Tag: Metals and Non-metals

Class 10th Science Chapter 3 – Metals and Non-metals – Exercises

Q1. Which of the following pairs will give displacement reactions?

(a) NaCl solution and copper metal
(b) MgCl₂ solution and aluminium metal
(c) FeSO₄ solution and silver metal
(d) AgNO₃ solution and copper metal

Answer:

Correct option: (d) AgNO₃ solution and copper metal

Explanation:

A displacement reaction occurs when a more reactive metal displaces a less reactive metal from its salt solution.

Reactivity series (part):

$K > N a > C a > M g > A l > Z n > F e > P b > H > C u > A g > A u$

Q2. Which of the following methods is suitable for preventing an iron frying pan from rusting?

(a) Applying grease
(b) Applying paint
(c) Applying a coating of zinc
(d) All of the above

Answer:

Correct option: (c) Applying a coating of zinc

Explanation:

Rusting of iron occurs when iron reacts with oxygen and moisture.
To prevent rusting, the iron surface must be protected from air and water.

Q3. An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be

(a) calcium
(b) carbon
(c) silicon
(d) iron

Answer:

(a) calcium

Explanation:

Calcium reacts with oxygen to form calcium oxide (CaO):

$2 C a + O_{2} \to 2 C a O$

Properties of calcium oxide (CaO):

High melting point
Soluble in water, forming calcium hydroxide (lime water):

$C a O + H_{2} O \to C a (O H)_{2}$

Q4. Food cans are coated with tin and not with zinc because:

(a) zinc is costlier than tin.
(b) zinc has a higher melting point than tin.
(c) zinc is more reactive than tin.
(d) zinc is less reactive than tin.

Answer:

(c) zinc is more reactive than tin

Explanation:

Tin (Sn) is less reactive than zinc (Zn).
If zinc were used to coat food containers, it could react with acids present in food items, forming harmful compounds.
Tin does not react easily with food substances and therefore is safe for coating food cans.

Q5. You are given a hammer, a battery, a bulb, wires and a switch.

(a) How could you use them to distinguish between samples of metals and non-metals?

Answer:

Test 1 – Hammer Test (Malleability Test)

Place each sample on a hard surface.
Strike each sample gently with the hammer.

Observation:

Test 2 – Electrical Conductivity Test

Set up an electrical circuit using the battery, bulb, wires and switch.
Connect each sample between the open ends of the circuit.
Switch on the circuit.

Observation:

(b) Assess the usefulness of these tests in distinguishing between metals and non-metals.

Answer:

These tests are very useful because:

Metals are malleable whereas non-metals are brittle
Metals conduct electricity well whereas non-metals do not

Therefore, by using a hammer and conductivity test, we can easily identify whether an element is a metal or non-metal.

Q6. What are amphoteric oxides? Give two examples of amphoteric oxides.

Answer:

Amphoteric oxides are metal oxides that react with both acids and bases to form salt and water.

Examples:

Aluminium oxide (Al₂O₃)
Zinc oxide (ZnO)

Explanation with equations:

Aluminium oxide reacting with acid:

$A l_{2} O_{3} + 6 H C l \to 2 A l C l_{3} + 3 H_{2} O$

Aluminium oxide reacting with base:

$A l_{2} O_{3} + 2 N a O H \to 2 N a A l O_{2} + H_{2} O$

Zinc oxide reacting with acid:

$Z n O + 2 H C l \to Z n C l_{2} + H_{2} O$

Zinc oxide reacting with base:

$Z n O + 2 N a O H \to N a_{2} Z n O_{2} + H_{2} O$

Q7. Name two metals which will displace hydrogen from dilute acids, and two metals which will not.

Answer:

Metals that will displace hydrogen from dilute acids:

Magnesium (Mg)
Zinc (Zn)

Reaction example:

$Z n + H_{2} S O_{4} \to Z n S O_{4} + H_{2} ↑$

These metals are more reactive than hydrogen.

Metals that will not displace hydrogen from dilute acids:

Copper (Cu)
Silver (Ag)

These metals are less reactive than hydrogen, so no reaction occurs.

Q8. In the electrolytic refining of a metal M, what would you take as the anode, the cathode and the electrolyte?

Answer:

In the electrolytic refining of metal M:

Component	Used Material
Anode	Impure metal M
Cathode	Pure metal M plate
Electrolyte	Solution of a salt of metal M (e.g., MNO₃ or MCl₂)

Explanation:

During electrolysis, impure metal dissolves from the anode and pure metal gets deposited on the cathode.
Impurities settle down at the bottom as anode mud.

Q9. Pratyush took sulphur powder on a spatula and heated it. He collected the gas evolved by inverting a test tube over it.

(a) What will be the action of gas on:

(i) Dry litmus paper?
→ No change

(ii) Moist litmus paper?
→ Turns blue litmus red (acidic gas)

Reason:

The gas formed is sulphur dioxide (SO₂).
SO₂ dissolves in water forming sulphurous acid (H₂SO₃), which is acidic:

$S O_{2} + H_{2} O \to H_{2} S O_{3}$

Hence only moist litmus changes colour, dry litmus does not.

(b) Write the balanced chemical equation for the reaction taking place.

$S + O_{2} \to S O_{2}$

Q10. State two ways to prevent the rusting of iron.

Answer:

Two methods to prevent rusting are:

Galvanisation – coating iron with zinc
Painting / Greasing / Oiling – prevents air and moisture from coming in contact with iron

Other acceptable methods (if needed):

Alloying (e.g., making stainless steel)
Electroplating
Plastic coating

Q11. What type of oxides are formed when non-metals combine with oxygen?

Answer:

When non-metals react with oxygen, they form acidic oxides.

Example:

$C + O_{2} \to C O_{2} (acidic oxide)$

Explanation:

Acidic oxides dissolve in water to form acids:

$C O_{2} + H_{2} O \to H_{2} C O_{3}$

Q12. Give reasons:

(a) Platinum, gold and silver are used to make jewellery.

Answer:

Platinum, gold and silver are used to make jewellery because:

They are lustrous (shiny and attractive appearance)
They are malleable and ductile (can be beaten into sheets and drawn into wires)
They are least reactive, so they do not corrode or tarnish easily
They maintain their shine for a long time

(b) Sodium, potassium and lithium are stored under oil.

Answer:

Sodium, potassium and lithium are stored under oil because:

They are highly reactive metals
They react vigorously with oxygen and moisture present in air
They can catch fire or even explode when exposed to water or air

Storage under oil prevents their contact with air and moisture.

(c) Aluminium is a highly reactive metal, yet it is used to make utensils for cooking.

Answer:

Although aluminium is highly reactive, it is used to make utensils because:

It forms a thin protective layer of aluminium oxide (Al₂O₃) on its surface
This oxide layer prevents further reaction with air and water
It is lightweight, strong and good conductor of heat

Therefore, it becomes safe and suitable for utensils.

(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction.

Answer:

Carbonate and sulphide ores are converted into oxides because:

It is easier to reduce metal oxides to pure metal than carbonates or sulphides
Sulphides are first roasted to convert into oxides:

$2 Z n S + 3 O_{2} \to 2 Z n O + 2 S O_{2}$

Carbonates are calcined to form oxides:

$Z n C O_{3} \to Z n O + C O_{2}$

Once converted into oxides, metals can be extracted more easily by reduction.

Q13. You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels.

Answer:

Copper vessels become tarnished due to the formation of basic copper carbonate on their surface when copper reacts with moist air.

$2 C u + H_{2} O + C O_{2} + O_{2} \to C u C O_{3} \cdot C u (O H)_{2}$

Lemon and tamarind contain acids (citric acid and tartaric acid).
These acids react with the basic copper carbonate and dissolve it, bringing back the shine.

$C u C O_{3} \cdot C u (O H)_{2} + 2 H^{+} \to 2 C u^{2 +} + C O_{2} + 3 H_{2} O$

So, tarnish is removed and the vessel becomes shiny.

Q14. Differentiate between metals and non-metals on the basis of their chemical properties.

Chemical Property	Metals	Non-metals
Reaction with oxygen	Form basic oxides (e.g., MgO, CaO)	Form acidic or neutral oxides (e.g., CO₂, SO₂)
Reaction with water	Some react to release H₂ gas (e.g., Na, Mg)	Generally do not react
Reaction with acids	React to produce H₂ gas	Do not produce hydrogen gas
Reaction with salt solutions	More reactive metal displaces less reactive one	No displacement reaction
Conductivity	Conductors	Poor conductors (except graphite)

Q15. A man posed as a goldsmith and dipped gold bangles in a solution, which made them shine but reduced their weight. What was the solution likely to be?

Answer:

The solution used was aqua regia, a mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio 3:1.

Explanation:

Aqua regia dissolves a thin layer of gold from the surface.
This makes the jewellery look shiny, but at the same time reduces its weight, because some gold dissolves.

$A u + H N O_{3} + 4 H C l \to H A u C l_{4} + N O_{2} + H_{2} O$

So, the man fraudulently removed real gold to make money.

Q16. Give reasons why copper is used to make hot water tanks and not steel (an alloy of iron).

Answer:

Copper is used because:

It does not react with water, even at high temperature
It does not rust or corrode easily
It is a good conductor of heat

Steel (alloy of iron), however:

Rusts easily when exposed to water and air
Would get damaged or leak over time

Therefore, copper is a better and safer option.

November 17, 2025

Class 10th Science Chapter 3 – Metals and Non-metals – In-text Questions

TEXTBOOK QUESTION–ANSWERS WITH EXPLANATION

SECTION – PAGE QUESTIONS

Page 40 – Questions

Q1. Give an example of a metal which

(i) is a liquid at room temperature
(ii) can be easily cut with a knife
(iii) is the best conductor of heat
(iv) is a poor conductor of heat

Answer:

Property	Metal	Explanation
(i) Liquid at room temperature	Mercury (Hg)	Only metal existing as liquid at RT
(ii) Can be cut with knife	Sodium / Potassium	Very soft metals
(iii) Best conductor of heat	Silver (Ag)	Highest thermal conductivity
(iv) Poor conductor of heat	Lead (Pb)	Conducts heat very poorly

Q2. Explain the meanings of malleable and ductile.

Answer

Malleable → metals can be beaten into thin sheets (e.g., aluminium foil).
Ductile → metals can be drawn into thin wires (e.g., copper wires).

SECTION – CHEMICAL PROPERTIES OF METALS (Page 46)

Q1. Why is sodium kept immersed in kerosene oil?

Answer:
Sodium reacts violently with oxygen and water, producing heat and hydrogen gas.
To prevent accidental fire, it is stored under kerosene.

Q2. Write equations for reactions of

(i) Iron with steam
(ii) Calcium and potassium with water

Answer

(i)

$3 F e + 4 H_{2} O \overset{s t e a m}{\to} F e_{3} O_{4} + 4 H_{2} ↑$

(ii)

$C a + 2 H_{2} O \to C a (O H)_{2} + H_{2} ↑$ $2 K + 2 H_{2} O \to 2 K O H + H_{2} ↑ + heat$

Q3. Table of metals A, B, C, D

Metal	FeSO₄	CuSO₄	ZnSO₄	AgNO₃
A	No reaction	Displacement
B	Displacement		No reaction
C	No reaction	No reaction	No reaction	Displacement
D	No reaction	No reaction	No reaction	No reaction

Answers

(i) Most reactive metal = B (displaces Fe)
(ii) When B added to CuSO₄ → reddish brown copper is deposited
(iii) Decreasing reactivity order: B > A > C > D

Q4. Which gas is produced when dilute HCl is added to a reactive metal? Write reaction for Fe + H₂SO₄.

Answer

Gas released = Hydrogen (H₂)

$F e + H_{2} S O_{4} \to F e S O_{4} + H_{2} ↑$

Q5. What would you observe when zinc is added to iron(II) sulphate solution?

Answer

Zinc is more reactive than iron, so it displaces iron.

$Z n + F e S O_{4} \to Z n S O_{4} + F e$

Appearance: brown iron deposits, solution fades from green

PAGE NO. 49 – QUESTIONS & ANSWERS

Q1. (i) Write the electron-dot structures for sodium, oxygen and magnesium.

(ii) Show the formation of Na₂O and MgO by the transfer of electrons.
(iii) What are the ions present in these compounds?**

Answer:

(i) Electron-dot structures

Element	Atomic No.	Electronic Configuration	Valence Electrons	Electron-dot Structure
Sodium (Na)	11	2, 8, 1	1	Na·
Oxygen (O)	8	2, 6	6	·O: (6 dots around O)
Magnesium (Mg)	12	2, 8, 2	2	Mg:··

(ii) Formation of Na₂O and MgO

Formation of Sodium Oxide (Na₂O)

Sodium loses one electron each to become Na⁺

$2 N a \to 2 N a^{+} + 2 e^{-}$

Oxygen gains two electrons to become O²⁻

$O + 2 e^{-} \to O^{2 -}$

Combination

$2 N a^{+} + O^{2 -} \to N a_{2} O$

Formation of Magnesium Oxide (MgO)

Magnesium loses two electrons

$M g \to M g^{2 +} + 2 e^{-}$

Oxygen gains two electrons

$O + 2 e^{-} \to O^{2 -}$

Combination

$M g^{2 +} + O^{2 -} \to M g O$

(iii) Ions present in these compounds

Compound	Cation	Anion
Na₂O	Na⁺	O²⁻
MgO	Mg²⁺	O²⁻

Q2. Why do ionic compounds have high melting points?

Answer:

Ionic compounds have high melting points because the strong electrostatic forces of attraction between the oppositely charged ions require a large amount of energy to break.
Therefore, ionic compounds are usually solid at room temperature and have very high melting and boiling points.

PAGE NO. 53 – QUESTIONS & ANSWERS

Q1. Define the following terms:

(i) Mineral

A mineral is a naturally occurring substance found in the earth’s crust that contains one or more metals or their compounds.

(ii) Ore

An ore is a mineral from which a metal can be profitably extracted.

(iii) Gangue

Gangue refers to the impurities such as sand, soil, and rocky materials that are present in the ore and must be removed before metal extraction.

Q2. Name two metals which are found in nature in the free state.

Answer:

Gold and Silver

Explanation:
These metals are least reactive and do not combine with other elements, so they are found in free or native form.

Q3. What chemical process is used for obtaining a metal from its oxide?

Answer:

The process used is called reduction.

Explanation:

In reduction, oxygen is removed from metal oxide to obtain the pure metal.
Example:

$Z n O + C \to Z n + C O$

PAGE NO. 55 – Question & Answer

Q1. Metallic oxides of zinc, magnesium and copper were heated with the following metals.

Metal	Zinc oxide	Magnesium oxide	Copper oxide
Zinc	?	?	?
Magnesium	?	?	?
Copper	?	?	?

In which cases will you find displacement reactions taking place?

Answer:

To determine displacement reactions, we use the reactivity series:

$Most reactive: M g > Z n > C u : Least reactive$

Rule:

A more reactive metal can displace a less reactive metal from its oxide.

Case-by-case outcomes

1. Zinc heated with Zinc oxide

No reaction — a metal cannot displace itself.

2. Zinc heated with Magnesium oxide

No reaction — Zn is less reactive than Mg.

3. Zinc heated with Copper oxide

Reaction occurs because Zn is more reactive than Cu.

$Z n + C u O \to Z n O + C u$

4. Magnesium heated with Zinc oxide

Reaction occurs because Mg is more reactive than Zn.

$M g + Z n O \to M g O + Z n$

5. Magnesium heated with Magnesium oxide

No reaction — metal cannot displace itself.

6. Magnesium heated with Copper oxide

Reaction occurs because Mg is more reactive than Cu.

$M g + C u O \to M g O + C u$

7. Copper heated with any oxide

No reaction — Cu is least reactive, cannot displace any metal.

Final Result Summary Table

Metal Added	Zinc oxide (ZnO)	Magnesium oxide (MgO)	Copper oxide (CuO)
Zinc	❌ No reaction	❌ No reaction	✔ Reaction occurs
Magnesium	✔ Reaction occurs	❌ No reaction	✔ Reaction occurs
Copper	❌ No reaction	❌ No reaction	❌ No reaction

Therefore, displacement reactions take place in:

✔ Magnesium + Zinc oxide

✔ Magnesium + Copper oxide

✔ Zinc + Copper oxide

Q2. Which metals do not corrode easily?

Gold, silver and platinum
They are least reactive (do not react with air or moisture).

Q3. What are alloys?

An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal, made to improve strength, hardness or corrosion resistance.

Examples: Brass (Cu + Zn), Bronze (Cu + Sn), Stainless steel (Fe + Cr + Ni)

November 17, 2025