CBSE Class 10 Science — Chemical Equations, Colors & Physics Formulas
The definitive, statutory NCERT curriculum cheat sheet for Class 10 Science. Features every chemical reaction, observation, precipitate color transformation, activity setup, and physics optics/electricity formula tested in board theory and practical assessments.
🎨 Master Reaction Color Changes & Precipitate Chart
High-Yield Board PYQ & Practical Assessment FocusQuestions on color transitions account for 8–10 marks in multiple-choice, assertion-reasoning, and practical-based questions. Memorize these exact NCERT textbook observations:
| Reactants & Conditions | Balanced Chemical Equation | Initial Color $\to$ Final Observation | Type of Reaction |
|---|---|---|---|
| Magnesium ribbon burned in air | 2Mg(s) + O2(g) → 2MgO(s) | Silver-grey metal → Dazzling White Flame → White Powder | Combination / Oxidation |
| Ferrous sulfate crystals heated strongly | 2FeSO4(s) → Fe2O3(s) + SO2↑ + SO3↑ | Pale Green Crystals → Reddish-Brown Solid + burning sulfur choking odor | Thermal Decomposition |
| Lead nitrate powder heated | 2Pb(NO3)2(s) → 2PbO(s) + 4NO2↑ + O2↑ | White Powder → Yellow Lead Oxide + Brown Fumes of NO2 | Thermal Decomposition |
| Silver chloride in sunlight | 2AgCl(s) → 2Ag(s) + Cl2(g)↑ | White Salt → Grey Silver Metal | Photolytic Decomposition |
| Iron nail immersed in Copper sulfate solution | Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s) | Deep Blue Solution → Light Green Solution + Reddish-Brown Copper Coat | Displacement Reaction |
| Lead nitrate + Potassium iodide solutions | Pb(NO3)2(aq) + 2KI(aq) → PbI2↓ + 2KNO3(aq) | Colorless Solutions → Bright Yellow Precipitate (PbI2) | Double Displacement / Precipitation |
| Sodium sulfate + Barium chloride solutions | Na2SO4(aq) + BaCl2(aq) → BaSO4↓ + 2NaCl(aq) | Colorless Solutions → Insoluble White Precipitate (BaSO4) | Double Displacement / Precipitation |
| Copper powder heated in presence of oxygen | 2Cu(s) + O2(g) → 2CuO(s) | Reddish-Brown Copper → Black Copper(II) Oxide | Oxidation |
| Hydrogen gas passed over hot Copper oxide | CuO(s) + H2(g) → Cu(s) + H2O(l) | Black CuO → Reddish-Brown Pure Copper | Redox Reaction |
🧪 Chapter 1: Chemical Reactions & Equations
NCERT Text Pages 1–161. Fundamental Reaction Categories
| Classification | Definition & Governing Rule | Standard NCERT Chemical Equations |
|---|---|---|
| Combination Reaction | Two or more reactants combine to form a single product. Often highly exothermic. |
• CaO(s) + H2O(l) → Ca(OH)2(aq) + Heat (Slaking of lime) • C(s) + O2(g) → CO2(g) (Coal combustion) |
| Decomposition Reaction | A single reactant breaks down into two or more simpler products upon supplying energy (heat, light, or electricity). Always endothermic. |
• Thermal: CaCO3(s) → CaO(s) + CO2(g) • Electrolytic: 2H2O(l) → 2H2↑ + O2↑ (Ratio 2:1 by volume) • Photolytic: 2AgBr(s) → 2Ag(s) + Br2(g) (Black & white photography) |
| Displacement Reaction | A more reactive chemical element displaces a less reactive element from its aqueous salt solution. |
• Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s) • Pb(s) + CuCl2(aq) → PbCl2(aq) + Cu(s) |
| Double Displacement | Mutual exchange of ions between two ionic compounds in aqueous solution forming a precipitate or neutral compound. | • Na2SO4(aq) + BaCl2(aq) → BaSO4↓ + 2NaCl(aq) |
| Redox (Oxidation-Reduction) | Simultaneous oxidation (loss of electrons / addition of O / removal of H) and reduction (gain of electrons / removal of O / addition of H). |
• MnO2 + 4HCl → MnCl2 + 2H2O + Cl2↑ (HCl is oxidized to Cl2; MnO2 is reduced to MnCl2) |
Corrosion & Rancidity Formulas:
• Rusting of Iron: 4Fe + 3O2 + 2xH2O → 2Fe2O3·xH2O (Hydrated ferric oxide). Requires both oxygen and moisture.
• Corrosion of Copper: Forms a basic green carbonate coat CuCO3·Cu(OH)2.
• Tarnishing of Silver: Reacts with traces of H2S in air to form black Ag2S.
• Rancidity Prevention: Flushing oily foods with nitrogen (N2 unreactive gas) or adding antioxidants (BHA/BHT).
• Rusting of Iron: 4Fe + 3O2 + 2xH2O → 2Fe2O3·xH2O (Hydrated ferric oxide). Requires both oxygen and moisture.
• Corrosion of Copper: Forms a basic green carbonate coat CuCO3·Cu(OH)2.
• Tarnishing of Silver: Reacts with traces of H2S in air to form black Ag2S.
• Rancidity Prevention: Flushing oily foods with nitrogen (N2 unreactive gas) or adding antioxidants (BHA/BHT).
🧂 Chapter 2: Acids, Bases and Salts
NCERT Text Pages 17–361. Acid & Base Reactions Cheat Sheet
| Reactant Combination | General Rule | Standard Balanced Chemical Equations |
|---|---|---|
| Acid + Metal | Salt + Hydrogen gas (↑) | Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)↑ (Burns with pop sound) |
| Base + Amphoteric Metal | Complex Salt + Hydrogen gas (↑) | 2NaOH(aq) + Zn(s) → Na2ZnO2(aq) + H2(g)↑ (Sodium zincate) |
| Acid + Metal Carbonate | Salt + Water + Carbon dioxide (↑) | Na2CO3 + 2HCl → 2NaCl + H2O + CO2↑ (Brisk effervescence) |
| Lime Water Confirmation Test | Turns milky → clears on excess CO2 |
• Milky: Ca(OH)2 + CO2 → CaCO3↓ + H2O • Clears: CaCO3 + H2O + CO2 → Ca(HCO3)2(aq) |
| Acid + Metallic Oxide | Salt + Water (Basic nature of metal oxide) | CuO(s) + 2HCl(aq) → CuCl2(aq) + H2O(l) (Solution turns blue-green) |
| Base + Non-Metallic Oxide | Salt + Water (Acidic nature of non-metal oxide) | Ca(OH)2(aq) + CO2(g) → CaCO3(s) + H2O(l) |
🏭 Industrial Commercial Salts (The "Chlor-Alkali" Suite)
Formula, Preparation, and Statutory Board Applications| Commercial Salt Name | Chemical Formula & Name | Commercial Preparation Reaction | Primary Board Uses |
|---|---|---|---|
| Caustic Soda | NaOH Sodium Hydroxide |
Chlor-Alkali Process: 2NaCl(aq) + 2H2O(l) → 2NaOH + Cl2↑ + H2↑ (Cl2 at anode, H2 at cathode) |
Soap manufacture, paper de-inking, rayon fibers, metal degreasing. |
| Bleaching Powder | CaOCl2 Calcium Oxychloride |
Action of dry chlorine gas on dry slaked lime: Ca(OH)2 + Cl2 → CaOCl2 + H2O |
Disinfecting drinking water, bleaching cotton & linen in textile mills, chemical oxidizing agent. |
| Baking Soda | NaHCO3 Sodium Hydrogen Carbonate |
Solvay Process: NaCl + H2O + CO2 + NH3 → NH4Cl + NaHCO3 |
Baking powder (mixed with mild tartaric acid), antacid medicine, soda-acid fire extinguishers. |
| Washing Soda | Na2CO3·10H2O Sodium Carbonate Decahydrate |
Recrystallization of sodium carbonate: Na2CO3 + 10H2O → Na2CO3·10H2O |
Removing permanent hardness of water, glass, soap, and paper factories, borax manufacture. |
| Plaster of Paris (POP) | CaSO4·½H2O Calcium Sulfate Hemihydrate |
Controlled heating of Gypsum to 373 K (100 °C): CaSO4·2H2O → CaSO4·½H2O + 1½H2O |
Setting fractured bones in orthopedic casts, decorative false ceilings, smooth statue molds. |
⛏️ Chapter 3: Metals, Non-Metals & Metallurgy
NCERT Text Pages 37–56
⚡ Reactivity Series Mnemonic (Decreasing Reactivity):
K > Na > Ca > Mg > Al > Zn > Fe > Pb > [H] > Cu > Hg > Ag > Au
"Please Stop Calling Me A Careless Zebra Instead Try Learning How Copper Saves Gold"
"Please Stop Calling Me A Careless Zebra Instead Try Learning How Copper Saves Gold"
Metallurgical Extraction Reactions
| Extraction Step | Process Definition | Chemical Reaction Equations |
|---|---|---|
| Roasting | Heating sulfide ores below melting point in excess air to convert them to oxides. |
• 2ZnS(s) + 3O2(g) → 2ZnO(s) + 2SO2(g)↑ • 2Cu2S + 3O2 → 2Cu2O + 2SO2↑ |
| Calcination | Heating carbonate ores below melting point in limited or absence of air. | • ZnCO3(s) → ZnO(s) + CO2(g)↑ |
| Reduction with Carbon | Heating metal oxide with carbon (coke) to yield free metal. | • ZnO(s) + C(s) → Zn(s) + CO(g)↑ |
| Thermit Reaction | Reduction of metal oxide using highly reactive Aluminum powder. Extremely exothermic. |
• Fe2O3(s) + 2Al(s) → 2Fe(l) + Al2O3(s) + Heat (Molten iron produced is used to join cracked railway tracks) |
🔥 Chapter 4: Carbon and Its Compounds
NCERT Text Pages 57–78Essential Organic Reaction Mechanisms
| Reaction Type | Substrates & Catalyst | Balanced Organic Equation & Key Note |
|---|---|---|
| Complete Combustion | Hydrocarbon + Excess Oxygen | CH4 + 2O2 → CO2 + 2H2O + Heat & Light Saturated hydrocarbons burn with clean blue flame; unsaturated burn with sooty yellow smoke. |
| Controlled Oxidation | Ethanol + Alkaline KMnO4 (or acidified K2Cr2O7) + Heat | CH3CH2OH + 2[O] → CH3COOH + H2O Oxidizing agents supply nascent oxygen to convert alcohol into carboxylic acid. |
| Addition (Hydrogenation) | Unsaturated Vegetable Oil + H2 (Nickel / Palladium catalyst) | R2C=CR2 + H2 → R2CH-CHR2 Converts liquid vegetable oils into solid vegetable ghee (vanaspati). |
| Substitution | Methane + Chlorine in presence of Sunlight (hν) | CH4 + Cl2 → CH3Cl + HCl Chlorine atoms progressively replace hydrogen atoms one by one. |
| Esterification | Ethanoic acid + Ethanol + Conc. H2SO4 (acid catalyst) | CH3COOH + C2H5OH → CH3COOC2H5 + H2O Produces Ethyl ethanoate (ester) characterized by a sweet, fruity odor. |
| Saponification | Ester + Sodium hydroxide (alkaline hydrolysis) | CH3COOC2H5 + NaOH → CH3COONa + C2H5OH Sodium ethanoate formed is the basis of soap manufacturing. |
🔍 Chapters 9 & 10: Light, Mirrors, Lenses & Human Eye
Physics Optics Master Formula Bank| Optical Formula | Mathematical Equation | Cartesian Sign Convention & Notes |
|---|---|---|
| Mirror Formula | 1/f = 1/v + 1/u | Concave mirror: f is negative (-); Convex mirror: f is positive (+). Object distance u is always negative. |
| Mirror Magnification | m = hi / ho = -v / u | If m is negative: Real & inverted image; If m is positive: Virtual & erect image. |
| Snell's Law of Refraction | n21 = sin i / sin r = v1 / v2 | Constant for given pair of media and color of light. Light bends towards normal when entering denser medium. |
| Absolute Refractive Index | n = c / v | c = 3.0 × 108 m/s (speed in vacuum). Optical density depends on speed of light, not mass density. |
| Lens Formula | 1/f = 1/v - 1/u | Convex lens (converging): f is positive (+); Concave lens (diverging): f is negative (-). |
| Lens Magnification | m = hi / ho = +v / u | Notice positive (+v/u) sign, unlike spherical mirrors which carry negative (-v/u). |
| Power of a Lens | P = 1 / f (in meters) | Unit: Dioptre (D). Convex lens has positive power (+D); Concave lens has negative power (-D). Combination: P = P1 + P2. |
⚡ Chapter 11: Electricity & Joule's Heating
Current, Potential, Resistance & Power Formulas| Electrical Concept | Formula Equation | SI Units & Constants |
|---|---|---|
| Electric Current | I = Q / t = n·e / t | Ampere (A) = Coulomb / second. e = 1.6 × 10-19 C. 1 Coulomb ≈ 6.25 × 1018 electrons. |
| Potential Difference | V = W / Q | Volt (V) = Joule / Coulomb. Work done moving 1 C charge between two points. |
| Ohm's Law | V = I·R | At constant temperature, current is directly proportional to potential difference. |
| Resistivity Formula | R = ρ · (l / A) | ρ is resistivity in Ω·m. Independent of length and area; depends only on material and temperature. |
| Series Combination | Rs = R1 + R2 + R3 | Current I remains identical across all series resistors; total voltage divides: V = V1 + V2 + V3. |
| Parallel Combination | 1/Rp = 1/R1 + 1/R2 + 1/R3 | Voltage V remains identical across all branches; equivalent resistance is lower than smallest individual resistor. |
| Joule's Law of Heating | H = I2Rt = VIt = (V2/R)t | Heat produced in Joules (J). Heating is directly proportional to square of current. |
| Electric Power | P = VI = I2R = V2 / R | Watt (W) = Volt × Ampere = J/s. Commercial unit: 1 kWh = 3.6 × 106 J. |
🧲 Chapter 12: Magnetic Effects of Electric Current
Rules, Field Patterns & Domestic Circuits
👍 Right-Hand Thumb Rule
Imagine holding a current-carrying straight wire with your right hand such that the thumb points along the current direction. The curled fingers encircle the wire in the direction of magnetic field lines (concentric circles).
✋ Fleming's Left-Hand Rule
Stretch thumb, forefinger, and middle finger mutually perpendicular: Forefinger = Magnetic Field (B), Middle Finger = Current (I), Thumb = Motion / Mechanical Force (F). Principle of electric motors.
🔌 Domestic Circuit Specifications
• Standard voltage: 220 V AC at 50 Hz.
• Live wire: Red / Brown insulation (+220 V).
• Neutral wire: Black / Blue insulation (0 V).
• Earth wire: Green / Yellow insulation (safety low resistance path).
• Live wire: Red / Brown insulation (+220 V).
• Neutral wire: Black / Blue insulation (0 V).
• Earth wire: Green / Yellow insulation (safety low resistance path).