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Class 8 Science competency-based questions 2026-27: what they look like, with 8 of our own

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A competency-based question gives you a situation, a small table of results or two linked statements, and asks you to use what you learnt in the chapter, not to repeat a line from it. This guide shows what the NCERT Class 8 Science book, Curiosity, says about competencies, the kinds of these questions already in its exercises, and then 8 practice questions of our own, two each from four chapters, with worked answers.

The 8 questions are our own, drafted with AI help. Every number was re-checked by a script and every answer was checked against the textbook page named under it, but no practising teacher has reviewed them yet. The data in the questions is made up for practice unless a page number says it comes from the book. If you find a mistake, please tell us.

What the Class 8 book means by competencies

Curiosity, the Grade 8 Science textbook (Reprint 2026-27), says in its opening pages that it follows the National Education Policy (NEP) of 2020 and the 2023 school curriculum framework (NCF-SE), and that it expects students to reach all the competencies set for Grade 8, the last year of the Middle Stage.

The book's end-of-chapter section, "Keep the curiosity alive", mixes picture questions, puzzles and multiple-choice questions. The book's note on it says these questions help to assess the competencies built in each chapter, and it recommends that teachers use similar questions for evaluation. So for Class 8, competency-based questions are not a separate syllabus: they are the chapter's ideas asked in a new way, and your school sets the tests.

Three kinds appear in the book's own exercises:

In the Class 10 board papers, CBSE makes about half the questions competency-focused; our Class 10 Science competency-based questions guide explains that pattern. Practising the same kinds of question in Class 8 makes Classes 9 and 10 easier.

How to answer them

The four choices used for every assertion-reason question below are the usual ones: (i) both are correct and the reason explains the assertion; (ii) both are correct but the reason does not explain the assertion; (iii) the assertion is correct but the reason is wrong; (iv) both are wrong.

The Invisible Living World (Chapter 2)

Question 1. A school fills three bins with the same kitchen peels and a layer of garden soil (made-up results). Bin A is kept dry; after 12 weeks the peels have hardly changed. Bin B is sprinkled with water so it stays damp; after 6 weeks it is dark, crumbly manure. Bin C is flooded with water; after 10 weeks it is only partly broken down. (a) Which bin had the best conditions? (b) What living things turn the peels into manure? (c) Why did so little happen in Bin A?

Answer: (a) Bin B; (b) microorganisms such as bacteria and fungi; (c) the microbes did not have the moisture they need. (a) Bin B made manure in the shortest time. (b) Microorganisms break the peels down into simpler substances rich in nutrients; this is decomposition, and the nutrients return to the soil. (c) The chapter says manure forms at the right temperature and at an appropriate level of moisture. Bin A was too dry, and the flooded Bin C did not have the appropriate level either, so both were slower than Bin B. (Decomposition and manure, page 19.)

Question 2. Assertion: Dead leaves left in a compost pit slowly turn into soil-like manure. Reason: Yeasts, which are fungi, are used to make bread and idli batter rise. Choose (i), (ii), (iii) or (iv).

Answer: (ii), both are correct but the reason does not explain the assertion. The leaves are broken down by microorganisms that decompose waste and return its nutrients to the soil (page 19). Yeasts are fungi and are used in breads, cakes and idlis (page 25), so the reason is also true, but it is about fermentation in food, not about decomposition in the pit.

Exploring Forces (Chapter 5)

Question 3. A toy car is let go from the same point on a ramp each time and rolls out onto four different floor coverings. How far it travels on each before stopping (made-up results): marble 3.6 m, linoleum 2.5 m, jute mat 1.2 m, rubber mat 0.7 m. (a) Put the coverings in order, from the most friction to the least. (b) Rani says, "On the marble there was no friction at all." Is she right? (c) Which covering would you lay on a sloping hospital entrance, and why?

Answer: (a) rubber mat, jute mat, linoleum, marble; (b) no; (c) the rubber mat. (a) Friction acts against the motion and brings the car to rest, so the shorter the distance, the greater the friction. (b) The car did stop on the marble, so a force was still acting against its motion. Even surfaces that look smooth have many tiny irregularities that catch on each other. (c) The rubber mat gave the most friction, so feet and wheels are least likely to slip on it. Friction depends on the surfaces in contact and is greater on rough ones. (Friction, page 68.)

Question 4. Assertion: A plastic comb, run a few times through dry hair, can pull tiny bits of thermocol towards it without touching them. Reason: Electrostatic force acts only when the two objects touch each other. Choose (i), (ii), (iii) or (iv).

Answer: (iii), the assertion is correct but the reason is wrong. Rubbing certain materials together builds up static charges on them, and a charged object can pull light, uncharged things towards it (page 70). That pull works across a gap: the chapter calls electrostatic force a non-contact force (page 71). So the reason is the opposite of the truth.

Light: Mirrors and Lenses (Chapter 10)

Question 5. A student measures four rays striking a plane mirror and records the angles from the normal (made-up readings). Angle of incidence and angle of reflection: 15° and 15°; 30° and 30°; 45° and 54°; 60° and 60°. (a) Which reading must have been copied wrongly? (b) What should it have been? (c) Which law of reflection did you use?

Answer: (a) the third reading; (b) 45°; (c) the angle of incidence equals the angle of reflection. In the other three readings the two angles are the same, as the law says. For an angle of incidence of 45°, the angle of reflection must also be 45°, so 54° was most likely the digits written the wrong way round. (Laws of reflection, page 158.)

Question 6. Assertion: Whether you stand close to a plane mirror or a few steps back from it, your image stays upright and the same size as you. Reason: The image in a plane mirror is always upright and exactly as large as the object. Choose (i), (ii), (iii) or (iv).

Answer: (i), both are correct and the reason explains the assertion. The chapter compares the three kinds of mirror: the image in a plane mirror stays erect and the same size, while in concave and convex mirrors the size changes as the object moves (page 156). Your distance from a plane mirror therefore does not change the size or the way up of your image.

How Nature Works in Harmony (Chapter 12)

Question 7. For three summers, a farmer counts how many times bees visit the flowers of his fruit orchard in the same morning hour, and how many fruits he picks per tree (made-up data). Year 1: 120 visits, 400 fruits. Year 2: 70 visits, 260 fruits. Year 3: 30 visits, 150 fruits. (a) How do the two sets of numbers change together? (b) Using the chapter, explain how fewer bee visits could lead to fewer fruits. (c) Can the farmer be sure from these numbers alone that the bees are the cause?

Answer: (a) both fall each year; (b) fewer bees means less pollination; (c) no, but the data fit that explanation. (a) Bee visits fall from 120 to 70 to 30, and fruits per tree from 400 to 260 to 150. (b) Insects such as bees move pollen from a flower's stamens over to the carpels, of that flower or of others. This pollination is essential for fruits and seeds to form, so with fewer visits, fewer flowers become fruits (page 194). (c) Other changes, such as the weather, can also lower a harvest, so the numbers show the two go together but do not prove the cause on their own. Comparing with a nearby orchard where the bees did not decline would help. (Pollination, page 194.)

Question 8. Assertion: A tick feeding on a dog's blood is an example of mutualism. Reason: In mutualism, one partner gains and the other suffers. Choose (i), (ii), (iii) or (iv).

Answer: (iv), both are wrong. The tick gains and the dog is harmed (its skin gets irritated), which the chapter calls parasitism. In mutualism both organisms benefit, as with honeybees and flowers: the bee gets nectar and the flower is pollinated. (Interactions between organisms, page 203.)

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Sources

All opened and read on 4 November 2026. Page numbers are the printed page numbers of the textbook.

The science in each answer is from the textbook pages named. The situations, data, questions and worked answers are our own, and every number was re-checked by script. This guide is general information; follow your teacher and the textbook.

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