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KS3 Science · Year 9Chapter 7 · Reactivity, displacement and electrolysis
Year 9 · Chapter 7

Reactivity, displacement and electrolysis

By the end of this chapter you will be able to

  • Place metals and carbon in the reactivity series, and use it to predict reactions
  • Write word and ionic equations for displacement reactions
  • Explain which metal oxides carbon can reduce, and why reactive metals need electrolysis
  • Name the anode, cathode and products in an electrolysis, from a teacher demonstration
  • Use the series and the results of a test to draw a conclusion

You should already know

  • The reactivity of metals with water and acid (Year 8 Science, Chapter 8)
  • Word equations (Year 7 Science)

Where this leads

  • Rates of reaction and energy changes in Chapter 8

National Curriculum for England, Key Stage 3 science, Year 9. Content: 9C3 the reactivity series extended to carbon and hydrogen; metals placed by reactivity, 9C3 displacement reactions with word and ionic equations (basic; deepens Year 8, Chapter 8), 9C3 extraction of metals by reduction with carbon (metals below carbon in the series); electrolysis for reactive metals (basic), 9C3 electrolysis of an electrolyte: anode, cathode, electrolyte and products (teacher demonstration or simulation only).

Exercise P  Do you remember?

1
FWhat is the chemical symbol for copper? Write the symbol.
2
FWhat is the name of the product formed when a metal reacts with an acid, along with hydrogen? Write the word.
3
FWhat is 5 x 9? Write the number.
4
FWhat is the name of a substance that is made of two or more elements chemically joined? Write the word.
5
FWhich particle is a positive charge in an atom? Write the word.
7.1

The reactivity series

Year 9
9C3: the reactivity series extended to carbon and hydrogen; metals placed by reactivity
Video lesson: The reactivity seriesComing soon
Story. A pupil drops small pieces of potassium, magnesium and copper into water. Potassium fizzes violently, magnesium reacts slowly, and copper does not react at all. The teacher says these results can be put in order in the reactivity series.

The reactivity series lists metals in order, from the most reactive at the top to the least reactive at the bottom. Carbon and hydrogen are included in the series for comparison, though hydrogen is not a metal. Carbon is less reactive than aluminium but more reactive than zinc.

A more reactive metal reacts more vigorously with water, or with acid, and it takes oxygen or other elements from compounds more easily.

Reactivity series (most reactive at the top)potassium (K)sodium (Na)calcium (Ca)magnesium (Mg)aluminium (Al)carbon (C)zinc (Zn)iron (Fe)hydrogen (H)copper (Cu)silver (Ag)gold (Au)more reactive
The reactivity series, with carbon and hydrogen included for comparison

Key ideas

  • The reactivity series is ordered from most reactive (top) to least reactive (bottom).
  • Carbon sits between aluminium and zinc in the series.
  • Hydrogen is included for comparison, but it is not a metal.
  • A higher metal in the series reacts more readily.
Worked example 7.1.1
Which metal is more reactive: magnesium or copper? Write the word.

Method. Find each metal in the series.

  1. Look. Magnesium is near the top, and copper is near the bottom.
    top and bottom
  2. Name it. So magnesium is more reactive than copper.
    magnesium
  3. Write the answer.
    magnesium

Check. Magnesium is above copper in the series. ✓

Worked example 7.1.2
Is carbon more reactive than zinc? Write yes or no.

Method. Compare their positions.

  1. Look. Carbon is above zinc in the series.
    above zinc
  2. Decide. So carbon is more reactive than zinc, and the answer is yes.
    yes
  3. Write the answer.
    yes

Check. Carbon takes the oxygen from zinc oxide. ✓

Worked example 7.1.3
Which is the least reactive of these metals: iron, gold, zinc? Write the word.

Method. Find the lowest of the three in the series.

  1. Look. Gold is at the bottom of the series.
    bottom
  2. Name it. So gold is the least reactive.
    gold
  3. Write the answer.
    gold

Check. Iron is above zinc, and zinc is above gold. ✓

Watch out

Watch out: the series is about reactivity, not about cost or density. Gold is expensive, but it is not very reactive.

Exam tip

Exam tip. Remember the series by its order, not by its name. Potassium is most reactive; gold is least reactive.

Try it (with your teacher, or a grown-up at home). With your teacher, look at the reaction of a magnesium ribbon and a copper strip with dilute hydrochloric acid, in a fume cupboard, with eye protection. Teacher only: pupils watch and record. Say which metal reacts and place both in the series.

Exercise 7A  The reactivity series

1
FWhich metal is at the top of the reactivity series in this list: potassium, sodium, calcium? Write the word.
2
FWhich element is at the bottom of the reactivity series in this list? Write the word.
3
FIs carbon above or below zinc in the series? Write the word.
4
FIs hydrogen a metal? Write yes or no.
5
FWhich is more reactive: calcium or iron? Write the word.
6
FWhich is more reactive: aluminium or carbon? Write the word.
7
PSName the least reactive metal in the list: copper, silver, zinc. Write the word.
8
PSHow many of these metals are more reactive than copper: magnesium, zinc, gold? Write the number.
9
PSA pupil puts a piece of zinc into water and sees almost no reaction. A sodium piece reacts strongly. Which is more reactive? Write the word.
10
PSWrite the metals in this list in order, most reactive first: copper, magnesium, zinc. Write the words in order.
11
RExplain why copper does not react with cold water. Write one sentence. Accept any sentence saying copper is below hydrogen in the series, so it is not reactive enough to react with water.
12
RChallenge: a pupil says carbon is a metal because it is in the series. Write one sentence to correct her. Accept any sentence saying carbon is a non-metal, included in the series to compare its reactivity.
7.2

Displacement reactions and equations

Year 9
9C3: displacement reactions with word and ionic equations (basic)
Video lesson: Displacement reactions and equationsComing soon
Story. A class puts pieces of metal into solutions of other metal salts. Some mixtures change colour and form a new solid on the metal; others do nothing. The class uses the reactivity series to predict which mixtures will react.

In a displacement reaction, a more reactive metal takes the place of a less reactive metal in a compound. Magnesium displaces copper from copper sulfate solution: copper is deposited as a solid, and magnesium sulfate forms.

The word equation is: magnesium + copper sulfate → magnesium sulfate + copper. The ionic equation shows only the ions that change: Mg + Cu2+ → Mg2+ + Cu.

Metalmagnesium sulfatezinc sulfatecopper sulfate
Magnesium-reactionreaction
Zincno reaction-reaction
Copperno reactionno reaction-
Results of mixing metals with metal salt solutions: a reaction means displacement occurs

Key ideas

  • A more reactive metal displaces a less reactive metal from its salt solution.
  • Word equation: name every substance.
  • Ionic equation: show only the ions that change, and leave out the spectators.
  • A metal can only displace metals that are below it in the series.
Worked example 7.2.1
Using the table, does zinc displace copper from copper sulfate solution? Write yes or no.

Method. Read the table, then the series.

  1. Read. The table shows a reaction for zinc with copper sulfate.
    reaction
  2. Decide. Zinc is above copper, so zinc displaces copper, and the answer is yes.
    yes
  3. Write the answer.
    yes

Check. Zinc is more reactive than copper. ✓

Worked example 7.2.2
Write the word equation for magnesium and copper sulfate solution. Write the full equation.

Method. Name each substance, using the reactants and products.

  1. Reactants. Magnesium and copper sulfate.
    magnesium + copper sulfate
  2. Products. Magnesium sulfate and copper.
    magnesium sulfate + copper
  3. Write. The equation links them with an arrow.
    magnesium + copper sulfate -> magnesium sulfate + copper
  4. Write the answer.
    magnesium + copper sulfate -> magnesium sulfate + copper

Check. Each side has the same atoms. ✓

Worked example 7.2.3
In the ionic equation Mg + Cu2+ -> Mg2+ + Cu, which ion has changed to a metal? Write the symbol.

Method. Find the ion that becomes a solid.

  1. Look. Cu2+ gains two electrons to form copper metal.
    gains electrons
  2. Name it. So the copper ion becomes copper metal: Cu.
    Cu
  3. Write the answer.
    Cu

Check. Copper ions gain electrons to form the metal. ✓

Watch out

Watch out: a displacement needs the more reactive metal to be the one that is added. Zinc does not displace magnesium from magnesium sulfate.

Exam tip

Exam tip. In an ionic equation, the spectator ions are left out; write only the ions that change.

Try it (with your teacher, or a grown-up at home). With your teacher, drop a small piece of zinc into copper sulfate solution in a beaker, and watch for copper forming on the zinc. Do not drink or taste any solution. Record the colour change and say which metal is more reactive.

Exercise 7B  Displacement reactions and equations

1
FWhat is a displacement reaction? Write the words.
2
FDoes magnesium displace copper from copper sulfate solution? Write yes or no.
3
FDoes copper displace magnesium from magnesium sulfate solution? Write yes or no.
4
FWhat is the name of the salt formed when magnesium reacts with copper sulfate? Write the words.
5
FIn the full reaction of magnesium with copper sulfate solution, which ion is the spectator ion? Write the symbol.
6
FWrite the word equation for zinc and copper sulfate. Write the full equation.
7
PSDoes zinc displace copper from copper sulfate solution? Write yes or no.
8
PSDoes magnesium displace zinc from zinc sulfate solution? Write yes or no.
9
PSDoes zinc displace magnesium from magnesium sulfate solution? Write yes or no.
10
PSIn the ionic equation Zn + Cu2+ -> Zn2+ + Cu, what does the zinc atom become? Write the symbol.
11
RExplain why a displacement reaction is a reduction of the metal ion. Write one sentence. Accept any sentence saying the metal ion gains electrons to form the metal atom.
12
RChallenge: predict whether iron will displace copper from copper sulfate solution, using the series. Write yes or no, and give the reason in one sentence. Accept yes, if iron is above copper, with a reason naming the series.
7.3

Extraction of metals by reduction with carbon

Year 9
9C3: extraction of metals by reduction with carbon (metals below carbon in the series)
Video lesson: Extraction of metals by reduction with carbonComing soon
Story. An ore of zinc is mined, and it contains zinc oxide. Zinc is more useful as a metal, so it must be separated from the oxygen. The class asks which methods can be used to take the oxygen away.

Many metals are found in nature as oxides. To extract the metal, the oxygen must be removed. This is a reduction reaction. Carbon can reduce a metal oxide if carbon is more reactive than the metal, which means the metal is below carbon in the series.

The word equation for zinc oxide is: zinc oxide + carbon → zinc + carbon dioxide.

Metal oxideCan carbon reduce it?
zinc oxideyes
iron oxideyes
copper oxideyes
aluminium oxideno
magnesium oxideno
Metal oxides and whether carbon can reduce them to the metal

Key ideas

  • Reduction: removing oxygen from a metal oxide.
  • Carbon can reduce metal oxides for metals below carbon in the series.
  • Reactive metals above carbon (such as aluminium) cannot be extracted by carbon.
  • Carbon becomes carbon dioxide in the reaction.
Worked example 7.3.1
Can carbon reduce zinc oxide to zinc? Write yes or no.

Method. Compare zinc with carbon in the series.

  1. Compare. Zinc is below carbon in the series.
    below carbon
  2. Decide. So carbon can reduce zinc oxide, and the answer is yes.
    yes
  3. Write the answer.
    yes

Check. Carbon takes the oxygen from zinc oxide. ✓

Worked example 7.3.2
Can carbon reduce aluminium oxide? Write yes or no.

Method. Compare aluminium with carbon.

  1. Compare. Aluminium is above carbon in the series, so it is more reactive.
    above carbon
  2. Decide. So carbon cannot reduce aluminium oxide, and the answer is no.
    no
  3. Write the answer.
    no

Check. Aluminium needs electrolysis instead. ✓

Worked example 7.3.3
Write the word equation for the reduction of zinc oxide by carbon. Write the full equation.

Method. Name the reactants and products.

  1. Reactants. Zinc oxide and carbon.
    zinc oxide + carbon
  2. Products. Zinc and carbon dioxide.
    zinc + carbon dioxide
  3. Write. The arrow joins them.
    zinc oxide + carbon -> zinc + carbon dioxide
  4. Write the answer.
    zinc oxide + carbon -> zinc + carbon dioxide

Check. Oxygen moves from the zinc to the carbon. ✓

Watch out

Watch out: carbon is not always placed above the metal. Only metals below carbon can be reduced by carbon.

Exam tip

Exam tip. When asked whether carbon can extract a metal, compare the metal with carbon in the series, not with hydrogen.

Try it (with your teacher, or a grown-up at home). Teacher demonstration only: a teacher heats copper oxide with charcoal in a test tube, in a fume cupboard, with eye protection. Pupils watch for the copper colour. Say which metal oxide could be reduced in this way, and why.

Exercise 7C  Extraction of metals by reduction with carbon

1
FWhat is the name of the reaction that removes oxygen from a metal oxide? Write the word.
2
FWhat is carbon changed into when it reduces zinc oxide? Write the words.
3
FIs zinc below or above carbon in the reactivity series? Write the word.
4
FCan carbon reduce iron oxide to iron? Write yes or no.
5
FCan carbon reduce magnesium oxide to magnesium? Write yes or no.
6
PSWhich metal oxide can carbon reduce: copper oxide or aluminium oxide? Write the words.
7
PSIn the list of oxides, how many can carbon reduce: zinc oxide, iron oxide, aluminium oxide, copper oxide? Write the number.
8
PSWrite the word equation for the reduction of copper oxide by carbon. Write the full equation.
9
RWhy is aluminium not extracted by heating its oxide with carbon? Write one sentence. Accept any sentence saying aluminium is more reactive than carbon, so carbon cannot take the oxygen away.
10
RChallenge: explain why a metal above carbon in the series is extracted by electrolysis instead of carbon. Accept any sentence saying carbon is not reactive enough to reduce it, so electricity is used to split the compound.
7.4

Electrolysis of an electrolyte

Year 9
9C3: electrolysis of an electrolyte: anode, cathode, electrolyte and products (teacher demonstration or simulation only)
Video lesson: Electrolysis of an electrolyteComing soon
Story. A teacher places two copper electrodes in a beaker of copper sulfate solution and connects them to a low-voltage supply. After some time, copper appears on one electrode, and the other electrode looks thinner. The class asks which electrode is which, and why.

Electrolysis is the splitting of a compound by electricity. The liquid that conducts is the electrolyte. The anode is the positive electrode, and the cathode is the negative electrode. Positive ions move to the cathode, and negative ions move to the anode.

In copper sulfate solution with copper electrodes, copper dissolves from the anode, and copper is deposited on the cathode. No gas is made.

copper sulfate solutionanode (+)cathode (-)celllow-voltage supply (teacher demonstration only)
Electrolysis of copper sulfate solution with two copper electrodes and a low-voltage cell

Key ideas

  • Electrolyte: the liquid that conducts electricity by its moving ions.
  • Anode: the positive electrode. Cathode: the negative electrode.
  • Positive ions move to the cathode; negative ions move to the anode.
  • With copper electrodes, copper moves from the anode to the cathode.
Worked example 7.4.1
Which electrode is the positive electrode? Write the word.

Method. Recall the names.

  1. Recall. The anode is the positive electrode.
    positive electrode
  2. Name it. So the positive electrode is the anode.
    anode
  3. Write the answer.
    anode

Check. The cathode is negative. ✓

Worked example 7.4.2
In copper sulfate electrolysis with copper electrodes, what happens to the cathode? Write the words.

Method. Think about what is deposited.

  1. Think. Copper ions move to the cathode and gain electrons.
    gain electrons
  2. Name it. So copper is deposited on the cathode.
    copper is deposited
  3. Write the answer.
    copper is deposited

Check. The cathode gains mass. ✓

Worked example 7.4.3
What is the electrolyte in this experiment? Write the words.

Method. Find the liquid that conducts.

  1. Look. The liquid in the beaker is copper sulfate solution.
    copper sulfate solution
  2. Name it. So the electrolyte is copper sulfate solution.
    copper sulfate solution
  3. Write the answer.
    copper sulfate solution

Check. The electrolyte conducts through its ions. ✓

Watch out

Watch out: the anode is positive, and the cathode is negative. Do not write the names the other way round.

Exam tip

Exam tip. Use the mnemonic words: anode is for the positive (+) and cathode for the negative (-); then say what moves to each.

Try it (with your teacher, or a grown-up at home). Teacher demonstration only: the teacher sets up copper sulfate solution and copper electrodes on a low-voltage supply. Pupils observe and record the electrodes after 10 minutes. Do not touch the solution, and do not touch the electrodes while the supply is on.

Exercise 7D  Electrolysis of an electrolyte

1
FWhat is the name of the liquid that conducts electricity in electrolysis? Write the word.
2
FWhat is the name of the positive electrode in electrolysis? Write the word.
3
FWhat is the name of the negative electrode in electrolysis? Write the word.
4
FIn electrolysis, do positive ions move to the cathode or the anode? Write the word.
5
FIn copper sulfate electrolysis with copper electrodes, is copper deposited on the anode or the cathode? Write the word.
6
FIn copper sulfate electrolysis with copper electrodes, does copper dissolve from the anode? Write yes or no.
7
FIs any gas made in copper sulfate electrolysis with copper electrodes? Write yes or no.
8
PSWhich electrode gains mass in this experiment: the anode or the cathode? Write the word.
9
PSWhich ion carries a positive charge in copper sulfate solution? Write the symbol.
10
PSName the electrolyte used in this demonstration. Write the words.
11
RExplain why the solution must contain ions for electrolysis to happen. Write one sentence. Accept any sentence saying the ions carry the current by moving to the electrodes.
12
RChallenge: explain why the copper anode gets thinner while the copper cathode gets thicker. Accept any sentence saying copper atoms leave the anode as ions and are deposited as atoms on the cathode.
7.5

Electrolysis for reactive metals

Year 9
9C3: electrolysis for reactive metals such as aluminium (basic); teacher demonstration or simulation only
Video lesson: Electrolysis for reactive metalsComing soon
Story. A factory makes aluminium drink cans. The aluminium comes from aluminium oxide, which is too stable to be reduced by carbon. The engineer explains that electricity is used to split the oxide instead.

Reactive metals such as aluminium are above carbon in the series, so carbon cannot take their oxygen away. Instead, the metal is extracted by electrolysis. The aluminium oxide is dissolved in molten cryolite, and an electric current splits it. Aluminium forms at the cathode, and oxygen forms at the anode.

This process uses a lot of electricity, and it is done in industry, not in school. In school, it is only shown as a simulation or a teacher demonstration.

Metal oxideCan carbon reduce it?
zinc oxideyes
iron oxideyes
copper oxideyes
aluminium oxideno
magnesium oxideno
Metal oxides that carbon can and cannot reduce

Key ideas

  • Aluminium is more reactive than carbon, so carbon cannot extract it.
  • Aluminium is extracted by electrolysis of its oxide.
  • Aluminium forms at the cathode (negative electrode).
  • Electrolysis of reactive metals uses a lot of electricity.
Worked example 7.5.1
Why is aluminium extracted by electrolysis, not by carbon? Write the word for the reason.

Method. Compare aluminium with carbon.

  1. Compare. Aluminium is above carbon in the series, so it is more reactive.
    above carbon
  2. Name it. Carbon cannot reduce a metal above it, so electrolysis is used. The reason is reactivity.
    reactivity
  3. Write the answer.
    reactivity

Check. Reactivity decides the method. ✓

Worked example 7.5.2
At which electrode does aluminium form? Write the word.

Method. Recall the electrode for a positive metal ion.

  1. Recall. Positive aluminium ions move to the negative electrode.
    negative electrode
  2. Name it. The negative electrode is the cathode.
    cathode
  3. Write the answer.
    cathode

Check. Positive ions move to the cathode. ✓

Worked example 7.5.3
Is electrolysis of aluminium oxide done in school? Write yes or no.

Method. Recall the rule for school practicals.

  1. Recall. Electrolysis of reactive metals uses a lot of electricity and is done in industry.
    done in industry
  2. Decide. In school it is shown only as a simulation or a teacher demonstration, so the answer is no.
    no
  3. Write the answer.
    no

Check. Pupils do not carry out this electrolysis. ✓

Watch out

Watch out: aluminium is not extracted by carbon, even though carbon is used for iron and zinc.

Exam tip

Exam tip. If asked how a reactive metal is extracted, name the method (electrolysis) and give the reason (too reactive for carbon).

Try it (with your teacher, or a grown-up at home). Use a simulation or a video of a teacher demonstration of electrolysis of a metal compound. Describe where the metal forms, and what the other product is. Do not attempt any electrolysis of aluminium oxide in school.

Exercise 7E  Electrolysis for reactive metals

1
FWhich method is used to extract a reactive metal such as aluminium? Write the word.
2
FIs aluminium above or below carbon in the series? Write the word.
3
FCan carbon reduce aluminium oxide? Write yes or no.
4
FAt which electrode does aluminium form in electrolysis? Write the word.
5
FWhich product forms at the anode when aluminium oxide is electrolysed? Write the word.
6
FIs electrolysis of reactive metals done in a school laboratory? Write yes or no.
7
PSWhich metal is extracted by carbon reduction: zinc or aluminium? Write the word.
8
PSWhich metal is extracted by electrolysis: copper or aluminium? Write the word.
9
RExplain why electrolysis is expensive for extracting aluminium. Write one sentence. Accept any sentence saying it needs a lot of electricity to split the strong bonds of the oxide.
10
RChallenge: explain why aluminium is still used widely, even though its extraction is expensive. Accept any sentence saying it is light, strong and resists corrosion, so its uses justify the cost.

Chapter summary

SkillMethod
Reactivity seriesMost reactive at the top: K, Na, Ca, Mg, Al, C, Zn, Fe, H, Cu, Ag, Au.
DisplacementA more reactive metal displaces a less reactive metal from its salt; use word and ionic equations.
Carbon reductionCarbon removes oxygen from oxides of metals below carbon in the series (for example zinc and iron).
ElectrolysisAn electric current splits an electrolyte; the anode is positive and the cathode is negative.
Reactive metalsMetals above carbon, such as aluminium, are extracted by electrolysis (demonstration or simulation only).

Can you…?

  • I can place metals and carbon in the reactivity series, and use it to predict reactions
  • I can write word and ionic equations for displacement reactions
  • I can explain which metal oxides carbon can reduce, and why
  • I can name the anode, cathode, electrolyte and products of a demonstration electrolysis
  • I can explain why reactive metals such as aluminium need electrolysis

Key terms

reactivity series
a list of metals and carbon, ordered from most reactive to least reactive
displacement
a more reactive element taking the place of a less reactive one in a compound
word equation
a reaction written with the names of the substances
ionic equation
an equation showing only the ions and atoms that change
reduction
removing oxygen from a compound, or gaining electrons
electrolysis
splitting a compound by passing an electric current through it
electrolyte
the liquid that conducts electricity by its moving ions
anode
the positive electrode in electrolysis
cathode
the negative electrode in electrolysis
cryolite
a substance used to dissolve aluminium oxide before electrolysis
spectator ion
an ion that is present on both sides and does not change

Exercise 7Z  Check-up

1
Which metal is more reactive: magnesium or zinc? Write the word.
2
Does zinc displace copper from copper sulfate solution? Write yes or no.
3
Write the word equation for magnesium and copper sulfate solution. Write the full equation.
4
Can carbon reduce zinc oxide to zinc? Write yes or no.
5
Can carbon reduce magnesium oxide to magnesium? Write yes or no.
6
Which electrode is positive in electrolysis? Write the word.
7
In copper sulfate electrolysis with copper electrodes, where is copper deposited? Write the word.
8
Is any gas made in copper sulfate electrolysis with copper electrodes? Write yes or no.
9
Which metal is extracted by electrolysis: iron or aluminium? Write the word.
10
Explain why carbon can reduce copper oxide. Write one sentence. Accept any sentence saying copper is below carbon in the series, so carbon can take the oxygen away.

Total 20 marks. Allow about 20 minutes.

Exercise 7X  Practice test questions

1
FName the least reactive metal in this list: zinc, magnesium, gold. Write the word.[1 mark]
2
FDoes magnesium displace zinc from zinc sulfate solution? Write yes or no.[1 mark]
3
FName the electrode where positive ions gain electrons in electrolysis. Write the word.[1 mark]
4
FWrite the word equation for the reduction of zinc oxide by carbon. Write the full equation.[2 marks]
5
PSWrite the ionic equation for the reaction of magnesium with copper ions. Write the full equation.[2 marks]
6
RExplain why aluminium is not extracted by carbon. Write one sentence. Accept any sentence saying aluminium is more reactive than carbon, so carbon cannot take the oxygen away.[2 marks]
7
FIn copper sulfate electrolysis with copper electrodes, state what happens at the anode and at the cathode. Write two short sentences. Accept any answer that says copper dissolves at the anode and copper is deposited at the cathode.[2 marks]
8
PSUse the displacement table to say which metal is the most reactive of magnesium, zinc and copper. Explain in one sentence. Accept any answer naming magnesium, because it displaces both zinc and copper.[3 marks]
9
FA teacher electrolyses copper sulfate solution. Name the electrolyte, the anode and the cathode. Write three short answers. Accept copper sulfate solution; anode is copper that dissolves; cathode is where copper is deposited.[3 marks]
10
RExplain why reactive metals such as aluminium need electrolysis, and why it is not done in school. Write two sentences. Accept any answer saying carbon cannot reduce them, and electrolysis uses a lot of electricity and is done in industry.[3 marks]
← Chapter 6: The periodic table and bondingChapter 8: Rates of reaction and energy in reactions →

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