CBSE Class 10 Science Competency-Based Questions Chapter-Wise Practice 2027

In short: 50% of your CBSE Class 10 Science paper (40 out of 80 marks) consists of Competency-Based Questions. These include application MCQs, 4 assertion-reason questions in Section A, and 3 case-based questions of 4 marks each in Section E. The paper has 39 questions across three sub-sections — Physics, Chemistry, and Biology — and CBQs appear in every sub-section.

Understanding the CBQ Pattern in Class 10 Science

The CBSE Class 10 Science paper for 2027 follows the same competency-based structure as 2025-26. The paper is divided into three subject-specific sections (Physics, Chemistry, Biology), each containing its own mix of MCQs, assertion-reason, short answer, long answer, and case-based questions.

The Science chapter-wise marks weightage shows that Electricity, Light, Chemical Reactions, and Life Processes carry the heaviest marks. Case studies are drawn almost exclusively from these high-weight chapters.

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Case Study Questions: Physics

Case Study 1: Electricity — Household Circuit Problem

Ravi's family uses a 60 W bulb, a 1000 W heater, and a 100 W fan in their house. The supply voltage is 220 V. One day, they noticed the MCB tripping repeatedly. An electrician found that the heater's wire had a loose connection causing a short circuit.

(i) What is the total power consumed when all three appliances run together? (a) 1060 W (b) 1160 W (c) 1260 W (d) 1360 W

(ii) What is the current drawn by the heater alone? (a) 3.45 A (b) 4.55 A (c) 5.00 A (d) 2.27 A

(iii) Why does a short circuit cause the MCB to trip? (a) Voltage becomes zero (b) Current increases enormously (c) Resistance increases (d) Power decreases

(iv) All household appliances are connected in: (a) Series (b) Parallel (c) Mixed combination (d) None of these

Answers: (i) b — 60 + 1000 + 100 = 1160 W (ii) b — I = P/V = 1000/220 = 4.55 A (iii) b — Short circuit reduces resistance to near zero, causing very high current (iv) b — Parallel, so each appliance gets 220 V independently

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Case Study 2: Light — Refraction Through a Glass Slab

In a physics lab, a student shines a ray of light through a rectangular glass slab placed on a white sheet. She traces the incident ray, emergent ray, and marks the angles. She notices that the emergent ray is parallel to the incident ray but laterally displaced.

(i) The speed of light in glass compared to air is: (a) Same (b) Greater (c) Lesser (d) Cannot be determined

(ii) When light enters the glass slab from air, it bends: (a) Away from the normal (b) Towards the normal (c) Does not bend (d) Along the normal

(iii) The emergent ray is parallel to the incident ray because: (a) Glass has uniform thickness (b) The refractive index is 1 (c) Light does not refract in glass (d) Angle of incidence equals angle of reflection

(iv) If the angle of incidence is 45° and the refractive index of glass is √2, the angle of refraction inside the glass is: (a) 45° (b) 30° (c) 60° (d) 90°

Answers: (i) c (ii) b (iii) a — the two parallel surfaces cause equal and opposite bending (iv) b — sin 45°/sin r = √2, so sin r = 1/2, r = 30°

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Case Study Questions: Chemistry

Case Study 3: Chemical Reactions — Industrial Corrosion

A factory stores iron nails in open containers. After a few weeks, the workers notice a reddish-brown layer on the nails. The factory manager decides to apply a layer of zinc coating on the remaining nails to prevent further damage. A chemist explains that the reddish-brown substance is iron oxide formed by the reaction of iron with oxygen and moisture.

(i) The reddish-brown substance on iron nails is: (a) Iron sulphide (b) Iron oxide (hydrated) (c) Iron carbonate (d) Iron chloride

(ii) The process described is called: (a) Rancidity (b) Corrosion (c) Reduction (d) Decomposition

(iii) Coating iron with zinc is called: (a) Electroplating (b) Galvanisation (c) Alloying (d) Anodising

(iv) Which of the following is NOT a method to prevent rusting? (a) Painting (b) Oiling (c) Galvanisation (d) Adding water

Answers: (i) b — Fe₂O₃·xH₂O (ii) b (iii) b (iv) d

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Case Study 4: Life Processes — Blood and Circulation

During a health camp, a doctor explains to Class 10 students how the human heart works. She uses a diagram showing four chambers and describes how oxygenated and deoxygenated blood flow through separate circuits. She explains that the double circulatory system prevents mixing of oxygen-rich and oxygen-poor blood, which is essential for maintaining body temperature in mammals.

(i) Which chamber of the heart receives oxygenated blood from the lungs? (a) Right atrium (b) Right ventricle (c) Left atrium (d) Left ventricle

(ii) The valve between the left atrium and left ventricle is called: (a) Tricuspid valve (b) Bicuspid (mitral) valve (c) Aortic valve (d) Pulmonary valve

(iii) Why do mammals have a four-chambered heart? (a) To pump blood faster (b) To prevent mixing of oxygenated and deoxygenated blood (c) To increase blood pressure (d) To reduce heart rate

(iv) The blood vessel that carries deoxygenated blood from the heart to the lungs is: (a) Pulmonary vein (b) Aorta (c) Pulmonary artery (d) Vena cava

Answers: (i) c (ii) b (iii) b (iv) c

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Source-Based Questions: Data Interpretation

Source-Based: Periodic Classification — Trend Analysis

Study the following data table showing properties of elements in Period 3 of the modern periodic table:

(i) As we move left to right in Period 3, the atomic radius: (a) Increases (b) Decreases (c) Remains same (d) First increases then decreases

(ii) Which element in the above table has the highest electronegativity? (a) Na (b) Al (c) Cl (d) Ar

(iii) The element Si is classified as a metalloid because: (a) It has 4 valence electrons (b) It has properties of both metals and non-metals (c) It is in Group 14 (d) Its atomic radius is 117 pm

Answers: (i) b (ii) c — Chlorine (noble gases do not form bonds, so electronegativity is not applicable) (iii) b

Source-Based: Environment — Data from a Field Study

A group of students measured the dissolved oxygen (DO) level in a river at different points:

(i) Which location has the lowest dissolved oxygen? (a) Near Forest (b) Near Village (c) Near Factory (d) 2 km After Factory

(ii) Why is the DO level lowest near the factory? (a) Trees absorb oxygen (b) Factory releases hot water and pollutants (c) Fish consume all oxygen (d) Water evaporates

(iii) The partial recovery of DO level 2 km after the factory indicates: (a) Self-purification of water (b) More pollution downstream (c) Presence of algal blooms (d) Temperature increase

Answers: (i) c (ii) b (iii) a

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Assertion-Reason Questions: Chapter-Wise

Options for all:

• (a) Both A and R are true, and R is the correct explanation of A.
• (b) Both A and R are true, but R is NOT the correct explanation of A.
• (c) A is true but R is false.
• (d) A is false but R is true.

Heredity and Evolution

Q1. Assertion: When a tall pea plant (TT) is crossed with a short pea plant (tt), all F1 offspring are tall. Reason: Tallness is the dominant trait in pea plants.

Answer: (a) — Both true, and the dominance of tallness explains why all F1 are tall.

Q2. Assertion: Acquired traits are inherited by the next generation. Reason: Changes in non-reproductive tissues cannot be passed to offspring.

Answer: (d) — A is false (acquired traits are NOT inherited), R is true.

Q3. Assertion: Variation is beneficial for the survival of a species. Reason: Variations allow populations to adapt to changing environments.

Answer: (a) — Both true, and the reason explains the assertion.

Magnetic Effects of Electric Current

Q4. Assertion: A current-carrying conductor placed in a magnetic field experiences a force. Reason: This is the principle behind an electric motor.

Answer: (b) — Both true, but the reason describes an application, not an explanation of why the force occurs.

Q5. Assertion: Electromagnetic induction is the production of current due to a changing magnetic field. Reason: Faraday discovered that a changing magnetic flux through a circuit induces an EMF.

Answer: (a) — Both true, and Faraday's discovery directly explains electromagnetic induction.

Carbon and Its Compounds

Q6. Assertion: Carbon forms covalent bonds with other elements. Reason: Carbon has 4 valence electrons, making it difficult to gain or lose electrons.

Answer: (a) — With 4 valence electrons, carbon shares electrons rather than transferring them.

Q7. Assertion: Ethanol and ethanoic acid are functional group isomers. Reason: Both ethanol and ethanoic acid have the same molecular formula.

Answer: (d) — A is false (they are not isomers and have different molecular formulas: C₂H₅OH vs CH₃COOH). R is also false. Since both are false, this is technically outside standard options, but if forced to choose, (d) is closest as A is definitely false.

Q8. Assertion: Soaps do not work well in hard water. Reason: Soaps react with calcium and magnesium salts in hard water to form an insoluble precipitate (scum).

Answer: (a) — The scum formation directly explains why soaps are ineffective in hard water.

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How to Approach Science CBQs

Reading the Case Study Paragraph

Science case studies are dense with information. The paragraph typically describes a real-world scenario — a lab experiment, a medical case, an industrial process, or an environmental observation. Your job is to:

1. Identify the chapter and topic within the first two sentences.
2. Underline numerical data — voltages, resistances, concentrations, distances.
3. Note scientific terminology — these often point directly to the answer.
4. Read all four sub-questions before answering — sometimes a later question gives a hint for an earlier one.

Handling Assertion-Reason in Science

Science assertion-reason questions are often tricky because both statements may contain correct scientific facts that are from the same topic but do not have a causal relationship. The key test: Does the reason answer the question "Why is the assertion true?" If it only states a related fact, the answer is (b), not (a).

For chapter-specific preparation, see the Class 10 Science important questions guide.

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Common Mistakes in Science CBQs

1. Mixing up terms from similar topics. Students confuse refraction with reflection, or mitosis with meiosis, especially when the case study paragraph uses related vocabulary. Read carefully.

2. Ignoring the diagram or data table. Some case studies include a circuit diagram or a data table. The answer is often directly readable from the visual — do not ignore it.

3. Choosing (a) by default for assertion-reason. When both statements sound correct, students assume the reason explains the assertion. Verify the causal link before choosing (a).

4. Not converting units. Physics case studies may give resistance in kΩ but expect current in mA. Always check units.

5. Writing too much for case study sub-questions. These are MCQs — just mark the correct option. No explanation is needed unless specifically asked. Save time for Section D long answers.

Use the board exam answer sheet guide to structure your overall paper attempt.

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FAQs

How many case study questions appear in the CBSE Class 10 Science paper?

Three case study questions appear in Section E, carrying 4 marks each (12 marks total). Typically, one case study comes from Physics, one from Chemistry, and one from Biology. Each case study has 4-5 MCQ sub-questions.

Which chapters are most important for Science CBQs?

Electricity, Light (Reflection and Refraction), Chemical Reactions, Acids Bases and Salts, Life Processes, and Heredity are the most frequent sources. These chapters together carry over 60% of the paper marks.

Are assertion-reason questions only from specific chapters?

No, they can come from any chapter. However, Heredity, Magnetic Effects, Carbon Compounds, and Periodic Classification are the most common sources based on previous years' papers and sample papers.

Can I score full marks in case studies without solving the full paper?

Each case study sub-question is independent. You can score 4/4 on a case study even if you struggle with other sections. This makes case studies a reliable marks source — practise them well.

How is the Class 10 Science SQP 2027 different from 2025-26?

The SQP 2027 follows the same pattern as 2025-26. The 50% competency-based split, the three-section format (Physics, Chemistry, Biology), and the Section E case studies remain unchanged. Check the SQP analysis for details.

Should I practise from CBSE's official competency question bank?

Yes. CBSE has released official competency-focused practice questions on the DIKSHA platform and cbseacademic.nic.in. These are the closest representation of what you will face in the actual exam.

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Related Guides

• CBSE Class 10 Science Chapter-Wise Marks Weightage 2027
• CBSE Class 10 Maths Competency-Based Questions Chapter-Wise
• CBSE Class 10 Sample Paper 2027 Practice Set — All Subjects
• CBSE Class 10 Science Important Questions 2027
• Board Exam Time Management — 3-Hour Strategy
• CBSE SQP 2027 vs Actual Paper — Predict and Strategise

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