Extracting Metals - Carbon Reduction
- An ore is a rock containing enough metal to make it economically viable to extract it.
- Ores are mined and may be concentrated before the metal is extracted and purified.
- Most metals are found in compound so reactions are needed to extract the element.
- Some metals are pure such as gold which is found without a compound in the earth. This is known as the metal in its native state.
- Metals that are less reactive than carbon can be extracted with reduction by carbon.
- This is where carbon pushes the metal out of the compound and takes it's place.
- This is commonly used to extract iron in a blast furnace, where iron oxide and carbon is reduced to iron and carbon dioxide.
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Extracting Metals - Electrolysis
- The other way of extracting metals is electrolysis. This is used when the metal is more reactive that carbon.
- First, the atoms need to be free to move around so the ore is melted, known as smelting, or added to a solution.
- Then electricity is passed through the substance with the use of positive and negative electrodes.
- The positive ions in the substance are attracted to the negative electrode and the negative ions are attracted to the positive electrode.
- The ions attracted to the negative electrode are the pure forms of the metal.
- This process is used for extracting copper.
- Unfortunately, the large amounts of energy needed for the process makes it expensive.
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Extracting Metals - New Techniques
- Due to the rapid decline of remaining copper rich ores, we need to find new ways of getting copper.
- One way is Phytomining. This involves plants which take up copper in their roots. The plants can be burnt to produces ashes containing copper compounds.
- The other technique is Bio-leaching. This uses bacteria that produce leachate solutions containing the metal compounds. This can then be extracted.
- The final technique is the use of scrap iron. Scrap iron can be used to displace copper in a similar way to carbon displaces iron.
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Extracting Metals - Recycling
- Certain metals are very expensive to extract as they cannot be extracted by carbon and longer methods with more energy needed are necessary.
- Aluminium and Titanium are two metals that have to be extracted in alternative ways, hence they are so expensive.
- A way to avoid extracting metals is to recycle them.
- Recycling avoids using up limited resources and avoids major expense in terms of energy and the affects on the environment.
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- An alloy is a mixture of multiple elements that together improve the properties of the metal.
- For example, steel is an alloy of iron.
- Iron straight from the blast furnace is 96% iron and the impurities make it brittle and so it cannot be used for a lot of things.
- Steels are mixtures of iron and carbon.
- Low-carbon steels are soft and easily shaped whereas high-carbon steels are hard. Stainless steels are resistant to corrosion.
- Most everyday metals are alloys as they are too soft for many uses. For example, pure copper, gold, iron and aluminium.
- An alloy is stronger because different metals have atoms of different sizes. Therefore, it prevents the atoms from sliding over each other easily.
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Properties and Uses of Metals
- The elements is the central block of the periodic table (between groups 2 and 3) are the transition metals.
- Like other metals, they are good conductors (heat and electricity) and can be re-shaped.
- They are commonly used for building structures and for building things that require heat and electricity to pass through them easily.
- Copper is a transition metal. It is useful for wiring and plumbing because:
- It is a good conductor of electricity and heat
- It can be bent but is still strong
- It does not react with water
- Aluminium and titanium are useful metals because:
- They have a low density
- They are resistant to corrosion
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