C1.3 Metals and their uses Flashcards
Define ‘ore’
A rock containing enough metal to make it economically worthwhile extracting
What happens to ores before the metal is extracted?
- Mined
- Concentrated
How might the economics of extraction change over time?
- If the market price decreases, it might not be worth extracting it
- If the market price increases, it might be worth extracting more of it
- As technology improves, it becomes possible to extract more metal than was originally possible.
How are metals usually found in the earth?
As compounds - oxides of the metals - that need chemical reactions to extract the metals
Why are some metals found in the earth as the metal itself?
They are unreactive e.g gold
What is the ore of aluminium?
Bauxite
What is the ore of copper?
Chalcopyrite
What is the ore of iron?
Haematite
What is the ore of titanium?
Rutile
Define ‘reduction’
A chemical reaction in which oxygen is removed
Which metals can be reduced with carbon?
Metals less reactive than carbon
What is the process of reaction with carbon?
The ores are reacted with carbon to remove the oxygen in them e.g iron oxide (haematite) + carbon ===> iron + carbon dioxde
Explain how iron oxide is reduced in a blast furnace.
- Iron oxide, limestone and coke are put in the top of the blast furnace
- Hot air is blown in at the bottom
- Carbon monoxide reduces the iron core (at high temperatures carbon dioxide in the air reacts to form carbon monoxide)
- Molten slag and iron come out at the bottom
How are metals more reactive than carbon extracted?
With electrolysis of their molten compounds
Give an example of a metal extracted with electrolysis.
aluminium from aluminium oxide (bauxite)
Why is electrolysis expensive?
A high temperature is needed to melt the metals, which uses a high amount of energy
What is smelting?
Heating a copper ore in a furnace to reduce it with carbon
Why does copper undergo electrolysis after smelting?
To purify it so that it can conduct electricity
What is electrolysis?
The breaking down of a substance using electricity
What is the electrolyte and what is it usually made of?
The liquid that conducts the electricity in electrolysis, it’s usually made of molten metal oxides or a metal salt solution from the ore.
What is an important property of the electrolyte and why?
It contains free ions, they conduct electricity and allow the whole thing to work
What happens at the anode in the electrolysis of copper?
Electrons are taken away from the copper ions, causing them to become copper positive ions
What happens at the cathode in the electrolysis of copper?
The copper ions gain electrons and become copper atoms again.
What is displacement?
A reaction where a more reactive metal replaces a less reactive one in a dissolved metal compound.
Why does displacement happen?
The more reactive metal bonds more strongly to the non-metal part and pushes out the less reactive metal.
How is copper displaced?
Using scrap iron - useful because its cheap
Its put in a solution of copper sulfate:
copper sulfate + iron ==> iron sulfate + copper
Why is important to recycle copper?
- The supply of copper rich ores is limited
- The demand for copper is growing
What are scientists looking into to supply the demand for copper?
- Ways of extracting copper from low grade ores
- Ways of extracting copper from the waste produced from copper extraction
Explain bioleaching
- Bacteria separate copper from copper sulfide
- They get energy from breaking the bond between the copper and the sulfur
- The leachate (solution) they produce from this process contains copper which is extracted
Explain phytomining
- Plants absorb copper compounds through their roots in copper rich soil
- The plants can’t use the copper so it builds up in the leaves and roots
- The plants are then harvested, dried and burnt in a furnace
- The copper is collected from the ash
Why are the current methods of extracting aluminum and titanium expensive?
- There are many stages involved
- Large amounts of energy are needed
What are the advantages of extracting metals?
- Useful products
- Local people have jobs
- Improves the area’s economy
What are the disadvantages of extracting metals?
- Causes noise
- Scarring of the landscape
- Loss of habitats
- Abandoned deep mine shafts can be dangerous
Give 6 reasons to recycle metals.
- Mining and extracting metals uses up energy and therefore fossil fuels which causes more acid rain, global dimming and climate change
- Fossil fuels are running out and so need to be conserved
- Recycling saves money as energy is expensive
- Recycling conserves metal resources in the earth
- Recycling cuts down on the amount of rubbish = less landfill
How much iron does cast iron contain?
96% - the rest is carbon
Why does cast iron have limited uses?
It is brittle
What is the one good property of cast iron?
Good strength in compression
What is cast iron used for?
Ornamental railings
What is high carbon steel used for and why?
- Bridges and cutting tools
- It’s very hard, inflexible and brittle
What is low carbon steel used for and why?
- Car bodies
- Easily shaped
What is stainless steel used for and why?
- Cutlery and containers for corrosive substances
- Its corrosive resistant
Why are alloys harder than pure metals?
- Different elements have different sized atoms
- When carbon is added to pure iron, the smaller carbon atoms upset the regular arrangement of the pure iron atom layers
- This makes it more difficult for them to slide over each other
Why are pure metals such as copper, gold and aluminium mixed with small amounts of similar metals?
They would be too soft otherwise, they are mixed to make them harder for everyday use
Give 4 examples of alloys used today
- Copper + tin = bronze = hard = medals and statues
- Copper + nickel = cupronickel = hard and corrosion resistant = silver coins
- Gold alloys = harder = jewellery
- Aluminium alloys = strong and low density = aircraft
Give 4 properties of transitional metals
- Strong
- Can be bent and hammered into shapes
- Conductors of heat
- Conductors of electricity
What are transitional metals useful for?
- Bridges
- Something for heat to travel through e.g a saucepan base
- Electrical wires
What are the two main uses of copper and what properties make it useful for this?
- Electrical wiring = good conductor of electricity
- Plumbing = doesn’t react with water, hard and strong but can be bent
What is aluminium used for and what properties make it useful for this?
- Strong
- Can bent into shape
- Light
- Airplanes
What is titanium used for and what properties make it useful for this?
- Light
- Doesn’t corrode
- Doesn’t bend easily
- Replacement hips
What are the problems with metals as materials?
- Many corrode when exposed to air and water (need painting)
- Metals can get ‘tired’ when stress and strain is repeatedly on them over time (known as metal fatigue)
