CBSE Class 10 · Science
Prepared by: Muhammad Jaisal · Learnify Academy, Bahrain
Quick Revision Notes
All Chapters
Everything you need for your Class 10 Science exam — all 13 chapters per the CBSE 2025-26 syllabus. Equations rendered with MathJax LaTeX.
13Chapters Covered
80Theory Marks
20Practical Marks
3hExam Duration
📋 Exam Pattern & Strategy
CBSE Class 10 Science (2025-26): 80 marks theory + 20 marks practical. 13 chapters — Ch.5 (Periodic Classification), Ch.14 (Sources of Energy) & Ch.16 (Natural Resources) have been officially removed from the CBSE curriculum. Focus on NCERT and write balanced equations with state symbols.
20 MCQs × 1 mark
6 Short Answers × 2 marks
7 Short Answers × 3 marks
3 Long Answers × 5 marks
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Exam Tip
Attempt MCQs first, then short answers, saving time for 5-mark long answers. Always write balanced chemical equations with state symbols (s, l, g, aq).
1
Chemical Reactions and Equations
Balancing equations · Reaction types · Exo/Endothermic · Oxidation & Reduction · Rancidity
Key Points
Chemical equations must be balanced — same number of atoms on each side. State symbols: (s) solid, (l) liquid, (g) gas, (aq) aqueous.
Law of Conservation of Mass: Total mass of reactants = total mass of products. (Formula shown in the box below.)
Physical vs Chemical change: Evaporation of petrol = physical; burning LPG = chemical (new substances form, irreversible).
Oxidation: Gain of oxygen OR loss of hydrogen. Reduction: Loss of oxygen OR gain of hydrogen. In a redox reaction both occur simultaneously.
Corrosion & Rancidity are both caused by oxidation. Rancidity: oxidation of fats/oils in food causing bad smell. Prevented by antioxidants, airtight containers, refrigeration, or flushing with nitrogen gas.
Reaction Types
Combination (Synthesis)
\( \text{CaO}(s) + \text{H}_2\text{O}(l) \rightarrow \text{Ca(OH)}_2(aq) + \text{Heat} \)
Exothermic — two reactants combine to form a single product
Endothermic Decomposition (✔ Balanced)
\( 2\text{FeSO}_4(s) \xrightarrow{\Delta} \text{Fe}_2\text{O}_3(s) + \text{SO}_2(g)\uparrow + \text{SO}_3(g)\uparrow \)
Heat is absorbed (endothermic). Note: 2 mol FeSO₄ required to balance Fe atoms on both sides.
Photolytic Decomposition
\( 2\text{AgCl}(s) \xrightarrow{h\nu} 2\text{Ag}(s) + \text{Cl}_2(g)\uparrow \)
Used in black-and-white photography; light provides energy for decomposition
Displacement
\( \text{Zn}(s) + \text{CuSO}_4(aq) \rightarrow \text{ZnSO}_4(aq) + \text{Cu}(s) \)
Zn is more reactive than Cu — it displaces Cu from its salt solution
Double-Displacement (Precipitation)
\( \text{KCl}(aq) + \text{AgNO}_3(aq) \rightarrow \text{AgCl}(s)\downarrow + \text{KNO}_3(aq) \)
White AgCl precipitate forms; ↓ denotes insoluble precipitate
Combustion (Exothermic — Redox)
\( \text{C}_2\text{H}_4(g) + 3\text{O}_2(g) \rightarrow 2\text{CO}_2(g) + 2\text{H}_2\text{O}(l) + \text{Heat} \)
C₂H₄ is oxidised; ethylene oxidation is a redox reaction
Exothermic — Dilution of H₂SO₄
\( \text{H}_2\text{SO}_4(\text{conc.}) + \text{H}_2\text{O}(l) \rightarrow \text{H}_2\text{SO}_4(\text{dil.}) + \text{Heat} \)
⚠️ Always add acid to water, never water to acid
Formula
\( \sum m_{\text{reactants}} = \sum m_{\text{products}} \)
Law of Conservation of Mass
2
Acids, Bases and Salts
Arrhenius theory · pH scale · Indicators · Important salts · Chlor-alkali process
Key Points
Arrhenius — Acid: produces \(\text{H}^+\) ions in water. Base: produces \(\text{OH}^-\) ions in water.
Indicators: Blue litmus → red in acid; Red litmus → blue in base. Phenolphthalein: colourless in acid, pink in base.
pH Scale (0–14): pH < 7 = acidic; pH = 7 = neutral; pH > 7 = basic. Stomach acid pH ≈ 2; blood pH ≈ 7.4.
Olfactory indicators: Onion, clove oil, vanilla — their smell changes in acidic or basic solutions.
Important Reactions
Acid + Metal → Salt + H₂
\( \text{Zn}(s) + 2\text{HCl}(aq) \rightarrow \text{ZnCl}_2(aq) + \text{H}_2(g)\uparrow \)
Acid + Base → Salt + Water (Neutralization)
\( \text{NaOH}(aq) + \text{HCl}(aq) \rightarrow \text{NaCl}(aq) + \text{H}_2\text{O}(l) \)
Acid + Carbonate → Salt + Water + CO₂
\( \text{CaCO}_3(s) + 2\text{HCl}(aq) \rightarrow \text{CaCl}_2(aq) + \text{H}_2\text{O}(l) + \text{CO}_2(g)\uparrow \)
Hydronium ion formation
\( \text{HCl}(g) + \text{H}_2\text{O}(l) \rightarrow \text{H}_3\text{O}^+(aq) + \text{Cl}^-(aq) \)
Acids don't directly give H⁺ — they give hydronium ions H₃O⁺ in water
Chlor-alkali Process (Electrolysis)
\( 2\text{NaCl}(aq) + 2\text{H}_2\text{O}(l) \xrightarrow{\text{electrolysis}} 2\text{NaOH}(aq) + \text{Cl}_2(g) + \text{H}_2(g) \)
Products: NaOH (alkali), Cl₂ (bleaching powder/PVC), H₂ (fuel/margarine)
Bleaching Powder
\( \text{Ca(OH)}_2(s) + \text{Cl}_2(g) \rightarrow \text{CaOCl}_2(s) + \text{H}_2\text{O}(l) \)
Used for disinfecting water, bleaching cotton/linen
Baking Soda (NaHCO₃) heated
\( 2\text{NaHCO}_3(s) \xrightarrow{\Delta} \text{Na}_2\text{CO}_3(s) + \text{H}_2\text{O}(g) + \text{CO}_2(g)\uparrow \)
CO₂ released makes bread/cake rise; used in baking powder
Key Salts — Formulas
\(\text{NaHCO}_3\)Baking Soda (Sodium hydrogen carbonate)
\(\text{Na}_2\text{CO}_3 \cdot 10\text{H}_2\text{O}\)Washing Soda — softens hard water, cleaning agent
\(\text{CaSO}_4 \cdot \tfrac{1}{2}\text{H}_2\text{O}\)Plaster of Paris — sets hard on adding water
\(\text{CaOCl}_2\)Bleaching Powder
\(\text{NaCl}\)Common salt — raw material for NaOH, Cl₂, HCl, Na₂CO₃
pH Quick Reference
🔵
Acidic (pH < 7): HCl, H₂SO₄, CH₃COOH, lemon juice (pH 2.2), vinegar. Blue litmus → Red.
🟢
Basic (pH > 7): NaOH, Ca(OH)₂, ammonia, baking soda (pH 8.3), milk of magnesia. Red litmus → Blue.
3
Metals and Non-metals
Properties · Reactivity series · Extraction · Corrosion · Thermite reaction
Properties Comparison
⚙️ Metals
Lustrous, malleable, ductile, good conductors. Form positive ions (cations) by losing electrons. Produce basic oxides (Na₂O, CaO).
🌿 Non-metals
Dull (solid state), brittle, poor conductors (insulators). Form negative ions (anions) by gaining electrons. Produce acidic oxides (CO₂, SO₂).
Reactivity Series (Most → Least Reactive)
K1
Na2
Ca3
Mg4
Al5
Zn6
Fe7
Pb8
H9
Cu10
Ag11
Au12
← More reactive (displaces others from salt solution)(does not displace H₂ from acid) →
Key Reactions
Metal + Acid → Salt + H₂
\( \text{Mg}(s) + 2\text{HCl}(aq) \rightarrow \text{MgCl}_2(aq) + \text{H}_2(g)\uparrow \)
Thermite Reaction (Highly Exothermic)
\( \text{Fe}_2\text{O}_3(s) + 2\text{Al}(s) \rightarrow \text{Al}_2\text{O}_3(s) + 2\text{Fe}(l) + \text{Heat} \)
Al reduces Fe₂O₃ — used in welding railway tracks. Al is more reactive than Fe.
Rusting of Iron
\( 4\text{Fe}(s) + 3\text{O}_2(g) + x\,\text{H}_2\text{O}(l) \rightarrow 2\text{Fe}_2\text{O}_3 \cdot x\,\text{H}_2\text{O}(\text{rust}) \)
Both O₂ and H₂O are required for rusting
Extraction of Metals
Highly reactive (K, Na, Ca, Mg, Al): Extracted by electrolytic reduction (e.g. electrolysis of molten Al₂O₃ — Hall-Héroult process).
Moderately reactive (Zn, Fe, Pb): Extracted by reduction with carbon or CO in a blast furnace.
\( \text{ZnO}(s) + \text{C}(s) \rightarrow \text{Zn}(s) + \text{CO}(g)\uparrow \)
Less reactive (Cu, Ag, Au): Found native (free state) or heated in air (roasting).
\( 2\text{Cu}_2\text{S}(s) + 3\text{O}_2(g) \rightarrow 2\text{Cu}_2\text{O}(s) + 2\text{SO}_2(g) \)
Key ores: Fe₂O₃ (haematite), Al₂O₃ (bauxite), Cu₂S (copper glance), ZnS (zinc blende).
Corrosion prevention: Galvanising (Zn coating), painting, oiling, alloying (stainless steel = Fe + Cr + Ni), anodising (Al), electroplating.
4
Carbon and its Compounds
Catenation · Homologous series · Functional groups · Reactions · Soaps & Detergents
Key Concepts
Catenation: Carbon's unique ability to bond with itself, forming long chains, branches, or rings — basis of organic chemistry.
Tetravalency: Carbon has valency 4; forms 4 covalent bonds — single, double, or triple bonds.
Homologous series: Series of compounds with same functional group, differing by –CH₂– (14 u) each step. Same general formula, similar chemical properties, gradual change in physical properties.
Alkanes (saturated): \(C_n H_{2n+2}\) — e.g. methane CH₄, ethane C₂H₆. Undergo substitution reactions.
Alkenes (unsaturated): \(C_n H_{2n}\) — one C=C double bond; e.g. ethene C₂H₄. Undergo addition reactions.
Alkynes: \(C_n H_{2n-2}\) — one C≡C triple bond; e.g. ethyne C₂H₂.
Functional groups: –OH (alcohol), –COOH (carboxylic acid), –CHO (aldehyde), C=O (ketone), –Cl/–Br (haloalkane), –NH₂ (amine).
Soaps vs Detergents: Soaps form scum in hard water (react with Ca²⁺/Mg²⁺); detergents work in hard water — better cleaning action.
Key Reactions
Complete Combustion
\( \text{CH}_4(g) + 2\text{O}_2(g) \rightarrow \text{CO}_2(g) + 2\text{H}_2\text{O}(l) + \text{Heat} \)
Complete combustion gives blue flame; incomplete combustion (less O₂) gives sooty yellow flame and CO
Substitution (Alkane + Cl₂, UV light)
\( \text{CH}_4(g) + \text{Cl}_2(g) \xrightarrow{h\nu} \text{CH}_3\text{Cl}(g) + \text{HCl}(g) \)
Addition Reaction (Alkene + H₂)
\( \text{CH}_2{=}\text{CH}_2(g) + \text{H}_2(g) \xrightarrow{\text{Ni, }\Delta} \text{CH}_3\text{CH}_3(g) \)
Vegetable oil (unsaturated) + H₂ → vegetable ghee (saturated fat) — hydrogenation
Polymerization (Addition)
\( n\,\text{CH}_2{=}\text{CH}_2 \rightarrow {(-\text{CH}_2{-}\text{CH}_2-)}_n \)
Polythene (polyethylene) — addition polymer of ethene
Esterification (Reversible)
\( \text{C}_2\text{H}_5\text{OH} + \text{CH}_3\text{COOH} \underset{\Delta}{\overset{\text{H}^+}{\rightleftharpoons}} \text{CH}_3\text{COOC}_2\text{H}_5 + \text{H}_2\text{O} \)
Ethanol + Ethanoic acid ⇌ Ethyl ethanoate (sweet fruity smell) + Water; conc. H₂SO₄ as catalyst
Saponification (Soap Making)
\( \text{Fat/Oil} + \text{NaOH}(aq) \xrightarrow{\Delta} \text{Glycerol} + \text{Soap (sodium salt of fatty acid)} \)
Important Formulas
\(C_nH_{2n+2}\)Alkane (saturated; e.g. CH₄ when n=1)
\(C_nH_{2n}\)Alkene (one C=C bond; e.g. C₂H₄ when n=2)
\(C_nH_{2n-2}\)Alkyne (one C≡C bond; e.g. C₂H₂ when n=2)
\(\text{C}_2\text{H}_5\text{OH}\)Ethanol — formed by fermentation of glucose
\(\text{CH}_3\text{COOH}\)Ethanoic acid (acetic acid) — present in vinegar
6
Life Processes
Photosynthesis · Respiration · Nutrition · Circulation · Excretion · Transportation in plants
Photosynthesis
Photosynthesis Equation
\( 6\text{CO}_2 + 6\text{H}_2\text{O} \xrightarrow{\text{Sunlight + Chlorophyll}} \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \)
Occurs in chloroplasts; CO₂ enters via stomata; H₂O absorbed by roots. Light reaction (grana) + Dark reaction/Calvin cycle (stroma).
Factors affecting photosynthesis: Light intensity, CO₂ concentration, water availability, temperature, chlorophyll content.
Autotrophs make their own food via photosynthesis — plants, algae, cyanobacteria.
Heterotrophs depend on other organisms for food — animals, fungi, most bacteria.
Respiration
Aerobic Respiration (mitochondria)
\( \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O} + \text{Energy (ATP)} \)
Anaerobic — Fermentation in Yeast
\( \text{C}_6\text{H}_{12}\text{O}_6 \rightarrow 2\text{C}_2\text{H}_5\text{OH} + 2\text{CO}_2 + \text{Energy} \)
In human muscle cells (anaerobic): Glucose → Lactic acid + Energy → causes muscle cramps
Nutrition, Digestion & Circulation
Digestion — Enzymes: Salivary amylase (starch → maltose in mouth); Pepsin (proteins → peptides in stomach, acidic pH); Trypsin (proteins → amino acids in small intestine); Lipase (fats → glycerol + fatty acids); Bile (emulsifies fats).
Absorption: Occurs in small intestine via villi (finger-like projections with microvilli) — huge surface area for absorption into blood and lymph.
Double Circulation (4-chambered heart): Pulmonary circuit (heart → lungs → heart for oxygenation) + Systemic circuit (heart → body → heart). Ensures oxygenated and deoxygenated blood do not mix.
Blood Pressure: Measured in mm Hg. Normal ≈ 120/80 mm Hg. Measured using sphygmomanometer.
Transportation in Plants
Xylem: Transports water and dissolved minerals from roots to leaves (upward). Driven by transpiration pull (suction) and root pressure.
Phloem: Transports food (sucrose) from leaves to all parts of the plant (bidirectional). Process = translocation; requires energy (ATP).
Stomata: Open in light (guard cells absorb water → turgid → stomata open); close in dark/water deficit. Regulate transpiration and gas exchange.
Excretion
Kidney (Nephron): Ultrafiltration in Bowman's capsule → Selective reabsorption (glucose, water, salts) in nephron tubules → Urine (urea + excess salts + water) → ureter → bladder → urethra.
Osmoregulation: ADH (antidiuretic hormone) from pituitary regulates water reabsorption by kidneys.
Excretion in plants: CO₂ and O₂ via stomata; excess water via transpiration; waste stored in leaves (shed seasonally).
7
Control and Coordination
Reflex arc · Nervous system · Hormones · Tropic movements · Feedback
Nervous System
Reflex Arc: Stimulus → Receptor → Sensory neuron → Relay neuron (spinal cord) → Motor neuron → Effector (muscle/gland) → Response. Does NOT involve the brain — very rapid.
Types of neurons: Sensory (afferent — carries impulse to CNS); Motor (efferent — carries impulse from CNS); Relay/Interneuron (connects sensory to motor in CNS).
Synapse: Gap between neurons; neurotransmitters carry impulse across the gap chemically.
Brain regions: Cerebrum (thinking, memory, voluntary actions); Cerebellum (balance, coordination); Medulla oblongata (involuntary actions — breathing, heartbeat).
Hormonal (Endocrine) Control
Endocrine glands are ductless glands that secrete hormones directly into the bloodstream. Hormones are chemical messengers that act on specific target organs.
Adrenaline (adrenal glands) — "fight or flight"; raises heart rate, dilates pupils, diverts blood to muscles.
Insulin (pancreas — β cells) — lowers blood glucose; promotes glucose uptake and glycogen storage. Deficiency → Diabetes mellitus.
Glucagon (pancreas — α cells) — raises blood glucose; converts glycogen → glucose. Antagonistic to insulin. This is a negative feedback mechanism.
Thyroxine (thyroid gland) — regulates metabolism and growth; requires iodine. Deficiency → goitre.
Growth Hormone (secreted by pituitary gland) — regulates overall body growth. Excess secretion → gigantism; deficiency → dwarfism.
Plant Hormones (Phytohormones)
Auxins: Promote cell elongation; responsible for phototropism (shoot bends towards light) and geotropism (root grows towards gravity).
Gibberellins: Promote stem elongation, germination, and fruit development.
Cytokinins: Promote cell division; delay ageing (senescence).
Abscisic Acid (ABA): Inhibitory hormone; promotes seed dormancy, causes stomata to close under water stress.
Nervous vs Endocrine
⚡
Nervous: Fast (electrical impulse). Short-lived, precise targeting of specific organs/muscles.
🧪
Endocrine: Slow (chemical hormone via blood). Long-lasting, widespread effect on multiple target organs.
8
How do Organisms Reproduce?
Asexual methods · Sexual in plants · Sexual in humans · Contraception
Asexual Reproduction
Only one parent; offspring are genetically identical clones. No variation introduced.
Binary fission: Amoeba, bacteria — single cell divides into two equal daughter cells. In Leishmania, fission occurs at a specific orientation.
Budding: Yeast, Hydra — small outgrowth (bud) forms, enlarges and eventually detaches.
Spore formation: Rhizopus (bread mould) — sporangia produce thousands of spores, dispersed by air, germinate in favourable conditions.
Regeneration: Planaria — if cut, each part regenerates a complete organism. Involves specialised cells (neoblasts).
Vegetative propagation: Potato (tuber), Bryophyllum (leaf buds), runners in grass — used in horticulture (grafting, cutting).
Sexual Reproduction in Plants
Flower = reproductive organ. Stamen (male — anther produces pollen) + Pistil/Carpel (female — stigma, style, ovary containing ovule).
Sequence: Pollination → Pollen tube grows down style → Fertilization (male gamete + egg in ovule) → Zygote → Embryo → Seed; ovary wall → Fruit.
Pollination types: Self-pollination (same flower/plant); Cross-pollination (different plant — by wind, insects, water).
Seed dispersal: Wind (feathery/winged — dandelion, maple), Water (buoyant — coconut), Animals (hooked — Xanthium; fleshy fruits — berries), Explosive dehiscence (Balsam).
Sexual Reproduction in Humans
Male: Testes produce sperm (spermatogenesis); sperm + seminal fluid = semen. Sperm travel through vas deferens → urethra.
Female: Ovaries release one ovum/month (ovulation, ~day 14); menstrual cycle ~28 days regulated by FSH, LH, estrogen, progesterone.
Fertilization: Sperm meets ovum in fallopian tube → Zygote → undergoes mitosis → Embryo → implants in uterine wall → Placenta develops.
Gestation: ~9 months (38–40 weeks). Placenta provides nutrition and oxygen; removes CO₂ and waste from foetus.
Contraception: Barrier (condom, diaphragm — also prevents STIs); Chemical (oral pills — alter hormone levels); IUD (copper-T); Surgical (vasectomy, tubectomy).
9
Heredity and Evolution
Mendel's laws · Punnett squares · Sex determination · Natural selection · Evidence
Heredity — Mendel's Experiments
Traits are passed from parents to offspring via genes on chromosomes. Mendel used pea plants (Pisum sativum) for 7 contrasting traits.
Dominant (T): Expressed with only one copy. Recessive (t): Expressed only when homozygous (tt).
F₂ generation (monohybrid cross): Phenotype ratio = 3 dominant : 1 recessive. Genotype ratio = 1 TT : 2 Tt : 1 tt.
Law of Segregation: During gamete formation, the two alleles of a gene separate so each gamete carries only one allele.
Law of Independent Assortment: Genes for different traits are inherited independently (when on different chromosomes). Dihybrid cross F₂ ratio = 9:3:3:1.
Sex Determination in Humans
🧬
Humans have 23 pairs of chromosomes. 22 pairs = autosomes; 1 pair = sex chromosomes.
Female: XX (homogametic — produces only X-bearing eggs)
Male: XY (heterogametic — produces X-bearing or Y-bearing sperm)
Sex of child is determined by the father's sperm (X → girl; Y → boy). Probability = 50 : 50.
Female: XX (homogametic — produces only X-bearing eggs)
Male: XY (heterogametic — produces X-bearing or Y-bearing sperm)
Sex of child is determined by the father's sperm (X → girl; Y → boy). Probability = 50 : 50.
Evolution
Natural Selection (Darwin, 1859): Organisms with favourable heritable variations survive and reproduce more successfully → traits passed to offspring → gradual change in population.
Variations: Arise due to sexual reproduction (genetic recombination) and mutations. Variations are the raw material for evolution.
Evidence — Fossils: Preserved remains in rock strata; older fossils in deeper layers. Show intermediate forms (e.g. Archaeopteryx = bird-reptile).
Homologous structures: Same basic bone structure, different functions (e.g. forelimb of whale, bat, horse, human — pentadactyl limb). Indicates common ancestry.
Analogous structures: Different origin, similar function (e.g. wings of birds and insects). Indicates convergent evolution, NOT common ancestry.
Vestigial organs: Reduced, non-functional remnants of structures useful in ancestors (e.g. coccyx/tailbone in humans, vermiform appendix, nictitating membrane).
Acquired vs Inherited traits: Acquired traits (e.g. a scar) are NOT inherited; only genetic variations are heritable. Lamarck's theory of acquired characteristics is rejected.
Speciation: Formation of new species due to geographic isolation → genetic drift → reproductive isolation. No gene flow between isolated populations.
10
Light – Reflection and Refraction
Mirror & Lens formula · Magnification · Sign convention · Snell's Law · Refractive index
Sign Convention (New Cartesian)
All distances measured from the pole (P) of the mirror or optical centre (O) of the lens.
Distances in the direction of incident light = positive (+); opposite to incident light = negative (−).
Heights above principal axis = positive; below = negative.
Concave mirror & convex lens: focal length \(f\) is negative for concave mirror, positive for convex lens.
Reflection — Mirrors
Laws of reflection: ∠i = ∠r; incident ray, reflected ray, and normal are coplanar.
Concave mirror: Forms real, inverted images (object beyond F); virtual, erect, magnified image (object between F and P). Used in torches, shaving mirrors, solar furnaces.
Convex mirror: Always forms virtual, erect, diminished image — wide field of view. Used as rear-view mirrors and in security cameras.
Mirror Formula & Magnification
\(\dfrac{1}{f} = \dfrac{1}{v} + \dfrac{1}{u}\)
Mirror formula — f = focal length, v = image distance, u = object distance (all with sign)
\(m_{\text{mirror}} = \dfrac{h_i}{h_o} = -\dfrac{v}{u}\)
Mirror magnification: m < 0 → real, inverted; m > 0 → virtual, erect
Refraction — Lenses
Light bends towards the normal when entering a denser (optically) medium (speed decreases).
Convex lens (converging): \(f > 0\). Forms real, inverted images (object beyond F); virtual, erect, magnified (object within F). Used in magnifying glass, cameras, eye.
Concave lens (diverging): \(f < 0\). Always forms virtual, erect, diminished image. Used to correct myopia.
Lens Formula, Magnification & Power
\(\dfrac{1}{f} = \dfrac{1}{v} - \dfrac{1}{u}\)
Lens formula (⚠ sign differs from mirror — note minus sign)
\(m_{\text{lens}} = \dfrac{h_i}{h_o} = \dfrac{v}{u}\)
Lens magnification (⚠ no negative sign — differs from mirror)
\(P = \dfrac{1}{f(\text{m})}\)
Lens power in Diopters (D). Convex: +P; Concave: −P
Snell's Law & Refractive Index
\(n_1 \sin\theta_1 = n_2 \sin\theta_2\)
Snell's Law of Refraction
\(n = \dfrac{c}{v} = \dfrac{\sin\theta_i}{\sin\theta_r}\)
Refractive index (n) — c = speed of light in vacuum, v = speed in medium
Dispersion & Phenomena
Dispersion: White light splits into VIBGYOR by prism. Red deviates least (longest wavelength, highest speed in glass); Violet deviates most (shortest wavelength).
Rainbow: Refraction → Internal reflection → Dispersion in spherical water droplets. Primary rainbow: red outside, violet inside. Secondary (double) rainbow: colours reversed.
11
Human Eye and the Colourful World
Eye structure · Vision defects & corrections · Atmospheric refraction · Tyndall effect
Parts of the Human Eye
Cornea: Transparent curved front surface; responsible for ~2/3 of the eye's focusing power.
Iris & Pupil: Iris (coloured ring) controls pupil diameter to regulate light entry. In bright light: pupil contracts; in dim light: pupil dilates.
Crystalline Lens: Flexible; changes shape via ciliary muscles for accommodation (focusing near or far). Near point of normal eye ≈ 25 cm.
Retina: Light-sensitive layer. Rods (dim light — night vision, no colour); Cones (bright light — colour vision). Fovea (yellow spot) — highest visual acuity. Blind spot — no receptors where optic nerve exits.
Power of Accommodation
The ability of the eye to change focal length (by changing lens curvature) to see objects at different distances. Range: near point (25 cm) to far point (infinity for normal eye).
Vision Defects & Corrections
| Defect | Cause | Correction |
|---|---|---|
| Myopia (Short-sight) | Image focuses in front of retina; eyeball too long or lens too convex; far point < ∞ | Concave (diverging) lens; \(P < 0\) |
| Hypermetropia (Long-sight) | Image focuses behind retina; eyeball too short or lens too flat; near point > 25 cm | Convex (converging) lens; \(P > 0\) |
| Presbyopia | Age-related loss of lens elasticity; cannot accommodate | Bifocal lenses (concave + convex) |
| Cataract | Clouding of crystalline lens; progressive vision loss | Surgical lens replacement |
| Astigmatism | Irregular curvature of cornea; different focal lengths in different planes | Cylindrical (toric) lenses |
Atmospheric Phenomena
Blue sky (Rayleigh scattering): Blue light (short λ) scattered most by air molecules. \(\text{Scattering} \propto \frac{1}{\lambda^4}\)
Red sunrise/sunset: Light travels a longer path; blue scattered away; red/orange wavelengths (long λ, scatter least) reach our eyes.
Tyndall effect: Scattering of light by colloidal particles (e.g. dust, smoke, fog). Makes the beam visible. Sky appears blue due to Tyndall effect by air molecules.
Advanced sunrise / Delayed sunset: Atmospheric refraction bends light from the sun when it is below the horizon — the sun appears about 2 minutes earlier at sunrise and sets 2 minutes later.
Stars twinkle: Atmospheric refraction causes fluctuating bending of starlight → apparent position and brightness change. Planets do NOT twinkle (they are extended sources).
12
Electricity
Ohm's Law · Charge · Resistance & Resistivity · Series & Parallel · Power · Joule's Law
Fundamental Laws & Formulas
\(V = IR\)Ohm's Law (V = voltage V, I = current A, R = resistance Ω)
\(Q = It\)Charge Q in coulombs (C); 1 C = charge of 6.25×10¹⁸ electrons
\(R = \rho\,\dfrac{l}{A}\)Resistivity: ρ (Ω·m) is material property; l = length, A = cross-sectional area
\(P = VI = I^2R = \dfrac{V^2}{R}\)Electric power (P in watts W)
\(H = I^2Rt\)Joule's Law of Heating — heat produced H in joules J
\(W = QV = VIt = I^2Rt\)Work done by electric current
\(1\,\text{kWh} = 3.6\times10^6\,\text{J}\)Commercial unit of electrical energy (1 unit = 1 kWh)
Resistance in Circuits
➕
Series: \(R_s = R_1 + R_2 + R_3 + \cdots\)
Same current I through all; voltage divides. \(R_s > \) any individual R.
Same current I through all; voltage divides. \(R_s > \) any individual R.
⫾
Parallel: \(\dfrac{1}{R_p} = \dfrac{1}{R_1} + \dfrac{1}{R_2} + \dfrac{1}{R_3} + \cdots\)
Same voltage V across all; current divides. \(R_p < \) smallest R.
Same voltage V across all; current divides. \(R_p < \) smallest R.
Key Points
Factors affecting resistance: (i) Length l — R ∝ l; (ii) Cross-sectional area A — R ∝ 1/A; (iii) Material (resistivity ρ); (iv) Temperature — R increases with temperature for metals.
Heating effect applications: Electric bulb (tungsten filament — high mp, high ρ); Electric fuse (low mp alloy — melts on excess current, breaks circuit); Nichrome in heaters/toasters.
Electric fuse: Connected in series in the live wire; made of low-melting-point alloy (tin-lead). Rating in amperes. MCB (miniature circuit breaker) is a modern alternative.
Ohmic conductors: Obey Ohm's law (V∝I, graph is a straight line through origin). Non-ohmic: LED, junction diode — I-V graph is non-linear.
13
Magnetic Effects of Electric Current
Oersted · Magnetic field · Fleming's rules · Motor · Generator · Domestic circuits
Magnetic Field Due to Current
Oersted's discovery (1820): A current-carrying conductor produces a magnetic field around it — established the link between electricity and magnetism.
Straight wire: Magnetic field lines are concentric circles. Direction given by Right-Hand Thumb Rule (grasp wire with right hand; thumb points in direction of current → fingers curl in direction of B field).
Circular loop: Field at centre resembles a bar magnet. For a solenoid (many turns), field inside is uniform and parallel — acts like a bar magnet with N and S poles.
Electromagnet: Soft iron core inside solenoid — strong, temporary magnet. Strength ∝ number of turns × current.
Force on a Current-Carrying Conductor
\(F = BIl\)
Force on conductor: B = magnetic field (T), I = current (A), l = length in field (m)
Fleming's Left-Hand Rule (Motor effect): Stretch thumb, index, and middle finger mutually perpendicular. Forefinger → Field (B); Middle finger → Current (I); Thumb → Motion/Force (F). FBI mnemonic.
Electric Motor (DC)
Principle: A current-carrying coil in a magnetic field experiences a torque (couple) that causes it to rotate. Converts electrical energy → mechanical energy.
Key components: Armature coil, strong magnets (or field coils), commutator (splits ring — reverses current direction every half rotation to maintain continuous rotation), carbon brushes.
Uses: Electric fans, mixers, washing machines, electric vehicles, water pumps.
Electromagnetic Induction & Generator
Faraday's discovery: A changing magnetic flux through a coil induces an EMF (and hence current) in the coil. EMF ∝ rate of change of magnetic flux.
Fleming's Right-Hand Rule (Generator effect): Fore finger → Field; thumb → Motion; middle finger → induced Current. Used to find direction of induced current.
AC Generator: Rotating coil in magnetic field — slip rings (instead of commutator) allow output to be AC. Converts mechanical → electrical energy. India: 220 V, 50 Hz AC.
DC Generator: Uses commutator like motor — output is DC.
Difference — Motor vs Generator: Motor converts electrical → mechanical; Generator converts mechanical → electrical.
Domestic Electric Circuits
India uses 220 V, 50 Hz AC. Three wires: Live (brown/red — 220 V), Neutral (blue — 0 V reference), Earth (green/yellow — safety, 0 V).
Appliances are connected in parallel at home — each gets the same 220 V and can be switched independently.
Short circuit: Live and neutral touch → very high current → fuse melts/MCB trips, protecting circuit.
Overloading: Too many high-power appliances on one circuit → current exceeds safe limit → fuse blows. Use separate circuits for high-power devices.
15
Our Environment
Ecosystem · Food chains · 10% Energy Law · Pollution · Ozone · 3R's
Ecosystem & Energy Flow
Ecosystem components: Biotic (producers, consumers, decomposers) + Abiotic (air, water, soil, sunlight, temperature).
Food chain: Producers (green plants — autotrophs) → Primary consumers (herbivores) → Secondary consumers (carnivores) → Tertiary consumers → Decomposers (bacteria/fungi — recycle nutrients).
Food web: Multiple interconnected food chains — more stable than a single food chain; disruption of one pathway has less impact.
10% Energy Rule (Lindemann, 1942): Only ~10% of energy at one trophic level transfers to the next; ~90% is lost as heat. This limits food chains to 3–4 links.
\( E_{\text{next}} = 10\% \times E_{\text{current}} \)
Biomagnification (Biological magnification): Concentration of non-biodegradable chemicals (DDT, mercury) increases at higher trophic levels. Humans (top of food chain) accumulate highest concentrations.
Biodegradable vs Non-biodegradable: Biodegradable (food waste, paper, cotton) broken down by microorganisms. Non-biodegradable (plastics, DDT, polythene) persist and cause pollution.
Energy Pyramid
Producers (Plants) — 10,000 J (100%)
Herbivores — 1,000 J (10%)
Carnivores — 100 J (1%)
Top carnivores — 10 J (0.1%)
Pollution & Environmental Issues
Greenhouse effect & Global warming: CO₂, CH₄, N₂O, CFCs trap heat re-radiated from Earth's surface → rising global temperatures → melting ice caps, rising sea levels, climate change.
Acid rain: SO₂ + H₂O → H₂SO₃; NO₂ + H₂O → HNO₃ → acid rain (pH < 5.6) damages monuments (e.g. Taj Mahal), kills aquatic life, damages vegetation.
Ozone layer (stratosphere, 15–35 km): \(\text{O}_3\) absorbs harmful UV-B and UV-C radiation. CFCs (chlorofluorocarbons from refrigerants, aerosols) deplete ozone → ozone hole over Antarctica. UV causes skin cancer, cataracts, and kills phytoplankton.
Eutrophication (water): Excess nitrates/phosphates (fertilisers, sewage) → algal bloom → depletes dissolved oxygen → aquatic organisms die (dead zones).
Conservation — Waste Management
♻️ Reduce — minimise consumption
🔄 Reuse — use items multiple times
♻ Recycle — process waste into new materials
🌳 Afforestation — plant trees
Control industrial emissions
Avoid single-use plastics
Segregate biodegradable & non-biodegradable waste
Quick Revision Tips & Exam Strategy
Last-minute pointers based on CBSE question patterns to maximise your score
📋
Formulas Cheat Sheet
Mirror: \(1/f=1/v+1/u\), \(m=-v/u\). Lens: \(1/f=1/v-1/u\), \(m=v/u\). Ohm's: \(V=IR\). Power: \(P=VI=I^2R\). Photosynthesis & respiration equations. \(F=BIl\). Series/Parallel \(R\). Resistivity \(R=\rho l/A\).
⚡
Attempt Order
All 20 MCQs first (1 mark each) → 2-mark short answers → 3-mark short answers → 5-mark long answers with diagrams. Marks per minute is highest for MCQs.
✍️
Balance All Chemical Equations
Always write balanced equations with state symbols. Key correction: \(2\text{FeSO}_4 \xrightarrow{\Delta} \text{Fe}_2\text{O}_3 + \text{SO}_2 + \text{SO}_3\) — note the 2 in front of FeSO₄.
🖊️
Label All Diagrams
Human eye, nephron, reflex arc, ray diagrams for mirrors/lenses — draw neatly with all parts labelled. A well-labelled diagram earns full marks even if explanation is brief.
🔍
Mirror vs Lens — Critical Difference
Mirror magnification: \(m = -v/u\). Lens magnification: \(m = v/u\). Lens formula has a minus sign: \(1/f = 1/v - 1/u\). These differences are frequently tested in MCQs.
🎯
High-Yield Topics (Most Marks)
Chemical equations (Ch 1–4), Life processes diagrams (Ch 6), Electricity numericals (Ch 12), Reflection/Refraction numericals (Ch 10), Heredity Punnett squares (Ch 9), Periodic table trends (Ch 5).
🧬
Sex Determination (Often Asked)
Females = XX; Males = XY. Father determines sex of child. Probability of boy = girl = 50%. It is scientifically wrong to blame the mother for the sex of a child.
📖
Stick to NCERT
All CBSE questions are NCERT-based. These notes cover the full Class 10 Science NCERT syllabus. MathJax renders all LaTeX equations — works in Odoo HTML embed blocks with internet access.
CBSE Class 10 · Science
Prepared by: Muhammad Jaisal · Learnify Academy, Bahrain
Quick Revision Notes
All Chapters
Everything you need for your Class 10 Science exam — all 13 chapters per the CBSE 2025-26 syllabus. Equations rendered with MathJax LaTeX.
13Chapters Covered
80Theory Marks
20Practical Marks
3hExam Duration
📋 Exam Pattern & Strategy
CBSE Class 10 Science (2025-26): 80 marks theory + 20 marks practical. 13 chapters — Ch.5 (Periodic Classification), Ch.14 (Sources of Energy) & Ch.16 (Natural Resources) have been officially removed from the CBSE curriculum. Focus on NCERT and write balanced equations with state symbols.
20 MCQs × 1 mark
6 Short Answers × 2 marks
7 Short Answers × 3 marks
3 Long Answers × 5 marks
📚
⚡
Exam Tip
Attempt MCQs first, then short answers, saving time for 5-mark long answers. Always write balanced chemical equations with state symbols (s, l, g, aq).
1
Chemical Reactions and Equations
Balancing equations · Reaction types · Exo/Endothermic · Oxidation & Reduction · Rancidity
Key Points
Chemical equations must be balanced — same number of atoms on each side. State symbols: (s) solid, (l) liquid, (g) gas, (aq) aqueous.
Law of Conservation of Mass: Total mass of reactants = total mass of products. (Formula shown in the box below.)
Physical vs Chemical change: Evaporation of petrol = physical; burning LPG = chemical (new substances form, irreversible).
Oxidation: Gain of oxygen OR loss of hydrogen. Reduction: Loss of oxygen OR gain of hydrogen. In a redox reaction both occur simultaneously.
Corrosion & Rancidity are both caused by oxidation. Rancidity: oxidation of fats/oils in food causing bad smell. Prevented by antioxidants, airtight containers, refrigeration, or flushing with nitrogen gas.
Reaction Types
Combination (Synthesis)
\( \text{CaO}(s) + \text{H}_2\text{O}(l) \rightarrow \text{Ca(OH)}_2(aq) + \text{Heat} \)
Exothermic — two reactants combine to form a single product
Endothermic Decomposition (✔ Balanced)
\( 2\text{FeSO}_4(s) \xrightarrow{\Delta} \text{Fe}_2\text{O}_3(s) + \text{SO}_2(g)\uparrow + \text{SO}_3(g)\uparrow \)
Heat is absorbed (endothermic). Note: 2 mol FeSO₄ required to balance Fe atoms on both sides.
Photolytic Decomposition
\( 2\text{AgCl}(s) \xrightarrow{h\nu} 2\text{Ag}(s) + \text{Cl}_2(g)\uparrow \)
Used in black-and-white photography; light provides energy for decomposition
Displacement
\( \text{Zn}(s) + \text{CuSO}_4(aq) \rightarrow \text{ZnSO}_4(aq) + \text{Cu}(s) \)
Zn is more reactive than Cu — it displaces Cu from its salt solution
Double-Displacement (Precipitation)
\( \text{KCl}(aq) + \text{AgNO}_3(aq) \rightarrow \text{AgCl}(s)\downarrow + \text{KNO}_3(aq) \)
White AgCl precipitate forms; ↓ denotes insoluble precipitate
Combustion (Exothermic — Redox)
\( \text{C}_2\text{H}_4(g) + 3\text{O}_2(g) \rightarrow 2\text{CO}_2(g) + 2\text{H}_2\text{O}(l) + \text{Heat} \)
C₂H₄ is oxidised; ethylene oxidation is a redox reaction
Exothermic — Dilution of H₂SO₄
\( \text{H}_2\text{SO}_4(\text{conc.}) + \text{H}_2\text{O}(l) \rightarrow \text{H}_2\text{SO}_4(\text{dil.}) + \text{Heat} \)
⚠️ Always add acid to water, never water to acid
Formula
\( \sum m_{\text{reactants}} = \sum m_{\text{products}} \)
Law of Conservation of Mass
2
Acids, Bases and Salts
Arrhenius theory · pH scale · Indicators · Important salts · Chlor-alkali process
Key Points
Arrhenius — Acid: produces \(\text{H}^+\) ions in water. Base: produces \(\text{OH}^-\) ions in water.
Indicators: Blue litmus → red in acid; Red litmus → blue in base. Phenolphthalein: colourless in acid, pink in base.
pH Scale (0–14): pH < 7 = acidic; pH = 7 = neutral; pH > 7 = basic. Stomach acid pH ≈ 2; blood pH ≈ 7.4.
Olfactory indicators: Onion, clove oil, vanilla — their smell changes in acidic or basic solutions.
Important Reactions
Acid + Metal → Salt + H₂
\( \text{Zn}(s) + 2\text{HCl}(aq) \rightarrow \text{ZnCl}_2(aq) + \text{H}_2(g)\uparrow \)
Acid + Base → Salt + Water (Neutralization)
\( \text{NaOH}(aq) + \text{HCl}(aq) \rightarrow \text{NaCl}(aq) + \text{H}_2\text{O}(l) \)
Acid + Carbonate → Salt + Water + CO₂
\( \text{CaCO}_3(s) + 2\text{HCl}(aq) \rightarrow \text{CaCl}_2(aq) + \text{H}_2\text{O}(l) + \text{CO}_2(g)\uparrow \)
Hydronium ion formation
\( \text{HCl}(g) + \text{H}_2\text{O}(l) \rightarrow \text{H}_3\text{O}^+(aq) + \text{Cl}^-(aq) \)
Acids don't directly give H⁺ — they give hydronium ions H₃O⁺ in water
Chlor-alkali Process (Electrolysis)
\( 2\text{NaCl}(aq) + 2\text{H}_2\text{O}(l) \xrightarrow{\text{electrolysis}} 2\text{NaOH}(aq) + \text{Cl}_2(g) + \text{H}_2(g) \)
Products: NaOH (alkali), Cl₂ (bleaching powder/PVC), H₂ (fuel/margarine)
Bleaching Powder
\( \text{Ca(OH)}_2(s) + \text{Cl}_2(g) \rightarrow \text{CaOCl}_2(s) + \text{H}_2\text{O}(l) \)
Used for disinfecting water, bleaching cotton/linen
Baking Soda (NaHCO₃) heated
\( 2\text{NaHCO}_3(s) \xrightarrow{\Delta} \text{Na}_2\text{CO}_3(s) + \text{H}_2\text{O}(g) + \text{CO}_2(g)\uparrow \)
CO₂ released makes bread/cake rise; used in baking powder
Key Salts — Formulas
\(\text{NaHCO}_3\)Baking Soda (Sodium hydrogen carbonate)
\(\text{Na}_2\text{CO}_3 \cdot 10\text{H}_2\text{O}\)Washing Soda — softens hard water, cleaning agent
\(\text{CaSO}_4 \cdot \tfrac{1}{2}\text{H}_2\text{O}\)Plaster of Paris — sets hard on adding water
\(\text{CaOCl}_2\)Bleaching Powder
\(\text{NaCl}\)Common salt — raw material for NaOH, Cl₂, HCl, Na₂CO₃
pH Quick Reference
🔵
Acidic (pH < 7): HCl, H₂SO₄, CH₃COOH, lemon juice (pH 2.2), vinegar. Blue litmus → Red.
🟢
Basic (pH > 7): NaOH, Ca(OH)₂, ammonia, baking soda (pH 8.3), milk of magnesia. Red litmus → Blue.
3
Metals and Non-metals
Properties · Reactivity series · Extraction · Corrosion · Thermite reaction
Properties Comparison
⚙️ Metals
Lustrous, malleable, ductile, good conductors. Form positive ions (cations) by losing electrons. Produce basic oxides (Na₂O, CaO).
🌿 Non-metals
Dull (solid state), brittle, poor conductors (insulators). Form negative ions (anions) by gaining electrons. Produce acidic oxides (CO₂, SO₂).
Reactivity Series (Most → Least Reactive)
K1
Na2
Ca3
Mg4
Al5
Zn6
Fe7
Pb8
H9
Cu10
Ag11
Au12
← More reactive (displaces others from salt solution)(does not displace H₂ from acid) →
Key Reactions
Metal + Acid → Salt + H₂
\( \text{Mg}(s) + 2\text{HCl}(aq) \rightarrow \text{MgCl}_2(aq) + \text{H}_2(g)\uparrow \)
Thermite Reaction (Highly Exothermic)
\( \text{Fe}_2\text{O}_3(s) + 2\text{Al}(s) \rightarrow \text{Al}_2\text{O}_3(s) + 2\text{Fe}(l) + \text{Heat} \)
Al reduces Fe₂O₃ — used in welding railway tracks. Al is more reactive than Fe.
Rusting of Iron
\( 4\text{Fe}(s) + 3\text{O}_2(g) + x\,\text{H}_2\text{O}(l) \rightarrow 2\text{Fe}_2\text{O}_3 \cdot x\,\text{H}_2\text{O}(\text{rust}) \)
Both O₂ and H₂O are required for rusting
Extraction of Metals
Highly reactive (K, Na, Ca, Mg, Al): Extracted by electrolytic reduction (e.g. electrolysis of molten Al₂O₃ — Hall-Héroult process).
Moderately reactive (Zn, Fe, Pb): Extracted by reduction with carbon or CO in a blast furnace.
\( \text{ZnO}(s) + \text{C}(s) \rightarrow \text{Zn}(s) + \text{CO}(g)\uparrow \)
Less reactive (Cu, Ag, Au): Found native (free state) or heated in air (roasting).
\( 2\text{Cu}_2\text{S}(s) + 3\text{O}_2(g) \rightarrow 2\text{Cu}_2\text{O}(s) + 2\text{SO}_2(g) \)
Key ores: Fe₂O₃ (haematite), Al₂O₃ (bauxite), Cu₂S (copper glance), ZnS (zinc blende).
Corrosion prevention: Galvanising (Zn coating), painting, oiling, alloying (stainless steel = Fe + Cr + Ni), anodising (Al), electroplating.
4
Carbon and its Compounds
Catenation · Homologous series · Functional groups · Reactions · Soaps & Detergents
Key Concepts
Catenation: Carbon's unique ability to bond with itself, forming long chains, branches, or rings — basis of organic chemistry.
Tetravalency: Carbon has valency 4; forms 4 covalent bonds — single, double, or triple bonds.
Homologous series: Series of compounds with same functional group, differing by –CH₂– (14 u) each step. Same general formula, similar chemical properties, gradual change in physical properties.
Alkanes (saturated): \(C_n H_{2n+2}\) — e.g. methane CH₄, ethane C₂H₆. Undergo substitution reactions.
Alkenes (unsaturated): \(C_n H_{2n}\) — one C=C double bond; e.g. ethene C₂H₄. Undergo addition reactions.
Alkynes: \(C_n H_{2n-2}\) — one C≡C triple bond; e.g. ethyne C₂H₂.
Functional groups: –OH (alcohol), –COOH (carboxylic acid), –CHO (aldehyde), C=O (ketone), –Cl/–Br (haloalkane), –NH₂ (amine).
Soaps vs Detergents: Soaps form scum in hard water (react with Ca²⁺/Mg²⁺); detergents work in hard water — better cleaning action.
Key Reactions
Complete Combustion
\( \text{CH}_4(g) + 2\text{O}_2(g) \rightarrow \text{CO}_2(g) + 2\text{H}_2\text{O}(l) + \text{Heat} \)
Complete combustion gives blue flame; incomplete combustion (less O₂) gives sooty yellow flame and CO
Substitution (Alkane + Cl₂, UV light)
\( \text{CH}_4(g) + \text{Cl}_2(g) \xrightarrow{h\nu} \text{CH}_3\text{Cl}(g) + \text{HCl}(g) \)
Addition Reaction (Alkene + H₂)
\( \text{CH}_2{=}\text{CH}_2(g) + \text{H}_2(g) \xrightarrow{\text{Ni, }\Delta} \text{CH}_3\text{CH}_3(g) \)
Vegetable oil (unsaturated) + H₂ → vegetable ghee (saturated fat) — hydrogenation
Polymerization (Addition)
\( n\,\text{CH}_2{=}\text{CH}_2 \rightarrow {(-\text{CH}_2{-}\text{CH}_2-)}_n \)
Polythene (polyethylene) — addition polymer of ethene
Esterification (Reversible)
\( \text{C}_2\text{H}_5\text{OH} + \text{CH}_3\text{COOH} \underset{\Delta}{\overset{\text{H}^+}{\rightleftharpoons}} \text{CH}_3\text{COOC}_2\text{H}_5 + \text{H}_2\text{O} \)
Ethanol + Ethanoic acid ⇌ Ethyl ethanoate (sweet fruity smell) + Water; conc. H₂SO₄ as catalyst
Saponification (Soap Making)
\( \text{Fat/Oil} + \text{NaOH}(aq) \xrightarrow{\Delta} \text{Glycerol} + \text{Soap (sodium salt of fatty acid)} \)
Important Formulas
\(C_nH_{2n+2}\)Alkane (saturated; e.g. CH₄ when n=1)
\(C_nH_{2n}\)Alkene (one C=C bond; e.g. C₂H₄ when n=2)
\(C_nH_{2n-2}\)Alkyne (one C≡C bond; e.g. C₂H₂ when n=2)
\(\text{C}_2\text{H}_5\text{OH}\)Ethanol — formed by fermentation of glucose
\(\text{CH}_3\text{COOH}\)Ethanoic acid (acetic acid) — present in vinegar
6
Life Processes
Photosynthesis · Respiration · Nutrition · Circulation · Excretion · Transportation in plants
Photosynthesis
Photosynthesis Equation
\( 6\text{CO}_2 + 6\text{H}_2\text{O} \xrightarrow{\text{Sunlight + Chlorophyll}} \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \)
Occurs in chloroplasts; CO₂ enters via stomata; H₂O absorbed by roots. Light reaction (grana) + Dark reaction/Calvin cycle (stroma).
Factors affecting photosynthesis: Light intensity, CO₂ concentration, water availability, temperature, chlorophyll content.
Autotrophs make their own food via photosynthesis — plants, algae, cyanobacteria.
Heterotrophs depend on other organisms for food — animals, fungi, most bacteria.
Respiration
Aerobic Respiration (mitochondria)
\( \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O} + \text{Energy (ATP)} \)
Anaerobic — Fermentation in Yeast
\( \text{C}_6\text{H}_{12}\text{O}_6 \rightarrow 2\text{C}_2\text{H}_5\text{OH} + 2\text{CO}_2 + \text{Energy} \)
In human muscle cells (anaerobic): Glucose → Lactic acid + Energy → causes muscle cramps
Nutrition, Digestion & Circulation
Digestion — Enzymes: Salivary amylase (starch → maltose in mouth); Pepsin (proteins → peptides in stomach, acidic pH); Trypsin (proteins → amino acids in small intestine); Lipase (fats → glycerol + fatty acids); Bile (emulsifies fats).
Absorption: Occurs in small intestine via villi (finger-like projections with microvilli) — huge surface area for absorption into blood and lymph.
Double Circulation (4-chambered heart): Pulmonary circuit (heart → lungs → heart for oxygenation) + Systemic circuit (heart → body → heart). Ensures oxygenated and deoxygenated blood do not mix.
Blood Pressure: Measured in mm Hg. Normal ≈ 120/80 mm Hg. Measured using sphygmomanometer.
Transportation in Plants
Xylem: Transports water and dissolved minerals from roots to leaves (upward). Driven by transpiration pull (suction) and root pressure.
Phloem: Transports food (sucrose) from leaves to all parts of the plant (bidirectional). Process = translocation; requires energy (ATP).
Stomata: Open in light (guard cells absorb water → turgid → stomata open); close in dark/water deficit. Regulate transpiration and gas exchange.
Excretion
Kidney (Nephron): Ultrafiltration in Bowman's capsule → Selective reabsorption (glucose, water, salts) in nephron tubules → Urine (urea + excess salts + water) → ureter → bladder → urethra.
Osmoregulation: ADH (antidiuretic hormone) from pituitary regulates water reabsorption by kidneys.
Excretion in plants: CO₂ and O₂ via stomata; excess water via transpiration; waste stored in leaves (shed seasonally).
7
Control and Coordination
Reflex arc · Nervous system · Hormones · Tropic movements · Feedback
Nervous System
Reflex Arc: Stimulus → Receptor → Sensory neuron → Relay neuron (spinal cord) → Motor neuron → Effector (muscle/gland) → Response. Does NOT involve the brain — very rapid.
Types of neurons: Sensory (afferent — carries impulse to CNS); Motor (efferent — carries impulse from CNS); Relay/Interneuron (connects sensory to motor in CNS).
Synapse: Gap between neurons; neurotransmitters carry impulse across the gap chemically.
Brain regions: Cerebrum (thinking, memory, voluntary actions); Cerebellum (balance, coordination); Medulla oblongata (involuntary actions — breathing, heartbeat).
Hormonal (Endocrine) Control
Endocrine glands are ductless glands that secrete hormones directly into the bloodstream. Hormones are chemical messengers that act on specific target organs.
Adrenaline (adrenal glands) — "fight or flight"; raises heart rate, dilates pupils, diverts blood to muscles.
Insulin (pancreas — β cells) — lowers blood glucose; promotes glucose uptake and glycogen storage. Deficiency → Diabetes mellitus.
Glucagon (pancreas — α cells) — raises blood glucose; converts glycogen → glucose. Antagonistic to insulin. This is a negative feedback mechanism.
Thyroxine (thyroid gland) — regulates metabolism and growth; requires iodine. Deficiency → goitre.
Growth Hormone (secreted by pituitary gland) — regulates overall body growth. Excess secretion → gigantism; deficiency → dwarfism.
Plant Hormones (Phytohormones)
Auxins: Promote cell elongation; responsible for phototropism (shoot bends towards light) and geotropism (root grows towards gravity).
Gibberellins: Promote stem elongation, germination, and fruit development.
Cytokinins: Promote cell division; delay ageing (senescence).
Abscisic Acid (ABA): Inhibitory hormone; promotes seed dormancy, causes stomata to close under water stress.
Nervous vs Endocrine
⚡
Nervous: Fast (electrical impulse). Short-lived, precise targeting of specific organs/muscles.
🧪
Endocrine: Slow (chemical hormone via blood). Long-lasting, widespread effect on multiple target organs.
8
How do Organisms Reproduce?
Asexual methods · Sexual in plants · Sexual in humans · Contraception
Asexual Reproduction
Only one parent; offspring are genetically identical clones. No variation introduced.
Binary fission: Amoeba, bacteria — single cell divides into two equal daughter cells. In Leishmania, fission occurs at a specific orientation.
Budding: Yeast, Hydra — small outgrowth (bud) forms, enlarges and eventually detaches.
Spore formation: Rhizopus (bread mould) — sporangia produce thousands of spores, dispersed by air, germinate in favourable conditions.
Regeneration: Planaria — if cut, each part regenerates a complete organism. Involves specialised cells (neoblasts).
Vegetative propagation: Potato (tuber), Bryophyllum (leaf buds), runners in grass — used in horticulture (grafting, cutting).
Sexual Reproduction in Plants
Flower = reproductive organ. Stamen (male — anther produces pollen) + Pistil/Carpel (female — stigma, style, ovary containing ovule).
Sequence: Pollination → Pollen tube grows down style → Fertilization (male gamete + egg in ovule) → Zygote → Embryo → Seed; ovary wall → Fruit.
Pollination types: Self-pollination (same flower/plant); Cross-pollination (different plant — by wind, insects, water).
Seed dispersal: Wind (feathery/winged — dandelion, maple), Water (buoyant — coconut), Animals (hooked — Xanthium; fleshy fruits — berries), Explosive dehiscence (Balsam).
Sexual Reproduction in Humans
Male: Testes produce sperm (spermatogenesis); sperm + seminal fluid = semen. Sperm travel through vas deferens → urethra.
Female: Ovaries release one ovum/month (ovulation, ~day 14); menstrual cycle ~28 days regulated by FSH, LH, estrogen, progesterone.
Fertilization: Sperm meets ovum in fallopian tube → Zygote → undergoes mitosis → Embryo → implants in uterine wall → Placenta develops.
Gestation: ~9 months (38–40 weeks). Placenta provides nutrition and oxygen; removes CO₂ and waste from foetus.
Contraception: Barrier (condom, diaphragm — also prevents STIs); Chemical (oral pills — alter hormone levels); IUD (copper-T); Surgical (vasectomy, tubectomy).
9
Heredity and Evolution
Mendel's laws · Punnett squares · Sex determination · Natural selection · Evidence
Heredity — Mendel's Experiments
Traits are passed from parents to offspring via genes on chromosomes. Mendel used pea plants (Pisum sativum) for 7 contrasting traits.
Dominant (T): Expressed with only one copy. Recessive (t): Expressed only when homozygous (tt).
F₂ generation (monohybrid cross): Phenotype ratio = 3 dominant : 1 recessive. Genotype ratio = 1 TT : 2 Tt : 1 tt.
Law of Segregation: During gamete formation, the two alleles of a gene separate so each gamete carries only one allele.
Law of Independent Assortment: Genes for different traits are inherited independently (when on different chromosomes). Dihybrid cross F₂ ratio = 9:3:3:1.
Sex Determination in Humans
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Humans have 23 pairs of chromosomes. 22 pairs = autosomes; 1 pair = sex chromosomes.
Female: XX (homogametic — produces only X-bearing eggs)
Male: XY (heterogametic — produces X-bearing or Y-bearing sperm)
Sex of child is determined by the father's sperm (X → girl; Y → boy). Probability = 50 : 50.
Female: XX (homogametic — produces only X-bearing eggs)
Male: XY (heterogametic — produces X-bearing or Y-bearing sperm)
Sex of child is determined by the father's sperm (X → girl; Y → boy). Probability = 50 : 50.
Evolution
Natural Selection (Darwin, 1859): Organisms with favourable heritable variations survive and reproduce more successfully → traits passed to offspring → gradual change in population.
Variations: Arise due to sexual reproduction (genetic recombination) and mutations. Variations are the raw material for evolution.
Evidence — Fossils: Preserved remains in rock strata; older fossils in deeper layers. Show intermediate forms (e.g. Archaeopteryx = bird-reptile).
Homologous structures: Same basic bone structure, different functions (e.g. forelimb of whale, bat, horse, human — pentadactyl limb). Indicates common ancestry.
Analogous structures: Different origin, similar function (e.g. wings of birds and insects). Indicates convergent evolution, NOT common ancestry.
Vestigial organs: Reduced, non-functional remnants of structures useful in ancestors (e.g. coccyx/tailbone in humans, vermiform appendix, nictitating membrane).
Acquired vs Inherited traits: Acquired traits (e.g. a scar) are NOT inherited; only genetic variations are heritable. Lamarck's theory of acquired characteristics is rejected.
Speciation: Formation of new species due to geographic isolation → genetic drift → reproductive isolation. No gene flow between isolated populations.
10
Light – Reflection and Refraction
Mirror & Lens formula · Magnification · Sign convention · Snell's Law · Refractive index
Sign Convention (New Cartesian)
All distances measured from the pole (P) of the mirror or optical centre (O) of the lens.
Distances in the direction of incident light = positive (+); opposite to incident light = negative (−).
Heights above principal axis = positive; below = negative.
Concave mirror & convex lens: focal length \(f\) is negative for concave mirror, positive for convex lens.
Reflection — Mirrors
Laws of reflection: ∠i = ∠r; incident ray, reflected ray, and normal are coplanar.
Concave mirror: Forms real, inverted images (object beyond F); virtual, erect, magnified image (object between F and P). Used in torches, shaving mirrors, solar furnaces.
Convex mirror: Always forms virtual, erect, diminished image — wide field of view. Used as rear-view mirrors and in security cameras.
Mirror Formula & Magnification
\(\dfrac{1}{f} = \dfrac{1}{v} + \dfrac{1}{u}\)
Mirror formula — f = focal length, v = image distance, u = object distance (all with sign)
\(m_{\text{mirror}} = \dfrac{h_i}{h_o} = -\dfrac{v}{u}\)
Mirror magnification: m < 0 → real, inverted; m > 0 → virtual, erect
Refraction — Lenses
Light bends towards the normal when entering a denser (optically) medium (speed decreases).
Convex lens (converging): \(f > 0\). Forms real, inverted images (object beyond F); virtual, erect, magnified (object within F). Used in magnifying glass, cameras, eye.
Concave lens (diverging): \(f < 0\). Always forms virtual, erect, diminished image. Used to correct myopia.
Lens Formula, Magnification & Power
\(\dfrac{1}{f} = \dfrac{1}{v} - \dfrac{1}{u}\)
Lens formula (⚠ sign differs from mirror — note minus sign)
\(m_{\text{lens}} = \dfrac{h_i}{h_o} = \dfrac{v}{u}\)
Lens magnification (⚠ no negative sign — differs from mirror)
\(P = \dfrac{1}{f(\text{m})}\)
Lens power in Diopters (D). Convex: +P; Concave: −P
Snell's Law & Refractive Index
\(n_1 \sin\theta_1 = n_2 \sin\theta_2\)
Snell's Law of Refraction
\(n = \dfrac{c}{v} = \dfrac{\sin\theta_i}{\sin\theta_r}\)
Refractive index (n) — c = speed of light in vacuum, v = speed in medium
Dispersion & Phenomena
Dispersion: White light splits into VIBGYOR by prism. Red deviates least (longest wavelength, highest speed in glass); Violet deviates most (shortest wavelength).
Rainbow: Refraction → Internal reflection → Dispersion in spherical water droplets. Primary rainbow: red outside, violet inside. Secondary (double) rainbow: colours reversed.
11
Human Eye and the Colourful World
Eye structure · Vision defects & corrections · Atmospheric refraction · Tyndall effect
Parts of the Human Eye
Cornea: Transparent curved front surface; responsible for ~2/3 of the eye's focusing power.
Iris & Pupil: Iris (coloured ring) controls pupil diameter to regulate light entry. In bright light: pupil contracts; in dim light: pupil dilates.
Crystalline Lens: Flexible; changes shape via ciliary muscles for accommodation (focusing near or far). Near point of normal eye ≈ 25 cm.
Retina: Light-sensitive layer. Rods (dim light — night vision, no colour); Cones (bright light — colour vision). Fovea (yellow spot) — highest visual acuity. Blind spot — no receptors where optic nerve exits.
Power of Accommodation
The ability of the eye to change focal length (by changing lens curvature) to see objects at different distances. Range: near point (25 cm) to far point (infinity for normal eye).
Vision Defects & Corrections
| Defect | Cause | Correction |
|---|---|---|
| Myopia (Short-sight) | Image focuses in front of retina; eyeball too long or lens too convex; far point < ∞ | Concave (diverging) lens; \(P < 0\) |
| Hypermetropia (Long-sight) | Image focuses behind retina; eyeball too short or lens too flat; near point > 25 cm | Convex (converging) lens; \(P > 0\) |
| Presbyopia | Age-related loss of lens elasticity; cannot accommodate | Bifocal lenses (concave + convex) |
| Cataract | Clouding of crystalline lens; progressive vision loss | Surgical lens replacement |
| Astigmatism | Irregular curvature of cornea; different focal lengths in different planes | Cylindrical (toric) lenses |
Atmospheric Phenomena
Blue sky (Rayleigh scattering): Blue light (short λ) scattered most by air molecules. \(\text{Scattering} \propto \frac{1}{\lambda^4}\)
Red sunrise/sunset: Light travels a longer path; blue scattered away; red/orange wavelengths (long λ, scatter least) reach our eyes.
Tyndall effect: Scattering of light by colloidal particles (e.g. dust, smoke, fog). Makes the beam visible. Sky appears blue due to Tyndall effect by air molecules.
Advanced sunrise / Delayed sunset: Atmospheric refraction bends light from the sun when it is below the horizon — the sun appears about 2 minutes earlier at sunrise and sets 2 minutes later.
Stars twinkle: Atmospheric refraction causes fluctuating bending of starlight → apparent position and brightness change. Planets do NOT twinkle (they are extended sources).
12
Electricity
Ohm's Law · Charge · Resistance & Resistivity · Series & Parallel · Power · Joule's Law
Fundamental Laws & Formulas
\(V = IR\)Ohm's Law (V = voltage V, I = current A, R = resistance Ω)
\(Q = It\)Charge Q in coulombs (C); 1 C = charge of 6.25×10¹⁸ electrons
\(R = \rho\,\dfrac{l}{A}\)Resistivity: ρ (Ω·m) is material property; l = length, A = cross-sectional area
\(P = VI = I^2R = \dfrac{V^2}{R}\)Electric power (P in watts W)
\(H = I^2Rt\)Joule's Law of Heating — heat produced H in joules J
\(W = QV = VIt = I^2Rt\)Work done by electric current
\(1\,\text{kWh} = 3.6\times10^6\,\text{J}\)Commercial unit of electrical energy (1 unit = 1 kWh)
Resistance in Circuits
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Series: \(R_s = R_1 + R_2 + R_3 + \cdots\)
Same current I through all; voltage divides. \(R_s > \) any individual R.
Same current I through all; voltage divides. \(R_s > \) any individual R.
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Parallel: \(\dfrac{1}{R_p} = \dfrac{1}{R_1} + \dfrac{1}{R_2} + \dfrac{1}{R_3} + \cdots\)
Same voltage V across all; current divides. \(R_p < \) smallest R.
Same voltage V across all; current divides. \(R_p < \) smallest R.
Key Points
Factors affecting resistance: (i) Length l — R ∝ l; (ii) Cross-sectional area A — R ∝ 1/A; (iii) Material (resistivity ρ); (iv) Temperature — R increases with temperature for metals.
Heating effect applications: Electric bulb (tungsten filament — high mp, high ρ); Electric fuse (low mp alloy — melts on excess current, breaks circuit); Nichrome in heaters/toasters.
Electric fuse: Connected in series in the live wire; made of low-melting-point alloy (tin-lead). Rating in amperes. MCB (miniature circuit breaker) is a modern alternative.
Ohmic conductors: Obey Ohm's law (V∝I, graph is a straight line through origin). Non-ohmic: LED, junction diode — I-V graph is non-linear.
13
Magnetic Effects of Electric Current
Oersted · Magnetic field · Fleming's rules · Motor · Generator · Domestic circuits
Magnetic Field Due to Current
Oersted's discovery (1820): A current-carrying conductor produces a magnetic field around it — established the link between electricity and magnetism.
Straight wire: Magnetic field lines are concentric circles. Direction given by Right-Hand Thumb Rule (grasp wire with right hand; thumb points in direction of current → fingers curl in direction of B field).
Circular loop: Field at centre resembles a bar magnet. For a solenoid (many turns), field inside is uniform and parallel — acts like a bar magnet with N and S poles.
Electromagnet: Soft iron core inside solenoid — strong, temporary magnet. Strength ∝ number of turns × current.
Force on a Current-Carrying Conductor
\(F = BIl\)
Force on conductor: B = magnetic field (T), I = current (A), l = length in field (m)
Fleming's Left-Hand Rule (Motor effect): Stretch thumb, index, and middle finger mutually perpendicular. Forefinger → Field (B); Middle finger → Current (I); Thumb → Motion/Force (F). FBI mnemonic.
Electric Motor (DC)
Principle: A current-carrying coil in a magnetic field experiences a torque (couple) that causes it to rotate. Converts electrical energy → mechanical energy.
Key components: Armature coil, strong magnets (or field coils), commutator (splits ring — reverses current direction every half rotation to maintain continuous rotation), carbon brushes.
Uses: Electric fans, mixers, washing machines, electric vehicles, water pumps.
Electromagnetic Induction & Generator
Faraday's discovery: A changing magnetic flux through a coil induces an EMF (and hence current) in the coil. EMF ∝ rate of change of magnetic flux.
Fleming's Right-Hand Rule (Generator effect): Fore finger → Field; thumb → Motion; middle finger → induced Current. Used to find direction of induced current.
AC Generator: Rotating coil in magnetic field — slip rings (instead of commutator) allow output to be AC. Converts mechanical → electrical energy. India: 220 V, 50 Hz AC.
DC Generator: Uses commutator like motor — output is DC.
Difference — Motor vs Generator: Motor converts electrical → mechanical; Generator converts mechanical → electrical.
Domestic Electric Circuits
India uses 220 V, 50 Hz AC. Three wires: Live (brown/red — 220 V), Neutral (blue — 0 V reference), Earth (green/yellow — safety, 0 V).
Appliances are connected in parallel at home — each gets the same 220 V and can be switched independently.
Short circuit: Live and neutral touch → very high current → fuse melts/MCB trips, protecting circuit.
Overloading: Too many high-power appliances on one circuit → current exceeds safe limit → fuse blows. Use separate circuits for high-power devices.
15
Our Environment
Ecosystem · Food chains · 10% Energy Law · Pollution · Ozone · 3R's
Ecosystem & Energy Flow
Ecosystem components: Biotic (producers, consumers, decomposers) + Abiotic (air, water, soil, sunlight, temperature).
Food chain: Producers (green plants — autotrophs) → Primary consumers (herbivores) → Secondary consumers (carnivores) → Tertiary consumers → Decomposers (bacteria/fungi — recycle nutrients).
Food web: Multiple interconnected food chains — more stable than a single food chain; disruption of one pathway has less impact.
10% Energy Rule (Lindemann, 1942): Only ~10% of energy at one trophic level transfers to the next; ~90% is lost as heat. This limits food chains to 3–4 links.
\( E_{\text{next}} = 10\% \times E_{\text{current}} \)
Biomagnification (Biological magnification): Concentration of non-biodegradable chemicals (DDT, mercury) increases at higher trophic levels. Humans (top of food chain) accumulate highest concentrations.
Biodegradable vs Non-biodegradable: Biodegradable (food waste, paper, cotton) broken down by microorganisms. Non-biodegradable (plastics, DDT, polythene) persist and cause pollution.
Energy Pyramid
Producers (Plants) — 10,000 J (100%)
Herbivores — 1,000 J (10%)
Carnivores — 100 J (1%)
Top carnivores — 10 J (0.1%)
Pollution & Environmental Issues
Greenhouse effect & Global warming: CO₂, CH₄, N₂O, CFCs trap heat re-radiated from Earth's surface → rising global temperatures → melting ice caps, rising sea levels, climate change.
Acid rain: SO₂ + H₂O → H₂SO₃; NO₂ + H₂O → HNO₃ → acid rain (pH < 5.6) damages monuments (e.g. Taj Mahal), kills aquatic life, damages vegetation.
Ozone layer (stratosphere, 15–35 km): \(\text{O}_3\) absorbs harmful UV-B and UV-C radiation. CFCs (chlorofluorocarbons from refrigerants, aerosols) deplete ozone → ozone hole over Antarctica. UV causes skin cancer, cataracts, and kills phytoplankton.
Eutrophication (water): Excess nitrates/phosphates (fertilisers, sewage) → algal bloom → depletes dissolved oxygen → aquatic organisms die (dead zones).
Conservation — Waste Management
♻️ Reduce — minimise consumption
🔄 Reuse — use items multiple times
♻ Recycle — process waste into new materials
🌳 Afforestation — plant trees
Control industrial emissions
Avoid single-use plastics
Segregate biodegradable & non-biodegradable waste
Quick Revision Tips & Exam Strategy
Last-minute pointers based on CBSE question patterns to maximise your score
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Formulas Cheat Sheet
Mirror: \(1/f=1/v+1/u\), \(m=-v/u\). Lens: \(1/f=1/v-1/u\), \(m=v/u\). Ohm's: \(V=IR\). Power: \(P=VI=I^2R\). Photosynthesis & respiration equations. \(F=BIl\). Series/Parallel \(R\). Resistivity \(R=\rho l/A\).
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Attempt Order
All 20 MCQs first (1 mark each) → 2-mark short answers → 3-mark short answers → 5-mark long answers with diagrams. Marks per minute is highest for MCQs.
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Balance All Chemical Equations
Always write balanced equations with state symbols. Key correction: \(2\text{FeSO}_4 \xrightarrow{\Delta} \text{Fe}_2\text{O}_3 + \text{SO}_2 + \text{SO}_3\) — note the 2 in front of FeSO₄.
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Label All Diagrams
Human eye, nephron, reflex arc, ray diagrams for mirrors/lenses — draw neatly with all parts labelled. A well-labelled diagram earns full marks even if explanation is brief.
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Mirror vs Lens — Critical Difference
Mirror magnification: \(m = -v/u\). Lens magnification: \(m = v/u\). Lens formula has a minus sign: \(1/f = 1/v - 1/u\). These differences are frequently tested in MCQs.
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High-Yield Topics (Most Marks)
Chemical equations (Ch 1–4), Life processes diagrams (Ch 6), Electricity numericals (Ch 12), Reflection/Refraction numericals (Ch 10), Heredity Punnett squares (Ch 9), Periodic table trends (Ch 5).
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Sex Determination (Often Asked)
Females = XX; Males = XY. Father determines sex of child. Probability of boy = girl = 50%. It is scientifically wrong to blame the mother for the sex of a child.
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Stick to NCERT
All CBSE questions are NCERT-based. These notes cover the full Class 10 Science NCERT syllabus. MathJax renders all LaTeX equations — works in Odoo HTML embed blocks with internet access.