Extraction and Uses of Metals Flashcards
Where are most metals found?
The earth’s crust
What is an ore?
A substance (usually a rock) that contains enough of a metal to make it worthwhile extracting
What are the two kinds of ores found?
- Compounds, usually metal oxides ( e.g. aluminium oxide)
- Pure elements in the case of unreactive metals (e.g. gold)
While unreactive metals are found naturally pure, metals such as aluminium which are found within compounds need to be extracted through various methods
What are the two main methods of extracting metals?
- Electrolysis
- Reacting with carbon
Of the two main methods for extracting metals, which ones are used for which metals and why?
- Electrolysis is used for metals which are more reactive than carbon, as reacting with carbon will not work for these metals
- Reacting with carbon is used for metals which are less reactive than carbon as it is much cheaper than electrolysis
Electrolysis will work for all metals, however it is simply more expensive so reacting with carbon will be used when possible
How does the reacting with carbon method of extracting metals work?
- A compound of the given metal, usually an oxide or chloride is heated with carbon
- Assuming it is less reactive than carbon, the chloride/oxide will be displaced by the carbon, forming carbon dioxide or carbon chloride respectively as well as the pure metal
- Carbon is thus oxidised and the metal is reduced
What is an alloy?
- A substance consisting of a metal mixed with other elements, often other metals or carbon
- They are physically mixed, but not chemically combined
Why are alloys harder than pure metals?
- The introduction of elements of a different size to the metallic lattice disrupts the regular arrangement
- There are now atoms of different sizes within the arrangement
- Therefore layers of atoms are unable to slide over each other as before
- Therefore the alloy is less malleable and ductile than the pure variant of the given metal
Brass is an example of an alloy which is comprised of 70% copper and 30% zinc
What are some uses of aluminium and what are its key properties which permit these uses?
Uses: Aeroplanes and vehicle bodies, sauce pans, window frames, food cans
Properties:
* Low density - high strength to weight ratio
* Good conductor of heat (and electricity)
* Resistant to corrosion - due to formation of thin oxide layer (so it will not corrode and can be used to protect other metals from corrosion)
* Unreactive and non-toxic - due to its formation of thin oxide layer (if not for this layer, aluminium is quite reactive)
What are some uses of copper and what are its key properties which permit these uses?
Uses: Electrical wires, water pipes
Properties:
* Very good conductor of electricity (and heat)
* Unreactive and non-toxic - due to its position in the reactivity series
* Abundant
What is low carbon (mild) steel, what are its uses and what are its key properties which permit these uses?
- Mild steel is iron which is alloyed with relatively low (0.25%) proportions of carbon
- Uses: Car body panels, nails, bridges
Properties:
* Strong - due to the infused carbon, but not extremely hard
* Malleable - due to the low levels of carbon
* Easily corrodible and dense
What is high carbon steel, what are its uses and what are its key properties which permit these uses?
- High carbon steel is iron which is alloyed with relatively high (0.5-1.5%) proportions of carbon
- Uses: Knives, tools
Properties:
* Very Strong - due to the alloyed carbon
* Hard and brittle (not malleable) - due to the high levels of carbon
* Easily corrodible and dense
What is stainless steel, what are its uses and what are its key properties which permit these uses?
- Iron alloyed with large proportions of chromium (20%) and often nickel (10%)
- Uses: Sinks, saucepans, utensils, food production
Properties:
* Resistant to corrosion - due to chromium forming an oxide layer like aluminium does
* Expensive - In comparison to mild steel due to the chromium and nickel
