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Detailed notes on Electrochemistry for IB MYP Science, covering key concepts, explanations, examples, and exam-focused revision points.
The things students keep getting wrong in this sub-topic, answered.
Why does sodium react explosively with water but gold sit unchanged for centuries? The activity series ranks metals by their tendency to lose electrons. This MYP Sciences note covers the order, the underlying reasoning, and how to use the series to predict displacement reactions.
Mapped to the IB MYP Sciences subject guide (2026 onwards).
Most reactive at the top, least at the bottom.
Memorise the order for common metals (mnemonics help):
| Position | Metal |
|---|---|
| Most reactive | Potassium (K) |
| Sodium (Na) | |
| Calcium (Ca) | |
| Magnesium (Mg) | |
| Aluminium (Al) | |
| Zinc (Zn) | |
| Iron (Fe) | |
| (Hydrogen) — for reference | |
| Copper (Cu) | |
| Silver (Ag) | |
| Least reactive | Gold (Au) |
A common mnemonic: Please Stop Calling Me A Zebra Instead Call Some Great Advice — letters match K, Na, Ca, Mg, Al, Zn, Fe, (H), Cu, Ag, Au.
A more reactive metal kicks a less reactive one out of its compound.
A displacement reaction happens when a more reactive metal pushes a less reactive one out of its compound. Classic example:
Reactivity dictates whether a metal is found pure or has to be extracted.
Metals at the BOTTOM of the series (Au, Ag, Pt) are so unreactive that they don't combine with other elements in nature — they're found native (as pure metal). This is why gold can be panned from rivers as nuggets, and ancient Egyptians could work with pure copper before they had any chemistry.
Metals further up exist as compounds (oxides, sulfides, carbonates). Getting the metal out depends on its reactivity:
This connects directly to MYP criterion D — discuss why aluminium became economically useful only after the invention of electrolysis (Hall-Héroult process, 1886), even though it's the third most abundant element in Earth's crust.
Verbatim phrases and definitions MYP criterion-A markschemes credit.
Criterion A tests recall of the series and prediction of displacement. Criterion D often asks for an evaluation of which extraction method is suitable for a given metal, and the historical/economic impact of the choice.
Sources: IB MYP Sciences guide (IBO, official subject guide). Last reviewed 2026-05-25.
Step-by-step solutions to past-paper-style questions on activity series of a metal, written exactly the way a tutor would explain them at the board.
Question
Predict whether each reaction will occur: (a) Zn + CuSO₄, (b) Cu + ZnSO₄, (c) Mg + FeCl₂.
Step-by-step solution
Step 1
(a) Zn above Cu → YES, Zn displaces Cu.
Step 2
(b) Cu below Zn → NO.
Step 3
(c) Mg above Fe → YES, Mg displaces Fe.
Answer
(a) yes, (b) no, (c) yes.
Question
Why is aluminium extracted by electrolysis but iron extracted by carbon reduction?
Step-by-step solution
Step 1
Aluminium is HIGH in the reactivity series (above carbon) — bonds in Al₂O₃ are too strong for carbon to break.
Step 2
Iron is BELOW carbon — carbon can take the oxygen from iron oxide, giving pure iron.
Step 3
Electrolysis uses electrical energy directly to break strong ionic bonds, so it works for the most reactive metals.
Answer
Aluminium is too reactive for carbon reduction; electrolysis supplies enough energy. Iron is less reactive than carbon, so carbon can reduce iron oxide.
Question
Explain why gold can be found as nuggets in rivers, but iron is never found pure in nature.
Step-by-step solution
Step 1
Gold is at the very BOTTOM of the reactivity series — it doesn't combine with O₂, H₂O or other substances.
Step 2
Iron is MID-LEVEL in reactivity — it readily forms iron oxide (rust) with oxygen and water in the environment.
Step 3
So gold stays pure forever in rivers; any iron exposed to the environment quickly oxidises and ends up as ore.
Answer
Gold is so unreactive it never combines with anything. Iron quickly oxidises to iron oxide, so it's only ever found as ore.
Definitions to memorise and the exact keywords mark schemes credit for activity series of a metal answers — sharpened from recent examiner reports for the 2026 IB MYP Sciences sitting.
A list of metals in order of how readily they lose electrons (most reactive at the top).
A reaction where a more reactive metal pushes a less reactive metal out of its compound.
A metal found in nature as the pure element rather than combined in a compound. Typical of unreactive metals (Au, Ag, Pt).
The traps other students keep falling into on activity series of a metal questions — taken from recent IB MYP Sciences examiner reports and mark schemes — and how to avoid them.
Why it happens
Same word.
How to avoid it
Displacement applies metal-with-metal-salt (or halogen-with-halide). Iron + NaCl wouldn't work because Na is way above Fe.
Why it happens
Electrolysis sounds modern.
How to avoid it
Iron is less reactive than carbon, so carbon reduction in a blast furnace is cheaper and works. Reserve electrolysis for K, Na, Ca, Mg, Al.
Why it happens
It's in the list.
How to avoid it
H is included as a REFERENCE — metals above react with acids; below don't. H itself is a non-metal.
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The further UP the series, the more easily the metal loses electrons → more vigorous reactions, more tendency to corrode, more drive to form positive ions.
Zinc is above copper → zinc displaces copper. The blue Cu²⁺ solution becomes colourless ZnSO₄, and brown copper metal coats the zinc.
In electron terms (redox!):
Use the series to predict any displacement. Can iron displace gold from gold chloride? Yes (Fe is above Au). Can gold displace iron from iron sulfate? No (gold is below iron).
Reaction with water and acid: