CBSE Class 10 Science — Metals and Non-metals

Chapter Overview & Weightage

Metals and Non-metals is one of the most scoring chapters in CBSE Class 10 Science, falling under the Chemistry section. This chapter contributes 5–8 marks in the board exam, with questions spread across all difficulty levels.

Recent CBSE board trends: 1-mark questions on properties, 2-mark questions on reactions (especially with water and acids), 3-mark questions on the reactivity series and corrosion, and 5-mark questions on extraction of metals (metallurgy). The extraction section has become more prominent in recent years.

Topic	Expected marks
Physical properties — metals vs non-metals	1–2 marks
Chemical reactions of metals	2–3 marks
Reactivity series	1–2 marks
Ionic bond formation	2 marks
Extraction of metals	3–5 marks
Corrosion and its prevention	2–3 marks

Key Concepts You Must Know

Physical properties — Metals:

Lustrous (shiny)
Malleable (can be hammered into sheets) — gold is most malleable
Ductile (can be drawn into wires) — gold is most ductile; silver is the best conductor of electricity
Good conductors of heat and electricity
High melting and boiling points (exception: mercury is liquid at room temperature; gallium melts in your hand)
Hard and dense (exception: sodium and potassium are so soft they can be cut with a knife; they float on water)
Sonorous (produce a ringing sound when struck)

Physical properties — Non-metals:

Mostly dull (non-lustrous), except iodine and graphite
Brittle (not malleable or ductile) — exception: carbon (graphite) and diamond
Poor conductors of heat and electricity — exception: graphite (conducts electricity)
Low melting and boiling points (exceptions: diamond, graphite have very high melting points)

Chemical Reactions of Metals

With Oxygen

Most metals form metallic oxides (basic in nature):

4\text{Na} + \text{O}_2 \rightarrow 2\text{Na}_2\text{O}

2\text{Mg} + \text{O}_2 \rightarrow 2\text{MgO}

Aluminium forms a protective oxide layer — this passivation is why aluminium doesn’t corrode easily despite being reactive.

With Water

Reactivity varies:

Na, K: React vigorously with cold water → metal hydroxide + hydrogen $2\text{Na} + 2\text{H}_2\text{O} \rightarrow 2\text{NaOH} + \text{H}_2\uparrow$ (exothermic — may ignite)
Mg: Reacts slowly with cold water, vigorously with steam
Fe: Reacts with steam only → iron(II, III) mixed oxide + hydrogen
Cu, Au, Ag: Do NOT react with water

With Dilute Acids

\text{Metal} + \text{Dilute acid} \rightarrow \text{Salt} + \text{Hydrogen}

\text{Zn} + \text{H}_2\text{SO}_4 \rightarrow \text{ZnSO}_4 + \text{H}_2

Copper does not react with dilute acids (below copper in reactivity series). Gold and platinum don’t react with any single acid — only aqua regia (3:1 HCl:HNO₃) dissolves gold.

Important Formulas

Most reactive to least reactive:

K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Hg > Ag > Au > Pt

Mnemonic: King Napoleon Came Mgreen Alpha Zapping Fevered Pigs; He Cured High Sickness, Act Gloriously Pure

Metal atoms lose electrons → form positive cations. Non-metal atoms gain electrons → form negative anions. Electrostatic attraction between cations and anions = ionic bond.

Example: Na → Na⁺ + e⁻ (loses 1e⁻) Cl + e⁻ → Cl⁻ (gains 1e⁻) NaCl = Na⁺Cl⁻

Solved Previous Year Questions

PYQ 1 — Properties (1-mark type)

Q: Name a metal that is stored in kerosene.

Answer: Sodium (or potassium). Sodium is so reactive that it ignites on contact with air or water — storing it in kerosene prevents this.

PYQ 2 — Chemical reaction (2-mark type)

Q: Write the chemical equation when iron reacts with steam. What type of product is formed?

Answer:

3\text{Fe} + 4\text{H}_2\text{O} \xrightarrow{\text{steam}} \text{Fe}_3\text{O}_4 + 4\text{H}_2

The product is iron(II, III) oxide ( $\text{Fe}_3\text{O}_4$ ), which is a mixed oxide (not purely ferrous or ferric — it’s a combination of FeO and Fe₂O₃).

PYQ 3 — Extraction (3-mark type)

Q: Why is it easier to extract metals like sodium and calcium from their ores compared to zinc and iron?

Answer: Sodium and calcium are highly reactive metals (high in the reactivity series). Highly reactive metals are extracted using electrolysis — a powerful method that directly decomposes the ore by passing electric current. The method is straightforward (but energy-intensive).

Zinc and iron are mid-reactivity metals. They are extracted by reduction using coke (carbon) or carbon monoxide at high temperatures — a chemical reduction method. The challenge is controlling temperature and preventing oxidation. Less reactive metals (Cu, Hg, Ag) can even be extracted by just heating their oxide (thermal decomposition), with no reducing agent needed.

Difficulty Distribution

Level	Question types	Marks
Easy	Properties, single-reaction equations	1
Medium	Reactivity comparison, corrosion explanation, ionic bond formation	2
Hard	Extraction steps for specific metals, displacement reactions in industry	3–5

Expert Strategy

The reactivity series is the backbone of this chapter — memorise it. Use it to predict: (1) which metals displace others from solutions, (2) how metals are extracted (electrolysis for highly reactive, carbon reduction for medium, heating for low), (3) which metals corrode easily.

For chemical equations, practise balancing them fully — half marks for unbalanced equations in CBSE.

Thermite reaction is a scoring topic: $2\text{Al} + \text{Fe}_2\text{O}_3 \rightarrow \text{Al}_2\text{O}_3 + 2\text{Fe}$ (with heat). Aluminium displaces iron because Al is more reactive. This reaction is used for welding railway tracks. The question “why can aluminium be used to displace iron?” = higher reactivity of Al.

Common Traps

Trap 1: Saying all metals are solid. Mercury (Hg) is a metal that is liquid at room temperature. Gallium melts slightly above room temperature (~30°C). These exceptions appear in MCQs.

Trap 2: Confusing extraction methods. Electrolysis is for highly reactive metals (K, Na, Ca, Mg, Al). Carbon reduction is for medium-reactive metals (Zn, Fe, Sn, Pb). Heating alone works for low-reactive metals (Cu, Hg from oxide). The rule: the more reactive the metal, the harder (more energy-intensive) to extract.

Trap 3: Saying corrosion is the same as rusting. Rusting specifically refers to iron corroding to form iron oxide (Fe₂O₃·xH₂O). Corrosion is the general term for any metal degrading by chemical reaction with its environment. All rusting is corrosion, but not all corrosion is rusting.

Trap 4: Forgetting that hydrogen is placed in the reactivity series even though it’s not a metal. Its position (between lead and copper) defines which metals can displace it from acids (metals above H in the series) and which cannot (metals below H).