Tamil Nadu SSLC March 2026 Science Question Paper with Step-by-Step Solutions

1. Identify the maximum amount of NaCl that can dissolve in 100 ml of water at the given temperature, which is 36 g.
2. Identify the amount of NaCl already dissolved in the solution, which is 25 g.
3. Calculate the additional amount of NaCl required to reach saturation by subtracting the dissolved amount from the maximum capacity: 36 g - 25 g = 11 g.

Answer: 11 g — option (b).

1. Powdered CaCO₃ has a much larger surface area compared to flaky CaCO₃.
2. A larger surface area allows more particles to be exposed to the reactant simultaneously.
3. This increases the frequency of collisions between reactant particles, leading to a faster reaction rate.

Answer: Powdered CaCO₃ reacts faster due to its large surface area — option (a).

1. A homologous series consists of compounds with the same general formula and functional group, where successive members differ by a -CH₂- group (14 u).
2. Check option (a): C₃H₈ (Propane) and C₄H₁₀ (Butane) are alkanes. C₄H₁₀ - C₃H₈ = CH₂. This fits the criteria.
3. Check option (b): C₂H₂ (Alkyne) and C₂H₄ (Alkene) have different functional groups and general formulas.
4. Check option (c): CH₄ (Alkane) and C₃H₆ (Alkene/Alkyne) have different functional groups.
5. Check option (d): C₂H₅OH (Ethanol) and C₄H₈OH (Butanol) differ by C₂H₃, not CH₂, so they are not successive members.

Answer: C₃H₈ and C₄H₁₀ (propane and butane) — option (a).

1. Endarch: the protoxylem lies towards the centre and the metaxylem towards the outside.
2. This is the arrangement in the stem; the root has exarch xylem (protoxylem outside).

Answer: Stem — option (b).

1. Recall the definition of chromosomal abnormalities.
2. Euploidy refers to the presence of complete sets of chromosomes.
3. Aneuploidy refers to the loss or gain of one or more individual chromosomes from a set.
4. Polyploidy refers to the addition of one or more complete sets of chromosomes.
5. Therefore, the loss of one or more chromosomes is called Aneuploidy.

Answer: Aneuploidy — option (b).

1. Excessive alcohol consumption over a long period causes chronic damage to the liver.
2. This damage leads to the formation of scar tissue and nodules, a condition known as cirrhosis.
3. Cirrhosis of the liver is the primary long-term pathological effect of alcoholism.

Answer: cirrhosis of the liver — option (b).

1. Identify the components of the Scratch interface.
2. Recall that the Stage is used to display the program output.
3. Recall that Sprites are the characters or objects in the program.
4. Recall that the Script Editor (or Scripting Area) is the panel where blocks are assembled to create code.
5. Select the component used for editing programs.

Answer: script editor — option (b).

1. State that the law applies to a fixed mass of gas.
2. State that the temperature must be kept constant.
3. State that the pressure is inversely proportional to the volume.
4. Write the mathematical relation as P ∝ 1/V or PV = constant.

Answer: Boyle's law states that for a fixed mass of gas at constant temperature, the pressure is inversely proportional to its volume (P ∝ 1/V).

1. Relative atomic mass is the ratio of the average mass of one atom of an element to 1/12th of the mass of one atom of carbon-12 isotope.
2. It is a dimensionless quantity and has no units.

Answer: Relative atomic mass is the ratio of the average mass of one atom of an element to 1/12th of the mass of one atom of carbon-12 isotope.

1. Rust is the reddish-brown hydrated iron(III) oxide formed when iron reacts with oxygen and moisture in the air.
2. The chemical equation for the formation of rust is: 4Fe + 3O₂ + xH₂O → 2Fe₂O₃·xH₂O

Answer: Rust is hydrated iron(III) oxide (Fe₂O₃·xH₂O). Equation: 4Fe + 3O₂ + xH₂O → 2Fe₂O₃·xH₂O

1. Identify the simplest ketone as Propanone (also known as Acetone).
2. Write the molecular formula as C₃H₆O.
3. Draw the structural formula: A central carbon atom is double-bonded to an oxygen atom (=O) and single-bonded to two methyl groups (CH₃).
4. The structure is represented as CH₃-CO-CH₃.

Answer: The simplest ketone is Propanone (Acetone). Its structural formula is CH₃-CO-CH₃.

1. Human circulation is called double circulation because the blood passes through the heart twice during one complete circuit around the body.
2. The first circuit is the pulmonary circulation, where deoxygenated blood goes from the right ventricle to the lungs and returns oxygenated to the left atrium.
3. The second circuit is the systemic circulation, where oxygenated blood goes from the left ventricle to the body parts and returns deoxygenated to the right atrium.

Answer: It is called double circulation because blood passes through the heart twice in one complete cycle: once for pulmonary circulation (to lungs) and once for systemic circulation (to body).

1. 1. Endocrine glands are ductless glands, whereas exocrine glands are ducted glands.
2. 2. Endocrine glands secrete hormones directly into the blood, whereas exocrine glands secrete their products (like saliva or sweat) through ducts to the outside of the body or into body cavities.

Answer: Endocrine glands are ductless and secrete hormones into the blood; exocrine glands are ducted and secrete products through ducts.

1. Wash the external genital area with clean water and mild soap at least twice a day.
2. Change sanitary pads or napkins every 4 to 6 hours to prevent infection.
3. Wear clean, cotton underwear that allows air circulation.
4. Avoid using scented soaps, douches, or perfumes in the genital area.

Answer: Maintain cleanliness by washing the genital area twice daily, changing sanitary pads every 4-6 hours, and wearing clean cotton underwear.

1. Archaeopteryx is called a connecting link because it shows features of both reptiles and birds.
2. It had feathers and wings like birds, but also a long bony tail, teeth, and clawed fingers like reptiles.

Answer: Archaeopteryx is a connecting link between reptiles and birds as it possesses characteristics of both groups.

1. Biogas is produced from the anaerobic decomposition of organic waste, so it is a renewable energy source.
2. Natural gas is a fossil fuel formed over millions of years, so it is a non-renewable energy source.
3. Carbon dioxide (CO₂) is the primary gas responsible for the greenhouse effect, so it is a greenhouse gas.
4. Compact Fluorescent Lamps (CFLs) consume less electricity than incandescent bulbs, so they are associated with energy saving.

Answer: Biogas – Renewable energy; Natural gas – Non-renewable energy; Greenhouse gas – CO₂; CFL bulbs – Energy saving

1. Identify the given values: Source frequency (f) = 500 Hz, Speed of sound (v) = 330 m/s, Speed of source (v_s) = 30 m/s.
2. Use the Doppler effect formula for a source moving towards a stationary listener: f' = f × (v / (v - v_s)).
3. Substitute the values into the formula: f' = 500 × (330 / (330 - 30)).
4. Calculate the denominator: 330 - 30 = 300.
5. Simplify the expression: f' = 500 × (330 / 300).
6. Calculate the final frequency: f' = 500 × 1.1 = 550 Hz.

Answer: The listener hears a frequency of 550 Hz.

1. (a) Two properties of light: 1. Light travels in straight lines (rectilinear propagation). 2. Light can be reflected, refracted, or dispersed.
2. (b) Ray diagram description: Draw a convex lens with principal axis. Mark optical centre O, focal point F, and 2F on the left side. Place an upright object (arrow) between F and 2F on the left.
3. Draw two rays from the top of the object: 1. A ray parallel to the principal axis which, after refraction, passes through the focal point F on the right side. 2. A ray passing through the optical centre O which goes straight without deviation.
4. The refracted rays intersect on the right side of the lens, beyond 2F. Draw the image from the principal axis to this intersection point. The image is real, inverted, and magnified (larger than the object).

Answer: (a) Light travels in straight lines and can be refracted. (b) The image formed is real, inverted, and magnified, located beyond 2F on the opposite side.

1. (a) Linear expansion: the increase in length of a solid on heating. Areal (superficial) expansion: the increase in its surface area on heating.
2. (b) The coefficient of real expansion of a liquid is the ratio of the true (real) rise in its volume per degree rise in temperature to its original volume. Its unit is K⁻¹.

Answer: Linear = change in length, areal = change in area; coefficient of real expansion = real rise in volume per degree ÷ original volume (unit K⁻¹).

1. 1. Density: the speed of sound in a gas is inversely proportional to the square root of its density (v ∝ 1/√d).
2. 2. Temperature: it is directly proportional to the square root of the absolute temperature (v ∝ √T).
3. 3. Relative humidity: sound travels faster in moist air than in dry air.

Answer: Density (v ∝ 1/√d), temperature (v ∝ √T) and relative humidity (faster in moist air).

1. (i) The atomic bombs dropped on Hiroshima and Nagasaki released intense ionizing radiation (gamma rays and neutrons). This radiation caused genetic mutations in the DNA of the parents, which were then passed on to their offspring, resulting in congenital diseases.
2. (ii) Use 1: Radioisotopes are used to study the uptake of nutrients (like nitrogen and phosphorus) by plants to determine the most effective fertilizer dosage.
3. (ii) Use 2: Radioisotopes are used in mutation breeding to induce genetic changes in seeds, leading to the development of new crop varieties with desirable traits such as higher yield or disease resistance.

Answer: (i) Due to genetic mutations caused by radiation from atomic bombs. (ii) Studying nutrient uptake and mutation breeding.

1. (a) The bond between H and F in HF is a covalent bond (specifically, a polar covalent bond).
2. (b) The property that determines this is the difference in electronegativity between the two atoms.
3. (c) Electronegativity increases from left to right across a period and decreases from top to bottom down a group.

Answer: (a) Covalent bond; (b) Difference in electronegativity; (c) Electronegativity increases across a period and decreases down a group.

1. Ethanoic acid is prepared by the oxidation of ethanol.
2. This process is carried out using an oxidising agent such as acidified potassium dichromate (K₂Cr₂O₇) or alkaline potassium permanganate (KMnO₄).
3. The reaction involves heating ethanol with the oxidising agent, which removes hydrogen atoms and adds an oxygen atom to form the carboxylic acid.
4. The chemical equation for this reaction is: C₂H₅OH + [O] → CH₃COOH + H₂O.

Answer: Ethanoic acid is made by oxidising ethanol with acidified potassium dichromate or alkaline potassium permanganate. The equation is C₂H₅OH + [O] → CH₃COOH + H₂O.

1. (i) The rings of cartilage hold the trachea open, so it does not collapse when air pressure inside drops; air passes freely.
2. (ii) The leech has suckers at both ends to hold on to the host, and its saliva has hirudin, which stops the host's blood from clotting while it feeds.

Answer: (i) To keep the trachea from collapsing. (ii) Suckers for attachment; hirudin in saliva to stop clotting.

1. Neurons are classified into three types based on their structure: Unipolar, Bipolar, and Multipolar.
2. Unipolar neurons have a single process extending from the cell body; they are found in the embryonic stage and in some invertebrates.
3. Bipolar neurons have two processes extending from the cell body (one axon and one dendrite); they are found in the retina of the eye and olfactory mucosa.
4. Multipolar neurons have multiple dendrites and a single axon extending from the cell body; they are the most common type found in the brain, spinal cord, and ganglia.

Answer: Neurons are structurally classified as Unipolar (one process), Bipolar (two processes), and Multipolar (multiple dendrites and one axon).

1. Forests provide oxygen for respiration and absorb carbon dioxide, helping to maintain the balance of gases in the atmosphere.
2. Trees prevent soil erosion by holding the soil with their roots and reducing the impact of rain, which conserves the topsoil.
3. Forests act as natural water regulators by absorbing rainwater and releasing it slowly, which prevents floods and maintains the water table.
4. Forests provide raw materials such as timber, paper, and medicinal herbs, and they serve as habitats for wildlife, maintaining biodiversity.

Answer: Forests are vital for maintaining ecological balance, preventing soil erosion and floods, providing raw materials, and supporting biodiversity.

1. Given: Initial volume of liquid V₁ = 50 ml, Final volume of liquid V₂ = 51.2 ml, Minimum volume reached V_min = 48.5 ml.
2. Apparent expansion is the change in the level of the liquid relative to the container. It is calculated as the difference between the final level and the initial level.
3. Apparent expansion = V₂ - V₁ = 51.2 ml - 50 ml = 1.2 ml.
4. Real expansion is the actual increase in the volume of the liquid. It is calculated as the difference between the final level and the minimum level reached (which accounts for the expansion of the container).
5. Real expansion = V₂ - V_min = 51.2 ml - 48.5 ml = 2.7 ml.

Answer: Apparent expansion = 1.2 ml; Real expansion = 2.7 ml

1. (i) Types of Inertia:
2. 1. Inertia of Rest: The tendency of a body to remain at rest. Example: When a bus suddenly starts, passengers fall backward because their feet move with the bus but their upper body tends to remain at rest.
3. 2. Inertia of Motion: The tendency of a body to continue moving with the same velocity. Example: When a moving bus stops suddenly, passengers fall forward because their feet stop with the bus but their upper body continues to move forward.
4. 3. Inertia of Direction: The tendency of a body to continue moving in the same direction. Example: When a car takes a sharp turn, passengers feel pushed outward (sideways) because their bodies tend to continue moving in the original straight-line direction.
5. (ii) Reason for pulling hands back:
6. When a fielder catches a fast-moving cricket ball, the ball has a large momentum. If the hands are held rigid, the time taken for the ball to stop is very small, resulting in a large force on the hands which can cause injury. By pulling the hands back, the fielder increases the time of impact. According to Newton's second law of motion (Force = Change in Momentum / Time), increasing the time of impact reduces the force exerted by the ball on the hands, preventing injury.

Answer: Inertia is of three types: Rest, Motion, and Direction. Fielders pull hands back to increase the time of impact, which reduces the force exerted by the ball and prevents injury.

1. Given resistors R₁ = 1 Ω, R₂ = 2 Ω, R₄ = 4 Ω are in parallel and current I₁ = 1 A flows through R₁.
2. Calculate potential difference V across R₁ using Ohm's law: V = I₁ × R₁ = 1 A × 1 Ω = 1 V.
3. In a parallel circuit, the potential difference is the same across all branches, so V = 1 V for R₂ and R₄.
4. Calculate current through R₂: I₂ = V / R₂ = 1 V / 2 Ω = 0.5 A.
5. Calculate current through R₄: I₄ = V / R₄ = 1 V / 4 Ω = 0.25 A.
6. State Ohm's law: The current flowing through a conductor is directly proportional to the potential difference across its ends, provided temperature and other physical conditions remain constant.
7. Express Ohm's law mathematically as V = IR, where V is potential difference, I is current, and R is resistance.

Answer: (i) Currents are 0.5 A and 0.25 A. (ii) Current is directly proportional to potential difference at constant temperature.

1. (i) A binary solution is a homogeneous mixture of two components, where one is the solute and the other is the solvent.
2. (ii) Examples: Gas in liquid: Oxygen dissolved in water; Solid in liquid: Salt dissolved in water; Solid in solid: Brass (Zinc in Copper); Gas in gas: Oxygen in nitrogen (Air).
3. (iii) Aqueous solutions are solutions where water is the solvent, e.g., salt in water. Non-aqueous solutions are solutions where a solvent other than water is used, e.g., iodine in ethanol.

Answer: Binary solution: mixture of two components. Examples: O₂ in water, NaCl in water, Brass, Air. Aqueous: water as solvent (salt water); Non-aqueous: non-water solvent (iodine in ethanol).

1. Part (i): Double displacement reactions involve the exchange of ions between two reactants. The two main types are precipitation and neutralization.
2. Precipitation reaction: Two aqueous solutions react to form an insoluble solid. Example: AgNO₃(aq) + NaCl(aq) → AgCl(s) + NaNO₃(aq).
3. Neutralization reaction: An acid and a base react to form salt and water. Example: HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O(l).
4. Part (ii): HNO₃ is a strong monoprotic acid that dissociates completely: HNO₃ → H⁺ + NO₃⁻.
5. The concentration of H⁺ ions is equal to the acid concentration: [H⁺] = 1.0 × 10⁻⁴ M.
6. Use the formula pH = −log₁₀[H⁺].
7. Substitute the value: pH = −log₁₀(1.0 × 10⁻⁴).
8. Calculate: pH = −(−4) = 4.

Answer: (i) Precipitation and neutralisation reactions. (ii) pH = 4.

1. (i) The three basic tissue systems of flowering plants are: 1. Dermal tissue system (protects the plant body), 2. Ground tissue system (fills the interior of the plant), and 3. Vascular tissue system (transports water, minerals, and food).
2. (ii) Photosynthesis is the process by which green plants use sunlight, water, and carbon dioxide to produce glucose and oxygen. It takes place in the chloroplasts of the mesophyll cells of the leaf.
3. (iii) The Respiratory Quotient (RQ) is the ratio of the volume of carbon dioxide (CO₂) released to the volume of oxygen (O₂) consumed during respiration. RQ = Volume of CO₂ released / Volume of O₂ consumed.

Answer: The three tissue systems are dermal, ground, and vascular. Photosynthesis occurs in chloroplasts. RQ is the ratio of CO₂ released to O₂ consumed.

1. (i) The pea plant has clear contrasting characters (tall/dwarf and others), is naturally self-pollinating but easy to cross, has a short life cycle and gives many seeds.
2. (ii) Okazaki fragments are short pieces of DNA made on the lagging strand during DNA replication; they are later joined by DNA ligase.
3. (iii) DNA consists of two polynucleotide chains (running in opposite directions and wound into a double helix).

Answer: (i) Contrasting characters, self-pollination, short life cycle, many seeds. (ii) Short DNA pieces on the lagging strand. (iii) polynucleotide.