CBSE Class 10 Science Board Paper Set 1 — MCQs with Answers
Original paper · CBSE patternWritten by our subject team, not a reprint of an official sample paper.
- Questions
- 20
- Time
- 25 min
- Marking
- +1, no negative marking
- Mix
- 8 Easy · 8 Medium · 4 Hard
Board Paper Set 1 — CBSE Class 10 Science is a full 20-question objective paper for Class 10 Science, written in the CBSE board pattern and marked the way the board marks: +1 for a correct answer and 0 for a wrong one — no negative marking, exactly like the real board paper. It follows Section A of a real CBSE paper: Q1–Q16 are single-correct MCQs, Q17–Q18 are case-based questions built on a short source, and Q19–Q20 are assertion–reason items using the board's own four option strings.
Difficulty is 8 Easy · 8 Medium · 4 Hard, weighted the way the board weights Section A. You get 25 minutes — about 75 seconds a question, the pace the real paper demands. 8 of the questions are solved in full below, with the correct option and a worked explanation for each; the remaining 12 are timed and scored when you sign in free.
From 2026-27 CBSE Class 10 has two board exams a year: the first around 15 February – 10 March 2027 is compulsory, and an optional improvement exam in May 2027 lets you re-attempt up to three subjects with the better score counting. That gives you two genuine attempts — and makes timed practice between February and May worth far more than it used to be.
8 solved questions from this paper
Answer and worked explanation shown for each. The remaining 12 are timed and scored when you sign in free.
- Q1Easy
Fried snacks left uncovered for several days develop an unpleasant smell and taste. This happens because the fats and oils present in them are:
A.oxidised by the oxygen of the air✓ CorrectB.reduced by the oxygen of the airC.hydrolysed by the moisture of the airD.neutralised by the carbon dioxide of the airAnswer: A. oxidised by the oxygen of the air
Explanation: Fats and oils slowly gain oxygen from the air, and gaining oxygen is oxidation. The oxidised products have a sharp smell and taste, and this spoiling is called rancidity, which is why food is packed in nitrogen or with antioxidants. Calling it reduction reverses the idea, since reduction means loss of oxygen or gain of hydrogen.
- Q2Easy
A student places a drop of a colourless solution on moist blue litmus paper and the paper turns red. The solution is most likely to be:
A.sodium hydroxide solutionB.lime waterC.dilute hydrochloric acid✓ CorrectD.sodium chloride solutionAnswer: C. dilute hydrochloric acid
Explanation: Blue litmus turns red only in the presence of hydrogen ions, so the solution must be acidic. Dilute hydrochloric acid supplies H⁺ ions in water and gives exactly this change. Sodium hydroxide and lime water are basic and would leave blue litmus unchanged, while a neutral sodium chloride solution has no effect on either litmus paper.
- Q3Easy
Which of the following metals is stored under kerosene in the laboratory?
A.Sodium✓ CorrectB.CopperC.ZincD.AluminiumAnswer: A. Sodium
Explanation: Sodium is so reactive that it catches fire on contact with the oxygen and moisture of the air, so it is kept immersed in kerosene, which contains neither. Copper, zinc and aluminium react far more slowly and can be left exposed, aluminium being protected further by the oxide layer that forms on its surface.
- Q4Medium
Which of the following chemical equations is correctly balanced?
A.3Fe + 4H₂O → Fe₃O₄ + 3H₂B.3Fe + 4H₂O → Fe₃O₄ + 4H₂✓ CorrectC.Fe + H₂O → Fe₃O₄ + H₂D.2Fe + 3H₂O → Fe₃O₄ + 3H₂Answer: B. 3Fe + 4H₂O → Fe₃O₄ + 4H₂
Explanation: An equation is balanced only when every element has the same number of atoms on both sides. With 3Fe and 4H₂O the left side has 3 Fe, 8 H and 4 O, and Fe₃O₄ with 4H₂ on the right also has 3 Fe, 8 H and 4 O. The common slip is to balance Fe and O and then forget hydrogen, which leaves 8 H on the left against only 6 H on the right.
- Q5Medium
On adding a substance to water, the pH of the solution falls from 7 to 4. The hydrogen ion concentration of the solution:
A.decreases 3 timesB.decreases 1000 timesC.increases 3 timesD.increases 1000 times✓ CorrectAnswer: D. increases 1000 times
Explanation: The pH scale is logarithmic, so a fall of one pH unit means ten times more hydrogen ions. A drop of three units therefore multiplies the H⁺ concentration by 10 × 10 × 10, that is 1000 times, and the solution becomes acidic. Reading the change of 3 units as a threefold change is the usual error, because it treats a logarithmic scale as if it were a linear one.
- Q6Medium
During vigorous exercise the supply of oxygen to human muscle cells becomes inadequate. Under these conditions pyruvate formed from glucose is converted into:
A.lactic acid✓ CorrectB.ethanol and carbon dioxideC.carbon dioxide and waterD.glucose and oxygenAnswer: A. lactic acid
Explanation: When oxygen runs short, muscle cells continue to break down pyruvate without it, and the product is lactic acid, whose build-up causes cramps. Ethanol and carbon dioxide are the anaerobic products in yeast, not in human muscle, while carbon dioxide and water appear only when oxygen is available for complete aerobic breakdown.
- Q7Hard
A metal X displaces copper from copper sulphate solution, but no reaction occurs when X is placed in zinc sulphate solution. Which statement about X is correct?
A.X is more reactive than zincB.X is less reactive than copperC.X lies between copper and zinc in the reactivity series✓ CorrectD.X lies below copper but above hydrogen in the reactivity seriesAnswer: C. X lies between copper and zinc in the reactivity series
Explanation: A metal can displace only a less reactive metal from its salt solution. Since X pushes copper out of copper sulphate, X is more reactive than copper, and since it cannot displace zinc, it is less reactive than zinc, which places it between the two. A position below copper is ruled out by the first reaction, and hydrogen already lies above copper, so nothing can sit below copper and above hydrogen.
- Q8Hard
A pure tall pea plant (TT) is crossed with a pure dwarf pea plant (tt), and the F₁ plants are then self-pollinated. What fraction of the F₂ plants will be tall and heterozygous?
A.1/4B.1/2✓ CorrectC.3/4D.1/3Answer: B. 1/2
Explanation: All F₁ plants are Tt, so selfing Tt × Tt gives the genotypes TT, Tt, Tt and tt in equal numbers. Two of these four are Tt, which are tall because T is dominant but heterozygous, giving a fraction of 1/2. The tempting answer 3/4 counts every tall plant, including the pure-breeding TT, and so overshoots what the question asks for.
Sit the full paper — free
All 20 questions on a 25-minute timer, scored automatically, with a worked solution for every one — including the 12 not shown above. Sign in with Google — no card needed.
Attempt this paper free →More Class 10 Science board papers
- Board Paper — 31 questions
- Board Paper Set 1 — you are here
- Board Paper Set 2 — 20 questions
- Board Paper Set 3 — 20 questions
Prefer chapter-by-chapter revision first? Class 10 Science notes & chapter MCQs →
Questions students ask about this paper
Is this an official CBSE sample paper?
No — and that is deliberate. This is an original paper written in the CBSE board pattern by our subject team, not a copy of CBSE's official Sample Question Paper. It means you get fresh questions you have not already seen on a dozen other sites, with instant scoring and worked solutions rather than a PDF.
How is this Class 10 Science paper marked?
+1 for a correct answer and 0 for a wrong one — no negative marking, exactly like the real board paper. So attempt every question — there is no penalty for a wrong answer on a board paper, and leaving a question blank can only cost you.
How long should this paper take?
25 minutes for 20 questions, roughly 75 seconds each. The timer runs whether or not you are watching it, which is the point: board marks are lost to pacing at least as often as to gaps in knowledge.
Do I need to pay to attempt it?
No. Sign in free with Google and the full paper opens with a live timer, automatic scoring and a worked solution for every question — including the ones not shown on this page.
Does the May 2027 improvement exam change how I should practise?
It raises the value of timed practice. Because the better of your two scores counts, a February attempt that goes badly is no longer final — but only if you know precisely which topics cost you the marks. A scored full-length paper tells you that; re-reading the chapter does not.