C1-Metals from Rocks

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Ores

A metal ore is a rock which contains enough metal to make it worthwhile extracting the metal from it. 

  • In many cases the ore is an oxide of the metal. For example: the main alluminium ore is called bauxite- it's alluminium ore.
  • Most metals have to be extracted from their ores using a chemical reaction.
  • A metal can be extracted from its ore by reduction or by electrolysis. 
  • Some ores may have to be concentrated before the metal is extracted-this just involves getting rid of the unwanted rocky material. 
  • Electroylysis can also be used to purify the extracted metal. 
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Reduction with carbon

  • A metal can be extracted from its ore chemically by reduction using carbon.
  • When an ore is reduced, oxygen is removed from it.
  • The position of the metal in the reactivity series determines whether it can be extracted by reduction with carbon.

- Metals below carbon in the reactivity series can be extracted by reduction using carbon. This is because carbon can only take the oxygen away from metals which are less reactive than carbon itself.

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Electrolysis

-Some metals have to be extracted by electrolysis. 

  1. Metals that are more reactive than carbon have to be extracted using electrolysis of molten compounds.
  2. The process is much more expensive than reduction with carbon because it uses a lot more energy.

-Copper is purified by Electrolysis.

  1. Copper can be easily ectracted by reduction with carbon. The ore is heated in a furnace in a furnace-this is called smelting.
  2. However, the copper produced in this way is impure- and impure copper does not conduct electricity very well.
  3. Electrolysis produces very pure copper, which s a much better conductor.

-Electrolysis means 'splitting up with electricity'

  1. It requires a liquid to conduct the electricity, called the electrolyte. 
  2. Electrolytes are often metal salt solutions made from the ore or molten metal oxides.
  3. The electrolyte hass free ions-these conduct the electricity and allow the whole thing to wor.
  4. The 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 realeased.
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Electrolysis: Copper

  1. Electrons are pulled off copper atoms at the anode, causing them to go into solution as Cu2+ ions.
  2. Cu2+ ions near the cathode gain electrons and turn back into copper atoms. 
  3. The impurities are dropped at the anode as a sludge, whilst pure copper atoms bond to the cathode.
  4. The cathode starts as a thin piece of pure copper and more pure copper adds to it. 
  5. The anode is a big pure lump of impure copper, which will dissolve.

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Displacement reaction: Copper

You can Extract copper from a solution using a displacement reaction.

  1. More reactive metals react more vigourously than less reactive metals. 
  2. If you put a reactive metal into a solutin of a dissolved metal compound, the reactive metal will replace the less reactive metal in the compound. 
  3. This is because the more reactive metal bonds more strongly to the non-metal bit of the compund and pushes out the less reactive metal.
  4. For example, scrap iron can be used to displace copper from solution- this is really useful because iron is cheap but copper is expensive. If some iron is put into a solution of copper sulfate, the more reactive iron will 'kick out' the less reactive copper from the solution. You end up with iron sulfate solution and copper metal. 
  5. Copper sulfate+Iron---->Iron sulfate+Copper. 
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Copper Ores

The supply of cooper-rich ores is limited, so it's important to recycle as much copper as much as possible.

- Scientists are looking into new ways of extracting copper from low-grade ores or from waste that is currently being produced when copper is extracted.

-Examples of new methods to extract copper are bioleaching and phytomining.

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Bioleaching

This uses bacteria to seperate copper from copper sulfide. The bacteria get energy from the bond between copper and sulfur, seperating out the copper from the ore in the process. The leachate (the solution produced by the process) contains copper, which can be extracted, e.g. by filtering. 

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Phytomining

This involves growing plants in soil that contains copper.

The plants can't use or get rid of the copper so it gradually builds up in the leaves. The plantscan be harvested, dried and burned in a furnace. The copper can be collected from the ash left in the furnace.

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Impacts of extracting metals: Good

  • Mining metal ores is good because it means that useful products can be made. 
  • It provides local people with jobs.
  • Brings money into the area.
  • Services such as transport and health can be improved by using this money.
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Impacts of extracting metals: Bad

  • Mining ores is bad for the environment as it causes noise.
  • Scarring of the landscape.
  • Loss of habitats.
  • Deep mine shafts can also be dangerous for a long time after the mine has been abandoned. 
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Recycling Metals

Recycling metals is IMPORTANT

  1. Mining and extracting metals takes lots of energy, most of which comes from burning fossil fuels.
  2. Fossil fuels are running out so it's important to conserve them. Not only this, but burning them contributes to acid rain, global dimming, and climate change.
  3. Recycling metals only causes a small fraction of the energy needed to mine and extract new metal.
  4. Energy doesn't come cheap, so recycling saves money too. 
  5. Also, there's a finite amount of each metal in the Earth. Recycling conserves these resources.
  6. Recycling metal cuts down on the amount of rubbish that gets sent to landfill. Landfill takes up space and pollutes the surroundings.
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Properties of Metals

-All matals have some fairly similar basic properties:

  • Metals are strong (hard to break), but they can be bent or hammered into different shapes.
  • Conduct heat.
  • Conduct electricity well.

-Metals ( and especially TRANSITION METALS) have loads of every day uses because of these properties:

  • Their strength and bendability makes them great for making things like bridges and car bodies.
  • Metals are ideal if you want to make something that heat needs to travel through , like a saucepan base.
  • Their conductivity maes them great for electrical wires.
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Specific metals and their properties

-Copper is  good conductor of electricity, so it's ideal for drawing out into electrical wires. It's hard and strong but can be bent. It doesn't react with water.

  • Used for making pipes and tanks in plumbing

-Aluminium is corrosion-resistant and has a low density. Pure aluminium isn't particularly strong, but it formshard, strong alloys. 

  • Making Aeroplanes

-Titanium is another low density metal. Unlike aluminium it's very strong. It is also corrosion-resistant.

  • Hip replacement - due to it not corroding when it comes into contact with water.
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Pure Iron

  • 'Iron' straight from the blast furnace is only 96% iron. The other 4% is impurities such as carbon. This impure iron is used as cast iron, but there are not many other uses because it is brittle.
  • So all the impurities have to be removed. 
  • The pure iron has a regular arrangement of identicle atoms. The layers of the atoms can slide over each other, which makes the iron soft and easily shaped. This iron is too bendy for most uses.
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Steel

Most iron is coverted into steel- an alloy.

  • Steels are formed by adding small amounts of carbon and sometimes other metals to the iron. 
  1. Low carbon steel (0.1% carbon)- Easily shaped- Can be used for car bodies.
  2. High carbon steel (1.5% carbon)- Very hard, inflexible- can be used for cutting tools, bridges.
  3. Stainless steel (chronium added, and sometimes nickel)- corrosion resistant- can be used for cutlery, containers for corrosive substances.
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Alloys

What is an alloy?

- Two or more elements (usually metals metals) 1 must be a metal.

Explain why steels (alloys of iron and carbon) are more useful tha pure iron?

-Because they are stronger and less corrosive and most resistant to corrosion.

Alloys are harder than pure metals

  • Different elements have different sized atoms. So when an element such as carbon is added to pure iron, the smaller carbon atom will upset the layers of pure iron atoms, making it more difficult for them to slide over each other. So alloys are harder.

What is a smart alloy?

-Specially designed, e.g shape memory alloys

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