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Metals-Olevel Cheat Sheet by

A brief summary of the topic on Metals

Properties of Metals

Metals have very high densities - A large number of metal atoms are closely packed in the giant metallic lattice
Metals are good conductors of heat and electr­icity - presence of sea of deloca­lised electr­ons­(help to conduct heat and electr­icity)
Metals are soft - When a force is applied, layer of metal atoms will slide over one another
Metals are malleable and ductile - When a force is applied, layer of metals slides over one another without disrupting metallic bonds
Metals have a high melting point - Large amount of energy is required to overcome the strong metallic bonds between lattice of positive cations and sea of deloca­lised electrons
Remember: Metallic bonding in metals

Alloys

What is an alloy - mixture of a metal with one or more other elements
Effect of alloying - makes the original metal stronger, harder and more resistive to corrosion
How does alloying strengthen metals - Neat, regular rows of metal atoms are disrupted by the presence of a new atom of a different size. Layers of metal atoms can no longer slide over one another when a force is applied. Hence the metal is stronger and harder
Common alloys - Steel/ Brass
 

Reactivity Series

K
Na
Ca
Mg
Al
C
Zn
Fe
Sn
Pb
H
Cu
Ag
Au
Trend of reactivity series: Reactivity decreases down the series

Reactions that establish the reactivity series

Metal + Water = Metal hydroxide + Hydrogen
Metal + Steam = Metal oxide +Hydrogen
Metal + HCL = Metal Chloride + Hydrogen gas
Metals that react with cold water - Potassium to Magnesium (decre­asing vigour)
Metals that react with steam: Potassium to Iron
Metals that react with hydroc­hloric acid: Potassium to Iron
Why does lead not react with water/­ste­am/HCl = Formation of lead hydroxide, lead oxide, lead chloride which are all insoluble (form layer)

Reactions based on reactivity series

Displa­cement - A more reactive metal displaces a less reactive metal from its salt solution/ oxide (more reactive metal in solid state/less reactive metal in ion state)
Thermal Stability of carbonates - Thermal stability of carbonates decreases down the reactivity series
Most thermally stable carbonates - Group 1 carbonates
Thermal decomp­osition of carbon­ates= metal oxide + carbon dioxide
Thermal decomp­osition of silver carbonate= silver + carbon dioxide + oxygen
 

Extraction of metals

Electr­olysis of molten ore - Potassium to Aluminium
Reduction of carbon : Below Carbon in reactivity series
Reduction of hydrogen : Iron - Copper
Found chemically uncomb­ined: Silver and Gold
Extraction of iron - Use carbon to reduce haematite to form molten iron ( blast furnace)

Rusting

Rusting - oxidation of iron to form hydrated iron(III) oxide
Conditions for rusting - Both oxygen and water
Prevention of rusting: Protective layer(­oil­/pa­int), Sacrif­icial Metals, Use of alloys
Protective layer (must cover entire surface): prevents iron from coming in contact with oxygen and water—­pre­vents rusting
Sacrif­icial Protec­tion(no need to cover entire surface): Metal A is more reactive than Metal B. Metal A acts as a sacrif­icial metal and corrodes in the place of iron
Example of sacrif­icial protec­tion- Galvan­isi­ng(­Zinc)
Use of alloys - alloys are more resistive to corrosion
Do not use sodium and potassium as sacrif­icial metals (too reactive)
Use zinc/m­agn­esium

Recycling of metals

Why must we recycle metals - Metals are finite resources. It is our respon­sib­ility to conserve metals for future purposes
Problems with mining: contribute to enviro­nmental pollution, burning of fossil fuel, contri­butes to unnece­ssary waste(take up landfill space)
Cons of recycling: Expensive process

Why is aluminium unreac­tive?

Reacts with oxygen in surrou­nding air to form aluminium oxide. Aluminium oxide forms an impervious layer on the surface of the metal
Prevents metal form coming into contact with the other reactant
Prevents metal form coming into contact with the other reactant
Hence aluminium is unreactive
   
 

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