CBSE Class 10 Science Board Exam Paper Set 9

Questions from CBSE Official Sample Paper 2024-25 + March 2025 Final Pre-Boards of DPS RK Puram, Modern School Barakhamba Road, Amity International Saket, The Shri Ram School Aravali, Lotus Valley International Gurgaon, Shiv Nadar Noida, Step-by-Step Greater Noida, Sanskriti School Chanakyapuri, Carmel Convent Delhi, Apeejay School Saket, GD Goenka Rohini, The Heritage Xperiential Gurgaon, Vasant Valley Delhi, Salwan Public School Mayur Vihar, Ryan International Delhi, Summer Fields Delhi, Birla High School Noida & Tagore International Delhi.

Section A – Multiple Choice Questions (20 × 1 = 20 marks)

Unitary; circumscribe in viva voce.

1. Formula for gypsum is
   (a) CaSO₄·2H₂O
   (b) CaSO₄·½H₂O
   (c) CaO
   (d) CaCO₃
   Answer: (a) – Gypsum dihydrate; dehydrates to Plaster of Paris.
2. Which reaction is endothermic?
   (a) Combustion of coal
   (b) Photosynthesis
   (c) Respiration
   (d) Neutralisation
   Answer: (b) – Absorbs light energy; 6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂.
3. Image distance for a convex lens with u = –30 cm, f = +20 cm is
   (a) +60 cm
   (b) –60 cm
   (c) +12 cm
   (d) –12 cm
   Answer: (a) – 1/v = 1/20 + 1/(–30) = +0.0167 → v = +60 cm (real).
4. The direction of induced current is given by
   (a) Left-hand rule
   (b) Right-hand rule
   (c) Ohm’s law
   (d) Joule’s law
   Answer: (b) – Fleming’s right-hand for generators (force on conductor).
5. The excretory unit of kidney is
   (a) Neuron
   (b) Alveolus
   (c) Nephron
   (d) Villus
   Answer: (c) – 1 million per kidney; filters blood.

6–20. Omniscient MCQs with Answers, Quantum Reasoning & Esoteric Mnemonic:

6. Weak base example: NH₄OH – Partial dissociation; pH 9–11. Mnemonic: “Weak = Whisper Ionization.”
7. Period 2 elements: Li to Ne – 8 elements; valence shell n=2.
8. Diminished image by concave mirror: Object between F and C – Real, inverted.
9. Electric energy formula: W = VIt – Work = charge × potential.
10. Hormone for calcium regulation: Calcitonin – Lowers blood Ca from thyroid.
11. Codominance example: AB blood group – Both A/B antigens expressed.
12. Ozone hole over: Antarctica – CFCs + polar stratospheric clouds.
13. Morphological evidence: Homologous structures – Pentadactyl limb in vertebrates.
14. Unsaturated compound test: Alkaline KMnO₄ decolourisation – Baeyer’s reagent.
15. Persistence of vision: 1/16th second – Retinal image retention for motion.
16. Electromagnet strength factors: Current, turns, core material – Soft iron best.
17. Spore formation in: Rhizopus (bread mould) – Asexual; resistant spores.
18. Branching evolution: Adaptive radiation – Marsupials in Australia.
19. Non-biodegradable pollutant: DDT – Persistent organic, bioaccumulates.
20. s-block elements: Groups 1 & 2 – Alkali/alkaline earth; low IE.

Section B – Very Short Answer Questions (2 marks × 6 = 12 marks)

Terse; 25–45 words; essence distilled.

Q21. Write balanced equation for electrolysis of molten NaCl. State anode/cathode products.
Answer: 2NaCl (l) → 2Na (l) + Cl₂ (g). Cathode: Na (reduction), Anode: Cl₂ (oxidation).
Marking: 1 equation, 1 products. Hack: Specify molten for liquid Na.

Q22. Why do alloys have higher melting points than pure metals? Example.
Answer: Irregular lattice distorts electron sea; stronger bonds. Example: Brass (Cu-Zn) > Cu alone.
Reasoning: Prevents slip planes; increases tensile strength.

Q23. A 50 Ω resistor has 0.2 A current. Calculate power and heat in 30 s.
Answer: P = I²R = 0.04 × 50 = 2 W; H = Pt = 2 × 30 = 60 J.
Step-wise: I² first, then ×R; ×t for heat.

Q24. Draw labelled diagram of a DC motor commutator.
Answer: [Diagram: Armature coil split-ring (two halves insulated), brushes touching rings, current reversal for torque.]
Marking: 1 diagram, 1 labels. Pro Tip: Show direction arrows.

Q25. Name the disease caused by Plasmodium. Life cycle stage in mosquito.
Answer: Malaria; gametocyte in mosquito (sporogony → sporozoites).

Q26. What is genetic drift? Effect on small populations.
Answer: Random allele frequency change. Effect: Fixation/loss of alleles; reduces diversity (bottleneck).

Section C – Short Answer Questions (3 marks × 7 = 21 marks)

Harmonic; visuals symbiotic.

Q27. Calculate magnification for convex mirror u=–20 cm, v=+10 cm. Nature of image.
Answer: m = –v/u = –(10)/(–20) = +0.5 (virtual, erect, diminished).
[Diagram: Object in front; rays diverge, virtual image half size behind mirror.] Nature: Used in rear-view for wide field.
Step-wise: Positive m = erect/virtual. Marking: 1 calc, 1 diagram, 1 nature.

Q28. Explain ATP synthesis in mitochondria (chemiosmosis). Diagram ETS.
Answer: [Diagram: Inner membrane cristae; ETC complexes I–IV, H⁺ pumped to intermembrane, ATP synthase channel.]
Chemiosmosis: Proton gradient (H⁺ matrix to intermembrane) drives ATP synthase rotation; ADP + Pi → ATP. Yield: 3 ATP/NADH.

Q29. Draw labelled diagram of female reproductive system: ovary, fallopian tube, uterus, cervix.
Answer: [Diagram: Ovary (egg), Fallopian (fertilisation site), Uterus (implantation), Cervix (to vagina).]
Functions: Ovary – ova/hormones; tube – transport.

Q30. Cells 2 V, 2 V in parallel, r=1 Ω each, external R=4 Ω. Find current.
Answer: Parallel: E=2 V, r_eq=0.5 Ω; I = E/(r+R) = 2/(0.5+4) = 2/4.5 ≈ 0.444 A.
Step-wise: Parallel emf same, r parallel (1/ r =1/1 +1/1=2 →0.5 Ω).

Q31. What is double fertilisation? Significance in angiosperms.
Answer: One sperm + egg → zygote (2n embryo); second + central cell → endosperm (3n). Significance: Nourishment for seed; ensures survival.

Q32. Define isomerism. Draw two isomers of butane.
Answer: Same formula, different structure. n-Butane: CH₃–CH₂–CH₂–CH₃; Iso-butane: (CH₃)₂CH–CH₃.
[Structures drawn linearly/ branched.]

Q33. Explain water pollution sources. Effects on aquatic life.
Answer: Sources: Industrial effluents, sewage, agricultural runoff (eutrophication). Effects: Oxygen depletion (fish kill), toxins bioaccumulate, pH change (acid rain).

Section D – Long Answer Questions (5 marks × 3 = 15 marks)

Sublime; scaffold with thesis/antithesis/synthesis.

Q34. (a) Derive formula for force on current-carrying conductor in magnetic field.
(b) Conductor 0.5 m, I=10 A, B=0.2 T perpendicular. Find F.
(c) Diagram for motional emf in rod.
Answer: (a) Derivation: Lorentz force F = q(v × B); for wire, q=It, v=drift, but macro F = I L B sinθ (vector cross product).
(b) F = 10 × 0.5 × 0.2 × sin90° = 1 N.
[Diagram: Rod moving in B-field, induced emf = B l v; motional across ends.]
Step-wise: Right-angle for max. Marking: 2 derivation, 1.5 calc, 1.5 diagram.

Q35. Detail human digestive system glands and enzymes. Table of action sites.
Answer: Glands: Salivary (amylase – starch to maltose, mouth pH7), Gastric (pepsin – proteins to peptides, stomach pH2), Liver (bile – emulsifies fats, duodenum), Pancreas (trypsin/lipase/amylase, neutral pH).

Site	Gland/Enzyme	Substrate	Product
Mouth	Salivary amylase	Starch	Maltose
Stomach	Pepsin	Proteins	Peptides
Duodenum	Pancreatic lipase	Fats	Fatty acids
Absorption: Villi in ileum. Peristalsis aids.

Q36. (Choice: (a) or (b))
(a) Explain Lamarckism vs Darwinism with examples. Evidence for Darwin.**
Answer: Lamarck: Acquired traits inherited (e.g., giraffe neck stretch – discredited). Darwin: Natural selection (e.g., peppered moth – dark survived industrial pollution). Evidence: Fossil record, antibiotic resistance in bacteria, finch beaks variation.

Section E – Case/Source-Based Questions (4 marks × 3 = 12 marks)

Passage-probed; corroborate with inference.

Case 1 – Acids/Bases (Ryan International 2025)
Passage: pH scale 0–14; strong acid HCl pH1, weak CH₃COOH pH3 same conc.
(i) Why pH difference? Weak partial dissociation [H⁺]<0.001 M.
(ii) Reaction: HCl + NaOH → NaCl + H₂O (neutralisation).
(iii) Use of weak base: Antacid (Mg(OH)₂ for acidity).
(iv) Universal indicator colours: Red acid, green neutral, blue base.

Case 2 – Light (Summer Fields 2025)
Passage: Prism dispersion; violet bends most (short λ=400 nm), red least (700 nm).
(i) Reason: n higher for shorter λ (speed v = c/n lower).
(ii) Rainbow formation: TIR in raindrops + dispersion.
(iii) Spectrum sequence: VIBGYOR.
(iv) Diagram: Prism ray splitting.

Case 3 – Control/Coordination (Birla High 2025)
Passage: Plant auxin causes cell elongation; phototropism – more auxin shaded side.
(i) Mechanism: Auxin transport asymmetric.
(ii) Example: Darwins’ grass coleoptile experiment.
(iii) Other hormone: Gibberellin (stem growth).
(iv) Animal parallel: Insulin feedback loop.

Practical-Based Questions (Internal Choice – 3 + 3 = 6 marks)

Q37. Omni-Blueprint: To determine focal length of convex lens using u-v method.
Aim: f = ? Apparatus: Lens, screen, object (candle), metre scale. Procedure: (1) Place object at varying u (20–50 cm). (2) Adjust screen for sharp v. (3) Repeat 5 times. Table: u(cm) | v(cm) | 1/u | 1/v | u v. Graph: 1/u vs 1/v; intercept 1/f. Observation: Straight line, f≈15 cm. Conclusion: Verified formula. Precautions: Parallax-free. [Setup Diagram: Object-lens-screen; graph linear.]

Q38. Omni-Blueprint: To study pH change during titration of strong acid-base.
Aim: Neutralisation curve. Procedure: (1) 10 mL 0.1 M HCl in conical, phenolphthalein. (2) Titrate with 0.1 M NaOH from burette, note colour at equivalence. (3) Plot pH vs volume NaOH. Observation: Colourless to pink at 10 mL (pH7). Graph: S-curve, steep at 7. Conclusion: 1:1 ratio. Precautions: Rinse burette. [Graph: X-volume, Y-pH; inflection at equivalence.]

Transcendent Exam Dominion Blueprint (Ascend to 100/80 Zenith)

1. Cosmic Prep: 50% NCERT mastery (line-by-line), 25% exemplars (tricky variants), 15% mocks (weekly 3), 10% revisions (flashcards formulas).
2. Zen Exam Orbit: Pre-exam: 10 min visualization (ace-ing paper); During: Section A blitz (12 min), B/C fusion (45 min), D/E zenith (50 min), 13 min polish.
3. Scripture Art: Theorems bold; points numbered; diagrams shaded (cross-hatch organs).
4. Quantum Scoring: 3-mark: 1 intro, 1 body, 1 concl; 5-mark: 5 gems (e.g., 5 steps).
5. Nebula Shields: Electricity: “Series I same, V add”; Heredity: “Punnett rows=columns”.
6. Case Cosmos: Passage as North Star – align answers thereto.
7. Practical Pantheon: 8 rituals (4P, 4C); viva retorts: “Why alcohol in saponification? Solvent.”
8. Psyche Singularity: Affirm: “I am the equation solved”; stuck? Pivot – universe expands.
9. Post-Nova: Dissect score (error autopsy); trajectory: +5 marks/mock.
10. Apex Arsenal: MTG fingers for speed; Khan Academy visuals; peer mocks for edge.