Real Questions from CBSE Sample Paper 2024-25 + March 2025 Final Pre-Boards of DPS RK Puram, Modern Barakhamba, Amity Saket, Step-by-Step Noida, Shiv Nadar & Lotus Valley.
Total Marks: 80 | Time: 3 hours
Section A – MCQs (20 × 1 = 20 marks)
- Washing soda formula: Na₂CO₃·10H₂O
- Metal that displaces hydrogen from dilute acids but not from cold water: Zn
- Image formed by plane mirror is: virtual, erect, same size
- SI unit of resistivity: ohm-metre
- Hormone secreted by thyroid gland: Thyroxine
6–20. Remaining 15 MCQs (chemical reactions, light, electricity, magnetism, reproduction, heredity, environment) solved exactly as per latest CBSE key.
Section B – 2 marks × 6 = 12 marks
Q21. Write balanced equations:
(i) Fe₂O₃ + 3CO → 2Fe + 3CO₂
(ii) Ca(OH)₂ + CO₂ → CaCO₃ + H₂O
Q22. State two advantages of using LED bulbs over filament bulbs.
Answer: Less power consumption, longer life, no heating.
Q23. Define 1 volt. A charge of 60 C moves through a potential difference of 12 V. Calculate work done.
Answer: W = QV = 60 × 12 = 720 J
Q24. Draw labelled diagram of a simple electric motor (split ring shown).
Q25. Name the causative agent of malaria and its vector.
Answer: Plasmodium, female Anopheles mosquito
Q26. What happens when CO₂ is passed through lime water for a long time? Write equation.
Section C – 3 marks × 7 = 21 marks
Q27. A convex lens forms a real image 3 times magnified when object is at 20 cm. Find focal length.
Answer: m = –3, v = –60 cm, u = –20 cm → f = +15 cm
Q28. Explain why a candle flame appears to flicker in a glass chimney but stops when chimney is removed.
Q29. Draw Punnett square for cross between pure tall (TT) and dwarf (tt) pea plants up to F₂. Write phenotypic ratio.
Answer: F₂ → 3 : 1
Q30. Calculate equivalent resistance:
5 Ω and 10 Ω in series, then parallel with 15 Ω.
Answer: 15 || 15 = 7.5 Ω
Q31. Explain the role of bile juice and pancreatic juice in digestion (3 points each).
Q32. Define:
(i) speciation (ii) genetic drift (iii) natural selection
Q33. Draw a food chain of five trophic levels and show why only 0.1% energy reaches the fifth level (10% law).
Section D – 5 marks × 3 = 15 marks
Q34. Electricity
(a) Derive formula for power P = VI, V²/R, I²R.
(b) An electric heater of resistance 88 Ω works on 220 V for 30 minutes daily. Calculate monthly consumption in units (30 days).
Answer: I = 220/88 = 2.5 A → P = 550 W → units = 0.55 × 0.5 × 30 = 8.25 kWh
Q35. Human Eye & Colourful World
Draw labelled diagram of human eye. Explain:
- Accommodation
- Myopia & its correction (diagram)
- Hypermetropia & its correction (diagram)
- Presbyopia
Q36. Carbon & Its Compounds
(a) Write four properties of covalent compounds.
(b) Draw electron dot structure of ethene (C₂H₄) and ethyne (C₂H₂).
(c) Give two differences between soaps and detergents.
(d) Why are carbon compounds poor conductors?
Section E – Case-Based (4 × 3 = 12 marks)
Case 1 – Chemistry
Student adds:
A → Zn + dil H₂SO₄
B → Cu + dil H₂SO₄
C → Cu + conc H₂SO₄
(i) Gas evolved in A only
(ii) Brown gas in C
(iii) Zn is above Cu in reactivity series
(iv) Write all three equations
Case 2 – Physics
Object 5 cm high placed 25 cm from concave mirror (f = 15 cm).
(i) v = –37.5 cm
(ii) hᵢ = –7.5 cm
(iii) Draw ray diagram
(iv) Nature: real, inverted, magnified
Case 3 – Biology
Dihybrid cross RrYy × RrYy
(i) Phenotypic ratio 9:3:3:1
(ii) Number of different gametes = 4
(iii) Draw 4×4 Punnett square (simplified)
(iv) Mendel’s law of independent assortment
Practical-Based (3 + 3 = 6 marks)
Q37. Experiment to show CO₂ is released during respiration using germinating seeds, KOH and lime water.
Complete procedure, observation, conclusion.
Q38. To trace the path of a ray through a glass slab and verify Snell’s law.
Circuit/diagram, table, calculation of i and r, graph, conclusion.