ChemistryICSE Class 8 · Water

Action of Metals on Cold Water, Hot Water and Steam: Products and Equations (ICSE Class 8 Chemistry)

Updated 17 October 2026 · Fact-checked

The more reactive metals (K to Fe) give hydrogen with water or steam: with cold water they give the hydroxide (2Na + 2H₂O → 2NaOH + H₂), and with steam the oxide (Mg + H₂O → MgO + H₂). Potassium and sodium react violently with cold water, calcium less so, magnesium with hot water or steam; lead, copper, silver and gold do not react. Lead, although above hydrogen, does not react with water or steam under ICSE conditions.

Higher metals in the series react with water to give hydrogen: hydroxide with cold water, oxide with steam; lower metals do not react.

Illustration drawn for QuestionBuddy.

Understand Action of Metals on Cold Water, Hot Water and Steam

How a metal reacts with water depends on its place in the reactivity series (K > Na > Ca > Mg > Al > Zn > Fe > Pb > [H] > Cu > Hg > Ag > Au). The more reactive metals (K to Fe) give hydrogen with water or steam. With water they give the hydroxide; with steam the oxide. Lead, although above hydrogen, does not react with water or steam under ICSE conditions.

Metal	Reacts with	Equation	Notes
Potassium	cold water, violently	$2 K + 2 H_{2} O \to 2 K O H + H_{2}$	hydrogen catches fire (lilac flame)
Sodium	cold water, vigorously	$2 N a + 2 H_{2} O \to 2 N a O H + H_{2}$	darts on water, melts to a ball
Calcium	cold water, less vigorously	$C a + 2 H_{2} O \to C a (O H)_{2} + H_{2}$	sinks; solution turns milky
Magnesium	hot water (very slowly with cold)	$M g + 2 H_{2} O \to M g (O H)_{2} + H_{2}$
Magnesium	steam, burns brightly	$M g + H_{2} O \to M g O + H_{2}$	white oxide
Aluminium	steam	$2 A l + 3 H_{2} O \to A l_{2} O_{3} + 3 H_{2}$	oxide layer slows it
Zinc	steam	$Z n + H_{2} O \to Z n O + H_{2}$	oxide yellow when hot, white when cold
Iron	red-hot iron with steam, reversible	$3 F e + 4 H_{2} O ⇌ F e_{3} O_{4} + 4 H_{2}$
Lead	no reaction		very unreactive
Copper, silver, gold	no reaction		below hydrogen, no reaction

Sodium and potassium are stored under kerosene because they react with water and with moist air.

Pattern to remember.

Very reactive (K, Na, Ca): cold water → hydroxide + hydrogen.
Moderately reactive (Mg): hot water → hydroxide + hydrogen; steam → oxide + hydrogen.
Less reactive (Al, Zn, Fe): steam only → oxide + hydrogen.
Pb, Cu, Ag, Au: no reaction.

Test for the gas. Hydrogen burns with a pop.

Action of Metals on Cold Water, Hot Water and Steam: formulas and key facts

Cold water: $2 N a + 2 H_{2} O \to 2 N a O H + H_{2} C a + 2 H_{2} O \to C a (O H)_{2} + H_{2}$; Hydroxide + hydrogen.
Steam: $M g + H_{2} O \to M g O + H_{2} Z n + H_{2} O \to Z n O + H_{2}$; Oxide + hydrogen.
Iron and steam: $3 F e + 4 H_{2} O ⇌ F e_{3} O_{4} + 4 H_{2}$; Reversible.
Order: $K > N a > C a > M g > A l > Z n > F e > P b > [H] > C u > H g > A g > A u$; Most reactive first.

How to solve Action of Metals on Cold Water, Hot Water and Steam questions

Locate the metal in the series, choose the conditions it needs, then write the product.

1Find the metal in the series: above or below hydrogen.
2High up: cold water gives the hydroxide; middle: hot water or steam; lower: steam only.
3Cold or hot water: hydroxide + H₂. Steam: oxide + H₂.
4Balance the equation; check oxygen and hydrogen last.

Action of Metals on Cold Water, Hot Water and Steam in real life

Each concept, met in an everyday situation. Read the situation, try the problem, then check the solution. The one-line hook is what to remember.

Why sodium is in kerosene

Suppose a lab keeps sodium and potassium in jars under kerosene.

Why?

Try it first, then show the solutionSolution

They react quickly with water and moist air.
Kerosene keeps air and moisture away.

Answer: To prevent reaction with water and moist air.

Memory hook: Reactive metals stay under oil.

Magnesium in a flame

Imagine magnesium ribbon is heated and held in steam; a bright white flame appears.

Name the products.

Try it first, then show the solutionSolution

Magnesium gives its oxide and hydrogen with steam.
$M g + H_{2} O \to M g O + H_{2}$ .

Answer: White magnesium oxide and hydrogen.

Memory hook: Steam gives oxides.

Tricks to remember Action of Metals on Cold Water, Hot Water and Steam

Short memory aids. Say each one aloud once, then use it on a question the same day.

Cold: hydroxide; steam: oxide
Water gives hydroxides, steam gives oxides.
Use it when: Products.
K, Na, Ca cold
Top three react with cold water.
Use it when: Conditions.
Under kerosene
K and Na are stored under kerosene.
Use it when: Storage.

Action of Metals on Cold Water, Hot Water and Steam: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Example 1: Stored under kerosene · 1 mark · MCQBoard level

Which metal is stored under kerosene?
(a) copper
(b) iron
(c) sodium
(d) silver

Try it first, then show the solutionSolution

Sodium reacts with water and moist air.

Answer: (c) sodium

Example 2: Sodium and water · 2 marks · Short answerBoard level

Write the balanced equation for sodium with cold water and state two observations.

Try it first, then show the solutionSolution

$2 N a + 2 H_{2} O \to 2 N a O H + H_{2}$ . (1)
The sodium darts about, melts into a ball and hydrogen is evolved. (1)

Answer: 2Na + 2H₂O → 2NaOH + H₂

Example 3: Match · 3 marks · Short answerHarder board level

Write the product(s) when (a) magnesium reacts with hot water, (b) magnesium reacts with steam, (c) zinc reacts with steam. Give equations.

Try it first, then show the solutionSolution

(a) $M g + 2 H_{2} O \to M g (O H)_{2} + H_{2}$ . (1)
(b) $M g + H_{2} O \to M g O + H_{2}$ . (1)
(c) $Z n + H_{2} O \to Z n O + H_{2}$ . (1)

Answer: See the working.

Example 4: Order of reactivity · 3 marks · Short answerHarder board level

Observations: K burns with a lilac flame on cold water; Na darts on cold water; Ca sinks and reacts with cold water; Mg reacts only in hot water; Fe reacts reversibly with red-hot steam; Cu shows no reaction. (a) Arrange in decreasing reactivity. (b) Why does K catch fire but Ca does not?

Try it first, then show the solutionSolution

(a) K > Na > Ca > Mg > Fe > Cu. (1½)
(b) Potassium reacts so violently that the heat released ignites the hydrogen; calcium reacts more slowly. (1½)

Answer: K > Na > Ca > Mg > Fe > Cu

Example 5: Calcium in water · 4 marks · Case-basedHOTS / competency

A small piece of calcium is dropped into cold water in a beaker. (a) State what you observe. (b) Write the equation. (c) Why does the solution turn milky? (d) How would you identify the gas?

Try it first, then show the solutionSolution

(a) The calcium sinks and bubbles of a gas rise slowly. (1)
(b) $C a + 2 H_{2} O \to C a (O H)_{2} + H_{2}$ . (1)
(c) Calcium hydroxide formed is only slightly soluble and appears milky. (1)
(d) Hydrogen burns with a pop on bringing a flame. (1)

Answer: (a) sinks, bubbles (b) as above (c) Ca(OH)₂ slightly soluble (d) pop test

Where students lose marks in Action of Metals on Cold Water, Hot Water and Steam

The slips examiners see most often, and what to write instead.

Mistake: Giving hydroxide for steam
Steam gives the oxide.
Wrong working
"Mg + H₂O → Mg(OH)₂ + H₂ with steam."
Right working
"Mg + H₂O → MgO + H₂ with steam."
Do this: Cold/hot water: hydroxide; steam: oxide.
Mistake: Wrong storage
Under kerosene, not water.
Wrong working
"Sodium is kept in water."
Right working
"Sodium is kept under kerosene."
Do this: Learn the reason.
Mistake: Unbalanced steam equations
Check H and O.
Wrong working
"2Al + H₂O → Al₂O₃ + H₂."
Right working
"2Al + 3H₂O → Al₂O₃ + 3H₂."
Do this: Balance O then H.

Exam tips

Link the conditions (cold, hot, steam) to the position of the metal.
Always give the formula of the hydroxide or oxide formed.
Mention the pop test for hydrogen.
Quote the series in full when comparing.

Practice questions on Action of Metals on Cold Water, Hot Water and Steam

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

Q1 · 1 mark · Very short answerBoard level
Name the products when potassium reacts with cold water.
Hint
Hydroxide and gas.
Answer
Potassium hydroxide and hydrogen.
Q2 · 2 marks · Short answerHarder board level
Why is the reaction of iron with steam written with a double arrow?
Hint
Reversible.
Answer
It is reversible: iron and steam form Fe₃O₄ and hydrogen, and the products can react back to form iron and steam.
Q3 · 3 marks · Short answerHarder board level
Write balanced equations for (a) aluminium with steam, (b) calcium with water. Count the atoms for (a).
Hint
Balance oxygen.
Answer
(a) $2 A l + 3 H_{2} O \to A l_{2} O_{3} + 3 H_{2}$ (Al 2, O 3, H 6 each side). (b) $C a + 2 H_{2} O \to C a (O H)_{2} + H_{2}$ .
Q4 · 2 marks · Short answerHarder board level
Why do copper, silver and gold not react with water or steam?
Hint
Position.
Answer
They are below hydrogen in the reactivity series (or very unreactive), so they cannot displace hydrogen from water.
Q5 · 4 marks · Long answerHOTS / competency
A student drops a large piece of sodium into water and the hydrogen explodes. Explain why this happens and state two safety precautions.
Hint
Heat and hydrogen.
Answer
The reaction gives out much heat, which can ignite the hydrogen. Safety: use only a tiny piece, handle with forceps, keep the sodium stored under kerosene, and wear safety glasses and keep away from flames.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1.Cold water gives?Show answer
Hydroxide + hydrogen.
2.Steam gives?Show answer
Oxide + hydrogen.
3.Which two are stored under kerosene?Show answer
Sodium and potassium.
4.Does copper react with steam?Show answer
No.
5.Is iron with steam reversible?Show answer
Yes.

Action of Metals on Cold Water, Hot Water and Steam: frequently asked questions

Which metals react with cold water?

Potassium, sodium and calcium react with cold water, giving a hydroxide and hydrogen.

Why does magnesium need steam?

It reacts only very slowly with cold water but reacts with hot water and burns brightly in steam to form magnesium oxide and hydrogen.

Why are sodium and potassium kept under kerosene?

Because they react with water and moist air; kerosene keeps these away.