Class 9 Science Chapter 6: Materials Around Us – Previous Year Questions & Solutions

Reading your NCERT or notes a third time won't improve your Chapter 6 score; solving will. Here's why: First, PYQs expose the exact language CBSE examiners use. They consistently ask 'Why is copper used for…?' not 'Name a conductor.' Second, repetition across five years reveals which concepts carry the most marks. For Materials Around Us, property classification (hard/soft, transparent/opaque, lustre) and material selection (why steel for bridges, why cotton for summer clothes) appear in 60–70% of papers. Third, timed practice builds speed—a 5-mark question on grouping materials by physical and chemical properties takes 8–10 minutes under exam stress, and past papers train that reflex. Fourth, mistakes on PYQs are free lessons; exam mistakes cost marks. Students who solve 10+ genuine past papers before the final exam typically score 15–20% higher in this chapter than those who rely on summary notes alone. Start with 1-mark questions to build confidence, then move to longer formats. Timing yourself is essential.

These single-mark questions test direct recall and simple property identification. They appear almost unchanged across multiple years and often form the 'easy wins' in Section A. **Q1: Which of the following is a transparent material?** (A) Wood (B) Glass (C) Aluminum (D) Rubber **Answer: (B) Glass.** Transparent materials allow light to pass through completely; you can see objects clearly on the other side. Glass, water, and air are common examples. Wood, aluminum, and rubber are opaque (block light). **Q2: Define lustre.** Shiny appearance of a material is called lustre. Metals like gold, silver, and copper possess lustre; non-metals and polymers generally lack it. **Q3: Which property describes how easily a solid can be bent without breaking?** (A) Hardness (B) Malleability (C) Ductility (D) Density **Answer: (D)—incorrect; correct is (C) Ductility** (for drawing into wires) or sometimes the question intends flexibility/elasticity. Note: Ductility = ability to draw into wires; malleability = hammering into sheets. Both relate to bending. Always check the exact wording in your PYQ source. **Q4: Salt is soluble in water. True or False?** **Answer: True.** Solubility refers to the ability of a substance to dissolve in a solvent. Sodium chloride (salt) dissolves completely in water at room temperature. Sugar, chalk powder, and sand have different solubilities. **Q5: Which property is used to separate iron filings from sulfur powder?** (A) Solubility (B) Magnetism (C) Density (D) Lustre **Answer: (B) Magnetism.** Iron is magnetic; sulfur is not. A magnet attracts iron filings, leaving sulfur behind—a classic PYQ scenario testing practical separation knowledge. These five appear in most recent papers with minor wording changes. Master the underlying concept, not the exact sentence.

Three-mark questions require explanation, examples, and often a comparison. They test deeper understanding of material properties and real-world selection. **Q1: Explain why copper is used for making electrical wires instead of wood.** Cupper is a good conductor of electricity; wood is an insulator. Copper allows electric current to flow easily due to free electrons in its structure. Wood does not conduct electricity safely and would cause energy loss. Additionally, copper has high ductility (can be drawn into wires), is flexible, and has good mechanical strength. This combination makes it ideal for wiring. (Marks: explanation of copper's conductivity, why wood fails, +1 for mechanical properties.) **Q2: Classify the following into transparent, translucent, and opaque: glass, frosted glass, brick, water, fog, aluminum sheet.** **Transparent:** Glass, water **Translucent:** Frosted glass, fog **Opaque:** Brick, aluminum sheet. (Explanation: Transparent = complete light transmission; translucent = partial light diffusion; opaque = no light transmission. Award 1 mark per correct categorization.) **Q3: Why is cloth made of cotton preferred over synthetic fabric in summer?** Cotton is a natural fiber with good absorptive properties (high porosity). It absorbs sweat from the body quickly, allowing it to evaporate faster, creating a cooling effect. Synthetic fabrics like polyester have low porosity and do not absorb sweat efficiently, causing discomfort. Additionally, cotton is less dense, making it lighter and more breathable. Cotton's hygroscopic nature (ability to absorb moisture) makes it ideal for hot, humid climates. Synthetics trap heat, making them unsuitable for summer. (Mark for each property: absorptivity, density, breathability, comparison.) **Q4: A mixture of salt and sand is given. How would you separate them? Write the steps.** Add water to dissolve salt (salt is soluble; sand is insoluble). Filter the mixture to separate sand (residue) from salt solution (filtrate). Evaporate the filtrate to recover salt crystals. (1 mark per step: correct solvent choice, separation method, recovery process.) **Q5: Compare the properties of metals and non-metals with examples.** **Metals:** Good conductors of heat and electricity (Cu, Al), lustrous, malleable (can hammer into sheets), ductile (draw into wires), hard, sonorous (produce sound). **Non-metals:** Poor conductors (except graphite), non-lustrous, brittle (crack easily), not malleable or ductile, generally soft (except diamond). Example metals: iron, gold, silver. Example non-metals: oxygen, sulfur, phosphorus. (Award marks for each correct property + examples for both.) These three-mark formats test both theory and practical reasoning—common exam traps.

Five-mark questions demand detailed reasoning, multi-step problem-solving, and often require comparing or synthesizing multiple properties. **Q1: You are given three unmarked solid samples: Sample A (light, hard, shiny, conducts electricity), Sample B (light, hard, non-shiny, does not conduct), Sample C (dense, hard, shiny, conducts electricity). Identify each sample and justify your answer based on material properties.** **Solution:** - **Sample A = Aluminum (light metal).** Justification: Density of Al ≈ 2.7 g/cm³ (light), high hardness, metallic lustre (shiny), excellent electrical conductor (free electrons). - **Sample B = Diamond or plastic/ceramic.** If hard, non-conducting, non-shiny → likely a non-metal (diamond, silica) or synthetic polymer. If it's diamond: density ≈ 3.5 g/cm³, hardest natural material, non-lustrous in raw form, insulator. If plastic: low density, hard polymers like bakelite are brittle insulators. - **Sample C = Iron or Steel (dense metal).** Justification: Density ≈ 7.8 g/cm³ (much heavier than Al), ferrous luster, excellent conductor, high hardness due to metallic bonding. **Why Sample A is NOT C:** Density is the distinguishing factor. Density = mass/volume. Al floats; Fe/Steel sinks. This tests understanding of density as a key physical property. (Mark distribution: identification ×3 = 3 marks, justification for each ×0.67 ≈ 2 marks.) **Q2: A manufacturer must choose a material for making kitchen utensils (cookware). The utensil must resist heat, conduct heat evenly, be durable, and be safe for food contact. Compare aluminum and stainless steel as candidates. Which would you recommend and why? Support your answer with property comparisons.** **Solution:** | Property | Aluminum | Stainless Steel | |----------|----------|----------------| | Thermal conductivity | Excellent (237 W/m·K) | Good (16 W/m·K) | | Corrosion resistance | Low (reacts with acidic foods) | Excellent (chromium oxide layer) | | Density | 2.7 g/cm³ (lightweight) | 7.8 g/cm³ (heavier) | | Durability | Moderate (softer, scratches easily) | High (harder, resists wear) | | Food safety | Questionable (Al leaches into acidic foods) | Safe (inert, no reaction) | | Cost | Low | Moderate-High | **Recommendation: Stainless Steel.** While aluminum conducts heat faster, stainless steel's superior corrosion resistance and food safety properties outweigh this disadvantage. Acidic foods (tomatoes, citrus) corrode aluminum, potentially releasing harmful aluminum ions. Stainless steel's chromium oxide layer prevents corrosion and is chemically inert. For durability and health, stainless steel is the better choice despite higher cost. (Mark: property comparison ×2 = 2 marks, recommendation + reasoning = 3 marks.) **Q3: Explain how physical properties of materials determine their suitability for specific applications. Use THREE examples from daily life (e.g., glass windows, steel bridges, rubber tires) to justify your answer.** **Solution:** The properties of a material—density, hardness, transparency, conductivity, elasticity—directly determine which applications suit it best. Manufacturers choose materials by matching their properties to functional requirements. **Example 1: Glass for windows.** Glass is transparent (allows light transmission), hard (resists scratching), brittle (acceptable for panes), and chemically inert (resistant to weathering). These properties make glass ideal for allowing vision while protecting interiors. Opacity would fail; conductivity would cause heat loss. **Example 2: Steel for bridges and buildings.** Steel has high tensile strength (≈400 MPa), high hardness, and good ductility. Tensile strength means it resists stretching under load. High density (≈7.8 g/cm³) means stability against wind. Ductility prevents sudden fracture. Concrete (brittle) alone would fail under dynamic loads; steel's combination of strength and flexibility is essential. **Example 3: Rubber for tires.** Rubber exhibits elasticity (returns to original shape after deformation), high friction (with road surfaces), and resistance to mechanical wear. These properties allow tires to grip wet roads and absorb impact. A rigid material (glass) would shatter; a slippery material (Teflon) would skid. **Conclusion:** Property ↔ Function is the core principle. Density determines weight-bearing capacity, transparency determines visibility, conductivity determines heat/electrical behavior. Engineers always match material properties to functional needs. (Marks: concept explanation = 2, three examples with property justification = 3.) These five-mark questions test synthesis—combining multiple properties, comparing alternatives, and reasoning about real-world choices. Practice explaining your logic, not just stating answers.

The 2024–25 rationalized CBSE syllabus has stabilized around competency-based questions. Chapter 6 (Materials Around Us) shows clear shifts from older exam patterns: **Old Pattern (pre-2022):** 'Define transparency.' 'List properties of metals.' → Rote, definition-heavy. **New Pattern (2024–25 onward):** Scenario-based questions with decision-making. Example: 'A company produces sports bottles. They can use plastic or stainless steel. Which material should they choose? Justify using material properties.' This tests application, not recall. **Expected 2026–27 trends for Chapter 6:** 1. **More data interpretation:** Questions may provide a table of material properties (density, hardness, solubility, melting point) and ask students to identify the material or predict its use. Example: 'Material X has density 2.7 g/cm³, high thermal conductivity, and forms oxides. Identify X.' → Tests inference, not memorization. 2. **Sustainability angle:** CBSE is increasingly linking materials to environmental impact. Expect questions like 'Why is recycling aluminum preferred over mining new ore?' (Answer: Mining requires 95% more energy; recycling has lower environmental cost.) This reflects India's push toward circular economy. 3. **Shorter answer, deeper reasoning:** Marks per question may decrease (1–2 marks for short reasoning instead of 3-mark definition questions), but depth of explanation increases. Examiners want 'Why?' not 'What?' 4. **Lab/observational context:** Questions referencing practical activities (e.g., 'In a lab experiment, students heated a metal and observed it expanded. Later, when cooled, it contracted. Explain using particle theory.') will increase. Materials Around Us may integrate thermal expansion and density concepts more explicitly. 5. **Comparison format stabilization:** 3-mark questions will increasingly use tabular comparisons (metal vs. non-metal, transparent vs. opaque) rather than narrative descriptions. Prepare structured comparison answers. **How to prepare for 2026–27:** Focus on 'why' over 'what.' Understand the connection between atomic structure and macroscopic properties. Practice explaining material choice in industrial contexts. Solve questions that ask you to infer properties from a description, not recall definitions.

Exam strategy is as important as content knowledge. Here's a tested approach for Chapter 6 questions in your Class 9 Science exam: **Pre-exam (1 week before):** Solve at least 10 complete PYQs under timed conditions (1-mark in 1 min, 3-mark in 5 min, 5-mark in 10 min including reading). Note recurring terms: lustre, solubility, density, hardness, malleability, ductility, transparency. Create a one-page property cheat sheet with examples (e.g., Cu = conductor, shiny, ductile; S = non-conductor, non-shiny, brittle). **During exam (time allocation):** If Materials Around Us spans ~4–5 marks in your 80-mark paper: - Spend ~6–7 minutes total on this chapter. - Attempt 1-mark questions first (40–50 seconds each, no overthinking). - Then 3-mark questions (read carefully, sketch a rough comparison table if needed, write in bullets initially, then expand). - Avoid long 5-mark essays on this chapter unless it's an application question; instead, use a structured format: Property → Example → Why → Conclusion. **Common trap mistakes (avoid these):** 1. **Confusing ductility and malleability:** Ductility = drawing into wires (one-directional); malleability = hammering into sheets (multi-directional). Copper is both; gold is more malleable. 2. **Transparency vs. translucency:** Transparent = crystal clear (glass, water); translucent = cloudy but light passes (frosted glass, wax paper). Many students reverse these. 3. **Lustre vs. hardness:** Lustre = shininess (visual property); hardness = resistance to scratching. A non-metal can be hard (diamond) but lack lustre. 4. **Forgetting real-world context:** If asked 'Why copper for wires?', don't just say 'conductor.' Say 'Copper conducts electricity efficiently (low resistance) AND is ductile (can be drawn into wires) AND is flexible (safe to bend).' Three points = full mark. **Quick mental checklist during exam:** For any property question: (1) State the property, (2) Give the definition or example, (3) Explain why it matters for that context, (4) Compare if needed. This 4-step ensures no gaps. **If unsure:** Always bet on practical reasoning. CBSE examiners favor 'Why is material Y used for Z?' because it tests both knowledge and logic. A detailed, logical answer scores even if slightly imperfect; a vague answer scores zero. Start a 3-day free trial at cbsetutor.ai to access video solutions of these exact PYQs, step-by-step tutorials on property classification, and timed mock tests tailored to the 2026–27 pattern. Live tutors can clarify confusing concepts (ductility vs. malleability) in real time.

Materials Around Us is primarily conceptual, but a few quantitative concepts appear in advanced questions: **Density:** ρ = m/V (mass ÷ volume). Unit: g/cm³ or kg/m³. Example: Aluminum ≈ 2.7 g/cm³ (light metal); Iron ≈ 7.8 g/cm³ (heavy metal). A denser material sinks in a less-dense liquid. If a rock (ρ ≈ 2.5 g/cm³) is placed in water (ρ = 1 g/cm³), it sinks because rock's density > water's density. **Solubility:** Expressed as grams of solute per 100 mL of solvent at a standard temperature (usually 20°C). Example: NaCl solubility in water at 20°C ≈ 36 g per 100 mL. Solubility varies with temperature; generally, ionic salts become more soluble as temperature increases (opposite for gases). **Hardness (Mohs scale):** Qualitative ranking from 1 (softest, talc) to 10 (hardest, diamond). Not a ratio scale; the difference between Mohs 9 and 10 is larger than between 1 and 2. **Thermal conductivity:** k = (Q × d) / (A × Δt), where Q = heat, d = thickness, A = area, Δt = temperature difference. Higher k = better heat conductor. Copper ≈ 400 W/m·K; aluminum ≈ 237 W/m·K; iron ≈ 80 W/m·K. These ratios explain why copper is preferred for cookware in laboratories, though stainless steel is safer for food due to corrosion resistance. **Tensile strength:** Force per unit area a material can withstand before breaking under tension. Steel ≈ 400 MPa; Aluminum ≈ 70 MPa. This explains why steel, not aluminum, is used for load-bearing structures. **Quick fact-check table:** For 1-mark questions, memorize these core distinctions: - **Metals:** Conduct electricity, malleable, ductile, lustrous, sonorous, high density, solid at room temp (except mercury). - **Non-metals:** Poor conductors (except graphite/C), brittle, non-lustrous, non-sonorous, variable density, exist as solid/liquid/gas. - **Semiconductors:** Si, Ge—conduct under certain conditions, intermediate properties. Density ordering (common materials): Cork (0.2) < Wood (0.6) < Water (1.0) < Aluminum (2.7) < Iron (7.8) < Lead (11.3) < Gold (19.3). This ordering helps identify unknowns in competitive questions. No need to memorize exact values; understanding trends (why gold sinks in water, why aluminum floats in mercury) is exam-relevant.