Chemical changes · GCSE Chemistry
The reactivity series
GCSE Chemistry revision on the reactivity series: potassium to gold, displacement, metal plus acid or water, and linking reactivity to how easily atoms form positive ions.
Please Send Charlie’s Monkeys And Zebras In Lead Cages Securely Guarded: potassium, sodium, calcium, magnesium, aluminium, zinc, iron, lead, copper, silver, gold. Hydrogen sits among them for acids.
The important bits
What you need to know
- 1
A more reactive metal displaces a less reactive metal from a compound: Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s). The blue Cu²⁺ colour fades as copper metal appears.
- 2
Reactivity is how easily the metal atom loses electrons to form a positive ion. Potassium loses its outer electron more readily than copper, so potassium is higher.
- 3
With water: K, Na and Ca react to give hydroxide + hydrogen. Mg reacts slowly with cold water but readily with steam: Mg(s) + H₂O(g) → MgO(s) + H₂(g).
- 4
With dilute acid: metals above hydrogen give salt + hydrogen. Copper, silver and gold do not. 2HCl(aq) + Fe(s) → FeCl₂(aq) + H₂(g).
- 5
Carbon and hydrogen are often placed in the series for extraction and acid reactions. Metals above carbon cannot be extracted from their oxides by reduction with carbon.
- 6
Aluminium appears unreactive because of a thin, unreactive Al₂O₃ layer. Remove or disrupt that layer and aluminium is more reactive than zinc.
- 7
Oxidation is loss of electrons (the metal atom becoming an ion). Reduction is gain of electrons (the less reactive ion becoming the metal). Displacement is a redox reaction.
- 8
Temperature rise in a displacement (for example, adding metals to CuSO₄) is a practical way to rank metals: the bigger the temperature rise, the more reactive the added metal, if you control mass and surface area.
Quotations worth analysing
Short evidence. Real method.
“Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s)”
Zinc is oxidised (loses 2e⁻). Copper ions are reduced (gain 2e⁻). Spectator sulfate ions are left out. This is the heart of the reactivity series.
“Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g)”
Magnesium is above hydrogen, so hydrogen is displaced as the gas. Copper would give no reaction with dilute HCl.
“K > Na > Ca > Mg > Al > Zn > Fe > Pb > (H) > Cu > Ag > Au”
Learn a mnemonic, then practise placing carbon for extraction and hydrogen for acids. Do not invent a new order in the exam.
Go deeper
Displacement is electrons moving from atom to ion
A zinc atom can force a copper ion to take two electrons because zinc holds its outer electrons less strongly. The zinc atom becomes Zn²⁺; the copper ion becomes a copper atom, which you see as a brown/orange coating. If you try the reverse — copper into zinc sulfate — nothing happens. That “no reaction” is as important as the reaction. On Higher tier write the half equations: Zn → Zn²⁺ + 2e⁻ and Cu²⁺ + 2e⁻ → Cu. OIL RIG. The more reactive metal is the better reducing agent.
Go deeper
Water and acid are two different lines on the same list
Only the top metals (K, Na, Ca, and Mg slowly) attack cold water. Steam lets magnesium, zinc and iron show themselves: iron plus steam gives Fe₃O₄ and hydrogen. Dilute acid is a fairer comparison for Mg, Zn, Fe and Pb: speed of fizzing, with equal surface area and concentration, ranks them. Copper sits below hydrogen, so no fizz. Gold sits at the bottom: unreactive, found native, used in jewellery and electronics because it does not oxidise. Do not test potassium in acid in a school lab — the water reaction is already violent.
Go deeper
Aluminium’s oxide layer is a trap question
Fresh aluminium is high in the series, which is why it is extracted by electrolysis, not by carbon. In air it is coated with Al₂O₃, so it appears to ignore water and dilute acid. A question that says “aluminium does not react with water but is more reactive than iron” wants that oxide layer. In thermite, aluminium reduces iron oxide: 2Al + Fe₂O₃ → Al₂O₃ + 2Fe, showing aluminium’s true reactivity when the coating is not in charge. Link this page to metal extraction: position in the series decides the method.
See the idea in action
Iron filings are added to blue copper(II) sulfate solution. A brown coating of copper forms and the solution turns paler green as Fe²⁺ appears: Fe(s) + CuSO₄(aq) → FeSO₄(aq) + Cu(s). Iron is oxidised; Cu²⁺ is reduced. Copper added to iron(II) sulfate gives no reaction because copper is less reactive. Magnesium would displace both copper and iron, and would also fizz in dilute acid, unlike copper.
Exam technique
Turn knowledge into marks
State which metal is more reactive, write the equation with state symbols, then say which species is oxidised and which is reduced if the paper is Higher. For “no reaction”, say the added metal is less reactive.
Common mistakes
Do not give these marks away
- 01
Writing a displacement that goes the wrong way, such as Cu displacing Zn²⁺.
- 02
Forgetting hydrogen’s place, and predicting that copper produces H₂ with dilute acid.
- 03
Ignoring aluminium’s oxide layer, or leaving out state symbols on Cu(s) and Cu²⁺(aq).
Which reaction occurs?
ACu(s) + ZnSO₄(aq) → CuSO₄(aq) + Zn(s)
BZn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s)
CAg(s) + CuSO₄(aq) → AgSO₄(aq) + Cu(s)
DCu(s) + 2HCl(aq) → CuCl₂(aq) + H₂(g)
Show the answer
Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s). Zinc is more reactive than copper, so it displaces Cu²⁺. Copper cannot displace zinc or hydrogen from dilute acid, and silver cannot displace copper.
Quick questions
If this is the bit you searched
What is the reactivity series GCSE Chemistry?
A list of metals in order of how easily they form positive ions, from potassium at the top to gold at the bottom. A more reactive metal displaces a less reactive one.
Why does zinc displace copper from copper sulfate?
Zinc atoms lose electrons more readily than copper atoms, so zinc is oxidised to Zn²⁺ and Cu²⁺ ions are reduced to copper metal.
Which metals react with dilute acid to make hydrogen?
Metals above hydrogen in the series, such as magnesium, zinc and iron. Copper, silver and gold do not.
Why does aluminium seem unreactive?
A thin layer of aluminium oxide, Al₂O₃, coats the metal and protects it. Aluminium is actually high in the series and is extracted by electrolysis.