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CBSE Class 10 Science sample paper 2026-27, section by section: what each part tests

CMDLearn · 21 October 2026

CBSE has published the Class 10 Science (086) sample question paper and its marking scheme for 2026-27. This guide goes through the paper section by section: how many questions and marks each part has, which chapters they come from, what the marking scheme pays for, and which topics the curriculum says will not be examined. Every fact is from CBSE's own documents, linked at the end with page numbers. The worked examples and self-check are our own.

Download the paper and the marking scheme first and keep them open: sample paper, marking scheme. CBSE also publishes both in Hindi on its Class X sample paper page.

The paper at a glance

• 39 questions, 80 marks, 3 hours. The paper is split by subject: Biology in Section A, Chemistry in Section B, Physics in Section C (sample paper, page 1).
• The design has not changed. Every page of the sample paper carries CBSE's note that the question paper design and assessment pattern are the same for 2026-27. The 2025-26 paper had the same 39 questions in the same three sections, with assertion-reason questions in the same places. The questions themselves are new.
• Some questions have an internal choice (attempt A or B). The curriculum says internal choice will be about 33% of the paper (Science curriculum, page 9).
• Some questions have an alternative for visually impaired students, printed below the main question, usually where the main question uses a picture or graph.
• The other 20 marks are internal assessment at school: periodic assessment 5, multiple assessment 5, portfolio 5 and practical work 5 (curriculum, page 9).

Across the paper that is 20 one-mark questions (4 of them assertion-reason), 6 two-mark, 7 three-mark, 3 four-mark and 3 five-mark questions: 39 questions, 80 marks.

Where the marks come from

The section totals match the curriculum's unit marks exactly (Science curriculum, page 4):

• Biology, 30 marks = World of Living (25) + Natural Resources (5). The Natural Resources marks are the "Our Environment" questions: Q7 (a food chain), Q9 (energy flow, assertion-reason) and Q14 (energy and pesticides in a food chain), 1 + 1 + 3 = 5 marks.
• Chemistry, 25 marks = Chemical Substances, Nature and Behaviour (25).
• Physics, 25 marks = Natural Phenomena (12: light, the eye, the prism; Q30, Q32, Q33, Q35, Q39) + Effects of Current (13: electricity and magnetism; Q31, Q34, Q36, Q37, Q38).

The curriculum also splits the paper by skill: about 50% knowledge and understanding, 30% applying it, and 20% analysing, evaluating and creating (page 9). In this paper that shows up as experiments to read (Q2, Q28), data and labels to interpret (Q22), and "who is right?" dialogues (Q29).

What will not be examined

The curriculum keeps some topics in the syllabus but assesses them only formatively, in class, not in the board paper:

• Chemistry: the periodic table chapter: Döbereiner, Newlands, Mendeléev and the modern table (page 4).
• Biology: the Evolution topics: acquired and inherited traits, speciation, fossils, evolution by stages, human evolution (page 5).
• Physics: the electric motor, electromagnetic induction and the electric generator (page 6). Also excluded: why the sun looks reddish at dawn and dusk (page 6).
• Boxed text: information in the boxes of the NCERT books is not assessed in the year-end exam (page 6).

One line to read carefully. The "Note for Teachers" on page 6 lists "Periodic Classification of Elements; Heredity and Evolution; and Electric Effects of Electric Current" as not assessed. But the Unit II list on page 5 keeps Heredity and Mendel's laws in the examined syllabus, and the sample paper asks them in Q15 (4 marks). Likewise the magnetic effects of current are examined (Q36, Q38); only the motor, induction and generator are formative. So prepare Mendel's crosses and the magnetic field of a current, and ask your teacher if your school reads the note differently.

Section A: Biology (Q1 to Q16, 30 marks)

What it tests. Life processes (photosynthesis, digestion, breathing, the kidneys, the heart), control and coordination, reproduction, heredity and the environment. The one-mark questions are mostly "apply it" rather than "recall it": Q4 asks what happens to flowers whose anthers were removed before pollination (no seeds or fruit), and Q6 gives the chromosome number of an apple gamete (17) and asks for the body cells (34).

How the long answers are marked.

• Q14 (3 marks): if 10 kJ reaches the fourth trophic level of a food chain, how much was at the producer level? Only about a tenth of the energy passes to each next level, and the fourth level is three steps above the producers, so the answer is 10 × 10 × 10 × 10 = 10,000 kJ. The same question asks which level collects the most pesticide: the top one, because of biological magnification.
• Q15 (4 marks), Mendel's crosses: violet flowers in F1 = 100%, in F2 = 75%; tall plants with white flowers in F2 = 3/16, that is 18.75%; medium-height plants with light violet flowers = zero, because a single dominant copy gives the full trait in pea plants; short plants with white flowers = 0 in F1 and 1/16, that is 6.25%, in F2. Each part has its own mark, and the reason is part of it.
• Q16 (5 marks): in the heart option, 1 mark for naming the four-chambered heart, 2 for explaining why separating oxygenated and deoxygenated blood matters to warm-blooded animals, then 1 + 1 for the fish heart. In the breathing option, the four steps of breathing in (ribs lifted, diaphragm flattened, chest cavity larger, air drawn in) earn half a mark each. Writing all four short points is worth more than one long sentence.

Section B: Chemistry (Q17 to Q29, 25 marks)

What it tests. Chemical reactions, acids, bases and salts, metals and non-metals, and carbon compounds. Several one-mark questions are set in daily life: a chameleon's colour change (Q17, a physical change: only the spacing between crystals changes), soap and detergent in hard water (Q19), and antioxidants on a biscuit label (Q22: nitrogen in food packets serves the same purpose).

Q20 (1 mark), worth learning as a set: which salts contain water of crystallisation? Plaster of Paris (CaSO₄·½H₂O), washing soda (Na₂CO₃·10H₂O) and gypsum (CaSO₄·2H₂O) do; baking soda (NaHCO₃) does not.

Q29 (5 marks), find the error. The paper gives two wrong equations and asks you to correct them. The marking scheme's answers, which we checked atom by atom:

• MgCl₂ + 2AgNO₃ → 2AgCl + Mg(NO₃)₂ (the paper's "AgCl₂" and "MgNO₃" have the wrong formulas, because silver forms Ag⁺ and the nitrate ion is NO₃⁻ with magnesium as Mg²⁺)
• 2Al + 3H₂SO₄ → Al₂(SO₄)₃ + 3H₂ (aluminium with dilute acid gives hydrogen gas, not water)

The other option asks who is right about decomposition reactions; the marking scheme gives 2 marks for the rule (one compound breaks into simpler substances, which can be elements or compounds) with the magnesium carbonate example, and 1 mark for applying it to water.

Q28 (4 marks), an experiment to read. Rods of five metals, candles fixed at their ends, and a graph of the time each candle takes to fall. The best conductor is the one whose candle falls first; a metal that conducts better than aluminium but worse than copper must fall between their times (20 s in the paper). The last part has two options. If all the rods are made 20% longer, every candle takes longer to fall but the order stays the same, because heat has further to travel. If the rods differ in thickness, the conclusion is not valid, because the rods must have the same dimensions (a thicker rod takes more time).

Section C: Physics (Q30 to Q39, 25 marks)

What it tests. Light (lenses, refraction, the eye, the prism, scattering) and electricity and magnetism.

• Q31 (1 mark): an appliance rated 1000 W and run on 250 V draws I = P ÷ V = 1000 ÷ 250 = 4 A.
• Q35 (3 marks), a concave lens: the image is one third the size of an object 24 cm from the lens. With the sign convention, u = −24 cm and the magnification is +1/3, so v = m × u = −8 cm (a virtual image on the same side as the object). The lens formula 1/f = 1/v − 1/u then gives f = −12 cm. One mark each for the type of lens, v and f. The visually impaired alternative uses a convex lens with f = 12 cm and the object 24 cm away: the image is real, 24 cm on the other side.
• Q37 (3 marks), a circuit with a 15 V battery. The marking scheme reduces the resistors to a total of 7.5 Ω, so the current is 15 ÷ 7.5 = 2 A (2 marks), and the potential difference across the part AB of 1 Ω is 2 × 1 = 2 V (1 mark). In the visually impaired alternative, 2 Ω, 3 Ω and 5 Ω in series give 10 Ω, a current of 1.5 A and 4.5 V across the 3 Ω resistor.
• Q38 (4 marks), a case study: a door lock worked by a solenoid. Why the iron core (it makes the field stronger), how to find the solenoid's poles, and what doubling the current does (the field gets stronger, so the bolt is pulled more firmly).
• Q39 (5 marks): either the eye (accommodation, near point, the lens for short sight, with a 2-mark diagram) or the prism and the sky (dispersion, which colour bends least, why space looks dark, with a 2-mark diagram). The diagram is 2 of the 5 marks in both options, so practise drawing it.

How to use the paper

• Write it once in 3 hours, in one sitting. A time plan (ours, not CBSE's): read the whole paper and choose your internal choices in the first 15 minutes; then about 50 minutes for Biology, 45 for Chemistry and 45 for Physics; keep the last 25 minutes to check. That adds up to 180 minutes.
• Mark it with the marking scheme, point by point. Many answers are split into half and one-mark points. Count which points you wrote, not whether your answer "felt right".
• Practise the four drawings that carry marks: the eye with its correcting lens, the prism, the breathing diagram and the heart.
• Learn the assertion-reason options by heart. There are 4 of them. The two biology ones (Q8, Q9) both have a false assertion and a true reason, so read the assertion as carefully as the reason.

Self-check: 6 questions in the style of the paper (our own)

Try them on paper first. Answers are below.

• Q1. A food chain has 20 kJ at the third trophic level. About how much energy was at the producer level?
• Q2. Two tall pea plants, both Tt, are crossed. What percentage of the offspring will be short?
• Q3. Correct this equation: Na + H₂O → NaOH + H₂.
• Q4. A 2000 W heater is connected to a 250 V supply. How much current flows?
• Q5. An object is 30 cm in front of a concave lens of focal length 15 cm. Where is the image, and what is its magnification?
• Q6. Resistors of 1 Ω, 2 Ω and 3 Ω are in series with a 12 V battery. Find the current and the voltage across the 2 Ω resistor.

Answers:

• Q1: The third level is two steps above the producers, so about 20 × 10 × 10 = 2,000 kJ.
• Q2: Tt × Tt gives TT, Tt, Tt and tt in the ratio 1 : 2 : 1, so 1 in 4 is short: 25%.
• Q3: 2Na + 2H₂O → 2NaOH + H₂ (2 Na, 4 H and 2 O on each side).
• Q4: I = 2000 ÷ 250 = 8 A.
• Q5: u = −30 cm and f = −15 cm. 1/v = 1/f + 1/u = −1/15 − 1/30 = −1/10, so v = −10 cm (virtual, same side as the object), and m = v/u = 1/3 (upright, one third the size).
• Q6: Total 6 Ω, so I = 12 ÷ 6 = 2 A, and the voltage across 2 Ω is 2 × 2 = 4 V.

How to check an AI's answer for this paper

• Check the topic is still examined. AI answers and older guides still drill the periodic table, evolution and the electric motor and generator. In 2026-27 these are taught but not examined in the board paper (see above).
• Check the signs in lens and mirror questions. A virtual image from a concave lens has a negative v and a negative f in the NCERT sign convention. An answer with f = +12 cm for Q35 has the sign wrong.
• Check the answer against the marking scheme, not just the textbook. The scheme shows how many points an answer needs. A long AI paragraph can still miss the half-mark points.
• Balance equations yourself. Count every atom on both sides. Chatbots often fix one element and break another.

More on using AI well: how to use ChatGPT for homework without cheating yourself.

Practise

• Timed: the free Class 10 revision papers include two Science papers, laid out in 1, 2, 3 and 5-mark sections and marked in your browser (shorter than the real paper, no case studies; our own questions, waiting for teacher review).
• Chapter by chapter: Class 10 worksheets and the practice page (pick Class 10), in English, Hindi and Marathi.
• Two chapters in depth: Chemical Reactions and Equations, explained and Electricity, explained.
• The whole year: Class 10 boards, a 60-day revision plan. The Maths paper in the same format: CBSE Class 10 Maths sample paper 2026-27.
• Practice questions with answers, chapter by chapter: Life Processes, Acids, Bases and Salts, Metals and Non-metals, Carbon and its Compounds and Light: Reflection and Refraction.

Where CMDLearn fits

CMDLearn is building an AI tutor for Classes 1 to 10 that explains a step and checks the child's working, but leaves the writing to the child. It is still in development, and no child uses it yet. If you would like to hear when there is something to try, you can join the waitlist.

Sources

All opened and read on 21 October 2026. Page numbers are PDF pages.

• CBSE, Science (086) Sample Question Paper, Class X, 2026-27: page 1 (39 questions, three sections, 80 marks, 3 hours), pages 1-5 (Section A), 5-11 (Section B), 11-15 (Section C). cbseacademic.nic.in/web_material/SQP/ClassX_2026_27/Science-SQP.pdf
• CBSE, Science (086) Marking Scheme, Class X, 2026-27: pages 1-3 (Section A: Q14, Q15, Q16), 3-6 (Section B: Q20, Q28, Q29), 7-12 (Section C: Q31, Q35, Q37, Q38, Q39). cbseacademic.nic.in/web_material/SQP/ClassX_2026_27/Science-MS.pdf
• CBSE, Science curriculum, Class X, 2026-27: page 4 (unit marks; periodic classification formative), page 5 (Unit II, heredity examined, evolution formative), page 6 (motor, induction and generator formative; sunrise and sunset excluded; note for teachers; boxed text not assessed), page 9 (question paper design, internal choice, internal assessment). cbseacademic.nic.in/web_material/CurriculumMain27/SecPart1/Science_SecP1_2026-27.pdf
• CBSE, Science (086) Sample Question Paper, Class X, 2025-26, page 1 (same 39-question, three-section design). cbseacademic.nic.in/web_material/SQP/ClassX_2025_26/Science-SQP.pdf
• CBSE, sample papers and marking schemes, Class X, 2026-27 (English and Hindi): cbseacademic.nic.in/SQP_CLASSX_2026-27.html

The structure, the marks, the answers quoted from the marking scheme and the curriculum facts are from the documents above. The explanations, the time plan and the self-check questions are our own, and every number on this page was checked by script against the documents and by calculation.

Practise this class: Class 10 worksheets, chapter by chapter · free practice, marked instantly · timed revision papers