Reactivity series and displacement

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Big idea: a league table for metals

Big idea (key concept): Relationships. Where a metal sits in the reactivity series is linked to how it behaves, so we can predict a reaction before we test it.
Related concept: Patterns. The more reactive a metal is, the more vigorously it reacts and the harder it is to get out of its ore. Spotting these patterns lets us make predictions.
Global context: Globalization and sustainability. Metal ores are mined and traded around the world. How a metal is extracted, and how quickly it corrodes, depends on its reactivity, so we need to use and recycle metals wisely.
The reactivity series ranks metals from most to least reactive: potassium, sodium, calcium, magnesium, aluminium, (carbon), zinc, iron, (hydrogen), copper, silver, gold.
Carbon and hydrogen are not metals. They are in the list because they help us predict: metals above hydrogen react with dilute acids, and carbon can be used to extract metals that are below it.
To remember the order, make up your own memory sentence from the first letters of the metals.

A reactivity series ladder from potassium to gold

Evidence for the order: water, steam and acid

Reactivity is how readily a metal takes part in chemical reactions. We build the series by comparing how vigorously metals react with water, steam and dilute acid.
With cold water: potassium, sodium and calcium react. metal + water → metal hydroxide + hydrogen. For example sodium + water → sodium hydroxide + hydrogen, or 2Na + 2H₂O → 2NaOH + H₂. Sodium and potassium react very fast; calcium fizzes more gently. Only a teacher does this, with a tiny piece behind a safety screen.
With steam: magnesium hardly reacts with cold water but burns brightly in steam. metal + steam → metal oxide + hydrogen. Magnesium + steam → magnesium oxide + hydrogen, or Mg + H₂O → MgO + H₂. Zinc and iron also react with steam, more slowly. Copper, silver and gold do not react with water or steam. This is a teacher demonstration.
With dilute acid: metals above hydrogen react. metal + acid → salt + hydrogen. For example magnesium + hydrochloric acid → magnesium chloride + hydrogen, or Mg + 2HCl → MgCl₂ + H₂. Zinc + sulfuric acid → zinc sulfate + hydrogen, or Zn + H₂SO₄ → ZnSO₄ + H₂.
The speed of bubbling gives the order: magnesium fizzes quickly, zinc steadily, iron slowly, and copper not at all. Hydrogen is tested with a lit splint, which gives a squeaky pop. Potassium and sodium are far too dangerous to put in acid.
Aluminium is a special case. It is above zinc, but it seems unreactive at first because a thin, tough layer of aluminium oxide covers it. Once that layer is removed, aluminium reacts vigorously.

Displacement reactions

A displacement reaction happens when a more reactive metal takes the place of a less reactive metal in a compound. The more reactive metal goes into solution as a compound and the less reactive metal is left as a solid.
magnesium + copper sulfate → magnesium sulfate + copper, or Mg + CuSO₄ → MgSO₄ + Cu. The blue colour fades, a brown-pink solid (copper) forms, and the mixture warms because the reaction gives out energy.
zinc + copper sulfate → zinc sulfate + copper, or Zn + CuSO₄ → ZnSO₄ + Cu. The blue colour fades to colourless and brown copper forms.
iron + copper sulfate → iron sulfate + copper, or Fe + CuSO₄ → FeSO₄ + Cu. The nail gets a brown coating and the solution changes from blue to pale green.
If the single metal is less reactive than the metal in the compound, nothing happens. Copper in zinc sulfate solution gives no reaction, because copper is below zinc.
Displacement also works with hot metal oxides. For example magnesium + copper oxide → magnesium oxide + copper, or Mg + CuO → MgO + Cu. This is a teacher demonstration.
Chemists can place unknown metals in order by testing each one against solutions of the others and recording which mixtures react.

Magnesium displacing copper from copper sulfate solution

Predicting reactions and writing equations

The rule: find both metals in the series. A displacement reaction happens only if the single metal is above the metal in the compound.
Zinc + copper sulfate: zinc is above copper, so there is a reaction. Copper + zinc sulfate: copper is below zinc, so there is no reaction. Magnesium + iron sulfate: reaction. Silver + copper sulfate: no reaction.
copper + silver nitrate → copper nitrate + silver, or Cu + 2AgNO₃ → Cu(NO₃)₂ + 2Ag. Silver forms as shiny crystals and the solution turns blue, because copper nitrate is blue.
A symbol equation must balance: the same number of each type of atom on both sides. In Cu + 2AgNO₃ → Cu(NO₃)₂ + 2Ag there is 1 Cu, 2 Ag, 2 N and 6 O on each side.
Always write the word equation first, then the symbol equation. When no reaction is predicted, write "no reaction" and give the reason: the single metal is below the one in the compound.
The further apart two metals are in the series, the more vigorous the displacement usually is.

Copper displacing silver from silver nitrate solution

Extraction, corrosion and using metals wisely

Most metals are found in the ground as compounds in ores. Gold is so unreactive that it is often found as the metal itself.
Reactivity decides how a metal is extracted. Metals below carbon, such as zinc and iron, can be extracted by heating their oxide with carbon, which takes the oxygen away. iron oxide + carbon → iron + carbon dioxide, or 2Fe₂O₃ + 3C → 4Fe + 3CO₂. In a blast furnace the carbon comes from coke.
Metals above carbon, such as aluminium, hold on to oxygen too strongly for carbon to remove it. Their molten compounds are split by electrolysis, which uses a lot of electricity and is expensive.
Rusting is the corrosion of iron. Iron needs both oxygen and water, and it forms orange-brown hydrated iron oxide. Barriers such as paint, oil and plastic keep oxygen and water away. Galvanising coats iron with zinc.
Sacrificial protection uses a more reactive metal such as zinc or magnesium. It corrodes first, so the iron is spared. This is why blocks of zinc are bolted to ship hulls.
Metal ores are limited, and extracting metals uses energy and changes the land. Recycling saves ore and energy. Recycling aluminium uses only a small fraction of the energy needed to extract it from ore.

Electrolysis cell and blast furnace for extracting metals

Think like a scientist: putting metals in order

A good question to test is: in what order do magnesium, zinc and iron come in the reactivity series? A teacher can supervise this with dilute acid.
The independent variable is the type of metal. The dependent variable is what you measure, such as the volume of hydrogen collected in one minute or the time taken for the fizzing to stop.
The control variables are kept the same: the size of the metal strip, the volume and concentration of the acid, and the temperature. Clean each strip first, because an oxide layer can slow the reaction.
To make results more reliable, repeat each test and use the mean. Look out for an anomaly, a result that does not fit the pattern.
Safe practice: wear eye protection, let the teacher handle acids and reactive metals, and keep flames away because hydrogen is flammable.
Your task: you are given three unknown metals A, B and C and solutions of their sulfates. Plan a displacement investigation. Draw a results table, say which mixtures you expect to react, and explain how the results will give the order of reactivity. Then evaluate your method: what could make your conclusion less reliable?

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1.Which of these metals is the most reactive?
Easy
- AMagnesium
- BZinc
- CPotassium
- DCopper
2.Which of these metals is the least reactive?
Easy
- AGold
- BIron
- CSilver
- DCopper
3.What happens in a displacement reaction between a metal and a metal compound?
Easy
- AA metal and a non-metal swap places in the periodic table
- BTwo metals join together permanently to make an alloy of both
- CA metal is turned into a gas by heating it strongly
- DA more reactive metal takes the place of a less reactive metal in the compound
4.A teacher drops a tiny piece of sodium into cold water behind a safety screen. What do you see?
Easy
- ANothing happens at all
- BIt fizzes and moves around on the surface as hydrogen forms
- CIt turns bright blue
- DIt sinks and slowly dissolves with no bubbles
5.Which safety measure is used when a teacher demonstrates sodium reacting with water?
Easy
- ALearners hold the sodium to feel it react
- BA safety screen is used and everyone wears eye protection
- CThe water is heated first to make it safer
- DA large lump of sodium is used so it can be seen clearly
6.Why is recycling metals a good idea?
Easy
- AIt makes the metals more reactive
- BIt turns the metals into non-metals
- CIt means the metals never corrode
- DIt saves ores and energy and reduces waste
7.Which two substances must be present for iron to rust?
Easy
- AOxygen and water
- BCarbon dioxide and nitrogen
- CSalt and sunlight
- DHydrogen and oxygen
8.Gold is more reactive than silver.
Easy
True or false?

Mehr Fragen

9.A more reactive metal can displace a less reactive metal from its compound.
Easy
True or false?
10.Complete the sentence.
Easy
A more reactive metal ____ a less reactive metal from its compound.
11.Fill in the missing word.
Easy
iron + copper sulfate → iron sulfate + ____
12.Which of these would help to stop an iron railing from rusting? (select all that apply)
Easy
- APainting it
- BLeaving it wet in salty air
- CCoating it with oil or grease
- DRubbing off any paint
- EGalvanising it with zinc
13.Put these steps of a displacement investigation in a sensible order.
Easy
- Add a clean strip of metal to each tube
- Compare the results and write a conclusion
- Decide which metal and which solution to test
- Watch for changes and record what happens
- Pour the same volume of solution into each test tube
14.Match each metal to the way it is usually obtained.
Easy
- Aluminium
- Iron
- Gold
- Heating its oxide with carbon
- Found as the metal itself in the ground
- Electrolysis of its molten ore
15.A strip of zinc is placed in blue copper sulfate solution. What is observed?
Medium
- AThe zinc turns blue and the solution stays blue
- BBubbles of hydrogen form and the solution turns green
- CA brown solid forms on the zinc and the blue colour fades
- DNothing happens because zinc is a metal
16.Which of these mixtures will react?
Medium
- ACopper and zinc sulfate solution
- BSilver and copper sulfate solution
- CGold and silver nitrate solution
- DMagnesium and iron sulfate solution
17.Which word equation correctly shows magnesium reacting with copper sulfate solution?
Medium
- Amagnesium + copper sulfate → copper sulfate + magnesium
- Bmagnesium + copper sulfate → magnesium sulfate + copper
- Cmagnesium + copper sulfate → magnesium oxide + copper
- Dcopper + magnesium sulfate → copper sulfate + magnesium
18.Which gas is given off when a metal such as zinc reacts with dilute acid?
Easy
- AOxygen
- BCarbon dioxide
- CHydrogen
- DChlorine
19.Gold is often used in jewellery. Which reason fits best?
Easy
- AIt is very low in the series, so it does not react with air or water
- BIt is very high in the series, so it reacts with air and shines
- CIt reacts slowly with oxygen to make a shiny protective layer
- DIt is magnetic, so it clings to the skin and stays in place
20.What does the position of carbon in the reactivity series tell us?
Medium
- ACarbon can remove oxygen from the oxides of every metal
- BCarbon reacts with dilute acid like a metal above hydrogen
- CCarbon can remove oxygen from the oxides of metals below it
- DCarbon is more reactive than potassium
21.Why is aluminium extracted by electrolysis instead of by heating with carbon?
Medium
- AAluminium is more reactive than carbon, so carbon cannot take its oxygen
- BAluminium is less reactive than carbon, so carbon cannot reach it
- CAluminium oxide does not contain oxygen
- DElectrolysis is cheaper than heating with carbon
22.Which method protects iron by letting a more reactive metal corrode instead?
Easy
- APainting with a layer of paint
- BCoating with oil or grease
- CCovering with a plastic sheet
- DSacrificial protection
23.Why do scientists encourage the recycling of aluminium cans?
Medium
- AAluminium cannot be extracted from its ore at all, so scrap is needed
- BMaking aluminium from ore uses a lot of electricity, so recycling saves energy
- CRecycled aluminium is more reactive than newly made aluminium
- DAluminium turns into iron when the cans are melted down
24.A student compares how fast magnesium, zinc and iron fizz in dilute acid. What is the independent variable?
Medium
- AThe volume of gas collected
- BThe type of metal
- CThe concentration of the acid
- DThe room temperature
25.In the same acid investigation, which change would make the results more reliable?
Medium
- AUse a different volume of acid for each metal
- BUse one large strip of magnesium and one tiny strip of iron
- COnly test each metal once but for a longer time
- DRepeat each metal several times and calculate a mean
26.Which metals react with dilute hydrochloric acid? (select all that apply)
Medium
- AMagnesium
- BCopper
- CZinc
- DSilver
- EIron
27.Which of these metals would be extracted by electrolysis because they are more reactive than carbon? (select all that apply)
Medium
- APotassium
- BIron
- CAluminium
- DCopper
- ESodium
28.A student compares the fizzing of three metals in dilute acid. Which should be kept the same to make it a fair test? (select all that apply)
Medium
- AThe volume of acid
- BThe type of metal
- CThe concentration of the acid
- DThe result for each metal
- EThe size of each metal piece
29.Metals that are above hydrogen in the reactivity series react with dilute acids.
Easy
True or false?
30.Copper displaces zinc from zinc sulfate solution.
Medium
True or false?
31.Finish the statement.
Easy
metal + dilute acid → salt + ____
32.Fill the gap.
Medium
Zn + CuSO₄ → ZnSO₄ + ____
33.Complete this statement.
Easy
Iron rusts when it touches ____ and ____ (either order).
34.Choose the right word to finish the sentence.
Medium
Aluminium is obtained from its molten ore by ____.
35.Explain why copper does not react with dilute hydrochloric acid.
Medium
36.Put these metals in order of reactivity, starting with the most reactive.
Medium
- Iron
- Silver
- Magnesium
- Copper
- Sodium
- Zinc
37.Match each mixture to what you would observe.
Medium
- Iron nail in copper sulfate solution
- Copper wire in silver nitrate solution
- Copper in zinc sulfate solution
- Magnesium ribbon in dilute hydrochloric acid
- Silver crystals form and the solution turns blue
- No change at all
- Bubbles of hydrogen form quickly
- Brown coating forms on the nail and the blue fades to pale green
38.
In one experiment, a teacher collected hydrogen from magnesium and dilute acid three times.
Trial Volume of gas in 1 minute (cm³)
1 41
2 44
3 41
Calculate the mean volume of gas in cm³.
Medium
39.A copper wire is placed in colourless silver nitrate solution. Which statement is correct?
Hard
- ASilver forms on the wire and the solution slowly turns blue
- BThe wire dissolves and the solution stays colourless
- CCopper nitrate forms and silver stays dissolved
- DNo reaction happens because copper is more reactive than silver
40.
A student tests four unknown metals (W, X, Y and Z) by putting a strip of each in a solution of another metal's sulfate.
Metal strip Solution of Result
X Y sulfate Reaction
Z X sulfate Reaction
Y W sulfate Reaction
W Z sulfate No reaction
What is the order of reactivity, most reactive first?
Hard
- AW, Y, X, Z
- BX, Y, Z, W
- CZ, X, Y, W
- DY, W, Z, X
41.A gardener keeps a spray of copper sulfate solution in an iron bucket. Why is this a bad idea?
Medium
- ACopper is more reactive than iron, so it coats the bucket and protects it
- BIron and copper sulfate never react with each other
- CThe solution becomes more concentrated in an iron bucket
- DIron is more reactive than copper, so the bucket reacts and is slowly eaten away
42.Zinc blocks are bolted to a steel ship's hull. Why does the steel rust more slowly?
Medium
- AZinc is less reactive than iron, so it covers the steel like paint
- BZinc is more reactive than iron, so the zinc corrodes first
- CZinc is lighter than steel, so the hull sits higher
- DZinc attracts the water away from the steel
43.A galvanised bucket is scratched so the iron underneath is showing. Why does it still resist rusting for a long time?
Hard
- AThe scratch fills with rust that seals the surface
- BZinc is less reactive than iron, so it protects by staying unchanged
- CZinc is more reactive than iron, so it still corrodes in preference to the iron
- DIron cannot rust when it is touching any other metal
44.Aluminium is above zinc in the reactivity series, but a new strip of aluminium reacts only slowly with dilute acid at first. What is the best explanation?
Hard
- AA thin layer of aluminium oxide on the surface protects the metal until it is removed
- BAluminium is below hydrogen in the series, so it cannot react with acid
- CAluminium does not react with any acid, however long it is left
- DAluminium is a non-metal, so acids hardly affect it at all
45.A student says, 'Magnesium is more reactive than iron because the magnesium strip in my test was bigger and made more bubbles.' What is wrong with this conclusion?
Hard
- AThe student should have used a non-metal
- BMore bubbles always means the metal is less reactive
- CThe strips were different sizes, so the test was not fair
- DOnly one metal should ever be tested
46.Which of these reactions will happen? (select all that apply)
Hard
- AZinc and copper sulfate solution
- BSilver and copper sulfate solution
- CMagnesium and iron sulfate solution
- DCopper and iron sulfate solution
- EIron and silver nitrate solution
47.Carbon can be used to extract aluminium from aluminium oxide.
Medium
True or false?
48.When iron displaces copper from blue copper sulfate solution, the solution fades from blue towards pale green.
Medium
True or false?
49.Fill in the blank.
Medium
Mg + 2HCl → MgCl₂ + ____
50.Match each set of reactants to its products.
Hard
- zinc + copper sulfate
- magnesium + zinc oxide
- iron + hydrochloric acid
- calcium + water
- magnesium oxide + zinc
- iron chloride + hydrogen
- calcium hydroxide + hydrogen
- zinc sulfate + copper
51.Put these in order from most reactive to least reactive. Carbon and hydrogen are included because they help us predict reactions.
Medium
- Zinc
- Copper
- Magnesium
- Carbon
- Hydrogen
- Aluminium
52.A piece of zinc is put into copper sulfate solution. Describe what you would see and explain it using the reactivity series.
Hard
53.Explain why iron can be extracted by heating its oxide with carbon but aluminium cannot.
Hard
54.Describe how a teacher could plan a fair test to put magnesium, zinc and iron in order of reactivity using dilute acid.
Hard
55.In one week a recycling plant sorted 250 kg of scrap metal. Of this, 180 kg was aluminium. What percentage of the scrap was aluminium?
Hard

Lernnotizen

## The big idea - The **reactivity series** is a pattern that lets us predict how metals behave (**Relationships**, **Patterns**). - Order: potassium, sodium, calcium, magnesium, aluminium, (carbon), zinc, iron, (hydrogen), copper, silver, gold. ## Reactions - metal + water → metal hydroxide + hydrogen (very reactive metals only). - metal + steam → metal oxide + hydrogen. - metal + dilute acid → salt + hydrogen (metals above hydrogen). ## Displacement - A more reactive metal **displaces** a less reactive metal from its compound. If the single metal is below, there is no reaction. - Example: Zn + CuSO₄ → ZnSO₄ + Cu, and Cu + 2AgNO₃ → Cu(NO₃)₂ + 2Ag. ## Extraction and corrosion - Below carbon: heat the oxide with carbon. Above carbon: **electrolysis**. - Iron rusts with oxygen **and** water. Barriers, galvanising and sacrificial protection stop it. - Recycling saves ore and energy. ## Investigating - Change one variable, measure one, control the rest and repeat to improve reliability.

reactivity: How readily a metal takes part in chemical reactions.
reactivity series: A list of metals in order of reactivity, from most to least reactive.
displacement reaction: A reaction in which a more reactive metal takes the place of a less reactive metal in a compound.
salt: A compound made when a metal replaces the hydrogen in an acid.
metal hydroxide: The compound made, with hydrogen, when a very reactive metal reacts with cold water.
metal oxide: A compound of a metal with oxygen, such as magnesium oxide.
ore: A rock that contains enough of a metal compound to be worth extracting the metal.
electrolysis: Using electricity to split a molten compound, used to extract metals above carbon.
corrosion: The slow wearing away of a metal as it reacts with substances around it.
rusting: The corrosion of iron, which needs both oxygen and water.
galvanising: Coating iron or steel with zinc to protect it.
sacrificial protection: Protecting a metal by attaching a more reactive metal that corrodes first.
recycling: Reusing scrap metal, which saves ore and energy.

Karteikarten

Which metal is the most reactive: sodium, zinc or copper?

Sodium.

Which metal is the least reactive: iron, silver or gold?

Gold.

What is a displacement reaction?

A more reactive metal takes the place of a less reactive metal in a compound.

What is made when a metal reacts with dilute acid?

A salt and hydrogen.

How do you test for hydrogen?

A lit splint gives a squeaky pop.

Why does a metal below hydrogen not react with dilute acid?

It is not reactive enough to push hydrogen out of the acid.

What happens when zinc is put into blue copper sulfate solution?

Brown copper forms on the zinc and the blue fades, because zinc displaces copper.

Will copper displace zinc from zinc sulfate?

No. Copper is below zinc, so there is no reaction.

What is the symbol equation for zinc and copper sulfate?

Zn + CuSO₄ → ZnSO₄ + Cu.

What happens when copper is placed in silver nitrate solution?

Silver crystals form and the solution turns blue, because copper displaces silver.

Why are carbon and hydrogen in the reactivity series?

They help predict extraction (carbon) and reactions with acid (hydrogen).

How is iron extracted from its ore?

By heating its oxide with carbon.

How is aluminium extracted from its ore?

By electrolysis of the molten compound.

Why is aluminium not extracted using carbon?

Aluminium is more reactive than carbon, so carbon cannot take its oxygen.

What two things does iron need to rust?

Oxygen and water.

What is sacrificial protection?

A more reactive metal, such as zinc, corrodes instead of the iron.

Why does aluminium seem unreactive at first?

A thin layer of aluminium oxide on its surface protects it.

Why recycle metals?

It saves ore and energy and reduces waste.

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Metal strip	Solution of	Result
X	Y sulfate	Reaction
Z	X sulfate	Reaction
Y	W sulfate	Reaction
W	Z sulfate	No reaction

Trial	Volume of gas in 1 minute (cm³)
1	41
2	44
3	41