CBSE Class 10 Science Board Exam Paper Set 10

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.

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

Monadic; ensphere selection.

1. The formula for dead burnt plaster is
   (a) CaSO₄·2H₂O
   (b) CaSO₄·½H₂O
   (c) CaSO₄
   (d) CaO
   Answer: (c) – Anhydrous CaSO₄; over-heated Plaster of Paris.
2. Which is a redox reaction?
   (a) Precipitation
   (b) 2KClO₃ → 2KCl + 3O₂
   (c) NaCl + AgNO₃ → AgCl + NaNO₃
   (d) CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂
   Answer: (b) – Cl⁺⁵ to –1 (reduction), O⁻² to 0 (oxidation).
3. For concave lens, focal length sign is
   (a) Positive
   (b) Negative
   (c) Zero
   (d) Infinite
   Answer: (b) – Diverging; virtual focus.
4. The heat produced in a wire is proportional to
   (a) I
   (b) V
   (c) I²
   (d) R
   Answer: (c) – Joule’s law H = I²Rt.
5. The transport tissue for food in plants is
   (a) Xylem
   (b) Phloem
   (c) Epidermis
   (d) Cambium
   Answer: (b) – Sieve tubes conduct sucrose downward.

6–20. Omniversal MCQs with Answers, Planck Reasoning & Kabbalistic Mnemonic:

6. Universal solvent: Water – High dielectric constant, H-bonding. Mnemonic: “Water = World’s Embrace.”
7. Atomic number 11 element: Sodium – Group 1, period 3; soft, reactive.
8. Enlarged image by convex lens: Object between F and lens – Virtual, erect.
9. Fuse wire material: Low melting point alloy – Tin-lead; safety cutoff.
10. Hormone for sleep-wake cycle: Melatonin – Pineal gland; dark-triggered.
11. Polygenic inheritance: Skin colour – Multiple genes, continuous variation.
12. Kyoto Protocol target: Reduce GHGs – Binding emission cuts for Annex I countries.
13. Biochemical evidence: DNA homology – Chimp-human 98.8% similarity.
14. Addition reaction in: Alkenes – H₂ adds across double bond (catalyst Ni).
15. Mirage cause: TIR in atmosphere – Density gradient like slab.
16. Hysteresis in: Soft iron core – Quick magnetisation/demagnetisation for transformers.
17. Tissue culture method: Micropropagation – Clones from explants.
18. Speciation type: Allopatric – Geographic isolation leads to divergence.
19. BOD measures: Oxygen demand by microbes – High = polluted water.
20. d-block elements: Transition metals – Variable valency, coloured compounds.

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

Ephemeral; 20–40 words; quintessence.

Q21. Write balanced equation for reaction of zinc with NaOH. Type?
Answer: Zn + 2NaOH → Na₂ZnO₂ + H₂↑ (Amphoteric; Zn acts as base).
Marking: 1 equation, 1 type. Hack: Note amphoteric for nuance.

Q22. Why is diamond hard but graphite soft?
Answer: Diamond: 3D tetrahedral network (strong C-C); Graphite: Layered hexagonal (weak van der Waals between planes, slippery).
Reasoning: Allotropes; same element, different bonding.

Q23. A 440 V, 2 kW heater runs 3 hours. Calculate cost at ₹4/unit.
Answer: Units = 2 × 3 = 6 kWh; Cost = 6 × 4 = ₹24.
Step-wise: P in kW direct; ×t = units.

Q24. Draw labelled diagram of an electric bell.
Answer: [Diagram: Electromagnet (coil on U-iron), armature (hammer), gong, spring, contact screw.]
Marking: 1 diagram, 1 labels. Pro Tip: Show circuit loop.

Q25. Name hormone for emergency response. Effect on heart rate.
Answer: Adrenaline (epinephrine); increases heart rate (fight/flight via sympathetic).

Q26. What is mutation? Harmful example.
Answer: Sudden gene change. Harmful: Sickle cell allele (malaria resistance but anaemia).

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

Symphonic; icons integral.

Q27. Object 4 cm at u=–25 cm from convex lens f=15 cm. Find v, m, draw rays.
Answer: 1/v = 1/15 + 1/(–25) = (5–3)/75 = 2/75 → v=37.5 cm; m= –37.5/(–25)=1.5 (real, inverted, magnified).
[Diagram: Object beyond 2F; rays – parallel to F, through O, through 2F to parallel; image beyond 2F.]
Step-wise: Positive v real. Marking: 1 calc, 1 diagram, 1 m/nature.

Q28. Explain role of RNA in protein synthesis. Types and functions.
Answer: RNA transcribes DNA, translates to protein. Types: mRNA (messenger – code from nucleus), tRNA (transfer – amino acid carrier), rRNA (ribosomal – assembly). Process: Transcription (DNA→mRNA), Translation (codon-anticodon).

Q29. Draw labelled diagram of neuron: dendrite, axon, synapse.
Answer: [Diagram: Dendrites (branches), cell body (nucleus), axon (long, myelinated), synaptic knob to next dendrite.]
Functions: Impulse reception, conduction, transmission (neurotransmitter).

Q30. Resistors 6 Ω, 6 Ω parallel, then series with 4 Ω. R_eq for 12 V?
Answer: Parallel 6||6=3 Ω; series 3+4=7 Ω; I=12/7 ≈1.71 A.
Step-wise: Parallel R/2=3; add series.

Q31. What is syngamy? Difference from triple fusion.
Answer: Syngamy: Male gamete + egg → zygote (diploid). Triple fusion: Male + 2 polar nuclei → endosperm (triploid). Both in double fertilisation; syngamy for embryo, fusion for nutrition.

Q32. Define allotropy. Examples for phosphorus.
Answer: Different physical forms same element. Phosphorus: White (toxic, waxy, P₄), Red (stable, amorphous), Black (graphite-like, semiconductor).

Q33. Explain thermal pollution. Sources and effects.
Answer: Rise in water temp from industries/power plants. Sources: Cooling water discharge. Effects: Reduced O₂ solubility, kills fish/eggs, alters ecosystem (e.g., algae bloom).

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

Apotheotic; triptych structure.

Q34. (a) Derive expression for refractive index n = c/v.
(b) Light in glass n=1.5, speed? (c=3×10⁸ m/s)
(c) Diagram Snell’s law.
Answer: (a) Derivation: n = real/optical path; v = fλ, c = fλ_vac → n = c/v (speed ratio).
(b) v = c/n = 3×10⁸ /1.5 = 2×10⁸ m/s.
[Diagram: Ray air-glass; i, r, normal; sin i / sin r = n.]
Step-wise: Vacuum reference. Marking: 2 derivation, 1.5 calc, 1.5 diagram.

Q35. Detail structure of chloroplast. Role in light/dark reactions.
Answer: [Diagram: Double membrane, stroma (matrix), thylakoids (stacked grana), chlorophyll in PS I/II.]
Structure: Site of photosynthesis. Light: Thylakoid (photolysis H₂O, ATP/NADPH via ETC). Dark: Stroma (Calvin cycle, CO₂ fixation to glucose). Equation: 6CO₂ + 12H₂O → C₆H₁₂O₆ + 6O₂ + 6H₂O.

Q36. (Choice: (a) or (b))
(a) Explain incomplete dominance with snapdragon flower cross. Punnett F₂.**
Answer: Red (RR) × white (rr) = pink (Rr) F₁; F₂ Rr × Rr → 1 RR red: 2 Rr pink: 1 rr white (1:2:1). No dominance; blend phenotype. [Punnett square: Rows R/r, columns R/r; colours filled.]

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

Passage-entwined; syllogism.

Case 1 – Metals (Tagore 2025)
Passage: Reactivity: K>Ca>Mg>Al>Zn>Fe>Sn>Cu>Ag>Au; displacement based on position.
(i) Why Zn displaces Cu? Zn above Cu.
(ii) Equation Zn + CuSO₄. (Zn + CuSO₄ → ZnSO₄ + Cu)
(iii) Non-reactive metal: Au (noble).
(iv) Corrosion prevention: Galvanisation (Zn coating).

Case 2 – Electricity (Delhi Public 2025)
Passage: Series: I same, V add; Parallel: V same, I add. Bulbs 40W, 60W parallel 220V.
(i) Total P = 40+60=100 W.
(ii) I total = P/V = 100/220 ≈0.45 A.
(iii) I through 40W = 40/220 ≈0.18 A.
(iv) Why parallel? Independent operation.

Case 3 – Reproduction (Modern Vasant 2025)
Passage: Contraceptives: Barrier (condom), hormonal (pills), IUD (Cu-T), surgical (vasectomy).
(i) Barrier prevents: Sperm entry.
(ii) Hormonal suppress: Ovulation.
(iii) IUD effect: Toxic to sperm, alters uterus.
(iv) Surgical: Permanent sterilisation.

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

Q37. Multiverse Blueprint: To find pH of solutions using pH paper/universal indicator.
Aim: Determine acidity/basicity. Procedure: (1) Dip pH paper in solution. (2) Match colour to chart. (3) Repeat for 5 solutions. Observation: HCl red (pH1), NaOH violet (pH14), water green (7). Conclusion: pH scale logarithmic. Precautions: Fresh paper. [Colour chart diagram.]

Q38. Multiverse Blueprint: To study refraction through glass prism.
Aim: Measure deviation. Procedure: (1) Place prism, incident ray at i=40°. (2) Find min deviation D. (3) n = sin((A+D)/2)/sin(A/2), A=60°. Table: i1=40, e1=40, D=30. Calc n≈1.5. Conclusion: Dispersion evident. [Prism diagram with angles.]

Apotheosis Exam Singularity Blueprint (Transcend to 100/80 Nirvana)

1. Eternal Prep: 60% NCERT apotheosis (verse memorisation), 20% Olympiad tangents, 10% AI mocks, 10% meditation (mind palace for formulas).
2. Nirvanic Exam Vortex: Pre: Quantum breathing; During: A singularity (10 min), B/C nexus (40 min), D/E abyss (50 min), 20 min transcendence (review).
3. Script Apotheosis: Hieroglyphs for keys; pentads for 5-marks; aureate prose.
4. Godhead Scoring: 3-mark trinity (fact, explain, example); 5-mark pentacle (5 facets).
5. Void Shields: Chemistry: “Catalysts unchanged”; Physics: “Waves superpose”.
6. Case Nirvana: Passage as koan – intuit essence.
7. Practical Godhead: 10 sacraments (5P, 5C); retorts: “Why boil leaf? Chloroplast isolation.”
8. Psyche Apotheosis: Mantra: “I am the wavefunction collapsed”; impasse? Surrender to flow.
9. Post-Apocalypse: Nirvana audit (karma of errors); ascension: +10 marks/iteration.
10. Singularity Sanctum: Feynman lectures echoes; VR labs for immersion; guru mocks.