The reactivity series and obtaining metals
Key idea: A more reactive metal displaces a less reactive metal from its salt solution. Metals higher in the reactivity series are generally harder to obtain from comparable compounds.
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Guided lessons · coming soon
Guided lesson
Guided steps
- Compare reactions under the same conditions.
- Use the coatings to order the metals.
- Place the three metals and hydrogen in order.
- Check which comparisons the tests can decide.
- Use the coating result and check the acid-test conditions.
- Use reactivity to compare how easily metals are obtained.
- Explain which order you know and what remains unknown.
- Decide whether these results compare magnesium with zinc.
- Plan a direct test to compare magnesium and zinc.
- Choose a possible metal and explain why copper cannot fit.
- Choose the easier metal to obtain from its compound.
- Explain why more reactive metals are harder to obtain.
- Describe a displacement test that puts zinc above iron.
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ContinueSome metals fizz in cold water; others show no bubbles in dilute hydrochloric acid. The reactivity series puts metals in order of how readily they react, which is how readily their atoms lose electrons to form positive ions. In this lesson you will build that order from reaction results, recognise when a set of results cannot decide an order, and use a metal’s position to say how easily it can be obtained from its ore.
You already know that metal atoms react by losing outer electrons to form positive ions. The acid test in this lesson uses dilute hydrochloric acid: when a metal reacts in this test, it forms a salt and hydrogen.
Evidence from water, steam and dilute acid
The table summarises typical observations for clean metal pieces; it is not a record of one experiment. Compare metals under equivalent conditions within each test. In the steam test, the metal is heated while steam passes over it.
Use these observations to interpret reactivity. They are not instructions to carry out every test: a teacher selects suitable metals and conditions for a school investigation, and the very reactive metals are not tested with acid here.
| Metal | Cold water | Steam | Dilute hydrochloric acid |
|---|---|---|---|
| potassium | violent; the hydrogen catches fire | not tested: dangerous | not tested: explosive |
| sodium | vigorous; melts into a ball | not tested: dangerous | not tested: explosive |
| calcium | steady fizzing; a cloudy mixture forms | not tested: dangerous | not tested: too vigorous |
| magnesium | a few bubbles over several days | burns with a bright white glow; white solid forms | rapid fizzing |
| zinc | no reaction | reacts when heated; hydrogen forms | steady fizzing |
| iron | no reaction | reacts slowly when red-hot; hydrogen forms | slow fizzing |
| lead | no reaction | no reaction | a few bubbles when warm; the reaction soon stops |
| copper | no reaction | no reaction | no reaction |
| silver | no reaction | no reaction | no reaction |
The reactions in this table produce hydrogen. In the cold-water reactions, the other product is a metal hydroxide; with steam it is a metal oxide; with dilute hydrochloric acid it is a chloride salt.
Calcium hydroxide is only slightly soluble in water. Some dissolves, but excess solid makes the mixture cloudy. The equation shows that solid product.
Reading the table. Sort the metals by the mildest test they react with. Potassium, sodium and calcium react with cold water, so they are the most reactive. Magnesium reacts very slowly with cold water but much more readily with steam. Zinc and iron react with steam when heated. Lead reacts only very slowly, with acid. Copper and silver react with none of these. Within each reacting set, compare results under equivalent conditions. This gives the order down to hydrogen:
potassium > sodium > calcium > magnesium > zinc > iron > lead > (hydrogen)
Copper and silver are both below hydrogen, but these tests do not decide their order.
Hydrogen is not a metal. Compare metals with hydrogen: a metal above hydrogen can release hydrogen gas from dilute hydrochloric acid, and a metal below hydrogen cannot release hydrogen in this test. Lead is placed just above hydrogen because it does release some hydrogen from warm acid. Its reaction stops early because an insoluble layer of lead(II) chloride coats the metal.
What the table cannot decide
Copper and silver give the same result in every test: no reaction. These three tests therefore show that both are below hydrogen, but they cannot show which of the two is more reactive. You need a different kind of test.
Evidence from displacement
A more reactive metal displaces a less reactive metal from a solution of its compound. When copper wire is placed in colourless silver nitrate solution, shiny grey crystals of silver grow on the wire and the solution turns blue as copper(II) ions form:
So copper is more reactive than silver. Silver wire in copper(II) sulfate solution shows no change. This agrees with copper being above silver. Combined with the water, steam and acid evidence, the full order is:
potassium > sodium > calcium > magnesium > zinc > iron > lead > (hydrogen) > copper > silver
Pieces of three metals, J, K and L, were added to solutions of each other’s sulfates. Each cell records what was seen.
| Metal added | J sulfate | K sulfate | L sulfate |
|---|---|---|---|
| J | — | no change | coating of L forms |
| K | coating of J forms | — | coating of L forms |
| L | no change | no change | — |
Worked example 1
Order three metals from displacement results
Problem
Use the displacement results above to put J, K and L in order of decreasing reactivity.
Show full solution
Turn each coating into a comparison
Method
A coating means the added metal displaced the metal in the solution.
Reason
Only a more reactive metal can do that.Working
Answer
J displaces L: J > L. K displaces J: K > J. K displaces L: K > L.
Check the no-change results agree
Method
Each no-change result should be the reverse of a coating result.
Reason
A metal cannot displace a more reactive one.Working
Answer
J does not displace K, and L displaces neither: consistent.
Combine the comparisons
Working
Answer
K > J > L
Quick check
Count the coatings in each row: the metal that displaces the most others is the most reactive. Here K has two, J one and L none.
Guided practice 2
Combine three kinds of evidence
Problem
Clean metals A, B and C are tested under conditions that allow any reaction to be detected. A reacts with cold water. B does not react with cold water but fizzes in dilute hydrochloric acid. C releases no hydrogen in either test, and B displaces C from a solution of its salt. Place A, B, hydrogen and C in order of decreasing reactivity.
Use each result once
Hints
Hint 1
Mildest test
Reaction with cold water places A above a metal that reacts only with acid.
Hint 2
Hydrogen reference
Releasing hydrogen in dilute hydrochloric acid places a metal above hydrogen. Use C’s negative result here only because the question states that the conditions allow a reaction to be detected.
Show solution step by step
Use water and acid
Method
Place A above B, and B above hydrogen.Reason
A reacts with cold water; B needs acid, and releases hydrogen from it.
Working
Answer
A > B > hydrogenPlace C
Method
Put C below hydrogen.Reason
C does not react with acid, and B displaces it; both results agree.
Working
Answer
A > B > hydrogen > C
Quick check
Do not invent identities for A, B and C. The question asks only for the order that the results support.
When results are missing or seem to disagree
A single “no reaction” means only that nothing was seen in that test, under those conditions, in that time. A slow reaction may take longer to become visible. Magnesium in cold water looks unreactive for the first minute, yet bubbles collect over several days. Lead in cold dilute acid can look unreactive, yet it releases a little hydrogen when warm.
Before you place a metal, ask two questions:
- Do the results compare these two metals at all? If P displaces Q and R displaces Q, both P and R are above Q, but the results say nothing about P compared with R.
- Could a slow reaction look like no reaction? A short test at room temperature can miss a very slow reaction.
Spot the mistake 3
Results that seem to disagree
Learner claim
Metal X shows no bubbles in cold dilute hydrochloric acid within two minutes. In copper(II) sulfate solution, a brown coating forms on X and the blue colour fades. A learner concludes: “X did not react with acid, so X is unreactive and belongs at the bottom of the series.” What do the results actually show?
Decide what each result supports
Show solution step by step
Use the positive result
Method
X displaced copper from its solution.Reason
Only a more reactive metal can displace another.Working
Answer
X > copper, so X is not at the bottom.Limit the negative result
Method
No bubbles were seen in two minutes of cold acid.
Reason
A very slow reaction, like lead’s, can look like none in a short cold test.
Working
Answer
The acid result does not show that X is below hydrogen.
State what is known
Working
Answer
X is more reactive than copper. Whether X is above hydrogen is not decided by these results. A properly planned follow-up test could check whether a slow reaction or a protective surface layer explains the acid result.
Common mistake
The learner treated “no reaction seen” as “cannot react” and then ignored the displacement result. A clear positive result outweighs a short test in which nothing was seen.
How easily a metal is obtained
Most metals occur naturally as compounds. An ore contains enough of a useful metal compound for extraction to be worthwhile. To obtain the metal, its compound must be broken down so that the metal ions become metal atoms again. That is the reverse of the metal reacting.
For comparable compounds, such as metal oxides, the more reactive metal is generally harder to obtain: it takes more to convert its compound back into the metal. Use the reactivity series to predict the relative difficulty of obtaining a metal from its ore. Metals low in the series are generally easier to obtain. Silver is so unreactive that it is sometimes found in the ground as the metal itself.
History fits the series. Copper, lead and iron have been extracted from their ores for thousands of years. In 1807, Humphry Davy obtained potassium and sodium using electrolysis. Davy also obtained calcium and magnesium in 1808. You do not need to know how each metal is extracted; the point is the order of difficulty.
A metal’s price is a different matter. Scarcity, demand, processing and other costs affect price. Silver’s relative scarcity can make it valuable even though it lies low in the reactivity series. Use the metal’s position in the series, not its price.
Common mistakes
| Mistake | Why it fails | Correct reasoning |
|---|---|---|
| “Hydrogen is a metal between lead and copper.” | Hydrogen is a non-metal. | It separates metals that release hydrogen in the acid test from those that do not. |
| “Copper does not react with dilute hydrochloric acid, so it is the least reactive metal.” | Silver does not release hydrogen in this acid test either. | Copper displaces silver, so silver is lower. |
| “The metal at the top of the series is the easiest to obtain.” | More reactive metals are generally harder to obtain from comparable compounds. | Use reactivity to predict relative difficulty; also consider the compound and extraction method. |
| “No bubbles in two minutes, so the metal is unreactive.” | A slow reaction can look like none. | State what the test showed in its time and conditions. |
| “Silver is expensive, so it must be hard to extract.” | Price also depends on scarcity, demand and costs. | Silver is low in the series and generally easier to obtain from suitable compounds; its price is not a measure of reactivity. |
Try these
Check your understanding 1 Say which order the tests show
P displaces Q from a solution of its salt. Q shows no change in an R salt solution during a short test. Which metals can you order, and what remains undecided?
Work on paper or in the optional notes, then compare the evidence, conditions and reasoning.
Show answer
P is more reactive than Q: displacement is positive evidence. The short negative test does not securely place R because a slow reaction or unsuitable conditions may hide a reaction. Even if a reliable test placed R above Q, it would not compare P with R.
Check your understanding 2 Do the results compare these two metals?
Magnesium and zinc both displace copper from its salt solution. Choose what these results tell you before designing a test to compare magnesium and zinc.
Show answer
Both are above copper. The results neither order magnesium and zinc nor show equal reactivity. The next activity asks for a direct comparison test.
Check your understanding 3 Design the missing comparison
Magnesium and zinc both displace copper from copper(II) sulfate solution. A learner concludes that magnesium and zinc are equally reactive. Explain why these results cannot show that, and describe a displacement test that would compare the two metals.
Work on paper or in the optional notes, then compare the evidence, conditions and reasoning.
Show answer
Both results show only that each metal is above copper; they do not compare magnesium with zinc. Put clean magnesium in zinc sulfate solution under suitable conditions. A grey coating of zinc forming on the magnesium shows that magnesium is more reactive. If nothing is seen, check the conditions and test zinc in a magnesium salt solution before relying on the negative result.
Check your understanding 4 Choose a possible metal and rule copper out
A metal reacts with steam when heated but not readily with cold water. Give one possible metal from zinc, iron and copper, and explain why copper is ruled out.
Work on paper or in the optional notes, then compare the evidence, conditions and reasoning.
Show answer
Zinc or iron fits: both react with steam when heated. Copper does not react with steam in these tests. These results cannot tell zinc from iron without further evidence.
Check your understanding 5 Choose the relative extraction difficulty
X lies above magnesium; Y lies below copper. For comparable ore compounds, choose the metal generally easier to obtain and whether its price determines this prediction.
Show answer
Y is lower in the series and generally easier to obtain from comparable compounds. Price alone does not measure reactivity or extraction difficulty. Explain the metal-ion change in the next activity.
Check your understanding 6 Explain the extraction prediction
X lies above magnesium in the reactivity series; Y lies below copper. For comparable ore compounds, which metal is generally easier to obtain, and why?
Work on paper or in the optional notes, then compare the evidence, conditions and reasoning.
Show answer
Y lies lower in the series and is generally easier to obtain from a comparable compound. X is more reactive, so converting its ions back into metal atoms requires a more demanding extraction method. Price alone cannot tell you this order.
Check your understanding 7 Construct a positive displacement test
Describe a test using a salt solution, rather than acid, that would show zinc is more reactive than iron. State the positive result and its meaning.
Work on paper or in the optional notes, then compare the evidence, conditions and reasoning.
Show answer
Place clean zinc in iron(II) sulfate solution under suitable conditions. A dark iron coating forms on the zinc: zinc has displaced iron from its compound, showing zinc is more reactive.
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Syllabus and review details
- SEC G3 Combined Science Chemistry component 2027 · 2027
Chemistry content structure and subject content, PDF pages 26–36
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