc sulphate + hydrogen
  • potassium (K)
  • sodium (Na)         explosive
  • lithium (Li)
  • calcium (Ca)       
  • magnesium (Mg) 
  • aluminium (Al)     
  • zinc (Zn)                react with decreasing vigerousness            
  • iron (Fe)             
  • tin (Sn)
  • lead (Pb)
  • copper (Cu)
  • silver (Ag)            no reaction
  • gold (Au)
  • platinum (Pt)
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displacement, oxidisation and reduction

simply put, a more reactive metal will displace a less reactive metal. for example if magnesium metal is added to a copper sulphate solution a reaction takes place becuase magnesium is more reactive than copper. the magnesium will displace the copper from the solution - therefore magnesium sulphate and copper would be formed.

magnesium + copper sulphate → magnesium sulphate + copper

Mg                  +  CuSO₄                   →  MgSO₄                           + Cu

Oil Rig -  oxidisation is loss, reduction is gain (electrons) but the opposite with oxygen. in magnesium + copper oxide → magnesium oxide + copper, the magnesium looses electrons and gains an oxygen, it is oxidised. the copper looses an oxgen but gains electrons, its reduced.

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Extrecting Metals from their Ores

  • potassium (K)
  • sodium (Na)        
  • lithium (Li)             electrolisis
  • calcium (Ca)       
  • magnesium (Mg) 
  • aluminium (Al)     
  • zinc (Zn)                           
  • iron (Fe)             
  • tin (Sn)                 reduction
  • lead (Pb)
  • copper (Cu)
  • silver (Ag)           
  • gold (Au)              digging (found as native metals)
  • platinum (Pt)

reduction is often done by heating with carbon which is between aluminium and zinc in the reactivity series, but is not a metal. this is a reletivly cheep method of extracting from ores

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industrial extraction of iron

this is done in a blast furnise with the ore iron (III) oxide or haematite (Fe₂O₃). limestone is used to remove acidic impurities by neutralisation, and coke or carbon is used as a reducing agent. the iron made in the furnace is pig iron.

(http://www.revisionworld.com/files/iron.jpg)

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electrolysis

the more reactive metals are extracted by electrolysis. compounds that contain a metal are ionic. the metal ion is posotive and is called the cation. the non-metal is negative and is called the anion. the metal compound is melted by heating it and an electric current is passed through it via two electrodes. the positive electrode is called the anode. the negative electrode is called the cathode.

the posotive ions (cations) are atracted to the negative electrode (cathode). here the metal is made.

aluminium is very expensive compared to iron because the electricity is very expensive.

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Alloys

pure copper, gold, iron and aluminium are too soft for many uses and so are mixed with small amounts of similar metals to make alloys which are harder for everyday use.

alloys are mixtures of metals. steel is an alloy of iron. it is made up of this metal plus a small amount of carbon. other metals can be added to steep to give it different properties. for example chronium and nickel can be added to make stainless steel. this type of steel is important because it does not corode.

brass is an alloy of copper and zinc. the copper is made harder by the addition of zinc. in brass the small copper atoms cant slide past eachother so easily because the larger zinc atoms get in the way.

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smart alloys

smart alloys 'memorise' the shape that they where made to. if the shape changes then when the metal is heated it will go back to its origional shape. smart alloys are nitino, nickle and tin. they are also known as shape memory alloys (SMA). examples of smart alloys are braces and glasses. if the glasses get bent out of shape then they can be heated up and go back to thier origional shape. this means that they are harder to snap. braces are made in the shape that a densist wants your teeth to be. the braces are fixed while they are cold. the body tempreature (inside the mouth) makes the smart alloly go back to its origional shape.

smart alloys can be used to  open colapsed arteries  called stents. they are inserted into the artery when cold and then heated up by the body and expand to open the artery.

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transition metals

the transition metals are found in the middle of the periodic table. they form colourful compounds. their properties are typical of metals but they are often harder than non-transition metals. for example iron can be used for man-hole covers because it is heavy and will stay in place. they are ductile and maleable.

transition metals are often good catalysts and speed up many reactions.

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leaching and bioleaching

a method which is sometimes used for mining copper. sulphuric acid is sprayed onto the rock. copper compounds com out of the rock and solution is collected. the copper is then removed either by electrolysis - breaking the compound apart using electricity or by adding scrap iron to the copper sulphate solution. leaching can cause problems if the acid gets into rivers.

bioleaching, low grade ore and discarded rock from conventional mining can still have metals like copper and iron extracted from them economically by bioleaching. these metals often occur as solphides which are insoluble in water. acid is sprayed onto the ore which encourages the growth of bio-leaching bacteria (they prefer acidic conditions). these bacteria convert the insoluble sulphide into soluble sulphates. the sulphates dissolve (or 'leach') into the water and the resulting metal solution can then be collected and the metal extracted by electrolysis.

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phytomining

plants are grown that absorb metal compounds in the soil. these plants are then harvested and burned. the energy released from burning can be used to generate electricity. the resulting ash contains metal compounds from which the metal can be extracted by either electrolysis or displacement.

advantages of biological methods of extraction - cost effective, use little energy, can function well at low concentrations of metals, dont usually produce harmful products.

plants can also be used to decontaminate land from metals such as lead, nickle or zinc, this process is called phytoremediation.

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