How are most metals extracted?
Most metals need to be extracted from their ores using a chemical reaction
How can the economics of metal extraction change over time?
If the market price of a metal drops a lot, it might not be worth extracting it
If the price increases a lot then it might be worth extractng more of it
As technlogy improves, it becomes possible to extract more metal from a sample of rock than was origionally possible - so it might now be worth extracting metal that wasn't worth extracting in the past
Explain how metals can be extracted from their ores chemically
A metal can be extracted from its ore chemically - by reduction or by electrolysis
Some ores may have to be concentrated before the metal is extracted - this just involved getting rid of the unwanted rocky material
Electrolysis can also be used to purify the extracted metals
How can some metals be extracted by reduction?
By using carbon - when an ore is reduced, oxygen is removed from it
What determines whether a metal can be extracted by reduction?
Its position in the reactivity series
Explain how a metals place in the reactivity series decides if it can be extaracted by reduction (explain which ones can be and which can't)
Metals higher than carbon in the reactivity series have to be extracted by electrolysis (which is expensive)
Metals below carbon in the reactivity series can be extracted by reduction using carbon eg iron oxide is reducted in a blast furnace to make iron
→ This is because carbon can only take oxygen away from metals which are less reactive than carbon itself
Why is electrolysis expensive?
Becaue it requires high temperatures meaning its expensive
How can copper be extracted? (whole process)
- By reduction with carbon, the ore is heated in a furnace - this is smelting
- However the copper produced this way is impure - and impure copper doesn't conduct electricity very well which is unuseful because a lot of copper is used to make elctrical wiring
- So electrolysis is used to purify it, this is quite expensive
- This produces very pure copper which is a much better conductor
What is electrolysis?
The breaking down of a substance using electricity
What is an electrolyte?
A liquid which conducts the electricity in electrolysis
How do the electrolytes allow electrolysis to work?
They have free ions which conduct electricity
look at electrolysis notes
How do dispacement reactions work?
If you put a reactive metal into a solution of a dissolved metal compound, the more reactive metal will replace the less reactive one
This is because the more reactive metal bonds more strongly to the non-metal bit of the compound and pishes out the less reactive metal
What are scientists doing to help with the shortage of copper?
Find new ways of extracting copper from low-grade ores (ores that only contain small amounts of the metal)
Or from the waste that is currently produced when copper is extracted
2 new methods of extracting copper? Explain them?
This uses bacteria to separate copper from copper sulfide. The bacteria get energy from the bond between copper and sulfur, separeating out the copper from the ore in the process. The leachate (the solution produced by the process) contains copper, which can be extracted eg by filtering
This involved growing plants in soil that contains copper
The plants cant use or get rid of the copper so it gradually builds up in the leaves. The plants can be harvested, dried and burned in a furnace. The copper can be collected from the ash left in the furnace
Advantage and disadvantage of new methods of extracting copper?
✓ It has a smaller impact on the environment than traditional methods eg mining
✗ It is slower than the traditional methods
Good and bad things about metal extraction
✓Useful products can be made
✓Provides local people with jobs and brings money into the area
✓Services such as transport and health can be improved
✗ Mining ores is bad for the environment as it causes noise, scarring of the landscape and loss of habitats
✗ Deep mine shafts can be dangerious for a long time after the mine has been abandones
Reasons why recycling metals is important?
- Mining and extracting metals takes a lot of energy most of which cokmes from burining fossil fuels
- Fossil fuels are running out so it's important to conserve them, not only this but burning then also contributes to acid rain, global dimming and climate change
- Recycling metals only uses a small fraction of the energy needed to mine and extract new meta l (eg recycling copper only takes 15% of the energy thats needed to mine and extract new copper)
- Energy doesn't come cheap, so recycing saves money too
- Theres a finite amount of each metal in the Earth, recycling conserves these resources
- Recycling metal cuts down on the amount of rubbish that gets sent to landfill, landfill takes up space and pollutes the srroundings. If all the aluminiom cans in the UK were recycles, there'd be 14 million fewer distbins to empty each year
Basic properties of metals?
- Strong but they can be bent or hammered into different shapes
- They're good at conducting electricity
- They conduct heat well
Some uses of metals due to basic properties?
- Strength and bendability makes them good for things like bridges and car bodies
- Good for anything that needs to conduct heat, eg saucepan base
- Elecrical wires due to good conductivity
Properties of copper?
- Good conductor of electricity (ideal for electric wires)
- Hard and strong but can be bent
- Doesn;t react with water
Properties of aluminium?
- It is corrosive-resistant
- Low density
- Isn't strong but forms good, strong alloys
Properties of Titanium?
- Low density
- Very strong
- Corrosive resistant
Problems with metals/.
- Some corrode when exposed to air and water (so need to be protected eg by painting)
→ If metals corrode, they loose their strenght and hardness
- They get 'metal fatigue' meaning they can break after lots of stress and strains, which can be very dangerous
How are steels formed?
By adding small amounts of carbon and sometimes other metal to iron
3 types of steel, their properties and uses?
Low carbon steel (0.1% carbon)
→ Easily shaped, used for car bodies
- High carbon steel (1.5% carbon)_
→ Very hard, infexible, used for blades for cutting tools, bridges
- Stainless steel (chromium added, and sometimes nickel)
→ Corrosive resistant, used for cutlety, containers for corrosive substances
Why are alloys harder than pure metals?
Different elements have different sized atoms, so when smaller atoms (eg carbon) are added to bigger atoms (eg iron) the smaller carbon atoms which make it more difficult for the layers of iron to slide over each other meaning its stronger
Metals we use today but are actually alloys? And why?
- Bronze = copper + tin
Bronze is harder than copper, it is good for making medals and statues from
- Cupronickel = copper + nickel
This is hard and corrisive resistant, used to make 'silver' coins
- Gold alloys
Used to make jewellery, as pure gold is too soft
- Aluminium alloys are used to make aircrafts
Aluminium has a low density, but is alloyed to make it stronger