🪐 Class 9 NCERT 2025–26

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🌡️ Chapter 1

Matter in Our Surroundings

Everything around us is matter — it has mass and occupies space. Matter exists in three states: solid, liquid, and gas. State changes with temperature and pressure. Evaporation causes cooling. Sublimation converts solid directly to gas.

Fig. 1.1

Three States of Matter — Particle Model

Solid: tightly packed, fixed positions, strong intermolecular forces — definite shape & volume. Liquid: close but mobile — definite volume, no fixed shape. Gas: far apart, random motion — no fixed shape or volume. Temperature determines state.

Fig. 1.4

Phase Changes — Heating Curve

Heat added at constant rate: temperature rises in single-phase regions, stays constant during phase changes (latent heat). Melting point (0°C) and boiling point (100°C) for water. Latent heat of fusion = 334 kJ/kg. Latent heat of vaporisation = 2260 kJ/kg.

Activity 1.3

Diffusion — KMnO₄ in Water

A crystal of KMnO₄ (purple) dropped in water gradually spreads — particles move from high to low concentration. Rate depends on temperature (higher temp → faster diffusion), mass of particles, and medium. Gases diffuse fastest.

Fig. 1.6

Evaporation vs Boiling — Key Differences

Evaporation: surface phenomenon, occurs at any temperature, slow, causes cooling (wet clothes feel cool). Boiling: bulk phenomenon, occurs only at boiling point, rapid, bubbles throughout. Factors affecting evaporation: temperature, surface area, humidity, wind speed.

Fig. 1.5

Sublimation — Direct Solid→Gas

Some solids convert directly to gas without passing through liquid state. Examples: dry ice (CO₂), camphor, naphthalene (mothballs), iodine crystals, ammonium chloride. Reverse: deposition (gas→solid). Used in freeze-drying and purification.

Activity 1.1

Effect of Temperature & Pressure on State

Increasing temperature provides kinetic energy to particles → state changes (solid→liquid→gas). Increasing pressure compresses matter → can change state (e.g. CO₂ liquefied under pressure). LPG: butane/propane stored as liquid under pressure.

🧪 Chapter 2

Is Matter Around Us Pure?

Pure substances have fixed composition and properties (elements and compounds). Mixtures have variable composition. Homogeneous mixtures (solutions) look uniform; heterogeneous don't. Separation techniques exploit differences in physical properties.

Fig. 2.1

Classification of Matter — Complete Tree

Matter → Pure Substance + Mixture. Pure Substance → Element + Compound. Mixture → Homogeneous (solution) + Heterogeneous. Solutions → True Solution, Colloid, Suspension. Elements → Metal, Non-metal, Metalloid.

Fig. 2.3

True Solution vs Colloid vs Suspension — Tyndall Effect

True solution: <1nm particles, transparent, no Tyndall effect, doesn't settle. Colloid: 1–1000nm, scatters light (Tyndall effect), doesn't settle — milk, blood, fog. Suspension: >1000nm, opaque, settles on standing — muddy water, chalk water.

Activity 2.2

Paper Chromatography — Ink Separation

Ink spot on paper strip → dipped in solvent (water). Solvent rises by capillary action carrying components. Different dyes travel different distances based on solubility. Rf = distance moved by component ÷ distance moved by solvent.

Fig. 2.4

Distillation — Separating by Boiling Points

Mixture heated → component with lower boiling point vaporises first → vapour condenses in condenser → pure liquid collected. Used to separate acetone/water, obtain pure water from seawater. Fractional distillation separates components with close boiling points (petroleum refining).

Activity 2.1

Separation Techniques — All Methods

Filtration (insoluble solid from liquid), Evaporation (soluble solid from solution), Centrifugation (dense from less dense), Magnetic separation (magnetic from non-magnetic), Sublimation (sublimable from non-sublimable), Distillation (liquids by boiling point).

Fig. 2.5

Alloys — Mixtures of Metals

Alloys are homogeneous mixtures of metals (or metals + non-metals). Bronze = Cu + Sn; Brass = Cu + Zn; Steel = Fe + C; Stainless steel = Fe + Cr + Ni; Solder = Pb + Sn. Alloys have better properties than pure metals (hardness, corrosion resistance, lower melting point).

⚛️ Chapter 3

Atoms and Molecules

Dalton proposed that matter is made of indivisible atoms. Law of Conservation of Mass (Lavoisier). Law of Definite Proportions (Proust). Relative atomic mass uses carbon-12 as standard. Mole = 6.022×10²³ (Avogadro's number). Molecular mass = sum of atomic masses.

Fig. 3.1

Dalton's Atomic Theory & Laws of Chemical Combination

1. All matter made of atoms (indivisible). 2. Atoms of same element identical. 3. Atoms combine in simple whole-number ratios. Law of Conservation of Mass: mass of reactants = mass of products. Law of Definite Proportions: compound always has same ratio by mass.

Activity 3.1

Law of Conservation of Mass — Experimental

Barium chloride + Sodium sulphate → Barium sulphate + Sodium chloride. Total mass before reaction = total mass after reaction. The scale stays balanced! Mass is neither created nor destroyed — only rearranged (Lavoisier, 1789).

Fig. 3.3

Mole Concept & Avogadro's Number

1 mole = 6.022×10²³ particles (atoms/molecules/ions). Molar mass = atomic/molecular mass in grams. 1 mole H₂O = 18g, contains 6.022×10²³ molecules. Mole bridges the microscopic world of atoms to the macroscopic world of grams we can measure.

Fig. 3.2

Atomic Mass, Molecular Mass & Chemical Formulae

Relative atomic mass: mass of atom compared to 1/12 of carbon-12. Molecular mass = sum of atomic masses of all atoms in molecule. H₂O = 2(1) + 16 = 18u. Chemical formulae show types and number of atoms. Valency determines combining capacity.

🔬 Chapter 4

Structure of the Atom

Thomson discovered electrons (1897). Rutherford's gold foil experiment revealed the nucleus (1909). Bohr proposed electrons orbit in fixed energy shells (1913). Modern atom: protons and neutrons in nucleus, electrons in shells (2, 8, 8 rule).

Activity 4.2

Rutherford's Gold Foil Experiment — Nuclear Discovery

Alpha particles fired at thin gold foil. Most pass through (mostly empty space). Some deflect at various angles. A few bounce straight back (dense positive nucleus). Conclusions: nucleus is tiny, dense, positively charged, most of atom is empty space.

Fig. 4.1–4.3

Evolution of Atomic Models — Thomson → Rutherford → Bohr

Thomson (1897): Plum pudding — electrons embedded in positive sphere. Rutherford (1911): Planetary — electrons orbit tiny nucleus. Bohr (1913): Quantised orbits — electrons in fixed energy shells with specific energies. Each model improved on experimental evidence.

Fig. 4.4

Bohr's Model — Electron Shells & Energy Levels

Electrons orbit in fixed shells (K, L, M, N…). Shell capacity: K=2, L=8, M=18, N=32. Maximum electrons = 2n² (n = shell number). Valence electrons (outermost shell) determine chemical reactivity. Electron jumps emit/absorb photons.

Fig. 4.5

Electron Configuration & Valence Electrons

Aufbau: fill from inner to outer shells. First 20 elements: H(1), He(2), Li(2,1), Be(2,2)…Ca(2,8,8,2). Valence electrons = electrons in outermost shell. Octet rule: atoms tend to gain/lose/share electrons to achieve 8 valence electrons (noble gas configuration).

Fig. 4.6

Isotopes, Isobars & Isotones

Isotopes: same element (same Z), different mass (different N) — ¹H, ²H(deuterium), ³H(tritium). ¹²C, ¹⁴C (radiocarbon dating). Isobars: same mass number, different atomic number — ⁴⁰Ca, ⁴⁰Ar. Isotones: same number of neutrons, different atomic number.

🦠 Chapter 5

The Fundamental Unit of Life

Cell theory: all living things are made of cells (Schleiden & Schwann, 1839). Cell is the structural and functional unit of life. Prokaryotes (no membrane-bound nucleus) vs Eukaryotes (membrane-bound nucleus). Plant cells have cell wall, chloroplasts, large vacuole.

Fig. 5.3

Plant Cell vs Animal Cell — Complete Comparison

Plant cell ONLY: cell wall (cellulose), chloroplasts, large central vacuole, plasmodesmata. Animal cell ONLY: centrioles, lysosomes, smaller/multiple vacuoles. BOTH: nucleus, mitochondria, ER, Golgi, ribosomes, cell membrane, cytoplasm. Plant cell: rectangular shape. Animal cell: irregular shape.

Fig. 5.4

Cell Organelles — Structure & Function

Mitochondria: ATP synthesis (powerhouse). Chloroplasts: photosynthesis. ER (rough): protein synthesis + transport. ER (smooth): lipid synthesis. Golgi: packaging + secretion. Vacuoles: storage, turgor. Lysosomes: digestion. Ribosomes: protein synthesis. Nucleus: control centre (DNA).

Fig. 5.1

Prokaryote vs Eukaryote — Key Differences

Prokaryote (bacteria): no membrane-bound nucleus, no membrane-bound organelles, circular DNA (nucleoid), 1–10 µm, cell wall (peptidoglycan). Eukaryote (plant/animal/fungi): true membrane-bound nucleus, membrane-bound organelles, linear DNA with histones, 10–100 µm.

Activity 5.1

Osmosis — Water Movement Across Membrane

Osmosis: movement of water from lower solute concentration to higher (through semi-permeable membrane). Hypotonic solution: cell swells (turgid) → plant cells firm, animal cells may burst. Hypertonic: cell shrinks (plasmolysis/crenation). Isotonic: no net movement. Crucial for all living cells.

Fig. 5.2

Cell Membrane — Fluid Mosaic Model

Phospholipid bilayer: hydrophilic heads face outward, hydrophobic tails inward. Proteins embedded (integral) or attached (peripheral). Cholesterol: regulates fluidity. Selective permeability: small nonpolar molecules freely pass; ions and polar molecules need carrier proteins.

🌿 Chapter 6

Tissues

A tissue is a group of cells similar in structure and function. Plant tissues: meristematic (dividing) and permanent (non-dividing). Animal tissues: epithelial, connective, muscular, nervous. Tissue organisation evolved to allow division of labour in multicellular organisms.

Fig. 6.1

Plant Tissues — Meristematic & Permanent

Meristematic: actively dividing — Apical (root/shoot tip, elongation), Lateral (cambium, increases girth), Intercalary (nodes, re-elongation after damage). Permanent: Parenchyma (storage, photosynthesis), Collenchyma (mechanical support, flexible), Sclerenchyma (dead cells, rigid support), Xylem (water), Phloem (food).

Fig. 6.2

Xylem & Phloem — Vascular Tissue Cross-Section

Xylem: carries water & minerals upward (root→leaves). Components: Tracheids, Vessels, Xylem fibres, Xylem parenchyma. Dead cells at maturity. Phloem: carries food (leaves→all parts, bidirectional). Components: Sieve tubes, Companion cells, Phloem fibres, Phloem parenchyma. Living cells.

Fig. 6.3

Animal Tissue Types — All Four

Epithelial: covers body surfaces, lining organs (squamous, cuboidal, columnar, ciliated). Connective: connects/supports organs — areolar, bone, blood, cartilage, adipose. Muscular: movement — striated (voluntary), smooth (involuntary), cardiac (heart). Nervous: transmits electrical impulses — neurons + neuroglia.

Fig. 6.4

Neuron — Structure & Impulse Transmission

Dendrites receive signals → Cell body (soma) contains nucleus → Axon transmits impulse → Axon terminals release neurotransmitters. Myelin sheath: speeds up impulse (Nodes of Ranvier enable saltatory conduction). Synaptic cleft: gap between neurons where neurotransmitters carry signal.

Fig. 6.5

Blood — Cells & Components

Plasma (55%): water, proteins, dissolved substances. RBC (erythrocytes): no nucleus, biconcave, haemoglobin carries O₂. WBC (leucocytes): immunity — neutrophils, lymphocytes, monocytes. Platelets (thrombocytes): clotting. Blood group antigens (ABO, Rh). Bone marrow produces all blood cells.

🏃 Chapter 7

Motion

Motion: change in position with time. Scalar (magnitude only): distance, speed. Vector (magnitude + direction): displacement, velocity, acceleration. Equations of motion for uniform acceleration: v=u+at, s=ut+½at², v²=u²+2as. Uniform circular motion: constant speed, changing velocity.

Fig. 7.1

Distance vs Displacement — Scalar vs Vector

Distance: total path length (scalar, always positive). Displacement: shortest distance between initial and final position in a specified direction (vector, can be negative). A person walking 4m East then 3m North: distance=7m, displacement=5m (NE). Same start/end = zero displacement.

Fig. 7.3

Distance-Time Graphs — Uniform & Non-Uniform Motion

Straight line with positive slope = uniform motion (constant speed). Steeper slope = higher speed. Horizontal line = at rest. Curved line = non-uniform motion (changing speed). Slope of tangent at a point on curve = instantaneous speed. Area under v-t graph = displacement.

Fig. 7.4

Velocity-Time Graphs & Equations of Motion

Uniform acceleration: straight line with positive slope. Slope = acceleration. Area under graph = displacement. Decelerating: negative slope. Uniform velocity: horizontal line. Equations: v=u+at, s=ut+½at², v²=u²+2as. Derived by plotting v-t graph and finding area geometrically.

Activity 7.1

Three Equations of Motion — Visual Derivation

v = u + at (velocity-time equation). s = ut + ½at² (position-time equation — area under v-t graph). v² = u² + 2as (position-velocity equation). All derived from v-t graph. Valid only for uniform acceleration in a straight line. u = initial velocity, v = final velocity, a = acceleration.

Fig. 7.5

Uniform Circular Motion

Object moves in a circle at constant speed but velocity constantly changes direction (tangential). Acceleration always points toward centre (centripetal). Period T = 2πr/v. Frequency f = 1/T. Examples: satellite, stone on string, car taking a turn. NOT uniform motion despite constant speed.

💥 Chapter 8

Force and Laws of Motion

Newton's First Law: body at rest/uniform motion stays so unless acted upon by net force (inertia). Second Law: F = ma (rate of change of momentum). Third Law: action = reaction (equal, opposite). Momentum: p = mv. Conservation of momentum in isolated systems.

Fig. 8.1

Newton's First Law — Inertia in Action

Inertia: resistance to change in state of motion. Inertia of rest (coin on card, tablecloth trick). Inertia of motion (passenger lurches forward when bus brakes). Greater mass = greater inertia. Galileo: ball on frictionless surface continues indefinitely. Balanced forces → no change in motion.

Fig. 8.2

Newton's Second Law — F = ma

Net force = rate of change of momentum = mass × acceleration. Double the force → double the acceleration. Double the mass → half the acceleration. Unit: Newton (1N = 1 kg·m/s²). Impulse = F×t = change in momentum. Free body diagrams show all forces acting on object.

Fig. 8.3

Newton's Third Law — Action & Reaction Pairs

Every action has an equal and opposite reaction. They act on DIFFERENT objects. Rocket: hot gases expelled backward (action) → rocket moves forward (reaction). Swimming: hands push water backward → person moves forward. Walking: foot pushes ground backward → ground pushes foot forward.

Fig. 8.4

Momentum & Impulse

Momentum p = mv (kg·m/s). Impulse = change in momentum = F·t. A cricket ball: force applied over longer time (follow through) → greater impulse. Crumple zones in cars increase collision time → reduce force. High speed + large mass → large momentum → harder to stop.

Activity 8.1

Conservation of Momentum — Collision

Total momentum before collision = total momentum after (no external forces). Elastic: KE conserved (billiard balls). Inelastic: KE lost (clay balls stick). p₁+p₂ = p₁'+p₂'. Example: Two balls approaching, colliding, bouncing — total momentum unchanged. Guns, rockets use this principle.

🌍 Chapter 9

Gravitation

Newton's Universal Law: F = Gm₁m₂/r² (G = 6.674×10⁻¹¹ N·m²/kg²). Free fall acceleration g = 9.8 m/s² (varies with altitude). Weight = mg (vector). Mass = constant. Archimedes' Principle: buoyant force = weight of fluid displaced.

Fig. 9.1

Universal Law of Gravitation — F = Gm₁m₂/r²

Every particle attracts every other particle. Force ∝ product of masses. Force ∝ 1/distance². Double mass → double force. Double distance → ¼ force. G = 6.674×10⁻¹¹ N·m²/kg². Universal (same everywhere). Explains: apple falling, Moon orbiting, tides, satellite orbits.

Fig. 9.2

Free Fall & Acceleration due to Gravity

All objects fall with same acceleration g = 9.8 m/s² (in vacuum). Galileo dropped two cannon balls — both hit ground together. g = GM/R² (G = gravitational constant, M = Earth mass, R = Earth radius). g decreases with altitude and at poles vs equator. Moon's g = 1.63 m/s² (1/6 of Earth).

Fig. 9.3

Weight vs Mass — Key Difference

Mass: amount of matter (constant everywhere, scalar, kg). Weight: gravitational force on object (changes with g, vector, N). W = mg. On Moon: same mass but weight = 1/6. Weightlessness in orbit: not zero gravity, but both spacecraft and astronaut fall together (free fall). Spring balance measures weight; beam balance measures mass.

Fig. 9.4

Archimedes' Principle & Buoyancy

Buoyant force = weight of fluid displaced. Object floats if buoyant force ≥ weight (density of object ≤ density of fluid). Object sinks if denser than fluid. Relative density = density of substance / density of water. Ship floats because it displaces large volume of water = heavy weight.

Fig. 9.5

Fluid Pressure — Pascal's Law & Hydraulics

Pressure = Force / Area. Fluid pressure increases with depth: P = ρgh. Fluid transmits pressure equally in all directions (Pascal's Law). Hydraulic lift: small force on small piston → large force from large piston (F₁/A₁ = F₂/A₂). Dam wider at base due to increasing water pressure.

⚡ Chapter 10

Work and Energy

Work = Force × displacement × cosθ (Joules). KE = ½mv². PE = mgh. Conservation of Energy: total energy (KE + PE) remains constant in absence of non-conservative forces. Power = Work/time (Watts). 1 kWh = commercial unit of energy = 3.6×10⁶ J.

Fig. 10.1

Work = F × d × cosθ — Interactive Angle Demo

Work done = magnitude of force × displacement × cosine of angle between them. θ = 0°: max work (cos0°=1). θ = 90°: zero work (cos90°=0) — carrying briefcase while walking. θ = 180°: negative work (friction). Work is scalar (joules). No displacement → no work (pushing a wall).

Fig. 10.3

Kinetic & Potential Energy — Roller Coaster

KE = ½mv². PE = mgh. At top: max PE, min KE. At bottom: min PE, max KE. Sum = constant (conservation). A ball falling: PE converts to KE. A spring: elastic PE ↔ KE. Total mechanical energy = KE + PE = constant (no friction). Roller coaster demonstrates perfect energy transformation.

Activity 10.1

Conservation of Energy — Ball Drop

Ball dropped from height h: PE = mgh, KE = 0. At any height x: PE = mgx, KE = mg(h-x). Just before ground: PE = 0, KE = mgh = ½mv². v = √(2gh) (same as from kinematics!). With friction: some energy lost as heat — total energy still conserved (1st law of thermodynamics).

Fig. 10.4

Power & Commercial Units of Energy

Power = Work / time = Energy / time (Watts). 1 kW = 1000 W. Horsepower: 1 hp = 746 W. Commercial energy unit: 1 kWh = 1000 W × 3600 s = 3.6×10⁶ J = 1 unit on electricity bill. 100W bulb on 10 hours = 1 kWh. Power of human body at rest ≈ 80W.

Fig. 10.2

Energy Transformations — Forms of Energy

Chemical → Electrical → Light (battery→bulb). Chemical → Mechanical (food→movement). Nuclear → Heat → Electrical (nuclear plant). Solar → Chemical (photosynthesis). KE → Sound (impact). All transformations obey conservation of energy. Efficiency = useful output / total input × 100%.

🔊 Chapter 11

Sound

Sound is a mechanical, longitudinal wave — requires a medium. Speed in air ≈ 343 m/s (at 20°C). Faster in solids > liquids > gases. Frequency (Hz) = 1/period. Audible range: 20 Hz–20,000 Hz. Echo requires >17m distance. SONAR uses ultrasound for underwater detection.

Fig. 11.1

Sound Wave Propagation — Longitudinal Wave

Sound is produced by vibrating objects → creates compressions (high density/pressure) and rarefactions (low density/pressure) alternately → longitudinal wave (particles vibrate in direction of wave travel). Transverse waves: particles vibrate ⊥ to travel (light, water). Sound CANNOT travel in vacuum.

Fig. 11.2

Wave Properties — Amplitude, Frequency, Wavelength & Speed

Amplitude: height of compression/rarefaction (loudness). Wavelength (λ): distance between two consecutive compressions. Frequency (f): compressions per second (pitch). Speed v = fλ. Loudness ∝ amplitude². Pitch ∝ frequency. v in air ≈ 343 m/s at 20°C, increases with temperature.

Fig. 11.4

Echo & Reverberation

Echo: reflected sound heard distinctly after at least 0.1 s. Minimum distance = 17m (speed 340 m/s). Uses: measuring depth of sea, detecting submarines, locating objects. Reverberation: multiple reflections overlap → prolonged sound (concert halls use absorbent material). Bats/dolphins: echolocation (biosonar).

Fig. 11.5

SONAR — Underwater Detection

SONAR = Sound Navigation And Ranging. Emits ultrasound pulses → bounces off objects → time measured → distance = (speed × time)/2. Speed of sound in seawater ≈ 1530 m/s. Used to detect submarines, schools of fish, map ocean floor, measure ocean depth. Medical ultrasonography same principle.

Fig. 11.6

Human Ear — Anatomy & Function

Outer ear: pinna collects sound → auditory canal → eardrum vibrates. Middle ear: 3 bones (malleus, incus, stapes = ossicles) amplify vibration ×20×. Inner ear: cochlea converts mechanical to electrical signal (hair cells in fluid). Auditory nerve → brain. Oval window connects middle to inner ear. Eustachian tube equalises pressure.

🌾 Chapter 12

Improvement in Food Resources

Food security: availability, accessibility, and affordability. Crop improvement: HYV seeds, hybridisation, GM crops. Crop production management: nutrients, irrigation, organic farming. Crop protection: pest management, weed control. Animal husbandry: cattle, poultry, fish farming.

Fig. 12.1

Kharif vs Rabi Crops — Seasonal Calendar

Kharif crops: sown in monsoon (June-July), harvested in October. Paddy, maize, soybean, groundnut, cotton. Require high temperature and rainfall. Rabi crops: sown in winter (November), harvested in April. Wheat, barley, gram, pea, mustard. Require cool temperatures. Zaid crops: short season between Rabi and Kharif (melon, cucumber).

Fig. 12.2

Crop Nutrients & Fertiliser Management

Macronutrients: N (leaf growth), P (root/flower), K (disease resistance), Ca, Mg, S. Micronutrients: Fe, Mn, B, Zn, Cu, Mo, Cl. Manures: organic, improve soil texture. Fertilisers: synthetic, specific nutrients (NPK). Compost: decomposed organic matter. Vermicompost: using earthworms. Biofertilisers: Rhizobium, Azolla.

Fig. 12.3

Irrigation Methods — Water Management

Traditional: wells, canals, tanks, rivers. Modern: sprinkler (uneven terrain, less water), drip irrigation (plants at roots, most efficient, 90%+ efficiency). Check dams, watershed management. 70% of India's water used in agriculture. Drip irrigation saves 30–50% water vs flood irrigation. Critical for water scarce regions.

Fig. 12.4

Animal Husbandry — Cattle, Poultry & Aquaculture

Cattle: milk (dairy) — Holstein (exotic), Sahiwal (desi); draught (Brahman). Cross-breeding improves yield. Poultry: egg + meat — Leghorn (egg), Broiler (meat). Aquaculture: fish (Rohu, Catla, Hilsa), prawn, oyster (mariculture). Bee-keeping: honey + beeswax. Integrated farming: multiple outputs from same land.