Smart Teach Chemistry Section 4 Extraction of metals
- Slides: 19
Smart Teach Chemistry Section 4 Extraction of metals 1 of 28 © Boardworks Ltd 2011
Key terms • Alloy – a mixture of a metal with another metal or carbon. • Ore – Rocks that metals can be extracted from. • Oxidised/Oxidation – Gain of oxygen. • Reduced/Reduction – Loss of oxygen or oxygen being removed. 2 of 28 © Boardworks Ltd 2011
Exam question 3 of 28 © Boardworks Ltd 2011
Answer 4 of 28 © Boardworks Ltd 2011
Properties of metals Typical metals have a lot of physical properties in common. They: l are lustrous (shiny) l are hard and strong l are malleable (can be bent and pressed into different shapes) and ductile (can be drawn into wires) l are good conductors of heat and electricity 5 of 28 © Boardworks Ltd 2011
Properties of metals Aluminium, copper and iron are metals. Aluminium has a low density (This means that they are lightweight for its size. ), copper is very unreactive and iron is strong when alloyed. These metals have many uses. Draw one straight line from each metal to a use of the metal. 6 of 28 © Boardworks Ltd 2011
Properties of metals Aluminium, copper and iron are metals. Aluminium has a low density, copper is very unreactive and iron is strong when alloyed. These metals have many uses. Draw one straight line from each metal to a use of the metal. 7 of 28 © Boardworks Ltd 2011
Methods of extracting metals There are two main ways of extracting metals from their ores: l reduction with carbon l electrolysis (using electricity). The method of extraction which is most appropriate depends on the reactivity of the metal being extracted. The reactivity series of metals can be determined by comparing the reactivity of metals with other compounds, such as acids, or by carrying out displacement reactions. 8 of 25 © Boardworks Ltd 2011
The reactivity series and extraction The reactivity of a metal determines how it is extracted. potassium sodium calcium increasing reactivity magnesium aluminium (carbon) zinc iron lead Metals less reactive than carbon can be extracted from their ores by reduction. (hydrogen) copper silver gold platinum 9 of 25 Metals above carbon in the reactivity series must be extracted using electrolysis because they need a more powerful method of extraction. Copper, silver, gold and platinum can occur native and do not need to be extracted. Sometimes copper needs to be extracted from an ore. © Boardworks Ltd 2011
What is reduction? Metals are often found combined with oxygen as oxides. To obtain the metal, the oxygen must be removed. The removal of oxygen from a substance is called reduction. metal oxide (in ore) reduction metal Carbon can be used to extract metals by reduction. Iron oxide 2 Fe 2 O 3 + + carbon Iron 3 C 4 Fe + + carbon dioxide 3 CO 2 In this reaction, the carbon removes oxygen from iron oxide. This occurs because carbon is more reactive than iron. The addition of oxygen to a substance is called oxidation. 10 of 25 © Boardworks Ltd 2011
Exam question 11 of 22 © Boardworks Ltd 2011
Answer Acceptable answers Mark (i) carbon dioxide (1) iron (1) carbon monoxide (2) (ii) loss of oxygen / gain of electrons (1) oxygen is ignore oxide removed removal 12 of 22 © Boardworks Ltd 2011
Exam question • (iii) Part of the reactivity series is shown. • sodium aluminium zinc iron copper • Aluminium is found in the ore bauxite. • Aluminium is obtained from bauxite by electrolysis. Explain why electrolysis has to be used to obtain aluminium from bauxite. (2) 13 of 22 © Boardworks Ltd 2011
Answer (iii) 14 of 22 An explanation linking two of aluminium is high in reactivity (1) aluminium oxide is stable (1) (needs) powerful means (of reduction) / hard to extract (1) use electricity (1) aluminium not reduced by carbon (1) Allow higher than (2) carbon is not reactive enough accept other (cheaper) methods if qualified. © Boardworks Ltd 2011
Advantages of recycling metals 15 of 17 © Boardworks Ltd 2011
Exam question • Scrap iron can be recycled. • Explain an advantage of recycling scrap iron rather than extracting iron from iron compounds found in the Earth. • (2) 16 of 17 © Boardworks Ltd 2011
Answer • an explanation linking two of • Conserves reserves (1) • Reduces a stated problem of mining (1) eg reduces carbon dioxide emissions (from machinery/trucks) / Noise pollution/dust pollution • reduces scrap iron going to landfill • less energy needed/less fuel used 17 of 17 © Boardworks Ltd 2011
Question 18 of 17 © Boardworks Ltd 2011
Answer Question Number Answer Acceptable answers an explanation linking the following points • (both) water and oxygen (are needed) (1) • only B has both / A has no oxygen / C has no water (1) allow air for oxygen allow reacts with water and oxygen allow air for oxygen A only has water/C only has air A and/or C only have one/do not have both Mark (2) 19 of 17 © Boardworks Ltd 2011
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