10th Science Quarterly Exam 2026 Question Paper & Answer Key

Accelerate your public exam preparation with the official Chennai District 10th Science Quarterly Exam 2026 Question Paper and Answer Key curated specifically for English Medium students. As one of the major educational hubs, analyzing the Chennai district paper gives you a competitive edge, helping you evaluate your performance, master high-weightage questions, and align your studies with the state board evaluation standards.

CHENNAI DISTRICT • 10407 Class: 10 Register Number: [__________]

COMMON QUARTERLY EXAMINATION - 2026-27

SCIENCE (ENGLISH MEDIUM) • QUESTION PAPER & DETAILED SOLUTIONS

Time Allowed: 3.00 Hours Max. Marks: 75

PART - I • 1. Choose the correct answer: 12 × 1 = 12

1. Where should an object be placed so that a real and inverted image of same size is obtained by a convex lens?
a) F b) 2F c) infinity d) between f and 2f

Answer: b) 2F
Explanation: When an object is placed at the centre of curvature (2F) of a convex lens, a real, inverted image of the exact same size is formed at 2F on the opposite side.

2. Temperature is the average _______ of the molecules of a substance:
a) difference in K.E and PE b) sum of PE and KE
c) difference in TE and PE d) difference in K.E and TE

Answer: c) difference in TE and PE
Explanation: Total Energy (TE) = Kinetic Energy (KE) + Potential Energy (PE). Hence, Kinetic Energy = TE − PE. Since temperature is defined as the measure of average kinetic energy of the molecules, it represents the average of the difference between total energy and potential energy.

3. A charge of 10C flows through a bulb in 5 seconds. The current through the bulb is:
a) 2A b) 50 A c) 0.5 A d) 2.4 A

Answer: a) 2A
Solution: Electric current I = Q / t = 10 C / 5 s = 2 A.

4. Mass of 1 mole of Nitrogen atom is:
a) 28 amu b) 14 amu c) 28 g d) 14 g

Answer: d) 14 g
Explanation: The mass of 1 mole of nitrogen atoms (N) equals its gram atomic mass, which is 14 g (note: 1 mole of nitrogen molecule N₂ is 28 g).

5. In the alumino thermic process the role of Al is:
a) oxidizing agent b) reducing agent c) hydrogenating agent d) sulphurising agent

Answer: b) reducing agent
Explanation: Aluminium acts as a powerful reducing agent, reducing metal oxides (like Fe₂O₃ or Cr₂O₃) to their molten metals.

6. A 25% alcohol solution means:
a) 25 ml alcohol in 100 ml of water b) 25 ml alcohol in 25 ml of water
c) 25 ml alcohol in 75 ml of water d) 75 ml alcohol in 25 ml of water

Answer: c) 25 ml alcohol in 75 ml of water
Explanation: 25 ml solute + 75 ml solvent gives 100 ml total solution, which represents 25% (v/v).

7. Mammals are _______ animals:
a) Cold blooded b) Warm blooded c) Poikilothermic d) All the above

Answer: b) Warm blooded (Homeothermic)

8. 'Heart of heart' is called:
a) SA node b) AV node c) Purkinje fibres d) Bundle of His

Answer: a) SA node (Sino-atrial node / primary pacemaker)

9. Nerve cells do not possess:
a) neurilemma b) sarcolemma c) axon d) dendrites

Answer: b) sarcolemma
Explanation: Sarcolemma is the plasma membrane covering skeletal muscle fibres, not nerve cells.

10. _______ is found abundantly in liquid endosperm of coconut:
a) Auxin b) Cytokinin c) Gibberellins d) Ethylene

Answer: b) Cytokinin

11. Syngamy results in the formation of:
a) Zoospores b) Conidia c) Zygote d) Chlamydospores

Answer: c) Zygote

12. The loss of one or more chromosome in a ploidy is called:
a) Tetraploidy b) Aneuploidy c) Euploidy d) polyploidy

Answer: b) Aneuploidy

PART - II • II. Answer any seven questions (Q.No. 22 is compulsory): 7 × 2 = 14

13. Classify the types of force based on their application.

Answer:
Based on the direction of application, parallel forces are classified into:
1. Like parallel forces: Two or more forces of equal or unequal magnitude acting along the same direction, parallel to each other.
2. Unlike parallel forces: Two or more forces of equal or unequal magnitude acting along opposite directions, parallel to each other.

14. State the law of Volume (Charles's law).

Answer:
According to Charles's law, at constant pressure, the volume of a given mass of gas is directly proportional to its absolute temperature.
Formula: V ∝ T or V / T = Constant.

15. Fill in the blanks:
a) _______ forms the basis of modern periodic table.
b) The chemical name of rust is _______.

Answer:
a) Atomic number
b) Hydrated ferric oxide (Fe₂O₃ · xH₂O)

16. Name the three basic tissue systems in flowering plants.

Answer:
1. Dermal or Epidermal tissue system
2. Ground or Fundamental tissue system
3. Vascular tissue system

17. Why is the circulation in man referred to as double circulation?

Answer:
In humans, blood passes through the heart twice during one complete cycle through the body:
1. Pulmonary circulation: Deoxygenated blood is pumped from the right ventricle to the lungs and returned oxygenated to the left atrium.
2. Systemic circulation: Oxygenated blood is pumped from the left ventricle to all body tissues and returned deoxygenated to the right atrium.

18. Draw a neat labelled diagram of a neuron.

Answer:
A typical neuron consists of three main structural parts to be drawn and labeled:
1. Cyton (Cell body): Contains neuroplasm, nucleus, and Nissl's granules.
2. Dendrites: Short, branched cytoplasmic projections receiving nerve impulses.
3. Axon: Long, single cylindrical fibre covered by Schwann cells, myelin sheath, Nodes of Ranvier, terminating at synaptic knobs.

19. Why are thyroid hormones referred to as personality hormone?

Answer:
Thyroid hormones (thyroxine) regulate basal metabolic rate (BMR), physical growth, mental alertness, and emotional balance, thus directly influencing an individual's overall personality.

20. Write the characteristics of insect pollinated flowers.

Answer:
1. Large, showy, and brightly colored petals to attract insects.
2. Produce pleasant fragrances and sweet nectar as food rewards.
3. Pollen grains are large, rough, and have a spiny, sticky exine (pollenkitt) to stick to the insect's body.

21. What do you understand by the term phenotype and genotype?

Answer:
• Phenotype: The physical, observable morphological expression of a particular genetic trait (e.g., Tall or Dwarf).
• Genotype: The genetic constitution of an organism responsible for determining a specific trait (e.g., TT, Tt, or tt).

22. [Compulsory] A solution was prepared by dissolving 45g of sugar in 180g of water. Calculate the mass percentage of solute.

Solution:
Mass of solute (sugar) = 45 g
Mass of solvent (water) = 180 g
Mass of solution = 45 g + 180 g = 225 g
Mass percentage of solute = (Mass of solute / Mass of solution) × 100
= (45 / 225) × 100 = (1 / 5) × 100 = 20%

PART - III • III. Answer any seven questions (Q.No. 32 is compulsory): 7 × 4 = 28

23. Differentiate convex lens and concave lens.

Convex Lens	Concave Lens
Thicker at the centre, thinner at edges.	Thinner at the centre, thicker at edges.
Converging lens.	Diverging lens.
Produces mostly real and inverted images.	Always produces virtual and erect images.
Used to correct hypermetropia (long-sightedness).	Used to correct myopia (short-sightedness).

24. a) Match the following:
1. Linear expansion — (a) hot body to cold body
2. Superficial expansion — (b) 1.38 × 10⁻²³ J K⁻¹
3. Heat transformation — (c) change in length
4. Boltzmann constant — (d) change in area
b) Fill in the blanks:
(i) The temperature and heat are _______ quantities.
(ii) According to Boyle's law, the shape of the graph between pressure and reciprocal of volume is _______.

Answer:
a) Correct Match:
1. Linear expansion — (c) change in length
2. Superficial expansion — (d) change in area
3. Heat transformation — (a) hot body to cold body
4. Boltzmann constant — (b) 1.38 × 10⁻²³ J K⁻¹
b) Blanks:
(i) scalar
(ii) a straight line passing through the origin

25. Write the differences between atoms and molecules.

Atom	Molecule
Smallest particle of an element.	Smallest particle of an element or compound.
Usually does not exist in free state (except noble gases).	Can exist independently in free state.
Highly reactive (except noble gases).	Less reactive than atoms.
Does not contain chemical bonds.	Held together by covalent or ionic chemical bonds.

26. What happens when MgSO₄ · 7H₂O is heated? Write the appropriate equation.

Answer:
When magnesium sulphate heptahydrate (Epsom salt) crystals are heated, they lose all seven molecules of water of crystallization to become anhydrous magnesium sulphate (MgSO₄):
MgSO₄ · 7H₂O ↔ MgSO₄ + 7H₂O (Heating / Cooling)

27. a) Write the dental formula of rabbit. b) Why is the teeth of rabbit called heterodont?

Answer:
a) Dental formula: (I 2/1, C 0/0, PM 3/2, M 3/3) or 2033 / 1023.
b) Heterodont dentition: Rabbit dentition is called heterodont because its teeth are differentiated into distinct morphological types with specialized functions (incisors for cutting, premolars and molars for grinding; canines are absent).

28. How are arteries and veins structurally different from one another?

Arteries	Veins
Thick, elastic, and muscular walls.	Thin and non-elastic walls.
Narrow internal lumen.	Wide internal lumen.
Valves are absent.	Internal semilunar valves are present.
Carry blood under high pressure away from the heart.	Carry blood under low pressure towards the heart.

29. a) Identify the parts A, B, C and D in the given cross-section of dicot stem vascular bundle / stem sector:
b) Which hormone is secreted during emergency situations in man?

Answer:
a) Identification:
A — Epidermis (Cuticle)
B — Cortex (Hypodermis / Collenchyma)
C — Phloem / Vascular bundle
D — Pith (Medulla)
b) Emergency hormone: Adrenaline (Epinephrine) [and Noradrenaline], secreted by the adrenal medulla.

30. a) Name the secondary sex organs in male. b) Draw and label the parts of a Sperm.

Answer:
a) Male secondary sex organs: Epididymis, vas deferens, seminal vesicles, prostate gland, Cowper's (bulbourethral) gland, and penis.
b) Structure of human sperm:
1. Head: Contains an elongated haploid nucleus capped by the acrosome (contains hyaluronidase enzyme for ovum penetration).
2. Neck: Short segment connecting head and middle piece, containing proximal and distal centrioles.
3. Middle piece: Contains spirally coiled mitochondria (nebenkern) that produce ATP energy for motility.
4. Tail: Slender terminal flagellum enabling whip-like swimming movements.

31. Explain briefly the structure of DNA.

Answer:
Watson and Crick proposed the double-helical model of DNA:
1. DNA consists of two complementary polynucleotide chains spiraling around a central axis in opposite directions (antiparallel: 5' → 3' and 3' → 5').
2. The backbone consists of alternating deoxyribose sugar and phosphate groups linked by phosphodiester bonds.
3. Nitrogenous bases project inwards: Adenine pairs with Thymine by two hydrogen bonds (A = T); Guanine pairs with Cytosine by three hydrogen bonds (G ≡ C).
4. One complete pitch measures 3.4 nm (34 Å) containing 10 base pairs, with 0.34 nm spacing between successive base pairs.

32. [Compulsory] Two resistors when connected in parallel give the resultant resistance of 2 ohm, but when connected in series the effective resistance becomes 9 ohm. Calculate the value of each resistance.

Solution:
Let the two individual resistances be R₁ and R₂.
In series: R₁ + R₂ = 9 Ω — (1)
In parallel: (R₁ · R₂) / (R₁ + R₂) = 2 Ω
Substitute (1): (R₁ · R₂) / 9 = 2 ⇒ R₁ · R₂ = 18 Ω² — (2)
Using the identity: (R₁ − R₂)² = (R₁ + R₂)² − 4R₁R₂
(R₁ − R₂)² = 9² − 4(18) = 81 − 72 = 9
R₁ − R₂ = 3 Ω — (3)
Adding (1) and (3): 2R₁ = 12 ⇒ R₁ = 6 Ω
Substituting into (1): R₂ = 3 Ω
Answer: The values of the two resistors are 6 Ω and 3 Ω.

PART - IV • Answer all the questions in detail: 3 × 7 = 21

33. a) State Newton's Laws of motion.

Answer:
1. Newton's First Law (Law of Inertia): Every object continues in its state of rest or of uniform motion along a straight line unless acted upon by an external unbalanced force.
2. Newton's Second Law (Law of Force): The rate of change of linear momentum of a body is directly proportional to the applied force and acts in the direction of the force (F = ma).
3. Newton's Third Law: For every action, there is an equal and opposite reaction (F_A = −F_B).

(OR) 33. b) (i) What is meant by electric current? (ii) Name and define its unit. (iii) Which instrument is used to measure the electric current? How should it be connected in a circuit?

Answer:
(i) Electric current: The rate of flow of electric charges across any cross-section of a conductor (I = Q / t).
(ii) Unit: The SI unit is ampere (A).
Definition of Ampere: A current of one ampere flows through a conductor when one coulomb of charge passes across any cross-section in one second (1 A = 1 C / 1 s).
(iii) Instrument & Connection:
• Instrument: Ammeter.
• Connection: Must always be connected in series with the circuit.

34. a) Derive the relationship between Relative molecular mass and vapour density.

Answer:
Vapour Density (V.D.) is the ratio of the mass of a certain volume of gas to the mass of an equal volume of hydrogen at the same temperature and pressure:
V.D. = [Mass of V volume of gas at STP] / [Mass of V volume of hydrogen at STP]
Applying Avogadro's law (equal volumes contain equal number 'n' of molecules):
V.D. = [Mass of n molecules of gas] / [Mass of n molecules of hydrogen]
Setting n = 1:
V.D. = [Mass of 1 molecule of gas] / [Mass of 1 molecule of hydrogen]
Since hydrogen is a diatomic molecule (H₂) with molecular mass 2:
V.D. = [Relative Molecular Mass of gas] / [2 × Mass of 1 hydrogen atom]
V.D. = Relative Molecular Mass / 2
Relative Molecular Mass = 2 × Vapour Density (V.D.)

(OR) 34. b) (i) Define solubility. (ii) Give an example for solid in solid. (iii) In what way do hygroscopic substances differ from deliquescent substances? Give an example for each.

Answer:
(i) Solubility: The number of grams of solute that can dissolve in 100 g of solvent to form a saturated solution at a specified temperature and pressure.
(ii) Solid in solid example: Alloys such as brass (copper + zinc) or bronze.
(iii) Difference:

Hygroscopic Substances	Deliquescent Substances
Absorb moisture from air without dissolving.	Absorb moisture from air and dissolve completely in it.
Do not change their physical state.	Lose crystalline form and change into liquid solutions.
E.g., Silica gel, Conc. H₂SO₄, Quicklime.	E.g., Caustic soda (NaOH), KOH, anhydrous CaCl₂.

35. a) (i) Differentiate monocot root and dicot root. (ii) Differentiate aerobic respiration and anaerobic respiration.

Answer:
(i) Monocot Root vs Dicot Root:

Feature	Dicot Root (e.g., Bean)	Monocot Root (e.g., Maize)
Xylem Bundles	Tetrarch (usually four)	Polyarch (many)
Cambium	Present during secondary growth	Absent
Secondary Growth	Present	Absent
Pith	Absent	Present

(ii) Aerobic vs Anaerobic Respiration:

Aerobic Respiration	Anaerobic Respiration
Occurs in the presence of oxygen.	Occurs in the absence of oxygen.
Occurs in cytoplasm and mitochondria.	Occurs only in cytoplasm.
End products: CO₂ and H₂O.	End products: Ethanol or lactic acid and CO₂.
Yields large energy (36 or 38 ATP).	Yields low energy (2 ATP).

(OR) 35. b) (i) Name the parts of hindbrain. (ii) Classify neurons based on their structure and find their locations.

Answer:
(i) Parts of Hindbrain:
1. Cerebellum: Coordinates voluntary movements and maintains body balance and equilibrium.
2. Pons: Bridge of nerve fibres relaying signals between cerebrum and cerebellum; regulates respiration.
3. Medulla Oblongata: Cardiac and respiratory regulatory centre controlling vital involuntary autonomic reflexes.

(ii) Classification of Neurons based on Structure:
1. Unipolar neurons: Only one nerve process arises from the cyton, acting as both axon and dendron.
• Location: Found in early embryonic nervous tissue.
2. Bipolar neurons: Two processes arise from opposite poles of the cyton — one axon and one dendron.
• Location: Found in the retina of the eye and olfactory epithelium.
3. Multipolar neurons: Many branched dendrons and a single long axon arise from the cell body.
• Location: Found in the cerebral cortex of the brain.