CBSE Class 10 Science Board Paper Set 3 — 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 3 — 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
An iron nail dipped in copper sulphate solution slowly acquires a reddish-brown coating, and the blue colour of the solution fades. The reaction Fe + CuSO₄ → FeSO₄ + Cu is an example of a:
A.combination reactionB.decomposition reactionC.displacement reaction✓ CorrectD.double displacement reactionAnswer: C. displacement reaction
Explanation: One element, iron, pushes another element, copper, out of its salt solution because iron is the more reactive of the two, and this single exchange is a displacement reaction. In a double displacement reaction the two reactants would swap ions with each other, as sodium sulphate does with barium chloride, and both reactants would have to be compounds, which is not the case here.
- Q2Easy
Dilute hydrochloric acid is poured over zinc granules and the gas evolved burns with a pop sound when a burning splinter is brought near it. The gas is:
A.Hydrogen✓ CorrectB.OxygenC.Carbon dioxideD.ChlorineAnswer: A. Hydrogen
Explanation: A dilute acid reacting with a metal gives the corresponding salt and hydrogen, here zinc chloride and H₂. The pop sound is the standard test for hydrogen, produced as the gas burns explosively in a small quantity of air. Carbon dioxide would put the splinter out instead of burning, and it is released by acids acting on carbonates, not on metals.
- Q3Easy
Which of the following is a metal that exists in the liquid state at room temperature?
A.SodiumB.Mercury✓ CorrectC.BromineD.GalliumAnswer: B. Mercury
Explanation: Mercury is the one metal that is liquid at ordinary room temperature, which is why it is used in thermometers, and like other metals it conducts electricity and has a lustrous surface. Bromine is also a liquid but it is a non-metal, so it fails the first condition, and gallium, though it melts in the warmth of the hand at about 30 °C, is still a solid at normal room temperature.
- Q4Medium
Plaster of Paris is obtained by heating gypsum to about 373 K. Its chemical formula is:
A.CaSO₄·2H₂OB.CaSO₄C.CaCO₃·H₂OD.CaSO₄·½H₂O✓ CorrectAnswer: D. CaSO₄·½H₂O
Explanation: Gypsum is CaSO₄·2H₂O, and controlled heating drives off three quarters of that water, leaving half a molecule of water for each formula unit of calcium sulphate. Written for two formula units this is (CaSO₄)₂·H₂O. When water is added back the material reverts to gypsum and sets hard, which is what makes it useful for plaster casts, and heating too strongly would leave the anhydrous salt, which no longer sets.
- Q5Medium
Silver ornaments left in the open for a long time slowly turn black. This happens because silver reacts with the ___ of the air to form ___.
A.oxygen; silver oxideB.carbon dioxide; silver carbonateC.hydrogen sulphide; silver sulphide✓ CorrectD.nitrogen; silver nitrideAnswer: C. hydrogen sulphide; silver sulphide
Explanation: Air contains traces of hydrogen sulphide, and silver reacts with it to form a thin black layer of silver sulphide on the surface, which is called tarnishing. Copper behaves differently, reacting with moist carbon dioxide to acquire a green coating of basic copper carbonate, and confusing the two is the usual error here.
- Q6Medium
Ethanol is warmed with ethanoic acid in the presence of a few drops of concentrated sulphuric acid, and a sweet-smelling liquid is obtained. This liquid is:
A.an ester✓ CorrectB.a soapC.an aldehydeD.an alcoholAnswer: A. an ester
Explanation: An alcohol heated with a carboxylic acid and a little concentrated sulphuric acid gives an ester and water, a change called esterification in which the acid acts as a dehydrating agent. Esters have pleasant fruity smells and are used in perfumes and flavourings. A soap would be formed only if the ester were afterwards heated with sodium hydroxide, a separate reaction known as saponification.
- Q7Hard
A person cannot see objects lying beyond 1 m clearly, although nearby objects are seen without difficulty. The power of the corrective lens required is:
A.−1.0 D✓ CorrectB.+1.0 DC.−4.0 DD.+4.0 DAnswer: A. −1.0 D
Explanation: The far point of this myopic eye is 1 m, so the lens must take rays from a very distant object and form their image at that far point. Using 1/f = 1/v − 1/u with v = −1 m and u at infinity gives f = −1 m, and P = 1/f = −1 dioptre, the minus sign showing a diverging lens. Forgetting that the corrective lens must be concave, and quoting +1.0 D instead, is the frequent slip.
- Q8Hard
A student connects a 4 Ω resistor and a 12 Ω resistor side by side across a 12 V battery so that each has its own branch. She inserts an ammeter in the branch containing the 12 Ω resistor. The ammeter reading will be:
A.1 A✓ CorrectB.3 AC.4 AD.0.33 AAnswer: A. 1 A
Explanation: The two resistors are in parallel, so each branch gets the full battery voltage of 12 V rather than a share of it. For the 12 Ω branch, Ohm's law gives I = V/R = 12/12 = 1 A. Working out the equivalent resistance of 3 Ω and quoting the resulting 4 A is a common trap, but that figure is the total current drawn from the battery, not the current in this one branch.
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 — 20 questions
- Board Paper Set 2 — 20 questions
- Board Paper Set 3 — you are here
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.