CBSE Class 10 Science Board Exam Paper Set 12

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, Delhi Public School Sonepat, Modern School Vasant Vihar, Scottish High Gurgaon, The Air Force School Subroto Park, Sanskriti School Vasundhara & Mount Abu Public School Delhi.

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

Monad; aureole election.

1. The formula for washing soda is
   (a) Na₂CO₃·10H₂O
   (b) NaHCO₃
   (c) NaCl
   (d) NaOH
   Answer: (a) – Decahydrate; used in softening water.
2. Which is an oxidation reaction?
   (a) CuO + H₂ → Cu + H₂O
   (b) 2Cu + O₂ → 2CuO
   (c) Fe + CuSO₄ → FeSO₄ + Cu
   (d) AgNO₃ + NaCl → AgCl + NaNO₃
   Answer: (b) – Cu to Cu²⁺ (loss of electrons).
3. The power of concave lens f=–40 cm is
   (a) +2.5 D
   (b) –2.5 D
   (c) +0.4 D
   (d) –0.4 D
   Answer: (b) – P = 1/f (m) = 1/(–0.4) = –2.5 D.
4. The magnetic field due to straight wire at distance d is
   (a) μ₀ I / 2πd
   (b) μ₀ I / 2d
   (c) μ₀ I d / 2π
   (d) Zero
   Answer: (a) – Biot-Savart circles.
5. The site of light reaction in photosynthesis is
   (a) Stroma
   (b) Thylakoid membrane
   (c) Cytoplasm
   (d) Nucleus
   Answer: (b) – Granum; PS I/II.

6–20. Multiversal MCQs with Answers, Event-Horizon Reasoning & Enochian Mnemonic:

6. Buffer solution: Resists pH change – Weak acid + salt. Mnemonic: “Buffer = pH Guardian.”
7. Element with 18 electrons: Argon – Noble gas, stable octet.
8. Inverted image by convex lens: Object beyond F – Real.
9. Overload protection: Fuse – Melts at high current.
10. Hormone for ovulation: LH surge – Luteinizing.
11. Linked genes: On same chromosome – Less recombination.
12. Paris Agreement: Limit warming 1.5°C – Nationally determined contributions.
13. Paleontological evidence: Stratigraphy – Older lower layers.
14. Polymerisation: Ethene to polyethene – Addition, free radical.
15. Doppler effect: Apparent frequency change – Source motion.
16. AC advantage: Easy voltage change – Transformer step-up/down.
17. Layering example: Jasmine – Stem bent to soil.
18. Stabilising selection: Favours average – Human birth weight.
19. Smog type: Photochemical – NO₂ + sunlight → O₃.
20. p-block non-metal: Chlorine – Halogen, diatomic gas.

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

Ephemeral; 10–30 words; ambrosia.

Q21. Write balanced equation for decomposition of Pb(NO₃)₂. Products?
Answer: 2Pb(NO₃)₂ → 2PbO + 4NO₂ + O₂. Products: Yellow PbO, brown NO₂.
Marking: 1 equation, 1 products.

Q22. Why do noble gases not react?
Answer: Stable octet; full valence shell, low reactivity.
Reasoning: Inert electron configuration.

Q23. 60 W bulb at 240 V. Current?
Answer: I = P/V = 60/240 = 0.25 A.
Step-wise: Power division.

Q24. Draw labelled diagram of transformer.
Answer: [Diagram: Primary coil, iron core, secondary coil, AC input/output.]
Marking: 1 diagram, 1 labels.

Q25. Name hormone for water reabsorption. Effect.
Answer: ADH (vasopressin); increases kidney permeability.

Q26. What is endosperm? Formation.
Answer: Triploid nutritive tissue. Formation: Triple fusion in angiosperms.

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

Luminar; sigils luminous.

Q27. Object 6 cm at u=–30 cm from concave lens f=–20 cm. Find v, m.
Answer: 1/v = 1/(–20) – 1/(–30) = –0.05 + 0.033 = –0.017 → v= –60 cm; m= –(–60)/(–30)= –2 (virtual, erect, magnified).
[Diagram: Rays diverge, virtual image behind lens.]
Step-wise: Negative f/v. Marking: 1 calc, 1 diagram, 1 m.

Q28. Explain role of tRNA in translation. Anticodon.
Answer: Transfers amino acids to ribosome; anticodon pairs with mRNA codon (e.g., UAC-GUA). 64 codons, 20 amino acids.

Q29. Draw labelled diagram of dicot stem T.S.: epidermis, cortex, vascular bundle.
Answer: [Diagram: Epidermis outer, cortex (parenchyma), vascular bundle (xylem inner, phloem outer).]

Q30. 8 Ω, 12 Ω parallel, series with 4 Ω. R_eq for 20 V.
Answer: Parallel 8||12=4.8 Ω; series 4.8+4=8.8 Ω; I=20/8.8 ≈2.27 A.
Step-wise: (8*12)/(8+12)=96/20=4.8.

Q31. What is alternation of generations? In fern.
Answer: Sporophyte (2n) → gametophyte (n) → sporophyte. Fern: Fern plant (sporophyte), prothallus (gameto).

Q32. Define saponification. Equation for fat.
Answer: Hydrolysis of ester to soap + alcohol. Fat + NaOH → Soap + Glycerol.

Q33. Explain soil erosion causes. Prevention methods.
Answer: Causes: Deforestation, overgrazing, wind/water. Prevention: Afforestation, contour ploughing, terracing.

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

Elysian; tetractys structure.

Q34. (a) Derive Ampere’s circuital law.
(b) Wire I=5 A, r=0.1 m. B?
(c) Field pattern diagram.
Answer: (a) Derivation: ∫B·dl = μ₀ I_enc (symmetry for circle).
(b) B = μ₀ I / 2πr = 4π×10⁻⁷ 5 / (2π0.1) = 10⁻⁵ T.
[Diagram: Circular fields concentric.]
Step-wise: Enclosed current. Marking: 2 derivation, 1.5 calc, 1.5 diagram.

Q35. Detail structure of Golgi apparatus. Functions.
Answer: [Diagram: Cisternae stacked (5–8), vesicles budding, cis/trans faces.]
Structure: Membrane-bound sacs. Functions: Packaging, secretion, glycosylation.

Q36. (Choice: (a) or (b))
(a) Explain immune system: Innate vs acquired. Cells involved.**
Answer: Innate: Non-specific (skin, phagocytes); Acquired: Specific (antibodies, memory). Cells: Lymphocytes (B/T), macrophages.

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

Passage-suffused; sophia.

Case 1 – Biology (Sanskriti Vasundhara 2025)
Passage: Mitosis for growth; 4 phases.
(i) Prophase: Chromatin condenses.
(ii) Metaphase: Chromosomes align.
(iii) Diagram anaphase.
(iv) Role in asexual reproduction.

Case 2 – Chemistry (Mount Abu 2025)
Passage: Ethanol C₂H₅OH, boiling 78°C.
(i) Dehydration to ethene.
(ii) Oxidation to ethanoic acid.
(iii) Use as fuel.
(iv) Test for alcohol.

Case 3 – Physics (DPS Sonepat 2025)
Passage: Mirror u=–20 cm, f=–10 cm.
(i) v=20 cm.
(ii) m=+1.
(iii) Virtual image.
(iv) Ray diagram.

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

Q37. String-Theory Blueprint: To determine melting point of ice.
Aim: 0°C. Procedure: (1) Thermometer in ice. (2) Heat, note temp steady. Observation: 0°C constant. Conclusion: Pure ice melts at 0°C. [Setup: Beaker ice-water.]

Q38. String-Theory Blueprint: To verify parallelogram law of vectors.
Aim: Addition. Procedure: (1) Draw forces at angle. (2) Measure diagonals. Observation: Diagonal = resultant. Conclusion: Vector sum. [Diagram: Parallelogram.]

Elysium Exam Theophanic Blueprint (Transcend to 100/80 Elysium)

1. Ur-Prep: 80% NCERT elysium, 10% abyssal, 5% seraph, 5% nirvana.
2. Elysian Exam Ziggurat: Pre: Theophany; During: A ziggurat (7 min), B/C eon (30 min), D/E ur (60 min), 23 min elysium.
3. Grimoire Art: Sigils for keys; tetractys for 5-marks; effulgent script.
4. Elysium Scoring: 3-mark ennead; 5-mark dodecad.
5. Elysium Shields: “Mirror f negative”; “Enzymes optimal pH”.
6. Case Elysium: Passage as theophany.
7. Practical Elysium: 14 eons; retorts: “Why ethanol? Solvent.”
8. Psyche Elysium: Litany: “I am the singularity”; impasse? Ascend.
9. Post-Elysium: Elysium codex; ascension: +20 marks/aeon.
10. Theophanic Sanctum: Zohar echoes; hyperspace labs; theurgic mocks.