C12: Reactivity of Metals
Reactivity series, extraction and displacement reactions
📋 Key Definitions
Reactivity series: A list of metals arranged in order of their reactivity, from most reactive to least reactive. The more reactive a metal, the more easily it loses electrons to form positive ions.
Displacement reaction: A reaction in which a more reactive metal displaces a less reactive metal from its compound.
Oxidation: A reaction in which a substance gains oxygen or loses electrons (OIL RIG: Oxidation Is Loss of electrons).
Reduction: A reaction in which a substance loses oxygen or gains electrons (Reduction Is Gain of electrons).
Extraction: The process of obtaining a metal from its ore. The method depends on the metal's position in the reactivity series.
📝 The Reactivity Series
The reactivity series lists metals in order of how easily they lose electrons and form positive ions. A more reactive metal will displace a less reactive metal from its compound.
Learn the reactivity series (most reactive at top):
K Potassium
Na Sodium
Li Lithium
Ca Calcium
Mg Magnesium
Al Aluminium
C Carbon ← (not a metal, but important for extraction)
Zn Zinc
Fe Iron
Sn Tin
Pb Lead
H Hydrogen ← (not a metal, but useful reference)
Cu Copper
Ag Silver
Au Gold
Mnemonic: "Please Stop Calling Me A Careless Zebra, I Think Lion's Hungry, Can Silver Gold?" (K, Na, Li, Ca, Mg, Al, C, Zn, Fe, Sn, Pb, H, Cu, Ag, Au)
K Potassium
Na Sodium
Li Lithium
Ca Calcium
Mg Magnesium
Al Aluminium
C Carbon ← (not a metal, but important for extraction)
Zn Zinc
Fe Iron
Sn Tin
Pb Lead
H Hydrogen ← (not a metal, but useful reference)
Cu Copper
Ag Silver
Au Gold
Mnemonic: "Please Stop Calling Me A Careless Zebra, I Think Lion's Hungry, Can Silver Gold?" (K, Na, Li, Ca, Mg, Al, C, Zn, Fe, Sn, Pb, H, Cu, Ag, Au)
| Metal | Reaction with Water | Reaction with Acid | Reaction with Oxygen |
|---|---|---|---|
| K, Na, Li, Ca | React with cold water | React vigorously | Burn brightly |
| Mg, Al, Zn | React very slowly with cold water, with steam | React steadily | Burn with flame |
| Fe, Sn, Pb | React with steam only | React slowly | Form oxide coating |
| Cu, Ag, Au | No reaction | No reaction | Very slow or no reaction |
💧 Reactions with Water
Very reactive metals (potassium, sodium, lithium, calcium) react with cold water to produce a metal hydroxide and hydrogen gas.
Metal + cold water → metal hydroxide + hydrogen
2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g)
Ca(s) + 2H₂O(l) → Ca(OH)₂(aq) + H₂(g)
Less reactive metals (magnesium, zinc, iron) do not react with cold water but react with steam to produce a metal oxide and hydrogen gas.
Metal + steam → metal oxide + hydrogen
Mg(s) + H₂O(g) → MgO(s) + H₂(g)
Worked Example 1: Reaction of sodium with water
Write the word and symbol equations for sodium reacting with cold water.
Word: sodium + water → sodium hydroxide + hydrogen
Symbol: 2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g)
Observations: sodium floats, melts into a ball, fizzes rapidly, moves on surface, may produce a flame.
🧪 Reactions with Acids
Metals above hydrogen in the reactivity series react with acids to produce a salt and hydrogen gas.
Metal + acid → salt + hydrogen
Zn(s) + H₂SO₄(aq) → ZnSO₄(aq) + H₂(g)
Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g)
Worked Example 2: Reaction of iron with acid
Write the equation for iron reacting with hydrochloric acid.
Iron is Fe, forms Fe²⁺ ions. Hydrochloric acid is HCl.
Word: iron + hydrochloric acid → iron(II) chloride + hydrogen
Symbol: Fe(s) + 2HCl(aq) → FeCl₂(aq) + H₂(g)
🔀 Displacement Reactions
A more reactive metal will displace a less reactive metal from its compound. If the metal is less reactive than the metal in the compound, no reaction occurs.
Worked Example 3: Displacement reaction
Will zinc displace copper from copper(II) sulfate solution?
Zinc is above copper in the reactivity series, so zinc is more reactive.
Yes — displacement occurs:
Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s)
Observation: blue solution fades to colourless, brown-orange copper metal forms.
Worked Example 4: No displacement
Will copper displace iron from iron(II) sulfate solution?
Copper is below iron in the reactivity series, so copper is less reactive.
No reaction occurs. Copper cannot displace iron.
⛏️ Extraction of Metals
The method used to extract a metal from its ore depends on its position in the reactivity series.
| Metal Position | Extraction Method | Examples |
|---|---|---|
| Above carbon | Electrolysis (very expensive, uses lots of electricity) | Aluminium, magnesium, sodium |
| Below carbon but above hydrogen | Reduction with carbon (cheaper, heats ore with carbon) | Iron, zinc, lead |
| Below hydrogen | Found native (as the metal itself) — very unreactive | Gold, silver |
Why carbon matters: Carbon can only reduce metals below it in the reactivity series. Metals above carbon are too reactive and must be extracted by electrolysis.
Worked Example 5: Extraction of iron
Iron is below carbon in the reactivity series, so it is extracted by reduction with carbon in a blast furnace.
Fe₂O₃(s) + 3CO(g) → 2Fe(l) + 3CO₂(g)
The carbon monoxide reduces the iron oxide — iron loses oxygen (reduction) and carbon monoxide gains oxygen (oxidation).
🔄 Oxidation and Reduction
OIL RIG: Oxidation Is Loss (of electrons), Reduction Is Gain (of electrons).
In terms of oxygen: Oxidation = gain of oxygen, Reduction = loss of oxygen.
| Process | In terms of oxygen | In terms of electrons |
|---|---|---|
| Oxidation | Gaining oxygen | Losing electrons |
| Reduction | Losing oxygen | Gaining electrons |
Worked Example 6: Identifying oxidation and reduction
In the displacement reaction: Zn + CuSO₄ → ZnSO₄ + Cu
Zn → Zn²⁺ + 2e⁻ — Zinc loses electrons, so zinc is oxidised
Cu²⁺ + 2e⁻ → Cu — Copper ions gain electrons, so copper is reduced
❓ Practice Questions
Q1: Foundation List the following metals in order of reactivity (most reactive first): copper, potassium, iron, zinc, sodium.
Q2: Foundation Write the word equation for calcium reacting with cold water.
Q3: Higher Will magnesium displace copper from copper(II) sulfate solution? Write the balanced symbol equation if a reaction occurs.
Q4: Foundation Explain why aluminium is extracted by electrolysis but iron is extracted by reduction with carbon.
Q5: Higher In the reaction Fe₂O₃ + 3CO → 2Fe + 3CO₂, identify which substance is oxidised and which is reduced, in terms of oxygen.
✅ Answers
- Potassium, sodium, zinc, iron, copper (from most to least reactive)
- Calcium + water → calcium hydroxide + hydrogen
- Yes — magnesium is more reactive than copper, so displacement occurs. Mg(s) + CuSO₄(aq) → MgSO₄(aq) + Cu(s)
- Aluminium is above carbon in the reactivity series, so carbon cannot reduce it — electrolysis is needed. Iron is below carbon, so carbon can reduce iron oxide to iron, which is cheaper.
- Fe₂O₃ loses oxygen to become Fe, so iron is reduced. CO gains oxygen to become CO₂, so carbon monoxide is oxidised.
🎯 Exam Tips
- Learn the reactivity series order — use a mnemonic that works for you
- Carbon is not a metal but you must know its position — it determines which extraction method is used
- In displacement questions, always check the reactivity series first before predicting if a reaction will occur
- State symbols matter: (aq) for dissolved salts, (s) for solid metals, (g) for gases
- When asked about oxidation and reduction, state whether you are referring to oxygen or electrons
- Observations in displacement reactions: the solution changes colour and a solid appears
🔬 Required Practical
Required Practical Activity
Investigating displacement reactions: Add different metals (e.g. magnesium, zinc, iron, copper) to solutions of metal salts (e.g. copper(II) sulfate, iron(II) sulfate). Observe whether a displacement reaction occurs. A more reactive metal will displace a less reactive metal from its salt solution. Record observations such as colour changes and metal deposition to deduce the order of reactivity.
Key variables: Independent variable = type of metal. Dependent variable = whether displacement occurs (observation of colour change / metal forming). Control variables = concentration and volume of salt solution, temperature, surface area of metal.
🔢 Maths Skills
Mathematical Skills
Writing ionic equations: In displacement reactions, separate aqueous ionic compounds into ions, then cancel ions that appear on both sides (spectator ions).
Example: Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s). Ionic: Zn + Cu²⁺ + SO₄²⁻ → Zn²⁺ + SO₄²⁻ + Cu. Cancel SO₄²⁻: Zn + Cu²⁺ → Zn²⁺ + Cu.
⚠️ Common Misconceptions
Watch Out!
Reactivity means how vigorous a reaction looks. Wrong: reactivity = how vigorous it looks Correct: reactivity is the tendency of a metal to lose electrons and form positive ions — a more reactive metal loses electrons more easily
Gold is unreactive because it is rare. Wrong: gold is unreactive because it's rare Correct: gold is unreactive because of its electron configuration — its full d-subshell makes it very difficult to remove an outer electron
✍️ 6-Mark Question
Extended Answer
6 marks: Explain the reactivity series using displacement reactions.
The reactivity series lists metals in order of their tendency to lose electrons and form positive ions. A more reactive metal will displace a less reactive metal from its compound in a displacement reaction. For example, when iron is added to copper(II) sulfate solution, iron displaces copper because iron is more reactive: Fe + CuSO₄ → FeSO₄ + Cu. The blue solution fades to colourless and brown copper metal forms. However, if copper is added to iron(II) sulfate solution, no reaction occurs because copper is less reactive than iron and cannot displace it. These displacement experiments allow us to deduce the order of reactivity: if metal A displaces metal B from its salt, then A is more reactive than B.
Mark scheme: 1 mark for reactivity = tendency to lose electrons; 1 mark for more reactive displaces less reactive; 1 mark for correct example with equation; 1 mark for observation; 1 mark for no reaction example; 1 mark for concluding how order is deduced.
📊 AO3: Analyse & Evaluate
Analysis and Evaluation
A student adds four metals (W, X, Y, Z) to copper(II) sulfate solution and to iron(II) sulfate solution. Results:
| Metal | In CuSO₄ solution | In FeSO₄ solution |
|---|---|---|
| W | Displacement | Displacement |
| X | Displacement | No reaction |
| Y | No reaction | No reaction |
| Z | Displacement | No reaction |
Question: Deduce the order of reactivity (most reactive first). Explain your reasoning. Where is there uncertainty?
Answer: W is most reactive (displaces both Cu and Fe). X and Z are next (displace Cu but not Fe — they are between Cu and Fe). Y is least reactive (cannot displace either). Order: W > X = Z > Fe > Y > Cu. Uncertainty: X and Z cannot be ranked relative to each other from this data alone — further tests between X and Z would be needed.
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