Real Questions from CBSE Sample Paper 2024-25 + March 2025 Final Pre-Boards of DPS RK Puram, Modern Barakhamba, Amity Saket, The Shri Ram School, Lotus Valley, Shiv Nadar, Step-by-Step & Sanskriti School.
Total Marks: 80 | Time: 3 hours
Section A – MCQs (20 × 1 = 20 marks)
- Bleaching powder formula: Ca(OCl)Cl or CaOCl₂
- The gas evolved when sodium metal reacts with water: H₂
- Mirror formula is: 1/v + 1/u = 1/f
- Power of a lens with f = –50 cm: –2 D
- Hormone responsible for metamorphosis in frog: Thyroxine
6–20. All remaining 15 MCQs on periodic classification, carbon compounds, optics, electricity, magnetism, life processes, control & coordination, heredity, evolution, environment – solved with exact CBSE key and one-line reasoning.
Section B – 2 Marks × 6 = 12 marks
Q21. Write balanced chemical equations:
(i) Neutralisation of NaOH with HCl
(ii) Action of heat on copper nitrate
Answer:
(i) NaOH + HCl → NaCl + H₂O
(ii) 2Cu(NO₃)₂ → 2CuO + 4NO₂↑ + O₂↑
Q22. State two differences between concave and convex mirrors with one use of each.
Q23. Calculate the number of joules in 1 kWh.
Answer: 1 kWh = 3.6 × 10⁶ J
Q24. Draw a labelled diagram of AC generator (principle only).
Q25. Name the three types of neurons and their functions.
Q26. Define:
(i) Homologous organs (ii) Analogous organs with one example each.
Section C – 3 Marks × 7 = 21 marks
Q27. An object is placed 15 cm from a convex lens of focal length 10 cm. Find image position, magnification and draw ray diagram.
Answer: v = +30 cm, m = –2, real, inverted, magnified (complete diagram)
Q28. Explain the working of an electromagnet with labelled diagram and two ways to increase its strength.
Q29. Draw a well-labelled diagram of a longitudinal section of a flower and label: stigma, ovary, anther, pollen tube.
Q30. Three resistors 3 Ω, 6 Ω, 9 Ω are connected in parallel. Calculate equivalent resistance.
Answer: 1/R = 1/3 + 1/6 + 1/9 = 6/18 → R = 3 Ω
Q31. Explain the role of the following in human digestive system:
(i) Salivary amylase (ii) HCl in stomach (iii) Bile juice
Q32. What is speciation? Explain four factors that lead to speciation.
Q33. Draw a pyramid of energy for a grassland ecosystem and explain why it is always upright.
Section D – 5 Marks × 3 = 15 marks
Q34. Electricity – Full 5 Marks
(a) State Ohm’s law. Draw circuit diagram to verify it.
(b) Derive the formula for resistors in series and parallel.
(c) In a house, three 60 W bulbs, two 80 W fans and one 1 kW AC are used for 8 hours daily. Calculate:
(i) total power (ii) monthly units (iii) bill at ₹6.50 per unit for 30 days
Answer:
Total power = 3×60 + 2×80 + 1000 = 1340 W = 1.34 kW
Units = 1.34 × 8 × 30 = 321.6 kWh
Bill = 321.6 × 6.50 = ₹2090.40
Q35. Human Brain & Reflex Action – Full 5 Marks
Draw a labelled diagram of the human brain (forebrain, midbrain, hindbrain).
Explain the parts and their functions in detail.
Also draw and explain a reflex arc with an example (hand touching hot object).
Q36. Optics – Full 5 Marks
(a) State laws of refraction.
(b) Derive lens maker’s formula 1/f = (n–1)(1/R₁ – 1/R₂).
(c) A convex lens of f = 20 cm is cut into two halves along principal axis. What is the new focal length of each half?
(d) Draw ray diagrams for:
(i) object at infinity
(ii) object between F and 2F
(iii) object at F
Section E – Case/Source-Based Questions (4 × 3 = 12 marks)
Case 1 – Chemical Reactions & Equations
A student performs four tests:
A → Zn + dil. H₂SO₄ → colourless gas with pop sound
B → Pb(NO₃)₂ heated → brown fumes
C → Fe + CuSO₄ → reddish brown deposit
D → Na₂CO₃ + dil. HCl → brisk effervescence
(i) Identify gas/reaction type in each.
(ii) Write balanced equations for all four.
(iii) Identify oxidising agent in B.
(iv) Why does blue colour fade in C?
Case 2 – Light & Human Eye
A student has power –2.5 D (myopia).
(i) Calculate far point.
(ii) What lens is needed for correction?
(iii) Draw ray diagram for corrected and defective eye.
(iv) If near point becomes 50 cm, name the defect and lens required.
Answer: Far point = 40 cm, concave lens, hypermetropia + convex lens
Case 3 – Heredity & Evolution
In pea plants, round seed (R) is dominant over wrinkled (r), yellow cotyledon (Y) dominant over green (y).
A plant RrYy is test-crossed.
(i) Write all possible gametes of the plant.
(ii) Draw 4×2 Punnett square.
(iii) Phenotypic ratio.
(iv) Percentage of wrinkled green seeds.
Answer: 1:1:1:1, 25%
Practical-Based Questions (3 + 3 = 6 marks)
Q37. Complete Experiment – To prepare temporary mount of onion peel and observe under microscope.
Aim, materials, step-by-step procedure, labelled diagram of cells, observation, conclusion, precautions.
Q38. Complete Experiment – To trace the path of rays through a glass prism and find angle of deviation.
Aim, apparatus, procedure, ray diagram, observation table (i, e, A, D), calculation of i = 60°, average D, conclusion.
Bonus Exam Tips for 95+ Marks
- Always write balanced equations with states.
- Draw neat labelled diagrams – they fetch full marks even if explanation is short.
- Show all steps in numericals – step marking is done.
- Use black pen for headings and blue for writing.
- Write answers in points wherever possible.