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Class 10 ScienceChapter Notes

13 chapters · Definitions, key points, formulas & exam tips · Updated 2025-26

Ch 1 Ch 2 Ch 3 Ch 4 Ch 5 Ch 6 Ch 7 Ch 8 Ch 9 Ch 10 Ch 11 Ch 12 Ch 13

Ch 1

Chemical Reactions and Equations

Key Definitions

Chemical Reaction: A process in which substances (reactants) are converted into new substances (products) with different properties.

Exothermic Reaction: A reaction that releases heat energy. E.g., burning of coal, respiration.

Endothermic Reaction: A reaction that absorbs heat energy. E.g., photosynthesis, decomposition of CaCO₃.

Oxidation: Gain of oxygen OR loss of hydrogen OR loss of electrons.

Reduction: Loss of oxygen OR gain of hydrogen OR gain of electrons.

Key Points to Remember

→A balanced equation follows the Law of Conservation of Mass.
→Signs of a chemical reaction: change in colour, temperature, state; evolution of gas; formation of precipitate.
→Combination reaction: A + B → AB
→Decomposition reaction: AB → A + B (opposite of combination).
→Displacement reaction: A + BC → AC + B (more reactive displaces less reactive).
→Double displacement: AB + CD → AD + CB (exchange of ions).
→Corrosion: slow oxidation of metals. Rancidity: oxidation of fats/oils.

Formulas & Equations

2Mg + O₂ → 2MgO (combination)

2H₂O → 2H₂ + O₂ (decomposition by electrolysis)

Fe + CuSO₄ → FeSO₄ + Cu (displacement)

Na₂SO₄ + BaCl₂ → BaSO₄↓ + 2NaCl (double displacement)

Exam Tips

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Always balance equations — unbalanced equations lose marks.

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Redox reactions: identify what is oxidised and what is reduced.

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Antioxidants slow rancidity — nitrogen flushing in chips packets.

Ch 2

Acids, Bases and Salts

Key Definitions

Acid: Produces H⁺ ions in solution. Turns blue litmus red. pH < 7.

Base: Produces OH⁻ ions in solution. Turns red litmus blue. pH > 7.

Neutralisation: Acid + Base → Salt + Water. pH = 7 at equivalence point.

pH: Measure of hydrogen ion concentration. pH 7 = neutral, <7 = acidic, >7 = basic.

Key Points to Remember

→Strong acids fully ionise in water: HCl, H₂SO₄, HNO₃.
→Weak acids partially ionise: CH₃COOH, carbonic acid.
→Baking soda: NaHCO₃ — used in baking, fire extinguisher.
→Washing soda: Na₂CO₃·10H₂O — used in glass, soap, paper making.
→Bleaching powder: Ca(OCl)Cl — made by passing Cl₂ over dry slaked lime.
→Plaster of Paris: CaSO₄·½H₂O — used in fractured bones, making chalks.
→pH scale: 0–14. Blood pH = 7.4. Gastric juice pH = 1.5–3.5.

Formulas & Equations

Acid + Base → Salt + Water

Metal + Acid → Salt + H₂↑

CaO + H₂O → Ca(OH)₂ + Heat (slaking of lime)

2NaHCO₃ → Na₂CO₃ + H₂O + CO₂↑ (on heating)

Exam Tips

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Remember: dilute acid in water, NOT water in acid (heat released can cause splashing).

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Common indicators: Litmus (natural — from lichens), Turmeric, China rose.

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Difference between baking soda and baking powder — baking powder has baking soda + tartaric acid.

Ch 3

Metals and Non-metals

Key Definitions

Malleability: Property of metals to be beaten into thin sheets.

Ductility: Property of metals to be drawn into thin wires.

Reactivity Series: Arrangement of metals in decreasing order of reactivity: K, Na, Ca, Mg, Al, Zn, Fe, Pb, H, Cu, Hg, Ag, Au.

Corrosion: Slow destruction of metals due to attack by air, moisture, or chemicals.

Key Points to Remember

→Most reactive metals: K, Na (stored in kerosene).
→Least reactive metals: Gold, Platinum (noble metals).
→Ionic bond: transfer of electrons from metal to non-metal.
→Ionic compounds: high melting point, conduct electricity in molten/solution state.
→Anodising: forming a protective oxide layer on aluminium by electrolysis.
→Galvanisation: coating iron with zinc to prevent corrosion.
→Alloys: homogeneous mixture of metals. E.g., Brass (Cu+Zn), Bronze (Cu+Sn), Steel (Fe+C).

Formulas & Equations

2Na + 2H₂O → 2NaOH + H₂↑ (sodium reacts violently with water)

4Al + 3O₂ → 2Al₂O₃

Fe₂O₃ + 2Al → Al₂O₃ + 2Fe (thermite reaction)

Exam Tips

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Memorise the reactivity series — displacement reactions depend on it.

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Exceptions: Mercury is a liquid metal; Graphite (non-metal) conducts electricity.

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Alloys resist corrosion better than pure metals.

Ch 4

Carbon and its Compounds

Key Definitions

Covalent Bond: Bond formed by sharing of electrons between atoms.

Isomers: Compounds with the same molecular formula but different structural formulas.

Homologous Series: A series of compounds with the same functional group and similar chemical properties, differing by CH₂.

Functional Group: An atom or group of atoms that determines the chemical properties of a compound.

Key Points to Remember

→Carbon forms 4 covalent bonds (tetravalent). Forms chains, branches, and rings.
→Saturated compounds: only single bonds (alkanes). Unsaturated: double/triple bonds.
→Alkanes (CₙH₂ₙ₊₂), Alkenes (CₙH₂ₙ), Alkynes (CₙH₂ₙ₋₂).
→Ethanol (C₂H₅OH): drinking alcohol, used as fuel, solvent.
→Ethanoic acid (CH₃COOH): acetic acid, vinegar, boiling point 391 K.
→Soap is sodium/potassium salt of long chain fatty acids.
→Soap cleans because micelles have hydrophilic head (water-loving) and hydrophobic tail (oil-loving).
→Hard water: contains Ca²⁺ and Mg²⁺ ions — soap doesn't lather well.

Formulas & Equations

CH₄ (methane), C₂H₆ (ethane), C₃H₈ (propane)

CH₂=CH₂ (ethene), CH≡CH (ethyne/acetylene)

Combustion: CH₄ + 2O₂ → CO₂ + 2H₂O

Esterification: Acid + Alcohol → Ester + Water

Exam Tips

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Draw structural formulas carefully — each C must show 4 bonds.

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Saponification = hydrolysis of ester = reverse of esterification.

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Difference between soap and detergent: detergents work in hard water too.

Ch 5

Life Processes

Key Definitions

Nutrition: Process of taking in food and converting it into energy for growth and repair.

Respiration: Breakdown of glucose to release energy. Aerobic (with O₂) or Anaerobic (without O₂).

Transpiration: Loss of water vapour through stomata of leaves.

Excretion: Removal of metabolic waste products from the body.

Key Points to Remember

→Photosynthesis: 6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂
→Stomata: open during day for photosynthesis, guarded by guard cells.
→Aerobic respiration: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + 38 ATP
→Anaerobic (yeast): C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂
→Anaerobic (muscle): C₆H₁₂O₆ → 2CH₃CHOHCOOH (lactic acid) — causes cramps.
→Human digestive system: mouth → oesophagus → stomach → small intestine → large intestine.
→Kidney: filters blood, produces urine. Dialysis replaces kidney function.
→Heart: double circulation — pulmonary (lungs) and systemic (body).

Formulas & Equations

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (Photosynthesis)

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy (Aerobic respiration)

Exam Tips

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Label diagrams of heart, kidney, and leaf section — 3-mark diagram questions.

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Difference between autotrophs and heterotrophs — always appears in exams.

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Villi in small intestine increase surface area for absorption — mention this.

Ch 6

Control and Coordination

Key Definitions

Neuron: Basic functional unit of the nervous system. Consists of cell body, dendrites, and axon.

Synapse: Junction between two neurons where nerve impulse is transmitted via neurotransmitters.

Reflex Action: Involuntary, rapid response to a stimulus. Does not involve the brain.

Hormone: Chemical messenger produced by endocrine glands, transported by blood.

Key Points to Remember

→CNS = Brain + Spinal cord. PNS = all nerves outside CNS.
→Reflex arc: Stimulus → Receptor → Afferent nerve → Spinal cord → Efferent nerve → Effector → Response.
→Brain: Forebrain (thinking, memory), Midbrain (visual/auditory), Hindbrain (breathing, balance).
→Tropic movements in plants: towards (positive) or away (negative) from stimulus.
→Phototropism: towards light. Geotropism: towards gravity. Hydrotropism: towards water.
→Plant hormones: Auxin (cell elongation), Gibberellin (stem elongation), Cytokinin (cell division), Abscisic acid (inhibits growth).
→Human hormones: Insulin (lowers blood sugar), Glucagon (raises blood sugar), Thyroxine (metabolism), Adrenaline (emergency).

Exam Tips

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Distinguish between nervous and hormonal control: speed vs duration.

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Draw and label a neuron — appears every year.

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Iodine deficiency → goitre (swelling of thyroid).

Ch 7

How do Organisms Reproduce?

Key Definitions

Asexual Reproduction: Reproduction involving only one parent. No gametes. E.g., binary fission, budding, spore formation.

Sexual Reproduction: Involves two parents, formation of gametes, and fertilisation.

Pollination: Transfer of pollen from anther to stigma.

Fertilisation: Fusion of male gamete (pollen) with female gamete (ovum) to form a zygote.

Key Points to Remember

→Binary fission: Amoeba, Bacteria — splits into two equal halves.
→Budding: Hydra, Yeast — small outgrowth (bud) forms and separates.
→Fragmentation: Spirogyra — organism breaks into fragments, each grows.
→Regeneration: Planaria — cut pieces regenerate into full organisms.
→Vegetative propagation: reproduction through roots, stems, leaves.
→Flower parts: Sepals, Petals, Stamens (anther + filament), Carpel (stigma + style + ovary).
→Contraception methods: barrier (condom, diaphragm), chemical (pills), surgical (vasectomy, tubectomy).

Exam Tips

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Difference between self and cross pollination.

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Advantages of sexual reproduction: genetic variation, evolution.

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STDs: HIV/AIDS, gonorrhoea, syphilis — how they spread and prevention.

Ch 8

Heredity

Key Definitions

Heredity: Transmission of traits from parents to offspring.

Gene: Unit of heredity. A segment of DNA that determines a trait.

Dominant Trait: Trait expressed even when only one copy of the allele is present.

Recessive Trait: Trait expressed only when both copies of the allele are recessive.

Key Points to Remember

→Mendel's laws: Law of Segregation, Law of Independent Assortment.
→Monohybrid cross: Tall × Short (TT × tt) → all Tt (tall) in F1, 3 tall : 1 short in F2.
→Dihybrid cross: F2 ratio = 9:3:3:1
→Sex determination in humans: XX = female, XY = male. Father determines sex.
→Acquired traits: changes in non-reproductive cells, NOT inherited (e.g., muscle built by exercise).
→Inherited traits: changes in reproductive cells, CAN be passed to offspring.
→Evolution: gradual change in organisms over generations. Supported by fossils.

Formulas & Equations

F1: Tt (all tall) — monohybrid cross

F2 ratio: 3 Tall (TT + 2Tt) : 1 short (tt)

Dihybrid F2: 9:3:3:1

Exam Tips

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Draw Punnett square neatly — each cross is worth 3 marks.

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Explain why father determines sex of child — X from mother, X or Y from father.

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Homologous organs show common ancestry; analogous organs show convergent evolution.

Ch 9

Light — Reflection and Refraction

Key Definitions

Reflection: Bouncing back of light from a surface. Angle of incidence = Angle of reflection.

Refraction: Bending of light when it passes from one medium to another due to change in speed.

Refractive Index: Ratio of speed of light in vacuum to speed of light in the medium. n = c/v.

Lens Formula: Relationship between image distance, object distance, and focal length: 1/v − 1/u = 1/f.

Key Points to Remember

→Concave mirror: converging, used in solar furnaces, car headlights, shaving mirrors.
→Convex mirror: diverging, used in rear-view mirrors (wider field of view).
→Mirror formula: 1/v + 1/u = 1/f
→Magnification (mirror): m = −v/u = h'/h
→Snell's Law: n₁ sin i = n₂ sin r
→Convex lens: converging, used in cameras, microscopes, spectacles for hypermetropia.
→Concave lens: diverging, used in spectacles for myopia.
→Power of lens: P = 1/f (in metres). Unit = Dioptre (D).

Formulas & Equations

Mirror: 1/v + 1/u = 1/f

Lens: 1/v − 1/u = 1/f

Magnification (lens): m = v/u

Refractive index: n = sin i / sin r

Power: P = 1/f(m)

Exam Tips

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Sign convention: all distances measured from pole/optical centre. Distances in direction of light = positive.

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For mirrors, u is always negative (object on same side as light).

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Power of combination of lenses: P = P₁ + P₂.

Ch 10

Human Eye and the Colourful World

Key Definitions

Accommodation: Ability of the eye lens to change focal length to focus on objects at different distances.

Myopia: Near-sightedness. Can see nearby objects clearly. Corrected by concave lens.

Hypermetropia: Far-sightedness. Can see distant objects clearly. Corrected by convex lens.

Scattering of Light: Redirection of light in all directions when it hits small particles.

Key Points to Remember

→Near point (least distance of distinct vision): 25 cm for normal eye.
→Far point of normal eye: infinity.
→Presbyopia: loss of accommodation with age — corrected by bifocal lenses.
→Tyndall effect: scattering of light by colloidal particles — explains blue sky.
→Blue sky: shorter wavelengths (blue, violet) scattered more by atmosphere.
→Red sunset: at sunrise/sunset, light travels longer path — blue is scattered away, red remains.
→Dispersion: white light splits into VIBGYOR by a prism.
→Rainbow: caused by dispersion and internal reflection in water droplets.

Exam Tips

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Defects of vision + correction + diagram — 5-mark question every year.

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Distinguish between Tyndall effect and Rayleigh scattering.

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Why danger signals are red: red light is least scattered, visible from far.

Ch 11

Electricity

Key Definitions

Electric Current: Rate of flow of electric charge. I = Q/t. Unit: Ampere (A).

Resistance: Opposition to flow of current. R = V/I. Unit: Ohm (Ω).

Ohm's Law: V = IR. Current is directly proportional to voltage at constant temperature.

Resistivity: Intrinsic property of a material. R = ρL/A.

Key Points to Remember

→Series circuit: same current flows, voltages add up, Rtotal = R₁ + R₂ + R₃.
→Parallel circuit: same voltage, currents add up, 1/Rtotal = 1/R₁ + 1/R₂ + 1/R₃.
→In parallel, total resistance is less than the smallest individual resistance.
→Heating effect: H = I²Rt (Joule's law).
→Power: P = VI = I²R = V²/R. Unit: Watt.
→Electric fuse: thin wire of high resistivity that melts if current exceeds safe limit.
→1 kWh = 1 unit of electrical energy = 3.6 × 10⁶ J.

Formulas & Equations

V = IR (Ohm's Law)

R = ρL/A

Series: R = R₁ + R₂ + R₃

Parallel: 1/R = 1/R₁ + 1/R₂ + 1/R₃

P = VI = I²R = V²/R

H = I²Rt (Joule's heating law)

Energy = P × t, 1 kWh = 3.6 × 10⁶ J

Exam Tips

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Draw circuit diagrams with correct symbols — marks are given for diagrams.

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Household appliances connected in parallel — state reason (each gets full voltage).

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Fuse vs circuit breaker: fuse is single-use, circuit breaker is reusable.

Ch 12

Magnetic Effects of Electric Current

Key Definitions

Magnetic Field: Region around a magnet where magnetic force is experienced. Direction: N to S outside the magnet.

Electromagnetic Induction: Production of electric current due to change in magnetic flux. Faraday's discovery.

Fleming's Left Hand Rule: For motors: thumb = force/motion, index = field, middle = current.

Fleming's Right Hand Rule: For generators: thumb = motion, index = field, middle = induced current.

Key Points to Remember

→Right-hand thumb rule: thumb = current direction, curled fingers = magnetic field direction around wire.
→Solenoid acts like a bar magnet when current flows.
→Electromagnet: a temporary magnet made using a solenoid with a soft iron core.
→Electric motor: converts electrical energy to mechanical energy.
→Electric generator: converts mechanical energy to electrical energy.
→AC (Alternating Current): reverses direction periodically. Frequency in India = 50 Hz.
→DC (Direct Current): flows in one direction only. Used in batteries.
→Domestic wiring: Live (red/brown), Neutral (black/blue), Earth (green/yellow).

Exam Tips

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Distinguish clearly between motor and generator — opposite conversions.

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Earth wire is a safety wire — prevents electric shock.

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Overloading and short circuit — causes of household fires.

Ch 13

Our Environment

Key Definitions

Ecosystem: A system formed by the interaction of all living organisms with each other and with their physical environment.

Food Chain: Transfer of food energy from producers to consumers in a series of steps.

Biodegradable: Substances that can be broken down by microorganisms. E.g., vegetable peels, paper.

Ozone Layer: Layer of ozone (O₃) in the stratosphere that absorbs harmful UV radiation.

Key Points to Remember

→Producers → Primary consumers → Secondary consumers → Tertiary consumers.
→Energy transfer: only 10% of energy passes to the next trophic level (10% law).
→Biological magnification: concentration of harmful chemicals increases up the food chain.
→Ozone depletion caused by CFCs (chlorofluorocarbons) from ACs, refrigerators.
→Non-biodegradable substances: plastic, DDT, metals, synthetic fibres.
→Garbage management: Reduce, Reuse, Recycle.
→Decomposers: bacteria and fungi break down dead organic matter, return nutrients to soil.

Exam Tips

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Example of biological magnification: DDT concentration highest in top predators (fish-eating birds).

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Ozone hole is mainly over Antarctica.

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Why are food chains limited to 3-4 steps? Energy loss at each level.

Frequently Asked Questions

Are these notes based on 2025-26 CBSE syllabus for Class 10 Science?

Yes. All chapter notes here are based on the latest 2025-26 CBSE syllabus for Class 10 Science. Deleted topics are clearly marked so you focus only on what will be tested in your board exam.

How to study Class 10 Science notes effectively for board exams?

Read each chapter's notes once to build understanding. Then close the notes and try to recall every key point, definition, and formula from memory. Anything you miss is your weak area — revisit only those points. This active recall method takes less time and retains far more than re-reading.

What is the difference between NCERT notes and chapter summaries?

Chapter notes contain detailed definitions, key terms, formulas, and concept breakdowns — they're for learning and understanding. Chapter summaries are shorter paragraph-style overviews — they're for quick revision. Use notes when you're studying a chapter for the first time; use summaries the night before the exam.

Do I need to memorise formulas for Class 10 Science CBSE board exam?

Yes. Formulas listed in these notes must be memorised precisely — CBSE doesn't give formula sheets during exams. Write each formula 5–10 times, then recall it without looking. In the exam, write the formula first, then substitute values — this helps you earn partial marks even if the final answer has a calculation error.

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