Metals and their uses Flashcards
Where do metals come from?
The Earth’s crust (combined with other chemical elements like oxygen)
What is an ore?
A rock where there is enough of the metal or metal compound to make it worth extracting
Why are silver and gold found as metals (pure) in the ground?
They are very unreactive and in their native state
What does native mean? (metals)
A metal which is found by itself, rather than in a compound- called a nugget
What is reduction?
When a metal is purified and we remove the oxygen from the compound
What is the reduction equation?
Metal oxide + carbon –> metal + carbon dioxide (If carbon is used to displace the oxygen)
Name the reactivity series from series from most reactive to least reactive…
Potassium Sodium Calcium Magnesium Aluminium (CARBON) Zinc Iron Tin Lead Copper Silver Gold Platinum
How are metals lower in the reactivity series than carbon extracted?
Reduction by carbon
What is an example of reduction by carbon?
E.g. iron oxide is reduced in a blast furnace to make iron
How are metals higher in the reactivity series than carbon extracted?
Electrolysis- this is because carbon can only take oxygen away from metals from metals which are less reactive than carbon itself
What are the problems of electrolysis?
- Expensive
- More energy required
- Latter may have been made from burning fossil fuels causing pollution
Give an example of a metal which requires electrolysis to extracted…
(Anything above carbon in the reactivity series)
Aluminium:
A high temperature is needed to melt aluminium oxide so that aluminium can be extracted- this requires a lot of energy making it expensive
What is smelting?
When a metal is extracted from its ore by the process of heating (in a furnace)
How is copper purified and what are the benefits of this?
Electrolysis:
Copper can easily be extracted by reduction with carbon but it comes out as impure- this means it cannot conduct electricity well so electrolysis is used to purify it
Benefit: very pure copper is a very good conductor even if electrolysis is expensive
What is electrolysis and what does the process involve?
Electrolysis is the breaking down of a substance using electricity
- requires a liquid to conduct electricity- the electrolyte
- electrolytes are often in metal salt solutions made from the ore or molten metal oxides
- the electrolyte has free ions- these conduct electricity and allow the whole thing to work
- electrons are taken away by the positive anode and given away by the negative cathode- as ions gain or lose electrons they become atoms or molecules and are released
How is electrolysis used to get copper?
- Electrons are pulled off copper atoms at the anode (positive rod), causing them to go into solution as Cu2+ ions
- Cu2+ ions near the cathode (negative rod) gain electrons and are turned back into copper atoms
- The impurities are dropped at the anode as sludge whilst the pure copper atoms bond to the cathode
Is pure iron useful?
No- pure iron is too soft to be useful and is therefore mixed with other elements to make alloys
What is pig iron?
Iron which has not had all of the carbon and impurities removed
What is the name for an iron alloy?
Steel
What is the name of iron which has been alloyed with a little carbon?
Carbon steel
What is the difference between high-alloy and low-alloy steels?
High-alloy steels are more expensive, containing a higher percentage of other metals- up to 12-15% from 1-5%
Why are surgical instruments made from steel? (What element has been added to the iron?)
Steel containing chromium and nickel are used because they have a greater resistance to corrosion and won’t rust
Name the properties of carbon steel... (- % iron to other element - other element - cost - uses)
- Iron= 98.5-99.97% Other element= 1.5-0.03%
- carbon
- cheapest steel to make
- bodies of cars, knives, machinery, ships, containers, structural steel for buildings
Name the properties of low-alloy steel... (- % iron to other element - other element - cost - uses)
- Iron= 95-99% Other element= 1-5%
- nickel, chromium, manganese, vanadium, titanium, tungsten
- more expensive than carbon steel
- long span bridges, bicycle chains, military armour plating
Name the properties of high-alloy steel... (- % iron to other element - other element - cost - uses)
- Iron= 85-88% Other element= 12-15%
- chromium, nickel
- even more expensive than low-alloy steel
- cooking utensils, cutlery, surgical instruments
What are the properties of aluminium?
- Silver, shiny with surprisingly low density for a metal
- Good conductor of heat and electricity
- Malleable (easily shaped) so can be drawn into wires easily
- Relatively reactive but does not corrode easily (reacts immediately with oxygen to form tough layer of aluminium oxide)
- Not particularly strong but can use it to form harder and stronger alloys
What are the uses of aluminium?
- Cans
- Cooking foil
- Saucepans
- High-voltage electricity cables
- Aeroplanes
- Space vehicles
How is aluminium extracted?
- The aluminium ore is mined containing extra impurities
- A high temperature is needed to melt aluminium oxide so that aluminium can be extracted- this requires a lot of energy making it expensive
- An electric current is passed through aluminium oxide at high temperatures to break it down
What are the properties of titanium?
- Silver-white metal
- Very strong
- Very resistant to corrosion
- Like aluminium it forms a protective oxide layer
- Denser than aluminium but less dense than most transition metals
- High melting point at 1660 degrees celsius
What are the uses of titanium?
- Bodies of high-performance aircraft and racing bikes (due to low density and strength)
- Nuclear reactors- pipes (due to high melting point)
- Replacement hip joints (due to resistance to corrosion)
How is titanium extracted?
- Can be displaced by carbon (being lower in the reactivity series) however they react together, making the titanium brittle
- A more reactive metal such as sodium or magnesium is used to displace it
- The ore must be processed by separating the titanium oxide and converting it to titanium chloride which is distilled and purified
- The titanium is then displaced by the sodium (or magnesium)- this process is very long and expensive
Why should metals be recycled?
- Lots of money is involved in extracting and using them
- It takes a lot of time to produce the metals
- There is a lot of energy involved which involves the burning of fossil fuels a lot of the time- this causes pollution
- No point in wasting already usable material
- Extra bi-products are given off in the metal’s production so this should be limited as much as possible
Why is copper in high demand?
- Useful properties
- Good for electrical wiring and plumbing
- Good conductor of heat and electricity
- Unreactive with water
Give examples of new methods used to extract copper from low-grade ores…
- Bioleaching
- Phytomining
What are the pros and cons of mining ores?
Pros:
- useful products can be made
- Provides jobs to local people
- Brings money to area
- Services such as transport and health can be improved (with influx of money)
Cons:
- Noise pollution
- Scars landscape
- Loss of natural habitats
- Can be dangerous (especially deep, old, abandoned mine shafts)
What is the process of bioleaching?
- Uses bacteria to separate copper from copper sulfide
- Bacteria gain energy from the bond between copper and sulfur, separating the copper out from the ore in the process
- The leachate (solution produced from the process) contains copper which can be extracted e.g. by filtering, displacement (using scrap iron), electrolysis
What is the process of phytomining?
- This involves growing plants in soils which contain copper
- The plants can’t use or get rid of the copper so they just absorb it and it builds up in the leaves
- The plants can then be harvested, dried and burned in a furnace
- The copper can be collected from the ash
What are the benefits and drawbacks of the new methods bioleaching and phytomining?
Benefits:
- Smaller impact on environment than traditional methods
- Much cheaper
- Bioleaching- 20% of the worlds copper is currently being extracted by this method
Drawbacks:
- Bioleaching- for some metals including copper it is not always economically feasible even with its low cost
- Not very fast processes
- Phytomining- burning releases carbon dioxide, a greenhouse gas, into the environment which increases global warming
What is the equation for smelting copper and what are its drawbacks?
Copper(+)sulfide + oxygen –> copper + sulfur dioxide
- Uses lots of energy
- Expensive
- Sulfur dioxide produces acid rain
Other than electrolysis, how else can copper be extracted from a solution?
Displacement
Scrap iron displaces copper which can then be filtered and collected
What are the properties of alloys? (9)
- Malleable
- Ductile
- Sonorous
- Conduct heat
- Conduct electricity
- Hard
- Strong
- High melting and boiling point
- Shiny
What are the properties and uses of aluminium? (simple)
- Cheap, light, conductor
- Electrical cables
What are the properties and uses of tungsten?
- Gets hot without melting
- Lamp filaments
What are the properties and uses of iron and steel (alloy)? (simple)
- Strong and cheap
- Bridges, boats
What are the properties and uses of silver?
- Soft, easy to shape
- Ring making processes
What are the properties and uses of mild steel?
- Stretched and shaped easily
- Car making, car parts
What are the properties and uses of steel rods (alloy)?
- Makes concrete stronger
- Used to reinforce concrete blocks
What are the properties and uses of mordand steel?
- Makes it more resistant to wear
- Gear teeth, cut metal
What are the properties and uses of aluminium alloy?
- Stronger, need less of it
- Used in aircraft
What are the properties and uses of silver alloy, nickel and copper?
- Easy to shape and cheaper
- Coins (silver coins e.g. 50p)
What metals can be displaced?
Those lower in the reactivity series than carbon
Why is pure iron more “bendy” than iron alloys?
The regular arrangement of identical atoms means that the layers can slide over each other, making it soft and easily shaped- iron alloys have different sized atoms making it more irregular as an arrangement and harder
