Chemistry: Metals, the Reactivity Series and Environmental Chemistry
Metals, the reactivity series and environmental chemistry covers how reactive different metals are compared with each other, how that reactivity determines the method used to extract a metal and how rusting can be prevented, and how burning fuels affects the environment.
Before you start
Make sure you're comfortable with these topics first:
Method
- Learn the order of the reactivity series for common metals, from most to least reactive: potassium, sodium, calcium, magnesium, zinc, iron, copper, silver, gold (a mnemonic such as 'Please Send Cats, Monkeys and Zebras In Cages, Silver Gold' can help you remember it).
- Learn that in a displacement reaction, a more reactive metal displaces (pushes out) a less reactive metal from a solution of its compound, for example iron displaces copper from copper sulfate solution.
- Recognise the evidence that a displacement reaction has taken place: a colour change in the solution, a solid coating forming on the added metal, and a temperature rise, since displacement reactions are exothermic; the metal added should be cleaned with emery paper (sandpaper) immediately beforehand to remove the dull oxide layer that would otherwise slow the reaction and make results inconsistent.
- Link the extraction method for a metal to its position in the reactivity series relative to carbon: metals more reactive than carbon (such as aluminium) are extracted by electrolysis; metals less reactive than carbon (such as iron) are extracted by reduction with carbon in a furnace; very unreactive metals (such as gold) are found native (uncombined) in the ground.
- Learn that rusting is the corrosion of iron, and needs both water and oxygen to be present; if either is missing, rusting does not occur.
- Learn three ways to prevent rusting: a barrier method, such as painting, oiling or plating, which keeps water and oxygen away from the iron; galvanising, coating iron with a layer of zinc, which acts as both a barrier and a sacrificial metal; and sacrificial protection, attaching a block of a more reactive metal (such as magnesium or zinc) so it corrodes in place of the iron.
- Learn that burning fossil fuels releases sulfur dioxide and nitrogen oxides, which dissolve in rainwater to form acid rain, damaging limestone buildings and statues, killing trees, and lowering the pH of lakes and rivers.
- Learn that burning fossil fuels also releases carbon dioxide, a greenhouse gas that traps heat in the atmosphere and contributes to global warming, and that recycling metals conserves limited ore resources and uses far less energy than extracting new metal from ore.
Worked example
A pupil adds iron filings to a beaker of blue copper sulfate solution and stirs. After a few minutes, the blue colour fades, a red-brown solid appears, and the temperature of the solution rises. (a) Name the red-brown solid formed. (b) Write a word equation for this reaction. (c) Explain why this reaction happens, referring to the reactivity series.
- Recall that a colour change and a solid deposit forming are evidence of a displacement reaction between the added metal (iron) and the metal already in solution (copper).
- The red-brown solid deposited must be copper, since iron has displaced it out of solution.
- Write the word equation, with the more reactive metal (iron) taking the place of the less reactive metal (copper) in the compound: iron + copper sulfate produces iron sulfate + copper.
- This happens because iron is higher (more reactive) than copper in the reactivity series, so it can displace copper from copper sulfate solution.
- Final answer: (a) copper; (b) iron + copper sulfate produces iron sulfate + copper; (c) iron is more reactive than copper, so it displaces copper from its compound, forming iron sulfate solution and depositing solid copper.
Practice questions
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Q1In the reactivity series, state which is more reactive: zinc or copper.Show answer
Answer: Zinc
Q2A piece of magnesium ribbon is added to silver nitrate solution. State whether a displacement reaction would occur, and explain why.Show answer
Answer: Yes, because magnesium is more reactive than silver, so it displaces silver from the solution
Q3State the method used to extract aluminium from its ore, and explain why this method is needed rather than reduction with carbon.Show answer
Answer: Electrolysis; because aluminium is more reactive than carbon, so carbon cannot displace/reduce it from its ore
Q4Name the two substances that must both be present for iron to rust.Show answer
Answer: Water (moisture) and oxygen (air)
Q5State one way that painting a garden gate helps to prevent it from rusting.Show answer
Answer: The paint forms a barrier that keeps water and oxygen away from the iron surface, so rusting cannot start
Q6Explain why attaching a block of zinc to the hull of a steel ship helps to protect the ship from rusting.Show answer
Answer: Zinc is more reactive than iron, so the zinc corrodes instead of the iron; this is called sacrificial protection
Q7Name the gas released when fossil fuels are burned that is the main cause of the enhanced greenhouse effect.Show answer
Answer: Carbon dioxide
Exam-style questions
Written in the style of a 13+ Common Entrance exam paper, with a full mark scheme.
A student heats powdered copper oxide (black) with powdered carbon, and a glowing solid forms that has a pink-orange colour once cooled. (a) Name the pink-orange solid formed. (b) State whether carbon is more or less reactive than copper, using the result to justify your answer. (c) Explain why carbon can be used to extract iron from iron oxide in industry, but cannot be used to extract aluminium from aluminium oxide.
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A cyclist notices that the chrome handlebars on her bicycle have not rusted after two years outside, but an old iron nail left in a damp shed has rusted badly. (a) Name the two conditions needed for the iron nail to rust. (b) Suggest one reason the chrome-plated handlebars have not rusted, in terms of the two conditions in part (a). (c) The cyclist is deciding whether to protect a different, unplated steel bicycle frame by painting it or by attaching a small bar of magnesium to it. State which method is an example of sacrificial protection, and explain how it works.
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A power station burns coal to generate electricity. (a) Name the gas released, other than carbon dioxide, that dissolves in rainwater to form acid rain. (b) State one effect of acid rain on the environment. (c) Name the gas released by burning coal that is linked to the enhanced greenhouse effect and global warming. (d) Suggest one reason why recycling aluminium cans, rather than extracting new aluminium from ore, is better for the environment.
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Free printable worksheet
Want more practice on paper? Download the chemistry: metals, the reactivity series and environmental chemistry worksheet pack - 18 pages of exam-style questions with a full mark scheme. One email opens every download in this browser for 14 days - no account, no card. Print it for personal and classroom use.
This topic is chapter 10 of 13+ Science Workbook, the whole course as one free printable PDF.
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