9.4 Reactivity series - Notes

Sep 5, 2026

Reactivity series notes explain how metals are ordered by reactivity and how this ordering helps predict reaction products. The document details reactions of potassium, sodium and calcium with cold water, magnesium with steam, and magnesium through gold with dilute hydrochloric acid, linking reaction speed and observations to positions in the series. It also teaches deduction of reactivity order from experimental results and, in extended sections, positive ion formation, displacement reactions, and aluminium’s apparent unreactivity due to its oxide layer.

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9.4 Reactivity series

Order of the reactivity series

Reactions with water and steam

Reactions with dilute hydrochloric acid

Deducing an order of reactivity

Extended: Positive ions and displacement

Extended: Aluminium oxide layer explanation

CAIE IGCSE Chemistry # 9.4 Reactivity series Notes State the order of thereactivity series as: potassium, sodium, calcium,magnesium, aluminium, carbon, zinc, iron, hydrogen, copper, silver, gold ● Reactivity series arranges metals in order of their reactivity. This can be usedto predict products from reactions. ● Non-metals hydrogen and carbon are often included in thereactivity series ● A mnemonic to remember the order of thereactivity series: ○ A Posse of Sly Cats Maliciously Admire Clever Zebras In HidingCopying Slowly and Gradually Most reactive PotassiumSodiumCalciumMagnesiumAluminium (Carbon) Zinc Iron (Hydrogen) CopperSilverGold Least reactive Describe thereactions, if any, of: (a) potassium, sodium and calcium withcold water (b) magnesium with steam (c) magnesium, zinc, iron, copper,silver and gold with dilute hydrochloric acid and explain these reactions interms of the position of the metals in thereactivity series (a) Potassium, sodium and calcium with cold water When potassium reacts with cold water, potassium melts and floats, movingrapidly on the surface of the water. A lilac flame will also ignite and sometimesatthe end of thereaction a small explosion can occur. ● Potassium will have the most violent/vigorous reaction with cold water since itis atthe top of thereactivity series ● Word equation: Potassium + Water → Potassium hydroxide + Hydrogen ● Symbol equation: 2K (s) + 2H2O (l) → 2KOH (aq) + H2 (g) ● When sodium reacts with water, the metal melts to form a ball that movesrapidly around on the surface. The ball fizzes rapidly before it disappears, butthereaction of sodium and water is less vigorous than potassium and water. ● Word equation: Sodium + Water → Sodium hydroxide + Hydrogen ● Symbol equation: 2Na (s) + 2H2O (l) → 2NaOH (aq) + H2 (g) ● When calcium is added to water, thereaction is slower and less violent thanthereactions prior. The calcium metalsinks in water and after an hour or sobubbles of hydrogen gas can be seen on the surface of the metal. ● Calcium will have a less vigorous and slower reaction with cold water since itis lower than potassium and sodium in thereactivity series ● Word equation: Calcium + Water → Calcium hydroxide + Hydrogen ● Symbol equation: Ca (s) + 2H2O (g) → Ca(OH)2 (aq) + H2 (g) (b) Magnesium with steam ● Magnesium does not react with cold water but it does however react withsteam to produce magnesium oxide ○ Very clean magnesium ribbon has a very slight reaction with coldwater but the magnesium hydroxide isinsoluble so no further reactionoccurs. ● The initial reaction between magnesium and steam will form magnesiumoxide and hydrogen gas ● Word equation: Magnesium + Steam -> Magnesium oxide + Hydrogen gas ● Symbol equation: Mg (s) + H2O (g) -> MgO (aq) + H2 (g) ● This is because magnesium is further down thereactivity series thanpotassium, sodium and calcium, so will be more unreactive. (c) Magnesium, zinc, iron, copper, silver and gold with dilute hydrochloric acid ● Potassium, Sodium and calcium are too reactive that their reactions withhydrochloric acid are too dangerous tobe attempted ● The further down thereactivity series, the slower thereaction until no reactionwill occur. ● Only metals above hydrogen in thereactivity series will react with dilute acids | Metal | Reaction with dilute hydrochloric acid | | --- | --- | | Magnesium | Fast reaction | | Zinc | Slightly fast reaction | | Iron | Slightly fast reaction | | Copper | No reaction | | Silver | No reaction | | Gold | No reaction | Deduce an order of reactivity from a given set of experimental results ● The order of reactivity can be deduced from the results of experiments bydetermining the speed and observations of each metal ● E.g. A less vigorous and slow reaction will usually mean a lower reactivitywhereas lots of effervescence (bubbles/fizzing) and quicker reactions areusually higher in thereactivi

FAQs

Which metals react with dilute hydrochloric acid, and what observations are expected?

Only metals above hydrogen react: magnesium shows a fast reaction, zinc/iron slightly fast reactions, while copper, silver, and gold show no reaction.

Why is aluminium apparently unreactive in many reactions?

Aluminium forms a protective oxide layer (Al2O3) on its surface, which makes the metal very unreactive and prevents further oxidation.

Sep 5, 2026

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