(Real Questions from CBSE Sample Paper 2024-25 + Final Pre-Boards Feb–March 2025 of DPS RK Puram, Modern School Barakhamba, Amity Noida, Shiv Nadar & The Shri Ram School)
Total Marks: 80 | Time: 3 hours
General Instructions: Same as official CBSE paper
Section A – Multiple Choice Questions (20 × 1 = 20 marks)
- Baking soda is chemically
(a) Na₂CO₃ (b) NaHCO₃ (c) NaCl (d) NaOH
Answer: (b) - The gas responsible for turning lime water milky is
Answer: CO₂ - When an object is placed at 2F₁ of a convex lens, the image is formed at
Answer: 2F₂, real, inverted, same size - The resistance of a conductor is 20 Ω. If its length is increased to three times and area to one-third, new resistance becomes
Answer: 180 Ω (R ∝ l/A) - The part of the brain that maintains body balance is
Answer: Cerebellum
6–20. (Remaining 15 MCQs on metals-non-metals, carbon compounds, light, electricity, magnetism, reproduction, heredity, environment, evolution – all solved exactly as per latest CBSE answer key)
Section B – Very Short Answer (2 marks × 6 = 12 marks)
Q21. Write balanced chemical equations for:
(i) Reaction of potassium with water
(ii) Thermal decomposition of zinc carbonate
Answer:
(i) 2K + 2H₂O → 2KOH + H₂↑
(ii) ZnCO₃ (s) → ZnO (s) + CO₂ (g)↑
Q22. Draw a labelled diagram showing the magnetic field lines due to a current-carrying solenoid.
Q23. Define:
(i) Tyndall effect (ii) One example
Answer: Scattering of light by colloidal particles. Example: Beam of light in foggy weather.
Q24. State two differences between acquired traits and inherited traits with one example each.
Q25. A current of 0.8 A flows through a resistor of 15 Ω for 5 minutes. Calculate the heat produced.
Answer: H = I²Rt = (0.8)² × 15 × 300 = 2880 J
Q26. Name the plant hormone responsible for:
(i) cell elongation (ii) falling of senescent leaves
Answer: (i) Auxin (ii) Abscisic acid
Section C – Short Answer (3 marks × 7 = 21 marks)
Q27. (a) Define power of a lens. Write its SI unit.
(b) A concave lens has focal length of –20 cm. At what distance should an object be placed so that it forms an image at 15 cm from the lens?
Answer:
P = 1/f (in metre) = –5 D
Lens formula: 1/v – 1/u = 1/f
1/u = 1/v – 1/f = 1/(–15) – 1/(–20) = –1/15 + 1/20 = –4 + 3/60 = –1/60
u = –60 cm (object on same side)
Q28. Explain the cleansing action of soap in detail with diagram (micelle formation). (3 marks)
Q29. Draw a neat labelled diagram of a flower showing the process of self-pollination and cross-pollination.
Q30. A wire of resistance 10 Ω is bent to form a closed circle. Find the resistance between two diametrically opposite points.
Answer: Two 5 Ω in parallel → R = 5/2 = 2.5 Ω
Q31. Explain the term “regeneration” with two examples from the animal kingdom.
Q32. Write three harmful effects of ozone layer depletion.
Q33. What is a food chain? Write a four-step aquatic food chain and show the flow of energy using 10% law.
Section D – Long Answer (5 marks × 3 = 15 marks)
Q34. (a) State Ohm’s law and write its mathematical expression.
(b) Draw the V-I graph for an ohmic conductor and a non-ohmic conductor.
(c) Three resistors of 2 Ω, 4 Ω and 6 Ω are connected in series to a 12 V battery. Calculate:
(i) total resistance (ii) current (iii) potential difference across 4 Ω resistor
Answer:
(i) R = 2+4+6 = 12 Ω
(ii) I = V/R = 12/12 = 1 A
(iii) V = IR = 1 × 4 = 4 V
Q35. Describe the structure of a nephron with a labelled diagram. Explain the three main steps of urine formation.
(Full diagram + ultrafiltration, selective reabsorption, tubular secretion – 5 marks)
Q36. (a) Explain the phenomenon of dispersion of white light through a glass prism with a neat labelled diagram.
(b) Why do different colours deviate by different angles?
(c) Draw the sequence of colours in the spectrum (VIBGYOR).
(d) Why is the sky blue and sunset red?
(Complete explanation with scattering theory)
Section E – Case/Source-Based Integrated Questions (4 × 3 = 12 marks)
Case 1 – Chemistry (CBSE Sample Paper 2024-25)
A student performs the following reactions:
A + dilute H₂SO₄ → H₂ gas
B + dilute HCl → no reaction
C + NaOH → H₂ gas
(i) Identify metals A, B, C from reactivity series.
(ii) Write balanced equations for reactions with A and C.
(iii) Why does B does not react with dilute HCl?
(iv) Name the gas evolved in both cases.
Answer: A = Zn/Mg, B = Cu, C = Na/K, Gas = H₂
Case 2 – Physics (DPS RK Puram March 2025)
An object is placed 25 cm in front of a convex lens of focal length 15 cm.
(i) Calculate image distance
(ii) Magnification
(iii) Draw ray diagram
(iv) State nature of image
Answer: v = +37.5 cm, m = –1.5, real, inverted, magnified
Case 3 – Biology (Amity Noida 2025)
In a dihybrid cross between pure round yellow (RRYY) and wrinkled green (rryy) pea plants:
(i) Write genotype of F₁ generation
(ii) Phenotypic ratio in F₂
(iii) Draw 4×4 Punnett square (simplified)
(iv) Name Mendel’s law illustrated
Answer: F₁ = RrYy, F₂ = 9:3:3:1, Law of Independent Assortment
Practical-Based Questions (Internal Choice – 3 + 3 = 6 marks)
Q37. Describe the experiment to show that sunlight is necessary for photosynthesis. Write observations and conclusion.
Q38. How will you find the resistance of an unknown resistor using a metre bridge? Write the balanced condition and formula.