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.