CBSE Class 10 Science is the subject that separates toppers from average scorers. It carries 80 marks in the external board examination plus 20 marks of internal assessment — 100 marks total. The good news: Science is one of the most predictable subjects in CBSE boards. If you master your NCERT textbook thoroughly, understand concepts (not just memorise), and practice diagrams, you can consistently score 75+ out of 80 in the external exam.
This chapter-wise guide covers all 16 chapters of CBSE Class 10 Science (2026-27 curriculum), with expected marks, key concepts, solved questions, and exam strategy.
Chapter-Wise Marks Distribution — CBSE Class 10 Science
| Chapter | Topic | Expected Marks | Key Concepts to Master |
|---|---|---|---|
| Chapter 1 | Chemical Reactions and Equations | 5–6 marks | Types of reactions (combination, decomposition, displacement, redox), balancing equations |
| Chapter 2 | Acids, Bases and Salts | 6–7 marks | pH scale, indicators, neutralisation, common salts (NaCl, NaOH, Na2CO3), cleaning agents |
| Chapter 3 | Metals and Non-Metals | 8–9 marks | Reactivity series, extraction (ore → metal), corrosion, alloys, properties comparison |
| Chapter 4 | Carbon and Its Compounds | 5–6 marks | Covalent bonding, homologous series, functional groups, ethanol vs ethanoic acid, soaps |
| Chapter 5 | Life Processes | 8–10 marks | Nutrition (photosynthesis, digestive system), respiration, transportation (heart, blood), excretion |
| Chapter 6 | Control and Coordination | 5–6 marks | Nervous system (neuron, reflex arc), endocrine system (hormones, glands), plant hormones |
| Chapter 7 | How Do Organisms Reproduce | 5–6 marks | Asexual (binary fission, budding, regeneration), sexual reproduction, pollination, fertilisation |
| Chapter 8 | Heredity and Evolution | 5–6 marks | Mendel’s laws, dominant/recessive traits, sex determination, evolution theories, homologous organs |
| Chapter 9 | Light: Reflection and Refraction | 7–8 marks | Mirror formula, lens formula, magnification, ray diagrams, refraction laws, glass slab |
| Chapter 10 | Human Eye and Colourful World | 5–6 marks | Eye defects (myopia, hyperopia, presbyopia) + correction, prism dispersion, rainbow, scattering |
| Chapter 11 | Electricity | 7–8 marks | Ohm’s law, series/parallel circuits, resistance, heating effect (H=I²Rt), power, domestic wiring |
| Chapter 12 | Magnetic Effects of Electric Current | 5–6 marks | Magnetic field around conductor, Fleming’s rules, electric motor, electromagnetic induction, generator |
| Chapter 13 | Our Environment | 3–4 marks | Food chains/webs, trophic levels, biodegradable vs non-biodegradable, ozone layer depletion |
| Chapter 14 | Management of Natural Resources | 3–4 marks | Conservation of forests, water harvesting, coal/petroleum use, sustainable development, 3 R’s |
5 Solved NCERT Exercise Questions — High Marks Chapters
From Chapter 11: Electricity
Q1. Two resistors of 4 Ω and 6 Ω are connected in parallel. Find the equivalent resistance. If this combination is connected to a 12V battery, find the total current drawn.
Solution:
For parallel combination: 1/R = 1/R₁ + 1/R₂ = 1/4 + 1/6 = 3/12 + 2/12 = 5/12
Therefore, R = 12/5 = 2.4 Ω
Total current I = V/R = 12/2.4 = 5 A
From Chapter 9: Light — Reflection and Refraction
Q2. An object 5 cm tall is placed 30 cm in front of a convex lens of focal length 20 cm. Find the image distance and nature of the image.
Solution:
Using lens formula: 1/v − 1/u = 1/f
u = −30 cm, f = +20 cm
1/v = 1/f + 1/u = 1/20 + 1/(−30) = 3/60 − 2/60 = 1/60
v = +60 cm (image is on the other side of the lens)
Magnification m = v/u = 60/(−30) = −2
Image is real, inverted, and magnified (10 cm tall).
From Chapter 5: Life Processes
Q3. What is the role of the liver in digestion?
Solution: The liver produces bile juice which is stored in the gall bladder and released into the small intestine. Bile emulsifies fats (breaks large fat droplets into smaller ones), increasing the surface area for lipase enzyme action. Bile also makes the medium alkaline, which is necessary for pancreatic enzymes to function properly.
From Chapter 3: Metals and Non-Metals
Q4. Why is sodium stored under kerosene oil?
Solution: Sodium is an extremely reactive metal. It reacts vigorously with oxygen in the air to form sodium oxide (Na₂O) and with moisture to form sodium hydroxide (NaOH), releasing hydrogen gas which can catch fire. To prevent this reaction with air and moisture, sodium is stored submerged in kerosene oil, which keeps it isolated from the atmosphere.
From Chapter 1: Chemical Reactions and Equations
Q5. Balance the following chemical equation: Fe + H₂O → Fe₃O₄ + H₂
Solution: Balanced equation: 3Fe + 4H₂O → Fe₃O₄ + 4H₂
Check: Fe: 3=3 ✓ | H: 8=8 ✓ | O: 4=4 ✓
How to Write 3-Mark and 5-Mark Answers in Board Exams
3-Mark Answer Structure (Expected: 60–80 words)
- Point 1: Define or state the main concept
- Point 2: Explain with one example or mechanism
- Point 3: State significance or application
- Diagram if asked: 1–2 marks usually assigned specifically to diagram accuracy
5-Mark Answer Structure (Expected: 100–150 words)
- Introduction: One sentence defining the topic
- Body (3 points): Three distinct, well-labelled points with sub-explanations
- Diagram: Mandatory for biology/physics topics; label every part
- Conclusion/Application: One line on real-world relevance
8 Diagrams You MUST Practice for CBSE Class 10 Science
- Human Digestive System (Chapter 5) — Label all organs: mouth, oesophagus, stomach, small intestine, large intestine, liver, pancreas
- Human Heart (Chapter 5) — Label: 4 chambers, valves (bicuspid, tricuspid, semilunar), aorta, pulmonary artery/vein, vena cava
- Reflex Arc / Neuron (Chapter 6) — Label: receptor, sensory neuron, spinal cord, motor neuron, effector, dendrites, axon, myelin sheath
- Concave Mirror — Ray Diagram (Chapter 9) — Object beyond C, at C, between C and F, at F, between F and P
- Convex Lens — Ray Diagram (Chapter 9) — All 6 object positions with image nature
- Electric Circuit — Series and Parallel (Chapter 11) — With labelled components (battery, switch, bulbs, ammeter, voltmeter positions)
- Electromagnet / Motor (Chapter 12) — Labelled solenoid diagram with magnetic field lines; DC motor components (coil, magnet, commutator, brushes, axle)
- Flower — Reproduction (Chapter 7) — Label: stigma, style, ovary, ovule, anther, filament, sepal, petal, receptacle
CBSE Marking Scheme Tips for Science
- Steps vs answers: CBSE awards marks for each step in numerical questions. Even if the final answer is wrong, you get step marks. Never skip working.
- Diagram labels: Unlabelled diagrams typically get zero marks. Every diagram must have all parts labelled with leader lines.
- Chemical equations: Always balance equations and state conditions (heat, catalyst) above/below the arrow.
- Key terms: Underline or bold technical terms (osmosis, transpiration, electrolysis) in your answers — examiners look for correct use of terminology.
- Unit of measurement: In numerical problems, always write the unit (Ω for resistance, V for voltage, A for current, J for joules). Missing units = lost marks.
Frequently Asked Questions — NCERT Solutions Class 10 Science
Which chapters carry the most marks in CBSE Class 10 Science?
The highest-scoring chapters are: Life Processes (8–10 marks), Metals and Non-Metals (8–9 marks), Light: Reflection and Refraction (7–8 marks), and Electricity (7–8 marks). These four chapters together can account for 30–35 marks, making them the highest-priority chapters.
Is NCERT enough for CBSE Class 10 Science board exam?
Yes, NCERT is entirely sufficient for CBSE Class 10 Science. Approximately 85–90% of CBSE board questions come directly from NCERT textbooks — the in-text questions, chapter-end exercises, and examples. Master NCERT first; only then refer to additional practice books for extra MCQs and numericals.
How many diagrams should I prepare for Class 10 Science boards?
Prepare at least 10–12 diagrams thoroughly. The 8 listed in this guide are mandatory. Additionally, practise diagrams of the nephron (excretory system), human brain, electromagnetic induction (Faraday’s experiment), and binary fission in amoeba. Diagrams often carry 1–2 marks independently in questions.
What is the internal assessment scheme for CBSE Class 10 Science?
The 20 marks of internal assessment include: Periodic Tests (10 marks), Practical Work/Lab Activities (5 marks), and Portfolio/Student Enrichment Activities (5 marks). These marks are awarded by the school and added to your external board score to give the final out of 100.
How should I revise NCERT Class 10 Science in the last 30 days before boards?
In the last 30 days: Week 1 — Revise high-marks chapters (Life Processes, Metals, Electricity, Light); Week 2 — Solve 3 previous year papers under timed conditions; Week 3 — Revise remaining chapters and all diagrams; Week 4 — Solve CBSE sample papers, review marking schemes, and do final formula and definition revision.
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