Ores are naturally occuring rocks that contain metal or metal compounds in sufficent amounts to make it worthwhile extracting them.
Most everyday metals are mixtures called alloys.
- The earths crust contains metals and metal compounds
- When found in the earth they are often mixed with other substances- Too become useful they must be extracted from whatever they are mixed with
- Ores are mined. They may need to be concentrated before the metal is extracted and purified.
Reactivity and Extraction Method
- Metals are produced when metal oxides are reduced (have their oxygen removed)
- The reduction method depends on the reactivity of the metal
- Potassium, sodium, calcium, magnesium and aluminium are extracted by electrolysis
- Zinc, Iron, Tin, Lead are extracted by reaction with carbon or carbon monoxide
- Copper, Silver, Gold, Platinum are extracted in various ways
Gold, because it is so unreactive is found as the native metal and not as a compound. It does not need to be chemically extracted from its ore.
- The transition metals are placed in the periodic table in a large block between groups 2 and 3.,Most metals including iron, titanium and copper are transition metals,They are good conductors of heat and electricity,Can be hammered or bent into shape easily
Extracting Metals and Making Alloys
Iron is extracted from iron ore in a blast furnace. Iron ores contain iron oxide. The oxygen must be removed from the iron oxide to leave the iron behind. Reactions in which oxygen is removed are called reuduction reactions
Carbon is more reactive than iron, so it can push out of displace the iron from iron oxide.
Iron Oxide + Carbon > Iron + Carbon Dioxide
In this reaction, the iron oxide is reduced to iron and the carbon is oxidised to carbon dioxide
In the blast furnace, it is so hot that carbon monoxide will also reduce to iron oxide
Iron oxidee + carbon monoxide > Iron + carbon dioxide
- Copper is soft and easily bend and so is a good conductor of electricity, which makes it useful for wiring.
- Copper is also a good conductor of heat and it does not react with water. This makes it useful for plumbing, and making pipes and tanks.
- Some copper ores are copper-rich (they have a high concentration of copper compounds.
- Copper can be extracted form these ores by heating them in a furncace, a process called smelting.
- The copper is then purified using a process called electrolysis
Electricity is passed through solutions containing copper compounds, such as copper sulphate. During electrolysis, posotively charged copper ions move towards the negative electrove as copper metal
Future of Copper
We are running out of copper-rich ores.
Phytomining, Bioleaching and scrap iron.
- Some plants absorb copper compounds through their roots.
- They concentrate these compounds as a result of this.
- The plants can be burned to produce an ash that contains copper compounds. This method is called phytomoning
- Some bacteria absorb copper compounds.
- They then produce solutions called leachates, which contain copper compounds
- This method of extraction is called bioleaching
Copper can also be extracted from solutions of copper salts using scrap iron. Iron is more reactive than copper, so it can displace copper from copper salts.
Iron + Copper sulfate > Iron sulfate + copper
Aluminium and Titanium
- Aluminium and Titanium are two metals with a low density. This means they are lightweight for their size.
- They also have a very thin layer of their oxides on the surface which stops air and water getting into the metal. They reisist corrosion.
- Unlike iron, Aliminium and Titanium cannot be extracted from their oxides by reduction with carbon.
- Exsisting methods are expensive because, The processes have many stages and large amounts of energy are needed
- Aluminium is extensively recycled because less energy is needed to produce recycled aluminium than to extract aluminium from its ore
- Recycling preserves limited resources and requires less energy, so it causes less damage to the enviroment
- The properties of a metal are changed by adding other elements to it
- A mixture of two or more elements, where at least one element is a metal, is called an Alloy
- Alloys contain atoms of different sizes which distort the regular arragements of atoms.
- This makes it more difficult for the layers to slide over each other
- Alloys are harder than the pure metal
Pure copper, gold, iron and aluminium are too soft for many uses. They are mixed with other similar metals to make them harder for everyday use e.g.
- Brass- Used in electrical fittings, is 70 percent copper and 30 percent zinc
- 18 carat gold, used in jewellery is 75 percent gold and 25 percent copper and other metals
- Duralumin, used in aircraft manufacture is 96 perfect aluminium and 4 percent copper and other metals
Iron and Steel
- Pure iron is soft and easily shaped because its atoms are arranged in a regular way that lets layers slide over each other.
- Iron from the blast furnace is an alloy of about 96 percent iron, with carbon and some other impurities.
- It is hard, but too brittle for most uses, so most iron from the blast furnace is converted into steel by removing some of the carbon
- Carbon is removed from the molten iron by blowing oxygen into it. The oxygen reacts with the carbon, producing carbon monoxide and carbon dioxide which escape from the molten metal
- Enough oxygen is used to achieve steel with the desired carbon content.
- Other metals are often added, such as vanadium and chromium, to produce alloys with properties suited to specific uses.