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Unit 5: Reactivity

Reactivity And Displacement Reactions — HIA International - Grade 8 Revision Notes & Topical Questions

5 min read 6 parts Lesson 8 of 12 2 quizzes

📚 HIA International - Grade 8 Hub / Topical Revision
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Lesson summary

Reactivity and displacement reactions — HIA INTERNATIONAL notes: Use the reactivity series to explain and predict displacement reactions.Order (most to least reactive) — potassium, sodium, calcium, magnesium, aluminium, zinc, iron, lead, copper, silver, gold.Carbon and hydrogen —…

  • How it is made
  • Placing a new metal
  • No reaction
  • Other examples
  • Native metals
  • Thermite reaction

Section 1 of 6The reactivity series

The reactivity series
Order (most to least reactive)
  • Order (most to least reactive) potassium, sodium, calcium, magnesium, aluminium, zinc, iron, lead, copper, silver, gold.
Carbon and hydrogen
  • Carbon and hydrogen carbon sits between aluminium and zinc, and hydrogen between lead and copper.
How it is made
  • How it is made from the reactions of metals with oxygen, water or steam and dilute acid.
Trend
  • Trend the reactions become less vigorous as you go down the list.
Placing a new metal
  • Placing a new metal compare its reactions with those of known metals, e.g. platinum is placed near gold because it stays shiny.

Section 2 of 6Displacement reactions

Displacement
Displacement a more reactive metal replaces a less reactive metal in a salt.
Example
  • Example iron + copper sulfate → iron sulfate + copper (CuSO4 + Fe → FeSO4 + Cu).
Evidence
  • Evidence the iron nail becomes coated with copper and the blue solution becomes paler or pale green.
No reaction
  • No reaction a less reactive metal cannot displace a more reactive one, e.g. copper in iron sulfate.
Other examples
  • Other examples magnesium + zinc sulfate → magnesium sulfate + zinc; copper + magnesium sulfate → no reaction.

Section 3 of 6Investigating displacement

1
Put about a third of a test tube of copper sulfate, magnesium sulfate, iron sulfate and zinc sulfate solutions in separate tubes.
2
Add a small piece of each other metal to each solution.
3
Record observations in a results table.
4
Rank the metals: the one that displaces the most is the most reactive.
Safety
  • Safety wear safety glasses.
Energy
  • Energy displacement is usually exothermic, and a bigger gap in reactivity gives a larger temperature rise.

Section 4 of 6Examples of use

Native metals
  • Native metals gold and silver are found uncombined because they are so unreactive.
Thermite reaction
  • Thermite reaction aluminium + iron oxide → aluminium oxide + iron releases so much energy that the iron is molten.
Carbon
  • Carbon it displaces zinc, iron, tin, lead and copper from their oxides;
    • metals above carbon need electrolysis.

Section 5 of 6Key terms

TermMeaning
Reactivity seriesA list of metals from most to least reactive.
Displacement reactionA reaction in which a more reactive element replaces a less reactive one in a compound.
SaltA compound formed when the hydrogen in an acid is replaced by a metal.
ExothermicA reaction that gives out thermal energy.
OreA rock that contains a metal compound.
Native metalA metal found uncombined in nature.

Section 6 of 6Exam technique

1
A less reactive metal can displace a more reactive one — it cannot; there is no reaction.
2
The reactivity series is a list by hardness — it is ordered by how readily metals react.
3
The blue solution stays unchanged when iron displaces copper — the colour fades as iron sulfate forms.
4
Displacement is endothermic — it is usually exothermic.

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