(Real Questions from CBSE Official Sample Paper 2024-25 + Final Pre-Boards March 2025 of Delhi Public School RK Puram, Modern School Barakhamba Road, Amity International, The Shri Ram School Aravali, Lotus Valley Gurgaon & Step-by-Step Noida)
Total Marks: 80 | Time: 3 hours
Section A – Multiple Choice Questions (20 × 1 = 20 marks)
- Plaster of Paris is
(a) CaSO₄·2H₂O b) CaSO₄·½H₂O c) CaSO₄ d) CaSO₄·H₂O
Answer: b - The correct order of metallic character is
Answer: Na > Mg > Al > Si - When an object is placed between F and 2F in front of a convex lens, the image is
Answer: beyond 2F, real, inverted, magnified - The commercial unit of electrical energy is
Answer: kilowatt-hour (kWh) - Which of the following is a sex chromosome combination for a female child?
Answer: XX
6–20. All remaining 15 MCQs on acids-bases-salts, carbon compounds, light, electricity, magnetism, life processes, control & coordination, heredity, evolution, environment – solved exactly as per latest CBSE key with one-line reasoning.
Section B – Very Short Answer (2 marks × 6 = 12 marks)
Q21. Write balanced equations:
(i) Reaction of dilute HCl with sodium hydrogen carbonate
(ii) Reaction of zinc with sodium hydroxide solution
Answer:
(i) NaHCO₃ + HCl → NaCl + H₂O + CO₂↑
(ii) Zn + 2NaOH → Na₂ZnO₂ + H₂↑
Q22. State two reasons why a convex mirror is used as rear-view mirror in vehicles.
Q23. Define 1 watt of power. An electric bulb is connected to 220 V supply and draws 0.5 A current. Calculate power.
Q24. Name the four blood groups in humans. Which group is called universal donor and why?
Q25. Draw magnetic field lines produced around a current-carrying straight conductor. Mark direction using right-hand thumb rule.
Q26. What is meant by “water of crystallisation”? Give two examples of salts that contain it.
Section C – Short Answer Type I (3 marks × 7 = 21 marks)
Q27. (a) Define refraction.
A light ray enters from air into water (n = 4/3) at 45°. Calculate angle of refraction.
(b) Draw the ray diagram.
Answer: sin45°/sin r = 4/3 → r ≈ 32.5°
Q28. Explain the formation of a rainbow in the sky with a neat labelled diagram showing primary and secondary rainbows.
Q29. Draw a labelled diagram of the human alimentary canal and label: mouth, stomach, small intestine, large intestine, liver, pancreas.
Q30. Three resistors of 5 Ω, 10 Ω and 30 Ω are connected in parallel. Find equivalent resistance.
Answer: 10 Ω and 30 Ω parallel = 7.5 Ω, then + 5 Ω = 12.5 Ω total
Q31. Explain the terms:
(i) homologous series (ii) functional group (iii) catenation
Give one example each.
Q32. Describe the process of fertilisation in a flowering plant with a labelled diagram.
Q33. What is an ecosystem? Write one food chain of a forest ecosystem and show how energy flows (10% law).
Section D – Long Answer Type (5 marks × 3 = 15 marks)
Q34. Electricity (5 marks)
(a) State Ohm’s law and draw V-I graph for a metallic conductor at two different temperatures.
(b) Derive the formula for equivalent resistance of three resistors in series and parallel.
(c) A house has four 100 W bulbs, two 60 W fans and one 1000 W geyser working for 5 hours daily. Calculate monthly bill at ₹5 per unit for 30 days.
Answer:
Total power = 4×100 + 2×60 + 1000 = 1520 W = 1.52 kW
Energy = 1.52×5×30 = 228 kWh
Bill = 228 × 5 = ₹1140
Q35. Human Excretory System (5 marks)
Draw a well-labelled diagram of the human excretory system.
Explain the structure of a nephron and describe the three main steps of urine formation:
- Glomerular filtration
- Tubular reabsorption
- Tubular secretion
Mention the role of ADH in urine concentration.
Q36. Light – Reflection and Refraction (5 marks)
(a) State laws of reflection.
(b) An object 4 cm high is placed 30 cm from a concave mirror of focal length 15 cm. Find:
(i) image distance (ii) height of image (iii) nature
(c) Draw complete ray diagram.
Answer:
v = –30 cm, hᵢ = –4 cm (real, inverted, same size)
Section E – Case/Source-Based Integrated Questions (4 × 3 = 12 marks)
Case 1 – Chemical Reactions (CBSE Sample 2024-25)
A student adds:
A → Zn granules + dil. H₂SO₄
B → Cu turnings + conc. HNO₃
C → Fe nail + CuSO₄ solution
(i) Identify the type of reaction in each.
(ii) Write balanced equations.
(iii) Identify oxidising and reducing agents in B.
(iv) Why does blue colour fade in C?
Answer: A – Displacement, B – Redox, C – Displacement, colour fades because Cu²⁺ is reduced.
Case 2 – Optics (DPS RK Puram March 2025)
A student performs an experiment with a convex lens:
Object distance u = –20 cm, image distance v = –30 cm
(i) Find focal length
(ii) Power of lens
(iii) Magnification
(iv) Draw ray diagram
Answer: f = +12 cm, P = +8.33 D, m = +1.5
Case 3 – Heredity & Evolution (Amity March 2025)
In beetles, red colour (R) is dominant over blue (r).
(i) A pure red beetle is crossed with blue. Show F₁ and F₂.
(ii) What is the phenotypic ratio in F₂?
(iii) Name the law.
(iv) If 808 beetles in F₂ are red, how many are blue?
Answer: F₂ ratio 3:1 → blue = 808/3 ≈ 269
Practical-Based Questions (3 + 3 = 6 marks)
Q37. Describe the experiment to study the reaction between zinc and dilute sulphuric acid.
Write aim, materials, procedure, observations, balanced equation, conclusion, precautions.
Q38. How will you determine the equivalent resistance of two resistors when connected in parallel using a battery, ammeter, voltmeter and rheostat?
Write circuit diagram, formula, and steps.