Metals Flashcards
2 components of the structure of a metal
Lattice of positive metal ions
A sea of delocalised electrons
Metallic bonding definition
Electrostatic attraction between positive metal ions and negative delocalised electrons
3 metallic properties
HIGH MELTING POINT - metallic bonding is very strong so lots of energy is required to break it
CONDUCT ELECTRICITY- delocalised electrons are free to move the rough the lattice
MALLEABLE- layers of metal can slide over eachother
Metal reactivity least to most
Gold Silver Copper HYDROGEN lead Iron Zinc CARBON Aluminium Magnesium Calcium Lithium Sodium Potassium
What are ores
Most metals are found in the Earth’s crust as compounds with oxygen and sulphur
The rocks containing specific metal compounds are called ores
(Copper- Potassium)
What are natives
Gold and silver are too unreactive to have combined with oxygen and sulphur. They are found native which means that they are chemically uncombined
extraction from ores
ELECTRICITY
Metals more reactive than carbon cannot be displaced by carbon
Instead, electricity is used to break down their compounds
extraction from ores
CARBON
Metals less reactive than carbon can be displaced by carbon
Eg copper can be displaced from its ore (copper oxide) by heating with carbon
Carbon + copper oxide —> carbon dioxide + copper
Reduction definition
Loss of oxygen
Oxidation definition
Gain of oxygen
Reducing agent definition
Takes oxygen away from something else
Oxidising agent definition
Gives oxygen to something else
Redox reaction definition
Reduction and oxidation in the same reaction
Eg carbon is used to extract zinc from zinc oxide
Chemical name for rust
Hydrated iron (III) oxide
Rusting definition
Chemical process by which iron is oxidised from rust
2 stages of rusting
- Iron is oxidised by oxygen to form iron (III) oxide:
4Fe(s) + 3O2(g) —> 2Fe2O3(s)
Fe has gained oxygen and lost electrons to form Fe3+ ions - Iron (III) oxide is hydrated by water
Fe2O3(s) + xH2O (l) —> Fe2O3 . xH2O (s)
The amount of water gained by the iron (III) oxide varies alot
Preventing rusting
USING BARRIERS
Coating the iron in paint, oil, grease or plastic prevents the iron from coming into contact with oxygen or water
This only works when coating is intact, as soon as it breaks rusting happens
Preventing rusting
SACRIFICIAL PROTECTION
Attach a block of a more reactive metal (eg magnesium) to the iron
This works by displacing the iron from rust as soon as rust forms
The downside of this is the block of magnesium has to be replaced often
Equation: Magnesium + Iron (III) oxide —> magnesium oxide + iron
3Mg (s) + Fe2O3 (s) —> 3MgO(s) + 2Fe(s)
Preventing rusting
GALVINISING
Involves coating iron in zinc
Coating protects O2 and H2O from coming into contact with the iron
Even if a crack appears the zinc is more reactive than the iron so acts as sacrificial protectin
What is an alloy
Mixture of a metal with one or more other elements or carbon
Alloys are harder than pure metals because the different sized atoms/ ions prevent the layers of metal ions from sliding over each other- less malleable
Iron use
Making steel- more useful than iron
Low carbon steel use
Ships cars bridges, sting but can be hammered into different shaped
High carbon steel
Tools knives
Stainless steel
Cutlery, kitchen sinks
Copper
Wires, water pipes, good conductor and unreacgive
Aluminium
Aircraft bodies, power cables
Low density high strength
