TN SSLC Science Model Paper 2027 — Full Paper With Answers

This model paper follows the official TNDGE SSLC Science pattern for 2027. Total: 75 marks theory + 25 marks practical = 100 marks. Theory time: 3 hours.

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Paper Structure

Section	Type	Questions	Marks
Part 1	MCQ (15 questions)	15	15
Part 2	Very Short Answer (6 of 9)	9	12
Part 3	Short Answer (9 of 14)	14	27
Part 4	Long Answer (3 of 5)	5	15
Part 5	Higher Order Thinking	2	6

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PART 1 — MCQ (1 Mark Each)

Q1. Which of the following is the correct electronic configuration of sodium (Na, atomic number 11)?

(a) 2, 8, 2 (b) 2, 9 (c) 2, 8, 1 (d) 2, 7, 2

Answer: (c) 2, 8, 1

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Q2. The mirror formula is:

(a) 1/f = 1/u + 1/v (b) 1/v = 1/u − 1/f (c) f = u + v (d) 1/u = 1/v + 1/f

Answer: (a) 1/f = 1/u + 1/v

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Q3. DNA replication takes place in which phase of the cell cycle?

(a) G1 phase (b) S phase (c) G2 phase (d) M phase

Answer: (b) S phase

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Q4. Which organ in the human body produces insulin?

(a) Liver (b) Kidney (c) Pancreas (d) Spleen

Answer: (c) Pancreas

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Q5. The formula for the compound formed between calcium (Ca²⁺) and chlorine (Cl⁻) is:

(a) CaCl (b) Ca₂Cl (c) CaCl₂ (d) Ca₂Cl₂

Answer: (c) CaCl₂

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Q6. The SI unit of magnetic flux is:

(a) Tesla (b) Weber (c) Henry (d) Farad

Answer: (b) Weber

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Q7. Ozone layer is present in which layer of the atmosphere?

(a) Troposphere (b) Mesosphere (c) Stratosphere (d) Thermosphere

Answer: (c) Stratosphere

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Q8. Which of the following is a renewable source of energy?

(a) Coal (b) Petroleum (c) Natural gas (d) Solar energy

Answer: (d) Solar energy

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Q9. The ratio of circumference to diameter of a circle equals:

(a) π/2 (b) 2π (c) π (d) π²

Answer: (c) π

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Q10. Blood pressure is measured by an instrument called:

(a) Thermometer (b) Barometer (c) Sphygmomanometer (d) Stethoscope

Answer: (c) Sphygmomanometer

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Q11. Which type of lens is used to correct myopia (short-sightedness)?

(a) Convex lens (b) Concave lens (c) Bifocal lens (d) Cylindrical lens

Answer: (b) Concave lens

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Q12. The atomic number of an element determines its:

(a) Mass (b) Neutron number (c) Position in periodic table (d) Isotope type

Answer: (c) Position in periodic table

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Q13. Which gas is produced when sodium reacts with water?

(a) Oxygen (b) Carbon dioxide (c) Hydrogen (d) Nitrogen

Answer: (c) Hydrogen
(2Na + 2H₂O → 2NaOH + H₂↑)

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Q14. The process by which plants lose water through their leaves is called:

(a) Respiration (b) Transpiration (c) Photosynthesis (d) Osmosis

Answer: (b) Transpiration

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Q15. Fleming's left hand rule is used to find the direction of:

(a) Magnetic field (b) Induced current (c) Force on current-carrying conductor (d) Electric field

Answer: (c) Force on current-carrying conductor

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PART 2 — Very Short Answer (2 Marks Each — Attempt 6 of 9)

Q16. State Newton's second law of motion and write its formula.

Answer: The rate of change of momentum of a body is directly proportional to the applied force and takes place in the direction of the force.
F = ma (Force = mass × acceleration)
SI unit of force: Newton (N) = kg·m/s²

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Q17. What is the difference between exothermic and endothermic reactions? Give one example each.

Answer:
Exothermic: Reactions that release heat energy.
Example: Burning of coal — C + O₂ → CO₂ + heat
Endothermic: Reactions that absorb heat energy.
Example: Photosynthesis — CO₂ + H₂O + light energy → C₆H₁₂O₆ + O₂

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Q18. What are chromosomes? What is their role in heredity?

Answer: Chromosomes are thread-like structures made of DNA and proteins found in the nucleus of cells.
Human body cells have 46 chromosomes (23 pairs).
Role in heredity: Chromosomes carry genes which are the units of inheritance. They are passed from parents to offspring during reproduction, transmitting inherited characteristics.

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Q19. Define electric potential difference. What is its SI unit?

Answer: Electric potential difference between two points in a circuit is the work done to move a unit positive charge from one point to another.
V = W/Q (Potential difference = Work done / Charge)
SI unit: Volt (V) = Joule/Coulomb

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Q20. What is biodiversity? Why should it be conserved?

Answer: Biodiversity refers to the variety of life forms on Earth — the different plants, animals, microorganisms and their genes.
Why conserve:

• Maintains ecological balance
• Many species provide food, medicine and raw materials
• Once extinct, species cannot be recovered
• Every species has a role in the ecosystem

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PART 3 — Short Answer (3 Marks Each — Attempt 9 of 14)

Q21. Describe the structure of the human eye and explain how it forms an image.

Answer:
Structure of Human Eye:

• Cornea: Transparent front part, refracts light entering the eye
• Iris: Coloured part, controls size of pupil
• Pupil: Opening that controls amount of light entering
• Lens: Convex, focuses light on retina, changes shape (accommodation)
• Retina: Screen at the back, contains rod and cone cells
• Optic nerve: Carries image signals to brain

Image formation: Light enters through cornea, passes through pupil, and is refracted by the lens to form a real, inverted image on the retina. The brain interprets this as the correct upright image.

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Q22. Write the differences between aerobic and anaerobic respiration with equations.

Answer:

Feature	Aerobic	Anaerobic
Oxygen	Required	Not required
End products	CO₂ + H₂O	Lactic acid (animals) or Ethanol + CO₂ (yeast)
Energy released	38 ATP (high)	2 ATP (low)
Location	Mitochondria	Cytoplasm

Aerobic: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + 38 ATP

Anaerobic (yeast): C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ + 2 ATP

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Q23. Explain the process of rusting of iron. Write the chemical equation and suggest two methods of prevention.

Answer:
Rusting is the corrosion of iron in the presence of oxygen and water (moisture).

Chemical equation:
4Fe + 3O₂ + 6H₂O → 4Fe(OH)₃ (hydrated iron oxide — rust)

Prevention methods:

1. Painting — Blocks contact between iron and moisture/oxygen
2. Galvanising — Coating iron with zinc; zinc acts as a sacrificial anode
3. Oiling or greasing — Forms protective barrier
4. Alloying — Making stainless steel (iron + chromium + nickel) resists rusting

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PART 4 — Long Answer (5 Marks Each — Attempt 3 of 5)

Q24. Draw a labelled diagram of the human reproductive system (female) and explain the process of fertilisation and implantation.

Answer:
Female Reproductive System components:

• Ovaries (produce eggs and hormones)
• Fallopian tubes / Oviducts (site of fertilisation)
• Uterus (site of development of foetus)
• Cervix (lower part of uterus)
• Vagina (birth canal)

Fertilisation:

1. Ovary releases a mature egg (ovulation) around day 14 of menstrual cycle
2. Egg travels down the fallopian tube
3. Sperm from male travels up through vagina and uterus
4. Sperm meets egg in fallopian tube
5. One sperm penetrates the egg membrane — fertilisation occurs
6. Fertilised egg (zygote) formed with 46 chromosomes (23 from each parent)

Implantation:

1. Zygote divides to form embryo (blastocyst)
2. Blastocyst travels to uterus over 3–4 days
3. Blastocyst embeds into the thick uterine wall (endometrium)
4. Placenta develops to nourish the embryo
5. Pregnancy begins — lasts approximately 9 months (40 weeks)

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PART 5 — Higher Order Thinking (3 Marks Each)

Q25. A student notices that a plant kept in a dark room for 48 hours and then exposed to sunlight produces starch only in the parts that receive direct light. Design an experiment to verify that sunlight is necessary for photosynthesis.

Answer:
Aim: To prove that light is necessary for photosynthesis

Materials: Potted plant, black paper, clips, iodine solution, alcohol, water bath

Procedure:

1. Keep the plant in darkness for 48 hours to de-starch the leaves
2. Cover part of one leaf with black paper on both sides, leaving the rest exposed
3. Place the plant in bright sunlight for 6 hours
4. Remove the leaf and remove the black paper
5. Boil the leaf in water, then in alcohol (to remove chlorophyll)
6. Wash with water and apply iodine solution

Expected Result:

• Exposed part of leaf → turns blue-black (starch present → photosynthesis occurred)
• Covered part of leaf → remains yellow-brown (no starch → no photosynthesis)

Conclusion: Sunlight is necessary for photosynthesis.

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Chapter-Wise Weightage

Chapter	Marks
Laws of Motion and Gravitation	8
Light and Optics	10
Electricity and Magnetism	10
Atomic Structure and Periodic Table	8
Chemical Reactions	8
Carbon and Its Compounds	6
Plant and Animal Biology	10
Reproduction and Heredity	8
Environment	7

Tip: TN SSLC Science Part 4 long answers carry 5 marks each. Always draw a neat labelled diagram wherever possible — diagrams are specifically awarded separate marks in TN Board evaluation.