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DSE Chemistry — The Metal Reactivity Series and Displacement: Lesson Prep Guide (Tutor Edition)
Students can chant the reactivity series but guess when asked which metal displaces which, and whether the mass rises or falls. This lesson turns the series into one calculable line: the more reactive metal loses electrons more readily, so electrons flow from it to the other metal ion, and mass, colour and gas volume all follow that line.
Objectives — Students can: (1) use the series to decide whether a displacement happens, write full and net ionic equations, and explain how 3.27 g of zinc (0.05 mol) becomes 3.18 g of copper in copper sulphate with a net mass change of -0.09 g; (2) turn 0.1 mol of magnesium in excess acid into 2,400.0 cm3 of hydrogen at a molar volume of 24,000 cm3, and show that 0.05 mol of zinc transfers 0.10 mol of electrons, or 9,650 coulombs; (3) read 160 g of iron oxide as 112 g of iron, a 70% mass relationship, and compare carbon reduction with electrolysis.
01 Prerequisites (3-minute check)
If any of these fails, fix it before the lesson starts.
| Skill | Quick check | Pass mark |
|---|---|---|
| The periodic table | How does metallic character change across a period? | It falls, so losing electrons gets harder |
| Ions and charge | What charge does a zinc ion carry? | 2+, written Zn2+ |
| The mole | How many particles are in one mole? | 6.02 times 10 to the 23 |
| Redox | What is losing electrons called? | Oxidation, while the other species is reduced |
02 Lesson flow (60 minutes)
| Time | Stage | Tutor does | Student does |
|---|---|---|---|
| 0–8 min | Series warm-up | Order potassium to gold and place hydrogen | Only metals above hydrogen react with acid |
| 8–18 min | Displacement decisions | Four metal and salt pairings, which react | A metal displaces ions to its right |
| 18–30 min | Mass and moles | 3.27 g of zinc: how much copper, what mass change | 3.18 g, -0.09 g |
| 30–42 min | Gas and electrons | 0.1 mol magnesium: hydrogen volume; 0.05 mol zinc: electrons | 2,400.0 cm3, 9,650 C |
| 42–52 min | Question drills | One decision, one mass, one gas, one extraction item | Eight minutes unaided |
| 52–60 min | Exit check | Three written items marked on the spot | Independent |
03 Teaching script (read it out)
Scene 1: The series is just an electron flow
The more reactive the metal, the more readily it loses electrons. Zinc in copper sulphate prefers to be Zn2+ and hands its electrons to Cu2+, so the half-equations are Zn to Zn2+ plus two electrons, and Cu2+ plus two electrons to Cu. Deciding whether a reaction occurs takes one move: place both metals on the series, and the left-hand metal displaces the right-hand ion while the reverse does nothing. Have students order the series themselves and explain why hydrogen matters — it separates the metals that release hydrogen from dilute acid from those that do not.
Ask students to restate why copper in zinc sulphate does nothing.
Scene 2: Mass changes need moles on both sides
3.27 g of zinc divided by 65.4 is 0.05 mol; one mole of zinc displaces one mole of copper, so 0.05 times 63.5 gives 3.18 g deposited. The mass moves from 3.27 g to 3.18 g, a net -0.09 g, and the solution pales as Cu2+ leaves it. Train the three lines every time: mole ratio, moles, mass. Never compare masses directly, because 65.4 and 63.5 sit close enough that instinct says “about the same”. Electrons follow the same route: 0.05 mol of zinc releasing two electrons each is 0.10 mol, and times 96,500 coulombs gives 9,650 C.
Ask students to restate why the mole ratio beats a mass ratio.
Scene 3: Gas, reduction and extraction share one line
0.1 mol of magnesium with excess acid gives one mole of hydrogen per mole of metal, so 0.1 mol of gas; at room conditions each mole fills 24,000 cm3, which is 2,400.0 cm3 or 2.4 litres. Extraction reads the far end of the same series: very reactive metals such as potassium, sodium and aluminium need electrolysis, moderately reactive ones such as iron and zinc yield to carbon, and the least reactive such as gold occur native. 160 g of iron oxide holds 112 g of iron, which is 70%, and the rest is oxygen — the ratio behind every yield and purity calculation.
Ask students to restate why aluminium is not extracted with carbon.
04 Question types and worked steps
| Type | Example | Steps | Answer |
|---|---|---|---|
| Displacement decision | Zinc in copper sulphate, copper in zinc sulphate | (1) place both on the series (2) left displaces right (3) write the net ionic equation | Only the first reacts |
| Mass change | 3.27 g of zinc reacts completely: how much copper | (1) divide by molar mass (2) apply the 1:1 ratio (3) multiply by copper molar mass | 3.18 g, net -0.09 g |
| Gas volume | 0.1 mol of magnesium in excess acid | (1) set the mole ratio from the equation (2) find moles of hydrogen (3) multiply by molar volume | 2,400.0 cm3 |
| Extraction choice | How much iron in 160 g of oxide | (1) use the molar mass ratio (2) scale to the mass (3) name carbon or electrolysis | 112 g, 70% |
Sanity check (teach this): Sanity checks: charges must balance in the net ionic equation, so 3.27 mol of zinc releasing 0.10 mol of electrons needs two Cu2+ ions per zinc; copper has a smaller molar mass than zinc, so the deposit must weigh slightly less and the net change is negative; gas volumes only use 24,000 cm3 at the stated conditions; the series is not an order of density or melting point; copper, silver and gold never release hydrogen from dilute acid; the iron content of an oxide must be below 100%.
05 Independent practice (3 questions)
| Question | Answer | What to watch |
|---|---|---|
| 3.27 g of zinc with excess copper sulphate deposits how much copper? | 3.18 g | Check they divide by {A_ZN} before multiplying by {A_CU} |
| 0.1 mol of magnesium in excess acid gives what volume of hydrogen? | 2,400.0 cm3 | Check they use the 1:1 mole ratio |
| How much iron is in 160 g of iron oxide? | 112 g | Check they use the {FE2O3}:{FE2} mass ratio |
06 Common mistakes and what to say
| Mistake | Student writes | Say this |
|---|---|---|
| Comparing masses directly | “Zinc is 65 and copper 63.5, so nearly the same” | Use moles: 0.05 mol against 0.05 mol gives 3.18 g, a net -0.09 g. |
| Claiming copper reacts with zinc sulphate | “Any metal reacts in any salt solution” | Copper sits below zinc, so it cannot remove Zn2+ and nothing happens. |
| Confusing 24 dm3 with 24 cm3 | “0.1 mol of hydrogen is 2.4 cm3” | The molar volume is 24,000 cm3, so the answer is 2,400.0 cm3. |
| Mixing up reduction and electrolysis | “Carbon reduces every metal” | Aluminium and sodium need electrolysis; carbon suits the iron and zinc band. |
07 Homework (paper, section and question numbers)
- Secondary Chemistry chapter index — Copy three key terms from the metals chapter and define each in one sentence
- Acids and alkalis (S4 chapter) — Redo question 3 in the practice set and write the net ionic equation for a metal with dilute acid
- Metal extraction (S5 chapter) — Read the teaching script and use the series to explain why iron uses carbon while aluminium uses electrolysis
08 Exit check (last 5 minutes)
| Question | Answer | Decision |
|---|---|---|
| 3.27 g of zinc reacts fully: how many moles of electrons transfer? | 0.10 mol | Wrong answer 0.05 means re-teach the 2+ charge |
| 0.1 mol of magnesium gives what volume of hydrogen? | 2,400.0 cm3 | Wrong answer 240 means re-teach molar volume |
| Does copper in zinc sulphate react? | No | Wrong answer yes means re-teach the direction of the series |
09 Tutor FAQ
Which year is this for?
S4 metals; S5 can revisit it alongside extraction and electrolysis.
Is 60 minutes enough?
Yes. If moles are shaky, spend ten minutes on mass and mole conversions and keep extraction to the conclusion.
Is there practice attached?
The homework column links to site chapters, and the practice set carries answers.
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A TutorZone lesson-prep guide. Written by the TutorZone team; questions and lesson flow are original and are not taken from any school or publisher material.