CBSE Class 10 Science Important Topics 2027
Every topic ranked by how often and how recently it was asked in 5 board + 2 official sample papers (2022–2026). Blue = board paper, green = sample paper.
Top 10 most important topics
| # | Topic | Chapter | Asked in | Importance |
|---|---|---|---|---|
| 1 | Image formation by spherical mirrors / ray diagrams | Light - Reflection and Refraction | Board 2023Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★★★★ |
| 2 | Food chains, food webs and trophic levels / 10% law | Our Environment | Board 2022Board 2023Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★★★☆ |
| 3 | Identifying type of reaction (combination/decomposition/displacement/double displacement) | Chemical Reactions and Equations | Board 2023Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★★★☆ |
| 4 | Nutrition in animals (human digestive system) | Life Processes | Board 2023Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★★★☆ |
| 5 | Plant hormones and tropic movements | Control and Coordination | Board 2023Board 2024Board 2025Board 2026Sample 2025 | ★★★★☆ |
| 6 | Chemical properties/reactions of acids and bases | Acids, Bases and Salts | Board 2023Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★★★☆ |
| 7 | Physical/chemical properties distinguishing metals and non-metals | Metals and Non-metals | Board 2023Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★★☆☆ |
| 8 | Heating effect of current and electric power numericals | Electricity | Board 2022Board 2023Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★★☆☆ |
| 9 | Mendel's monohybrid cross and laws of inheritance | Heredity | Board 2022Board 2023Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★★☆☆ |
| 10 | Extraction of metals / metallurgy steps | Metals and Non-metals | Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★★☆☆ |
Chapter-wise important topics
Chemical Reactions and Equations · Chemical Substances - Nature and Behaviour
| Identifying type of reaction (combination/decomposition/displacement/double displacement) asked 14× | Board 2023Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★★★☆ |
| Oxidation and reduction / redox and corrosion-rancidity asked 3× | Board 2023Board 2024Sample 2026 | ★☆☆☆☆ |
| Balancing a chemical equation asked 3× | Board 2023Board 2024Sample 2025 | ★☆☆☆☆ |
| Writing a balanced equation from a word/observation description asked 2× | Board 2023Board 2025 | ★☆☆☆☆ |
Acids, Bases and Salts · Chemical Substances - Nature and Behaviour
| Chemical properties/reactions of acids and bases asked 10× | Board 2023Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★★★☆ |
| pH scale and pH of common substances asked 9× | Board 2023Board 2024Board 2025Board 2026Sample 2026 | ★★★☆☆ |
| Preparation, properties and uses of important salts (washing soda, baking soda, bleaching powder, POP) asked 8× | Board 2023Board 2025Board 2026Sample 2025 | ★★☆☆☆ |
| Indicators and identifying acid/base asked 4× | Board 2026Sample 2025Sample 2026 | ★★☆☆☆ |
| Water of crystallisation / common salt family asked 2× | Board 2024Board 2025 | ★☆☆☆☆ |
Metals and Non-metals · Chemical Substances - Nature and Behaviour
| Physical/chemical properties distinguishing metals and non-metals asked 11× | Board 2023Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★★☆☆ |
| Extraction of metals / metallurgy steps asked 9× | Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★★☆☆ |
| Reactivity series and displacement of metals asked 8× | Board 2023Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★☆☆☆ |
| Ionic compound formation and properties asked 3× | Board 2025Sample 2026 | ★☆☆☆☆ |
| Corrosion and its prevention asked 2× | Board 2025Sample 2026 | ★☆☆☆☆ |
Carbon and its Compounds · Chemical Substances - Nature and Behaviour
| Properties and reactions of ethanol and ethanoic acid asked 6× | Board 2023Board 2024Board 2025Board 2026Sample 2025 | ★★☆☆☆ |
| Homologous series asked 3× | Board 2024Board 2026Sample 2026 | ★☆☆☆☆ |
| Soaps, detergents and micelle / cleansing action asked 3× | Board 2023Board 2026Sample 2025 | ★☆☆☆☆ |
| Combustion, oxidation, addition and substitution reactions asked 2× | Sample 2025Sample 2026 | ★☆☆☆☆ |
| Covalent bonding and electron-dot structures asked 4× | Board 2022Board 2023Board 2024 | ★☆☆☆☆ |
| Nomenclature and functional groups asked 2× | Board 2025Board 2026 | ★☆☆☆☆ |
| Isomers of alkanes asked 1× | Board 2022 | ★☆☆☆☆ |
Life Processes · World of Living
| Nutrition in animals (human digestive system) asked 12× | Board 2023Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★★★☆ |
| Respiration (aerobic/anaerobic, human respiratory system) asked 7× | Board 2023Board 2024Board 2025Sample 2025Sample 2026 | ★★☆☆☆ |
| Nutrition in plants (photosynthesis) and experiments asked 7× | Board 2023Board 2025Board 2026Sample 2025 | ★★☆☆☆ |
| Transport in humans (heart, blood circulation, double circulation) asked 6× | Board 2023Board 2025Board 2026Sample 2025Sample 2026 | ★★☆☆☆ |
| Transport in plants (xylem/phloem, transpiration) asked 5× | Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★☆☆☆ |
| Excretion in humans (nephron/kidney) and in plants asked 4× | Board 2023Board 2026Sample 2025Sample 2026 | ★☆☆☆☆ |
Control and Coordination · World of Living
| Plant hormones and tropic movements asked 12× | Board 2023Board 2024Board 2025Board 2026Sample 2025 | ★★★★☆ |
| Animal hormones (endocrine glands and functions) asked 4× | Board 2023Board 2024Board 2026Sample 2026 | ★☆☆☆☆ |
| Human brain structure and function asked 3× | Board 2026Sample 2025Sample 2026 | ★☆☆☆☆ |
| Human nervous system and neuron / reflex arc asked 2× | Board 2024Sample 2026 | ★☆☆☆☆ |
| Reflex action and its pathway asked 2× | Board 2024Board 2026 | ★☆☆☆☆ |
How do Organisms Reproduce · World of Living
| Asexual reproduction modes with examples asked 9× | Board 2022Board 2023Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★☆☆☆ |
| Sexual reproduction in flowering plants (flower parts, fertilisation) asked 7× | Board 2022Board 2023Board 2025Board 2026Sample 2026 | ★★☆☆☆ |
| Human reproductive system (male/female) asked 4× | Board 2022Board 2025Sample 2025 | ★☆☆☆☆ |
| Reproductive health, contraception and family planning asked 1× | Board 2024 | ★☆☆☆☆ |
Heredity · World of Living
| Mendel's monohybrid cross and laws of inheritance asked 11× | Board 2022Board 2023Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★★☆☆ |
| Dominant/recessive traits, F1 and F2 ratios asked 9× | Board 2022Board 2023Board 2024Board 2025Board 2026Sample 2026 | ★★☆☆☆ |
| Sex determination in humans asked 7× | Board 2022Board 2023Board 2024Sample 2025 | ★☆☆☆☆ |
Light - Reflection and Refraction · Natural Phenomena
| Image formation by spherical mirrors / ray diagrams asked 17× | Board 2023Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★★★★ |
| Image formation by lenses / ray diagrams asked 6× | Board 2024Board 2026Sample 2025Sample 2026 | ★★☆☆☆ |
| Lens formula, magnification and power numericals asked 5× | Board 2025Sample 2026 | ★★☆☆☆ |
| Mirror formula and magnification numericals asked 5× | Board 2023Board 2024Sample 2026 | ★☆☆☆☆ |
| Refraction and refractive index asked 2× | Board 2025Board 2026 | ★☆☆☆☆ |
The Human Eye and the Colourful World · Natural Phenomena
| Defects of vision and their correction asked 6× | Board 2023Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★☆☆☆ |
| Refraction through a prism and dispersion asked 4× | Board 2023Board 2024Board 2026Sample 2025 | ★☆☆☆☆ |
| Atmospheric refraction and scattering (twinkling, blue sky, red sun, Tyndall) asked 2× | Board 2023Sample 2026 | ★☆☆☆☆ |
| Human eye structure and accommodation asked 2× | Board 2024Board 2026 | ★☆☆☆☆ |
Electricity · Effects of Current
| Heating effect of current and electric power numericals asked 11× | Board 2022Board 2023Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★★☆☆ |
| Series and parallel combination of resistors (numericals) asked 8× | Board 2022Board 2023Board 2024Board 2025Sample 2025Sample 2026 | ★★★☆☆ |
| Electric circuit diagrams and current/voltage calculation asked 6× | Board 2023Board 2025Board 2026Sample 2025 | ★★☆☆☆ |
| Resistance, resistivity and factors affecting resistance asked 4× | Board 2024Board 2025Sample 2025Sample 2026 | ★☆☆☆☆ |
Magnetic Effects of Electric Current · Effects of Current
| Magnetic field due to current (straight conductor / loop / solenoid) asked 7× | Board 2022Board 2023Board 2024Board 2026Sample 2025Sample 2026 | ★★☆☆☆ |
| Field lines and right-hand / thumb rules asked 8× | Board 2022Board 2023Board 2024Board 2025Board 2026 | ★★☆☆☆ |
| Domestic electric circuits, fuse and safety measures asked 4× | Board 2023Board 2025 | ★☆☆☆☆ |
| Force on a current-carrying conductor and Fleming's Left Hand Rule asked 4× | Board 2022Board 2023Board 2024Board 2026 | ★☆☆☆☆ |
Our Environment · Natural Resources
| Food chains, food webs and trophic levels / 10% law asked 15× | Board 2022Board 2023Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★★★☆ |
| Ozone depletion and its effects asked 4× | Board 2022Board 2024Board 2025Sample 2026 | ★☆☆☆☆ |
| Biodegradable vs non-biodegradable waste and its effects asked 3× | Board 2025Board 2026Sample 2026 | ★☆☆☆☆ |
| Ecosystem components and flow of energy asked 3× | Board 2022Board 2023Sample 2025 | ★☆☆☆☆ |
Importance = how often a topic was asked × how recent, with extra weight for the latest official sample paper.