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Unit 9 DISPLACEMENT

REACTIONS

Fig. 1 This gold cup is almost 4000 years

old. An iron cup this old would be verydamaged by rust.

Gold survives for thousands of years.Why doesn't it rust?

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Getting startedWhich elements are in each of these compounds?

1. copper sulfide

2. copper sulfate

3. carbon dioxide

4. iron oxide

5. calcium carbonate

Which of these metals is most reactive with water?

Put a tick in the correct box.

sodium [ ]

magnesium [ ]

potassium [ ]

copper [ ]

Fig. 2 Reactions with water can damage things and cost us money.

Reactive

How easilya substanceundergoes

a chemicalreaction withothers.

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ConceptsIn completing this unit you will learn to:

• Explain one useful application ofdisplacement reactions (M6)

Key TermsThe meanings of these terms can be foundin the glossary on pages 275–90.

charcoal 

displacement reaction

ore

reactive

reactivity series

Investigating ScientificallyS11

Success CriteriaLearning outcome M6

Here is what you might aim to achieve by the end of this unit:

• Emerging  – state whether or notgiven reactants would undergo adisplacement reaction

• Developing  – construct wordequations for displacement reactions

• Mastery  – explain one usefulapplication of displacement reactions

  Learning Outcomes

I know what

these words

mean

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1 Magnesium + copper sulfateLook at this chemical equation:

magnesium + copper sulfate ➔ magnesium sulfate + copper 

Activity 1.1

What to do:

1. Put two centimeters depth of copper sulfate solution intothe test tube.

2. Add a small piece of magnesium ribbon.

3. Leave the test tube. What do you observe?

 

M6

Equipment:

Test tube,

 test tube rack,

small length ofmagnesium,

copper sulfatesolution

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What is in your test tube at the end of the experiment?

 

Look at the equation again:

magnesium + copper sulfate

metals metal compounds

magnesium sulfate + copper

On both sides of the equation there is a metal and a metalcompound. The reaction happens because magnesium is

more reactive than copper.When you mix a metal with a metal compound there willbe a reaction if the metal is more reactive than the metalalready in the compound. This is called a displacementreaction.

In normal English, to ‘displace’ means to move somethingaway from where it is. In a displacement reaction, the reactivemetal moves the less reactive element out of the compoundand takes its place.

 A   +  BC B  +  A C

If you put copper in a magnesium sulfate solution, it won’treact. From the information in this section, explain why not.

 

2 Reactivity seriesWe can predict whether a metal and a metalcompound will react by comparing the reactivityof the metal and the metal in the metal compound.Knowing the order of reactivity of the metals helps us makepredictions. This means that we need to understand thereactivity series.

Displacementreaction

This happenswhen a morereactive metalreacts with thecompound ofa less reactive

metal. Theproducts ofthe reactionare a newmetalcompoundand a metal.

M6S11Reactivityseries

A list ofthe metalelementsin order ofreactivity.

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potassium

sodium

calcium

magnesium

aluminium

carbon*

zinc

iron

tin

lead

copper

silver

gold

More reactive

Less reactive

carbon is not a metal, but it is often included in the reactivityseries. It is involved in some important displacementreactions.

*

We can use the reactivity series to decide whether or not therewill be a reaction.

Example 1

Will there be a reaction between copper sulfate and tin?

iron

tin

lead

copper

silver

gold

Tin is more reactive than copper, so the tin will displace thecopper in the copper sulfate:

tin + copper sulfate ➔ tin sulfate + copper 

Fig. 3 This list ofmetals shows the

reactivity series.

Fig. 4 

The reactivity seriesshows that tin is

more reactive thancopper.

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Example 2

Will there be a reaction between iron carbonate and lead?

iron

tin

lead

copper

silver

gold

Lead is less reactive than iron, so the lead will not displace theiron. There will not be a reaction.

For each equation below, decide whether there will be areaction. If there is, complete the equation. If there is not,write ‘no reaction’.

magnesium + copper sulfate ➔ 

copper + magnesium sulfate ➔ 

iron + copper sulfate ➔ 

iron + sodium chloride ➔ 

zinc + silver nitrate ➔ 

copper + potassium sulfate ➔ 

gold + potassium nitrate ➔ 

3 Uses of copper Copper is a familiar metal. Among other uses, weuse it in electrical wiring and electronics.

Fig. 5 The reactivity seriesshows that lead isless reactive thaniron.

M6

Fig. 6 Copper is used in

electrical wiring (left);copper is used incircuit boards (right).

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Copper is also used in buildings, especially for covering roofs.

Copper has been used by people for around 7000 years.

Sometimes we find copper as a metal in the ground. Butmore often, we find copper as an ore. Thousands of years agopeople discovered how to extract copper from copper oxide.

Fig. 7  

The older copperhas turned green. It

has reacted with theatmosphere to form

copper carbonate.

This protects the

copper beneath. Thenewer copper is stillred-brown.

Fig. 8 Here are some

ancient copper tools.The green coloris due to copper

carbonate.

Ore

An ore is arock thatcontains ametal oxide –we canextract themetal from

the ore.

Fig. 9 

This copper metalwas found in the

ground.

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There are several ores of copper. Cuprite is one of the oresof copper.

What two elements are in copper oxide?

 

We can extract copper from copper oxide by heating it withcarbon. Look at the reactivity series in Fig. 3 on page 182 tocheck that this is a possible displacement reaction.

The equation is:

carbon + copper oxide ➔ copper + carbon monoxide

Early humans used charcoal as a source of carbon.

Fig. 10 

Cuprite. This orecontains copperoxide.

Charcoal

Blackenedwood that

has beenburned ina fire. It isoften used forbarbecues.

Fig. 11 Charcoal lookslike this.

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4 Presentation Task Research and explain a use of displacement reactions. You can choose oneof these:

• extraction of a metal from its ore

• thermite reaction

• sacrificial anodes on boats

• galvanization.

Present your findings as a web page or PowerPoint presentation.

5 Feedback Medals and Missions

Self Assessment

Shade in the level you have achieved for each outcome in this unit.

Concept Learning

Outcome

Emerging Developing Mastery

M6State whether or not

given reactants would

undergo a displacement

reaction.

Construct word

equations for

displacement reactions.

Explain one useful

application of

displacement reactions.

Skill Learning

Outcome

Emerging Developing Mastery

S11Draw a conclusion. Draw a conclusion,

related to the scientific

question or prediction.

Draw a conclusion,

consistent with the data,

and explain it using

scientific knowledge and

understanding.

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Medals

What have been your greatest achievements during this unit? For example,mastering a concept outcome, improving a skill or feeling proud of yourorganizational abilities, team work or presentation.

What did you do well? How did you do it?

1.

2.

3.

Missions

What are your targets for improvement? Select two Learning Outcomes to focuson and set yourself a target. For example, if you have reached ‘developing’, whatdo you need to do next time to achieve ‘mastery’?

Learning Outcomes Target

1.

2.

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6 Science I have learned in this unit

 ● A metal reacts with a metal compound if the metal is morereactive than the metal in the compound.

 ● The type of reaction described above is called a displacementreaction.

 ● The reactivity series lists the metals in order of reactivity.

 ● We can use the reactivity series to decide whether a displacement

reaction will happen.

 ● Displacement reactions have practical uses, including extractionof metals from ores.

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