NCERT Solutions Class 10 Science Chapter 3 Metals and Non-Metals

Mastering NCERT Solutions Class 10 Science Chapter 3 Metals and Non-Metals is essential for students aiming to score full marks in their CBSE Board Examinations. In the Class 10 Science curriculum, Chapter 3 is one of the highest-weightage units under the chemistry section "Chemical Substances – Nature and Behaviour". This comprehensive guide provides accurate, step-by-step CBSE NCERT solutions for all in-text questions and the 16 end-of-chapter exercises, complete with balanced chemical equations, reaction mechanisms, and examination-focused explanations.

Chapter Overview: Metals and Non-Metals

Chapter 3 explores the physical and chemical behaviour of elements, classifying them into metals and non-metals based on electronic configuration and reactivity. The chapter bridges foundational chemistry concepts with practical industrial metallurgy and material science.

Key topics covered in this chapter include:

• Physical Properties and Exceptions: Malleability, ductility, thermal and electrical conductivity, sonority, and lustrous nature. Key exceptions include mercury (liquid metal), gallium and caesium (low melting points), iodine (lustrous non-metal), graphite (conducting non-metal), and diamond (hardest natural substance).
• Chemical Properties of Metals: Formation of basic and amphoteric oxides (Al₂O₃, ZnO), reactions with cold water, hot water, and steam, reactions with dilute acids, and the oxidising nature of nitric acid (HNO₃).
• The Reactivity Series and Displacement Reactions: Relative reactivity of metals (K > Na > Ca > Mg > Al > Zn > Fe > Pb > [H] > Cu > Hg > Ag > Au) and predicting displacement outcomes.
• Ionic Compounds: Electron transfer, Lewis electron-dot structures (NaCl, MgCl₂, Na₂O, MgO), high melting/boiling points, brittleness, and electrical conductivity in molten/aqueous states.
• Metallurgy and Extraction of Metals: Concentration of ores, conversion to oxides via roasting (sulphide ores) and calcination (carbonate ores), reduction using carbon or displacement (Thermit reaction), and electrolytic refining of copper.
• Corrosion and Prevention: Mechanism of rusting of iron, galvanisation, tin plating, anodising, and composition of important alloys (Brass, Bronze, Solder, Stainless Steel, Amalgam).

NCERT In-Text Questions and Solutions

Page 40: Physical Properties of Metals and Non-Metals

Question 1: Give an example of a metal which:

1. is a liquid at room temperature.
   Answer: Mercury (Hg) is the only metal that exists as a liquid at room temperature (25°C).
2. can be easily cut with a knife.
   Answer: Sodium (Na), Potassium (K), and Lithium (Li) are soft alkali metals with low densities that can be sliced easily with a knife.
3. is the best conductor of heat.
   Answer: Silver (Ag) is the best conductor of heat, followed closely by copper (Cu).
4. is a poor conductor of heat.
   Answer: Lead (Pb) and Mercury (Hg) are comparatively poor conductors of heat among metals.

Question 2: Explain the meanings of malleable and ductile.

Answer:

• Malleable: The physical property of a substance (primarily metals) that allows it to be beaten, hammered, or rolled into thin sheets without breaking. Gold (Au) and silver (Ag) are the most malleable metals.
• Ductile: The property of a metal that allows it to be drawn or stretched into thin, fine wires without snapping. Gold is the most ductile metal (1 gram of gold can be drawn into a wire approximately 2 kilometres long).

Page 46: Chemical Properties of Metals

Question 1: Why is sodium kept immersed in kerosene oil?

Answer: Sodium (Na) is an extremely reactive alkali metal. When exposed to ambient air, it reacts vigorously with atmospheric oxygen and moisture in a highly exothermic reaction, generating enough heat to ignite the evolved hydrogen gas:

4Na(s) + O₂(g) → 2Na₂O(s)
2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g) + Heat

To prevent accidental fires and cut off contact with air and moisture, sodium is stored immersed in unreactive kerosene oil.

Question 2: Write equations for the reactions of:

1. Iron with steam:
   Iron does not react with cold or hot water, but red-hot iron reacts with steam to form iron(II,III) oxide (magnetic iron oxide) and hydrogen gas.
   3Fe(s) + 4H₂O(g) → Fe₃O₄(s) + 4H₂(g)
2. Calcium and potassium with water:
   Potassium reacts violently with cold water, catching fire immediately:
   2K(s) + 2H₂O(l) → 2KOH(aq) + H₂(g) + Heat
   Calcium reacts less violently with water. The heat evolved is insufficient for hydrogen to catch fire, and calcium floats as bubbles of hydrogen stick to its surface:
   Ca(s) + 2H₂O(l) → Ca(OH)₂(aq) + H₂(g)

Question 3: Samples of four metals A, B, C and D were taken and added to the following solutions one by one. The results obtained have been tabulated as follows:

Metal	Iron(II) sulphate	Copper(II) sulphate	Zinc sulphate	Silver nitrate
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

Questions:

1. Which is the most reactive metal?
2. What would you observe if B is added to a solution of Copper(II) sulphate?
3. Arrange the metals A, B, C and D in the order of decreasing reactivity.

Answers:

1. Metal B is the most reactive because it displaces iron from iron(II) sulphate, meaning it is more reactive than iron, copper, and silver.
2. Since B is more reactive than iron and iron is more reactive than copper, B will displace copper from copper(II) sulphate, turning the blue solution colourless and depositing reddish-brown copper.
3. Decreasing reactivity order: B > A > C > D.

Question 4: Which gas is produced when dilute hydrochloric acid is added to a reactive metal? Write the chemical reaction when iron reacts with dilute H₂SO₄.

Answer: Hydrogen gas (H₂) is evolved when dilute hydrochloric acid reacts with an active metal. The reaction of iron with dilute sulphuric acid produces iron(II) sulphate and hydrogen gas:

Fe(s) + H₂SO₄(dilute) → FeSO₄(aq) + H₂(g)↑

Question 5: What would you observe when zinc is added to a solution of iron(II) sulphate? Write the chemical reaction that takes place.

Answer: Zinc is more reactive than iron (Zn lies above Fe in the activity series). Zinc displaces iron from green iron(II) sulphate solution, making the solution colourless due to the formation of zinc sulphate, and greyish-black iron metal precipitates onto the zinc strip.

Zn(s) + FeSO₄(aq) [Pale green] → ZnSO₄(aq) [Colourless] + Fe(s) [Greyish-black]

Page 49: Formation and Properties of Ionic Compounds

Question 1: (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:

1. Electron-dot structures:
   • Sodium (Na, atomic number 11, configuration 2, 8, 1): Na•
   • Magnesium (Mg, atomic number 12, configuration 2, 8, 2): •Mg•
   • Oxygen (O, atomic number 8, configuration 2, 6): :Ö: (6 valence electrons)
2. Formation by electron transfer:
   • Formation of Na₂O: Two sodium atoms each lose one valence electron to one oxygen atom:
     2 Na• → 2 Na⁺ + 2e^-
     O + 2e^- → O^2-
     Resulting compound: (Na⁺)₂ [ :Ö: ]^2- → Na₂O
   • Formation of MgO: One magnesium atom transfers its 2 valence electrons to one oxygen atom:
     Mg → Mg²⁺ + 2e^-
     O + 2e^- → O^2-
     Resulting compound: Mg²⁺ [ :Ö: ]^2- → MgO
3. Ions present:
   • In Na₂O: Sodium cation (Na⁺) and Oxide anion (O^2-).
   • In MgO: Magnesium cation (Mg²⁺) and Oxide anion (O^2-).

Question 2: Why do ionic compounds have high melting points?

Answer: Ionic compounds consist of positively and negatively charged ions held together in a rigid, three-dimensional crystal lattice by strong inter-ionic electrostatic forces of attraction. A large amount of thermal energy is required to overcome and break these powerful electrostatic bonds, resulting in high melting and boiling points.

Page 53: Metallurgy and Occurrence of Metals

Question 1: Define the following terms: (i) Mineral (ii) Ore (iii) Gangue.

Answer:

• Mineral: Naturally occurring inorganic homogeneous solid substances with a definite chemical composition found within the Earth's crust.
• Ore: A mineral from which one or more specific metals can be extracted profitably, conveniently, and on a commercial scale (e.g., Bauxite is the ore of Aluminium).
• Gangue: The unwanted earthy impurities like sand, clay, soil, and rocky materials associated with mined ores.

Question 2: Name two metals which are found in nature in the free state.

Answer: Gold (Au) and Platinum (Pt) (as well as Silver, Ag) are least reactive and occur in their native or free elemental state in nature.

Question 3: What chemical process is used for obtaining a metal from its oxide?

Answer: The chemical process is reduction. Depending on the metal's position in the reactivity series:

• Low-reactivity metals: Reduced by thermal heating alone (e.g., 2HgO → 2Hg + O₂).
• Medium-reactivity metals: Reduced using reducing agents like Carbon (coke) or reactive metals like Aluminium in Thermit processes (e.g., ZnO + C → Zn + CO).
• High-reactivity metals: Reduced by electrolytic reduction of their molten chlorides or oxides (e.g., molten NaCl → Na at cathode).

Page 55: Corrosion and Alloys

Question 1: Metallic oxides of zinc, magnesium and copper were heated with the following metals:

Metal Oxide	Zinc (Zn)	Magnesium (Mg)	Copper (Cu)
Zinc oxide	No reaction	Displacement	No reaction
Magnesium oxide	No reaction	No reaction	No reaction
Copper oxide	Displacement	Displacement	No reaction

Explanation: Magnesium is more reactive than Zinc and Copper; Zinc is more reactive than Copper (Reactivity order: Mg > Zn > Cu). Therefore, Mg displaces both ZnO and CuO, while Zn displaces only CuO.

Question 2: Which metals do not corrode easily?

Answer: Noble metals located at the bottom of the reactivity series, such as Gold (Au), Platinum (Pt), and Titanium (Ti), do not corrode easily because they do not readily react with oxygen, water, or atmospheric gases.

Question 3: What are alloys?

Answer: An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal, prepared by mixing the primary metal in a molten state with other elements in definite proportions. Examples include Brass (Copper + Zinc), Bronze (Copper + Tin), and Stainless Steel (Iron + Nickel + Chromium + Carbon).

NCERT Chapter End Exercise Solutions

Question 1: 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: (d) AgNO₃ solution and copper metal.
Explanation: Copper is more reactive than silver and is positioned above silver in the reactivity series. Hence, copper displaces silver from silver nitrate solution: Cu(s) + 2AgNO₃(aq) → Cu(NO₃)₂(aq) + 2Ag(s).

Question 2: 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: (c) Applying a coating of zinc (Galvanisation).
Explanation: While grease and paint prevent rusting, they burn off or contaminate food when heated during cooking. Zinc coating (galvanisation) resists high cooking temperatures and provides effective protection without burning.

Question 3: 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), an ionic compound with a very high melting point (~2572°C) that readily dissolves in water to form slaked lime, Ca(OH)₂.

Question 4: 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: Zinc is chemically more reactive than tin. If food cans were coated with zinc, it would react with organic food acids (like citric acid, tartaric acid) to form toxic compounds causing food poisoning. Tin is unreactive with food acids.

Question 5: You are given a hammer, a battery, bulb, wires and a switch.
(a) How could you use them to distinguish between samples of metals and non-metals?
(b) Assess the usefulness of these tests in distinguishing between metals and non-metals.

Answer:

1. Experimental Setup:
   • Using the Hammer (Malleability Test): Strike the given sample firmly with the hammer. If the sample flattens into a thin sheet without shattering, it is a metal (malleable). If it breaks into pieces or crumbles to powder, it is a non-metal (brittle).
   • Using Electrical Circuit (Conductivity Test): Set up a simple series circuit connecting the battery, bulb, switch, and clips with copper wires. Insert the sample between the test clips. Close the switch. If the bulb glows, the sample conducts electricity and is a metal. If the bulb does not glow, it is an insulator and represents a non-metal.
2. Assessment of Usefulness: These physical tests are generally practical and effective, but have exceptions:
   • Graphite (an allotrope of carbon, non-metal) conducts electricity and causes the bulb to glow.
   • Sodium and potassium are soft metals and do not display typical mechanical malleability under hammering.
   • Therefore, physical tests provide initial classification, but chemical tests (oxide nature, acid reaction) are needed for definitive confirmation.

Question 6: What are amphoteric oxides? Give two examples of amphoteric oxides with balanced chemical equations.

Answer: Metal oxides that react with both acids as well as bases to produce salt and water are called amphoteric oxides. Two classic examples are Aluminium oxide (Al₂O₃) and Zinc oxide (ZnO).

• Reactions of Aluminium Oxide (Al₂O₃):
  With Acid (HCl): Al₂O₃(s) + 6HCl(aq) → 2AlCl₃(aq) + 3H₂O(l) (acts as a basic oxide)
  With Base (NaOH): Al₂O₃(s) + 2NaOH(aq) → 2NaAlO₂(aq) [Sodium aluminate] + H₂O(l) (acts as an acidic oxide)
• Reactions of Zinc Oxide (ZnO):
  With Acid (HCl): ZnO(s) + 2HCl(aq) → ZnCl₂(aq) + H₂O(l)
  With Base (NaOH): ZnO(s) + 2NaOH(aq) → Na₂ZnO₂(aq) [Sodium zincate] + H₂O(l)

Question 7: Name two metals which will displace hydrogen from dilute acids, and two metals which will not.

Answer:

• Metals that displace hydrogen: Zinc (Zn) and Magnesium (Mg) (metals positioned above hydrogen in the activity series).
• Metals that do not displace hydrogen: Copper (Cu) and Silver (Ag) (metals positioned below hydrogen in the activity series).

Question 8: In the electrolytic refining of a metal M, what would you take as the anode, the cathode and the electrolyte?

Answer:

• Anode: A thick block/slab of the impure metal M.
• Cathode: A thin strip of the pure metal M.
• Electrolyte: An acidified aqueous solution of a soluble salt of metal M (e.g., for copper refining, acidified CuSO₄ solution).

Question 9: 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? (ii) moist litmus paper?
(b) Write a balanced chemical equation for the reaction taking place.

Answer:

1. Action on Litmus Paper:
   • (i) Dry litmus paper: No change in colour because the gaseous sulphur dioxide (SO₂) cannot dissociate to release H⁺ ions in the absence of moisture.
   • (ii) Moist litmus paper: The moist blue litmus paper turns red. Sulphur dioxide dissolves in water present on the paper to form sulphurous acid (H₂SO₃), which dissociates to give H⁺(aq) ions.
2. Balanced Chemical Equations:
   S(s) + O₂(g) → SO₂(g) (Burning of sulphur)
   SO₂(g) + H₂O(l) → H₂SO₃(aq) (Formation of sulphurous acid)

Question 10: State two ways to prevent the rusting of iron.

Answer:

1. Galvanisation: Applying a protective coating of molten zinc over iron surfaces. Even if the zinc layer is scratched, zinc corrodes preferentially, shielding the underlying iron.
2. Alloying: Mixing molten iron with measured proportions of nickel, chromium, and carbon to produce Stainless Steel, which is completely rust-resistant.

Question 11: What type of oxides are formed when non-metals combine with oxygen?

Answer: Non-metals combine with oxygen to form covalent oxides which are either acidic or neutral:

• Acidic Oxides: Dissolve in water to form acids and turn blue litmus red. Examples: Carbon dioxide (CO₂), Sulphur dioxide (SO₂), Phosphorus pentoxide (P₂O₅).
• Neutral Oxides: Do not exhibit acidic or basic properties and have no effect on litmus. Examples: Carbon monoxide (CO), Water (H₂O), Nitrous oxide (N₂O).

Question 12: Give reasons:

1. Platinum, gold and silver are used to make jewellery.
   Reason: These metals are highly unreactive (noble metals), lustrous, malleable, ductile, and do not corrode or tarnish when exposed to atmospheric air, moisture, and pollutants.
2. Sodium, potassium and lithium are stored under oil.
   Reason: Alkali metals have very low ionization energies and react violently with atmospheric oxygen and moisture at room temperature in an exothermic reaction, catching fire. Storage under mineral oil isolates them from air and moisture.
3. Aluminium is a highly reactive metal, yet it is used to make utensils for cooking.
   Reason: Aluminium reacts rapidly with atmospheric oxygen to develop an extremely stable, non-porous, and protective superficial layer of Aluminium Oxide (Al₂O₃). This oxide film prevents further corrosion. Furthermore, aluminium is lightweight and an excellent conductor of heat.
4. Carbonate and sulphide ores are usually converted into oxides during the process of extraction.
   Reason: It is thermodynamically and energetically much easier to reduce a metal oxide to free metal using carbon or other reducing agents than to reduce metal carbonates or sulphides directly.

Question 13: 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: When exposed to moist air containing CO₂, copper reacts slowly to form a dull green coating of basic copper carbonate [CuCO₃·Cu(OH)₂]. Sour substances like lemon juice (containing citric acid) and tamarind juice (containing tartaric acid) react chemically with the basic copper carbonate. The acid neutralises the basic compound, converting it into soluble copper citrate/tartrate salts that wash away easily with water, restoring the shiny copper surface.

Question 14: Differentiate between metal and non-metal on the basis of their chemical properties.

Answer:

Property	Metals	Non-Metals
Nature of Oxides	Form basic or amphoteric oxides (e.g., Na2O, MgO, Al2O3).	Form acidic or neutral oxides (e.g., SO2, CO2, CO, H2O).
Reaction with Dilute Acids	Displace hydrogen gas from dilute acids (e.g., Zn + 2HCl → ZnCl2 + H2).	Do not react with dilute acids to liberate hydrogen gas.
Reaction with Water	React with water/steam to evolve hydrogen gas.	Do not react with water or steam.
Nature of Ions & Redox Behaviour	Electropositive in nature; lose electrons to form cations (Reducing agents).	Electronegative in nature; gain electrons to form anions (Oxidising agents).
Nature of Chlorides	Form ionic chlorides with high melting points (e.g., NaCl, MgCl2).	Form covalent chlorides with low melting points (e.g., CCl4, PCl3).

Question 15: A man went door to door posing as a goldsmith. He promised to bring back the glitter of old and dull gold ornaments. An unsuspecting lady gave a set of gold bang