Class 9 Science — Model Question Paper (Set 2)

Model Paper · full syllabus · CBSE 2026-27 pattern

CBSE Class 9 · Science (NCERT ‘Exploration’) · Max Marks 80 · Time 3 hrs · HOTS / analytical

CBSE Class 9 Science — Model Question Paper (Set 2 · HOTS) · Max Marks 80 · Time 3 hrs

A fully higher-order-thinking paper — assertion-reason, analytical, application and case-study questions across all 13 chapters. Answers & marking scheme in the ✍️ Answers tab.

General Instructions: Five sections A–E, 39 compulsory questions. Section A (Q1–20) 1 mark; B (Q21–26) 2 marks; C (Q27–33) 3 marks; D (Q34–36) 5 marks; E (Q37–39) 4 marks. Internal choices given in some questions.

SECTION A — Objective (HOTS) [20 × 1 = 20]

Q1. Two bodies P and Q have the same momentum, but Q has twice the mass of P. The ratio of their kinetic energies (KEₚ : KE_Q) is:

(i) 2 : 1
(ii) 1 : 2
(iii) 1 : 1
(iv) 4 : 1

Q2. A dry raisin placed in water swells up. The best explanation is:

(i) endosmosis into the raisin
(ii) exosmosis out of the raisin
(iii) active transport of water
(iv) evaporation

Q3. Equal masses of two gases A (relative molecular mass 16) and B (44) are taken. The one with more molecules is:

(i) A
(ii) B
(iii) equal
(iv) cannot say

Q4. A ball is thrown up and returns to the thrower. Over the whole trip its displacement and distance are (height H):

(i) 0 and 2H
(ii) 2H and 0
(iii) H and H
(iv) 0 and H

Q5. Sound travels fastest in:

(i) steel
(ii) water
(iii) air
(iv) vacuum

Q6. If the number of protons in an atom changes, what necessarily changes?

(i) the element itself
(ii) only the mass number
(iii) only the number of neutrons
(iv) nothing

Q7. A multicellular organism with a chitin cell wall and heterotrophic absorptive nutrition belongs to:

(i) Fungi
(ii) Plantae
(iii) Animalia
(iv) Protista

Q8. A body moves with uniform speed in a circle. It is accelerating because:

(i) its direction (hence velocity) keeps changing
(ii) its speed keeps changing
(iii) it slows down
(iv) no force acts

Q9. Melting of bright polar ice tends to accelerate warming because it:

(i) lowers the albedo (darker surface absorbs more)
(ii) raises the albedo
(iii) stops ocean currents
(iv) reduces CO₂

Q10. Two identical flasks hold equal volumes of a true solution and a colloid. A light beam is passed. The colloid:

(i) scatters the beam (Tyndall effect)
(ii) absorbs the beam fully
(iii) bends the beam
(iv) does nothing

Q11. Doubling the speed of a moving car increases its kinetic energy by a factor of:

(i) 4
(ii) 2
(iii) 8
(iv) √2

Q12. A cross between genetically identical (cloned) plants gives offspring that are:

(i) identical, with no variation
(ii) highly varied
(iii) sterile
(iv) unable to survive

Q13. Which has the greatest number of shared features among its members?

(i) Genus
(ii) Class
(iii) Phylum
(iv) Kingdom

Q14. A tuning fork of higher frequency, struck equally hard, produces a sound of:

(i) higher pitch, same loudness
(ii) higher loudness
(iii) lower pitch
(iv) lower speed

Q15. In a food web, removing a keystone predator most likely leads to:

(i) imbalance and possible collapse
(ii) no change
(iii) more biodiversity
(iv) faster nutrient cycling

Q16–20 (Assertion–Reason): (a) Both true, R explains A; (b) Both true, R not the explanation; (c) A true, R false; (d) A false, R true.

Q16. Assertion: A passenger lurches forward when a moving bus stops suddenly. Reason: The body tends to keep its state of motion due to inertia.

Q17. Assertion: Fish lay thousands of eggs but birds lay only a few. Reason: External fertilisation has a lower survival rate than internal fertilisation.

Q18. Assertion: Vegetatively propagated crops are more vulnerable to a single disease. Reason: They are clones with no genetic variation.

Q19. Assertion: A diver curls the body to spin faster. Reason: Reducing the moment of inertia increases the speed of rotation while momentum is conserved.

Q20. Assertion: Venus is hotter than Mercury though Mercury is closer to the Sun. Reason: Venus has a thick CO₂ atmosphere causing a runaway greenhouse effect.

SECTION B — Very Short Answer (HOTS) [6 × 2 = 12]

Q21. Why does a cricket player move his hands backward while catching a fast ball? Explain using the idea of momentum and force. [2]

Q22. A red blood cell bursts when placed in distilled water but shrinks in strong salt solution. Explain both observations. [2]

Q23. Two sounds have the same loudness but one is shrill and the other is flat. Which wave property differs, and how? [2]

Q24. Why are bryophytes called the ‘amphibians of the plant kingdom’? Give two reasons. [2]

Q25. Equal masses of carbon are burned in (i) plenty of air and (ii) limited air. Name the products and state why they differ. [2]

Q26. Explain why a single-celled organism can survive without specialised tissues, whereas a large animal cannot. [2]

SECTION C — Short Answer (HOTS) [7 × 3 = 21]

Q27. A 1000 kg car moving at 20 m/s is brought to rest in 5 s by braking. Find (i) the retardation, (ii) the braking force, and (iii) the distance covered while stopping. [3]

Q28. A student claims ‘heavier objects always fall faster’. Design a simple argument/experiment (ignoring air resistance) to test and refute this claim, and state the correct conclusion. [3]

Q29. Using the law of conservation of energy, explain the energy changes when a stone is dropped from a height until just before it hits the ground. Where is KE and PE maximum? [3]

Q30. Organisms P (no true nucleus, extreme salinity), Q (multicellular, cell wall, no chlorophyll, on dead matter) and R (unicellular, true nucleus, photosynthetic in light) are found. Place each in its kingdom with a reason. [3]

Q31. Explain why increasing atmospheric CO₂ is harmful to marine life, linking it to ocean acidification and the carbon cycle. [3]

Q32. Two tuning forks of frequencies 256 Hz and 512 Hz are sounded in air (speed 340 m/s). Find their wavelengths and state which has the higher pitch. [3]

Q33. A farmer rotates legumes with cereals instead of using heavy fertiliser. Using the nitrogen cycle, explain why this keeps the soil fertile and protects nearby water bodies. [3]

SECTION D — Long Answer (HOTS) [3 × 5 = 15]

Q34. (a) State the law of conservation of momentum and derive it from Newton’s third law for two colliding bodies. (b) A 50 kg boy jumps off a 150 kg stationary trolley at 2 m/s. Find the recoil velocity of the trolley and state its direction. [5]
OR — Compare asexual and sexual reproduction (parents, cell division, variation) and explain, with an example, why variation is an advantage for survival of a species.

Q35. A potato osmoscope experiment: a peeled potato cup with sugar solution is kept in water; water collects in the cup. (a) Explain the result using osmosis. (b) Predict and explain what happens if a boiled potato is used. (c) State the role of the selectively permeable membrane. [5]
OR — Explain the three-domain and five-kingdom systems, and argue why classification keeps changing as science advances.

Q36. ‘A change in one sphere of the Earth disturbs the others.’ Justify this with two different real examples, and suggest three actions (individual + global) to restore the balance. [5]
OR — Derive the three equations of motion graphically for a uniformly accelerated body moving in a straight line.

SECTION E — Case / Source-based (HOTS) [3 × 4 = 12]

Q37. A velocity–time graph shows a body speeding up uniformly from 10 m/s to 30 m/s in 4 s, then slowing uniformly to rest in the next 10 s.

(i) Find the acceleration in the first 4 s. [1]
(ii) Find the retardation in the last phase. [1]
(iii) Find the distance in the first 4 s. [1]
(iv) What does the area under a v–t graph represent? [1]

Q38. A researcher studies four organisms: a yeast cell, an Amoeba, a Spirogyra filament and a hydra.

(i) Which one is a unicellular eukaryote of the kingdom Protista? [1]
(ii) Which belongs to Fungi, and what is its cell wall made of? [1]
(iii) Which is an animal, and what level of body organisation does it show? [1]
(iv) Spirogyra and hydra both live in water — why are they NOT in the same kingdom? [1]

Q39. Over 50 years the atmospheric CO₂ rose from ~315 ppm to ~420 ppm (Keeling curve), with faster glacier melt and more intense monsoons in India.

(i) Name the human activities mainly responsible for this rise. [1]
(ii) Explain how higher CO₂ can intensify monsoon rainfall. [1]
(iii) Why does a warmer ocean absorb LESS CO₂, worsening the problem? [1]
(iv) Suggest one scientific and one everyday action to reduce CO₂ emissions. [1]

Model Answers & Marking Scheme (Set 2 · HOTS)

Value-points; reward correct reasoning in the student’s own words.

Section A (1 mark each)

16 — (a). 17 — (a) both true, R explains A. 18 — (a). 19 — (a) both true, R explains A. 20 — (a).

Section B (2 marks each)

21. Pulling the hands back increases the time over which the ball’s momentum is reduced to zero. Since F = Δp/Δt, a larger Δt means a smaller force on the hands, so it hurts less.

22. In distilled water the surrounding solution is less concentrated, so water enters the RBC by endosmosis until it swells and bursts. In strong salt solution the outside is more concentrated, so water leaves by exosmosis and the cell shrinks.

23. Frequency (pitch) differs. The shrill sound has a higher frequency (higher pitch); the flat one a lower frequency. Equal loudness means equal amplitude.

24. Bryophytes (i) live in moist, shady places and (ii) need water for reproduction (male gametes must swim to the female). Like amphibians they live on land but depend on water — hence the name.

25. (i) Plenty of air → carbon dioxide (CO₂) (complete combustion). (ii) Limited air → carbon monoxide (CO) / soot (incomplete combustion). The amount of oxygen available decides the product.

26. A single cell has a large surface-area-to-volume ratio, so it can exchange gases, nutrients and wastes directly with its surroundings and carry out all functions itself. A large animal has many cells deep inside, so it needs specialised tissues/organs (for transport, exchange, coordination) to serve them.

Section C (3 marks each)

27. u = 20, v = 0, t = 5 s. (i) a = (0−20)/5 = −4 m/s² (retardation 4 m/s²). (ii) F = ma = 1000×(−4) = −4000 N (4000 N opposing motion). (iii) s = (v²−u²)/2a = (0−400)/(2×−4) = 50 m.

28. Argument: drop a heavy and a light stone together — they land at the same time; in a vacuum (or feather-and-coin tube) even a feather and coin fall together. All objects have the same acceleration g regardless of mass (because larger mass needs proportionally larger force, F = mg). Conclusion: ignoring air resistance, all bodies fall at the same rate — the claim is false.

29. At the top: PE maximum, KE = 0. As it falls, PE converts to KE; total (PE + KE) stays constant. Just before hitting the ground: KE maximum, PE minimum (≈ 0). Energy is conserved — only transformed from potential to kinetic.

30. P → Monera (prokaryote, no true nucleus; archaea-like, survives extreme salinity). Q → Fungi (multicellular, cell wall, no chlorophyll, saprophytic). R → Protista (unicellular eukaryote; photosynthetic in light, so protist like Euglena).

31. Oceans absorb excess atmospheric CO₂, forming carbonic acid → sea water becomes more acidic (ocean acidification). This harms plankton and corals that build calcium-carbonate shells/skeletons, disrupting marine food chains. It shows the carbon cycle links atmosphere and hydrosphere — too much CO₂ upsets the balance.

32. λ = v/f. For 256 Hz: λ = 340/256 = 1.33 m; for 512 Hz: λ = 340/512 = 0.66 m. The 512 Hz fork has the higher frequency, so higher pitch.

33. Legumes have Rhizobium in root nodules that fix atmospheric N₂ into the soil, enriching it naturally for the next cereal crop — so less chemical fertiliser is needed. Less fertiliser means less nitrate runoff into rivers/lakes, avoiding eutrophication (algal blooms that kill fish).

Section D (5 marks each)

34. (a) Law: in the absence of external force the total momentum of a system is conserved. From Newton’s third law the forces on two colliding bodies are equal and opposite over the same time, so their momentum changes are equal and opposite ⇒ m₁u₁+m₂u₂ = m₁v₁+m₂v₂. (b) Momentum before = 0. After: 50×2 + 150×v = 0 ⇒ v = −0.67 m/s — the trolley recoils at 0.67 m/s in the opposite direction. OR — Asexual: one parent, mitosis, identical clones (no variation); sexual: two parents, meiosis + fertilisation, offspring vary. Variation lets some individuals survive disease/environmental change (e.g. a varied crop survives a new pest while a clone crop is wiped out).

35. (a) The membrane-lined potato lets water move from the dilute outside into the concentrated sugar solution by osmosis, so liquid collects in the cup. (b) A boiled potato’s membranes are dead/damaged, no longer selectively permeable, so no osmosis — the level does not rise. (c) The selectively permeable membrane allows water but not sugar to pass, which is what drives osmosis. OR — Five-kingdom (Whittaker): Monera, Protista, Fungi, Plantae, Animalia by cell type, structure, organisation and nutrition. Three-domain (Woese, using DNA): Bacteria, Archaea, Eukarya. Classification changes because new tools (microscopes, DNA studies) reveal relationships, so science keeps revising — it is self-correcting.

36. Example 1: warming atmosphere → glaciers melt (cryosphere) → sea level rises, rivers flood (hydrosphere) → coastal habitats lost (biosphere). Example 2: deforestation (biosphere) → less transpiration → less rainfall (atmosphere/hydrosphere) and soil erosion (geosphere). Actions: switch to renewable (solar/wind) energy; plant trees and protect forests; save water/energy and reduce waste (individual, e.g. Mission LiFE); global cooperation (Montreal/Paris). OR — graphical derivations of v = u + at, s = ut + ½at², v² = u² + 2as from the v–t straight-line graph (slope = a, area = displacement).

Section E (4 marks each)

37. (i) a = (30−10)/4 = 5 m/s². (ii) retardation = (30−0)/10 = 3 m/s². (iii) s = average velocity × t = ((10+30)/2)×4 = 80 m. (iv) the area under a v–t graph = displacement/distance travelled.

38. (i) Amoeba (unicellular eukaryote → Protista). (ii) Yeast → Fungi; cell wall of chitin. (iii) Hydra → Animalia; shows tissue-level organisation. (iv) Spirogyra is a photosynthetic plant (Thallophyta/Plantae) while hydra is a heterotrophic animal — same habitat but different cell type/nutrition, so different kingdoms (habitat is not a classification criterion).

39. (i) Burning of fossil fuels and deforestation. (ii) A warmer atmosphere holds more water vapour, so when the monsoon arrives it dumps heavier rainfall. (iii) Warmer water holds less dissolved gas, so the ocean absorbs less CO₂, leaving more in the air (a weaker carbon sink). (iv) Scientific: shift to solar/wind energy or carbon capture; everyday: save electricity, use public transport, plant trees.

Section	Question type	Questions	Marks each	Total
A	Objective (MCQ + Assertion–Reason)	1–20	1	20
B	Very Short Answer	21–26	2	12
C	Short Answer	27–33	3	21
D	Long Answer	34–36	5	15
E	Case/Source-based	37–39	4	12
Theory total			39	80