The Reactivity Series

This lesson covers the reactivity series of metals as required by the AQA GCSE Combined Science Trilogy specification (8464). You must be able to recall the order of metals in the reactivity series, describe experiments to establish reactivity, and explain the link between a metal's position in the series and how it is extracted from its ore.

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What Is the Reactivity Series?

The reactivity series is a list of metals (and carbon and hydrogen as reference points) arranged in order of their reactivity, from the most reactive at the top to the least reactive at the bottom. A more reactive metal reacts more vigorously with water, acids and oxygen than a less reactive metal.

graph TB
    K["Potassium — K"] --> Na["Sodium — Na"]
    Na --> Li["Lithium — Li"]
    Li --> Ca["Calcium — Ca"]
    Ca --> Mg["Magnesium — Mg"]
    Mg --> Al["Aluminium — Al"]
    Al --> C["(Carbon — C)"]
    C --> Zn["Zinc — Zn"]
    Zn --> Fe["Iron — Fe"]
    Fe --> H["(Hydrogen — H)"]
    H --> Cu["Copper — Cu"]
    Cu --> Ag["Silver — Ag"]
    Ag --> Au["Gold — Au"]
    Au --> Pt["Platinum — Pt"]

    style K fill:#d32f2f,color:#fff
    style Na fill:#e53935,color:#fff
    style Li fill:#ef5350,color:#fff
    style Ca fill:#ff7043,color:#fff
    style Mg fill:#ff8a65,color:#fff
    style Al fill:#ffb74d,color:#000
    style C fill:#a1887f,color:#fff
    style Zn fill:#fff176,color:#000
    style Fe fill:#dce775,color:#000
    style H fill:#81c784,color:#000
    style Cu fill:#4db6ac,color:#fff
    style Ag fill:#4dd0e1,color:#000
    style Au fill:#4fc3f7,color:#000
    style Pt fill:#64b5f6,color:#fff

Exam Tip: A common mnemonic for the reactivity series is "Please Stop Letting Cows Moo And Cry Zen, It Hurts Copper, Silver, Gold, Platinum" — but you should practise until you can recall the order without a mnemonic.

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Reactions of Metals With Water

The most reactive metals react vigorously with cold water:

Metal	Observation	Products
Potassium	Catches fire with a lilac flame, fizzes vigorously, moves across the surface	Potassium hydroxide + hydrogen
Sodium	Melts into a ball, fizzes, moves across the surface	Sodium hydroxide + hydrogen
Lithium	Fizzes gently, moves across the surface	Lithium hydroxide + hydrogen
Calcium	Sinks, steady fizzing, solution turns milky with Ca(OH)₂	Calcium hydroxide + hydrogen

General Equation

$\text{metal} + \text{water} \rightarrow \text{metal hydroxide} + \text{hydrogen}$metal+water→metal hydroxide+hydrogen

For example:

$2\text{Na}(s) + 2\text{H}_2\text{O}(l) \rightarrow 2\text{NaOH}(aq) + \text{H}_2(g)$2Na(s)+2H2​O(l)→2NaOH(aq)+H2​(g)

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Reactions of Metals With Steam

Metals that do not react with cold water may react with steam:

$\text{metal} + \text{steam} \rightarrow \text{metal oxide} + \text{hydrogen}$metal+steam→metal oxide+hydrogen

Metal	Reactivity with Steam
Magnesium	Burns brightly, vigorous reaction
Zinc	Slow reaction when heated
Iron	Very slow reaction, reversible

Example — magnesium and steam:

$\text{Mg}(s) + \text{H}_2\text{O}(g) \rightarrow \text{MgO}(s) + \text{H}_2(g)$Mg(s)+H2​O(g)→MgO(s)+H2​(g)

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Reactions of Metals With Dilute Acids

Metals above hydrogen in the reactivity series react with dilute acids to produce a salt and hydrogen gas:

$\text{metal} + \text{acid} \rightarrow \text{salt} + \text{hydrogen}$metal+acid→salt+hydrogen

Metal + Acid	Products	Observation
Mg + 2HCl	MgCl₂ + H₂	Vigorous fizzing, metal dissolves quickly
Zn + H₂SO₄	ZnSO₄ + H₂	Steady fizzing
Fe + 2HCl	FeCl₂ + H₂	Slow fizzing, green solution forms
Cu + HCl	No reaction	Copper is below hydrogen

Testing for Hydrogen Gas

Hold a burning splint near the mouth of the test tube. Hydrogen gives a characteristic squeaky pop.

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Displacement Reactions

A more reactive metal can displace a less reactive metal from a solution of its salt. This is a key way to determine the relative reactivity of metals.

$\text{Zn}(s) + \text{CuSO}_4(aq) \rightarrow \text{ZnSO}_4(aq) + \text{Cu}(s)$Zn(s)+CuSO4​(aq)→ZnSO4​(aq)+Cu(s)

Observations: The blue copper sulfate solution turns colourless (zinc sulfate), and a brown/orange coating of copper appears on the zinc.

Rules for Displacement

• A more reactive metal displaces a less reactive metal from its compound.
• A less reactive metal cannot displace a more reactive metal — no reaction occurs.

Reaction	Occurs?
Fe + CuSO₄	Yes — iron is more reactive than copper
Cu + FeSO₄	No — copper is less reactive than iron
Mg + ZnCl₂	Yes — magnesium is more reactive than zinc
Ag + CuSO₄	No — silver is less reactive than copper

Exam Tip: If you are asked to predict whether a displacement reaction will occur, compare the positions of the two metals in the reactivity series. The metal in the compound must be less reactive than the free metal for displacement to happen.

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Common Mistakes

Mistake	Correction
Confusing the reactions of metals with cold water and steam	Metals that react with cold water form metal hydroxides; metals that react with steam form metal oxides
Forgetting that carbon and hydrogen are included as reference points, not metals	They are placed in the series to help decide on extraction methods
Thinking copper reacts with dilute acid	Copper is below hydrogen in the reactivity series and does not react with dilute acids
Mixing up the squeaky pop test	The squeaky pop tests for hydrogen, not any other gas

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Worked Example

Question: A student places a piece of magnesium ribbon into iron(II) sulfate solution. Predict and explain what happens.

Answer:

1. Magnesium is higher in the reactivity series than iron.
2. Therefore, magnesium displaces iron from iron(II) sulfate.
3. Equation: Mg(s) + FeSO₄(aq) → MgSO₄(aq) + Fe(s)
4. Observations: The magnesium ribbon dissolves, the green colour of the solution fades (the iron(II) ions are replaced by colourless magnesium ions), and dark grey iron metal appears.

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Summary

• The reactivity series ranks metals from most reactive (potassium) to least reactive (platinum), with carbon and hydrogen as reference points.
• The most reactive metals react vigorously with cold water, forming metal hydroxides and hydrogen.
• Less reactive metals react with steam, forming metal oxides and hydrogen.
• Metals above hydrogen react with dilute acids to produce a salt and hydrogen.
• A more reactive metal displaces a less reactive metal from its compound in solution.
• The reactivity series determines the method of extraction: metals above carbon require electrolysis; metals below carbon are extracted by reduction with carbon.

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Extended Worked Examples

Worked Example 1 — Balancing a Metal + Water Equation

Question: Write a fully balanced symbol equation, including state symbols, for the reaction of potassium with cold water.

Answer (step by step):

1. Identify products: metal hydroxide (KOH) and hydrogen (H₂).
2. Unbalanced: K + H₂O → KOH + H₂.
3. Balance hydrogen: each H₂O has 2 hydrogens, each KOH has 1, and H₂ has 2. Start with 2 waters and 2 KOH — that gives 4 H on each side.
4. Balance potassium: need 2 K.
5. Final balanced equation: 2K(s) + 2H₂O(l) → 2KOH(aq) + H₂(g).
6. Check: 2 K, 4 H, 2 O on both sides. Correct.

Worked Example 2 — Interpreting a Displacement Table

A student adds four metals (magnesium, zinc, iron and copper) to solutions of four salts and records their observations:

Metal \ Salt	MgSO₄	ZnSO₄	FeSO₄	CuSO₄
Magnesium	—	reaction	reaction	reaction
Zinc	none	—	reaction	reaction
Iron	none	none	—	reaction
Copper	none	none	none	—

Deductions:

• Magnesium displaces zinc, iron and copper, so magnesium is the most reactive of the four.
• Zinc displaces iron and copper but not magnesium, so zinc is below magnesium.
• Iron displaces only copper, so iron is less reactive than zinc.
• Copper does not displace any of the others, so copper is least reactive.
• Order (most to least reactive): Mg > Zn > Fe > Cu — matches the standard reactivity series.

Worked Example 3 — Calculating a Temperature Rise

A student adds 2.4 g of magnesium ribbon to 50 cm³ of dilute hydrochloric acid and records a temperature rise of 22 degC. For the same mass of iron filings under identical conditions, the temperature rise is only 6 degC. Explain the difference using the reactivity series.

Answer: Magnesium is significantly higher in the reactivity series than iron, so the metal–acid reaction releases more energy per second in the same volume of solution. Iron releases energy more slowly, and some is lost to the surroundings before the peak temperature is reached, so the measured rise is smaller even though both reactions are exothermic.

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Comparison Table — Three Probing Reactions

Test	Observation for a Reactive Metal	Observation for an Unreactive Metal
With cold water	Vigorous fizzing, hydrogen gas, possibly flame (K, Na)	No visible change (Fe, Cu)
With dilute HCl	Fast fizzing, metal dissolves (Mg, Zn)	No reaction (Cu, Ag)
In a salt solution of a less reactive metal	Coating forms, solution colour fades (Zn in CuSO₄)	No reaction (Cu in ZnSO₄)

Exam Tip: When asked to design an experiment to rank an unknown metal X, add equal masses of X and known metals to the same volume and concentration of dilute acid and compare rates of fizzing, or test whether X displaces known metals from their solutions.

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Common-Mistake Callouts (Extra)

Common mistake: Students write "2Na + H₂O → NaOH + H₂" without balancing. Remember to balance hydrogen atoms first when water appears on the reactant side.

Common mistake: Writing "Cu + HCl → CuCl + H₂". Copper is below hydrogen in the reactivity series — this reaction does not happen under normal conditions.

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Mermaid Diagram — Predicting a Reaction

flowchart TD
    A["Pair: Metal + Reagent"] --> B{"Is metal above the reagent<br/>in the reactivity series?"}
    B -- "Yes (above H or above metal in salt)" --> C["Reaction occurs"]
    B -- "No" --> D["No reaction"]
    C --> E{"Reagent is...?"}
    E -- "Water (cold)" --> F["metal hydroxide + H₂"]
    E -- "Dilute acid" --> G["salt + H₂"]
    E -- "Metal salt solution" --> H["new metal + new salt (displacement)"]

    style C fill:#2e7d32,color:#fff
    style D fill:#d32f2f,color:#fff

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Answering at different grade levels

Grade band	What a response should contain
Grades 1–3 (foundation secure)	Name where a metal sits in the reactivity series and state whether a reaction will happen (e.g. "Zinc is more reactive than copper so it reacts"). Recall that acids produce hydrogen and that the test is a squeaky pop.
Grades 4–5 (standard pass)	Link the reactivity series to observations (vigour of fizzing, colour change). Write word equations for displacement reactions and recall that the more reactive metal displaces the less reactive one from its salt solution. Identify the metal as oxidised when it loses electrons.
Grades 6–7 (strong pass)	Write balanced symbol equations with state symbols. Use displacement results to deduce an order of reactivity. Explain observations using the terms oxidation and reduction (oxygen or electron transfer). Identify the electrolyte required for electrolysis of the most reactive metals.
Grades 8–9 (top)	Use the reactivity series to justify why carbon reduction cannot extract aluminium. Write half-equations (Higher) such as Mg → Mg²⁺ + 2e⁻ and Cu²⁺ + 2e⁻ → Cu. Link pH scale values of metal hydroxide solutions (>7) to the OH⁻ ions produced and predict relative reactivities from trends in Group 1 and Group 2.

Exam-Style Short Response

Question: A student tests an unknown metal X by adding it to dilute hydrochloric acid and to copper(II) sulfate solution. The metal fizzes gently with the acid and a pink-brown deposit forms on the strip in copper sulfate. Suggest where X is in the reactivity series relative to iron and copper.

Answer: Metal X reacts with acid so it must be above hydrogen. It also displaces copper from copper sulfate solution, so X is above copper. The gentle fizzing (rather than vigorous) suggests X is not in the very reactive group at the top — it is therefore likely to be similar to or slightly above iron in the reactivity series, for example zinc. To confirm, the student could test whether X displaces iron from iron(II) sulfate solution: if it does, X is above iron.

AQA alignment: This content is aligned with AQA GCSE Combined Science: Trilogy (8464) specification section 5.4 Chemical changes — specifically 5.4.1 Reactivity of metals (5.4.1.1 Metal oxides, 5.4.1.2 Reactivity series, 5.4.1.3 Extraction of metals and reduction). Assessed on Chemistry Paper 1.