CHEMISTRY · Stage 8 · Chapter 9: Chemical Reactions 2
Chemistry 9.9 The reactivity series — Comparing Metal Reactivity
5 min read 8 parts Lesson 9 of 12
Lesson summary
9.9 The reactivity series — Comparing Metal Reactivity — Alhussan International Academy — Chemistry (Stages 7–9) notes: Define inert and the reactivity series, order metals by reactivity from experimental evidence and use the series to make predictions.Copper pipes — copper is ma…
- Copper pans
- Unreactive and inert
- Inert metals
- Inert non-metals
- Below hydrogen
- Positive ions
Part 1 of 8Why copper is useful
- Copper pipes — copper is malleable, so pipes can be bent to the angles needed.
- It does not react with water flowing through the pipes or with oxygen from the air.
- Copper pans — copper is a good conductor of heat and does not react with water, acidic food or oxygen in the air.
- Value — copper is valuable because its properties make it useful, which is why copper cables are stolen.
Part 2 of 8Inert substances
- Inert a substance that does not take part in chemical reactions.
- Unreactive and inertcopper reacts with few substances and is unreactive, whereas gold is even less reactive and is inert.
- Inert metalsgold, platinum, rhodium and palladium.
- Inert non-metalshelium, neon and argon.
Part 3 of 8What the reactivity series is
1Reactivity series1 point
= a list of metals in order of how readily they react with other substances.
- It is built from experimental evidence: reactions with oxygen, water and dilute acid, and displacement of other metals.
2Pattern
— metals at the top react vigorously, and reactivity decreases going down the list until the metals at the bottom are inert.
3Order1 point
— potassium, sodium, lithium, calcium, magnesium, aluminium, (carbon), zinc, iron, (hydrogen), copper, silver, gold.
- Carbon and hydrogen are non-metals included for reference.
4Prediction
— calcium is above magnesium, so it reacts with dilute hydrochloric acid to form calcium chloride and hydrogen.
Part 4 of 8Patterns in the series
- Topmetals react very vigorously with cold water, acid and oxygen.
- Middlemetals react with acid and steam, but slowly or not at all with cold water.
- Below hydrogenmetals do not react with dilute acid.
- Positive ionsthe most reactive metals form positive ions most easily by giving up outer-shell electrons.
- In naturemetals at the bottom, such as gold, are found uncombined.
Part 5 of 8Displacement reactions
- Rule — a more reactive metal displaces a less reactive metal from a solution of its compound.
- zinc + copper sulfate → zinc sulfate + copper.
- Evidence — the blue colour fades, a brown-pink solid of copper forms and the temperature rises.
- Less reactive metal — if the metal added is less reactive, such as copper in zinc sulfate, nothing happens.
| Metal added | Solution | Reaction? |
|---|---|---|
| Magnesium | Iron sulfate | Yes |
| Iron | Copper sulfate | Yes |
| Copper | Magnesium sulfate | No |
- Grid — put metals across the top and solutions down the side and tick where a reaction occurs.
- The metal with the most ticks is the most reactive, and a metal that displaces none is at the bottom.
Part 6 of 8Planning a fair comparison
- Control variableskeep the acid concentration, acid volume, metal size and starting temperature the same.
- Measurethe rate of bubbling or the temperature rise.
- Repeatrepeat and calculate means, present the data in a table and bar chart, and use the results to rank the metals.
Part 7 of 8Uses of the series: extraction
- Reduction with carbon — metals less reactive than carbon, such as iron, zinc and lead, can be obtained by heating their oxides with carbon.
- Carbon takes the oxygen because it is more reactive than the metal: iron oxide + carbon → iron + carbon dioxide.
- Electrolysis — metals above carbon, such as aluminium, magnesium and sodium, hold oxygen too strongly, so electrolysis is needed, which is more expensive.
Part 8 of 8Uses of the series: protecting steel
- Corrosion of steel — steel is an alloy of iron, and iron corrodes when its surface atoms react with oxygen and water.
- Paint — it protects steel ships well, except when scratched.
- Sacrificial protection — pieces of zinc joined to a steel boat react with water and oxygen instead of iron, because zinc is higher in the series.
- The zinc is sacrificed to save the iron.
- Magnesium also protects ships in this way because it is more reactive than iron.
- Galvanised steel — steel coated with zinc, which still protects the iron if the coating is scratched.
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