Carbon and its Compounds for Class 10: The Complete CBSE Guide (2026-27)

Carbon sits in Group 14 with atomic number 6 and electronic configuration 2,4. It has four valence electrons, making it tetravalent—it can form four covalent bonds by sharing electrons with hydrogen, oxygen, nitrogen, sulphur, halogens, and most importantly, other carbon atoms. Because carbon's atomic radius is small (77 pm), the C–C bond is strong (bond energy ≈348 kJ/mol), enabling catenation—the self-linking property that allows carbon atoms to form long chains, branched structures, and rings. No other element exhibits catenation to this extent; silicon (the next Group 14 element) forms weaker Si–Si bonds and cannot sustain long chains. This combination of tetravalency, small size, and strong covalent bonding is why over 10 million organic compounds exist, while inorganic compounds number only around 100,000. In carbon and its compounds class 10, students must be able to draw electron-dot (Lewis) structures for CH₄, C₂H₆, C₂H₄, and C₂H₂ showing shared electron pairs.

All carbon compounds discussed in carbon and its compounds class 10 are covalent—they share electrons rather than transfer them. A single covalent bond (σ bond) forms when one pair of electrons is shared (e.g. C–C in ethane, C–H in methane). A double bond (one σ + one π bond) involves two shared pairs (e.g. C=C in ethene, C=O in methanal). A triple bond (one σ + two π bonds) involves three shared pairs (e.g. C≡C in ethyne, C≡N in ethanenitrile, though nitriles are beyond Class 10 syllabus). Bond length decreases and bond strength increases as bond order rises: C–C (154 pm, 348 kJ/mol) > C=C (134 pm, 614 kJ/mol) > C≡C (120 pm, 839 kJ/mol). Because covalent compounds share electrons, they have low melting and boiling points (weak intermolecular van der Waals forces), do not conduct electricity (no free ions), and are often insoluble in water but soluble in organic solvents like benzene or ether. CBSE board exam questions frequently ask students to compare ionic versus covalent bonding or to explain why organic compounds are poor conductors.

Saturated hydrocarbons, or alkanes, contain only single C–C and C–H bonds, with the general formula CₙH₂ₙ₊₂. The NCERT textbook for carbon and its compounds class 10 lists methane (CH₄), ethane (C₂H₆), propane (C₃H₈), butane (C₄H₁₀), pentane (C₅H₁₂), and hexane (C₆H₁₄). IUPAC nomenclature: the root name indicates the number of carbons (meth- = 1, eth- = 2, prop- = 3, but- = 4, pent- = 5, hex- = 6), and the suffix is '-ane' for alkanes. Alkanes are chemically less reactive than unsaturated hydrocarbons because the C–C and C–H σ bonds are strong and non-polar. The two key reactions are combustion and substitution. Complete combustion in excess oxygen yields CO₂ and H₂O with release of heat (exothermic): CH₄ + 2O₂ → CO₂ + 2H₂O. Incomplete combustion in limited oxygen produces carbon monoxide (poisonous) or carbon (soot). Substitution reaction: In the presence of sunlight (UV light), chlorine replaces hydrogen atoms one by one. For methane: CH₄ + Cl₂ (sunlight) → CH₃Cl + HCl; further chlorination yields CH₂Cl₂, CHCl₃, CCl₄. This is a chain reaction mechanism and Class 10 students need only know the overall equation, not the free-radical mechanism.

Unsaturated hydrocarbons contain at least one C=C (alkenes, CₙH₂ₙ) or C≡C (alkynes, CₙH₂ₙ₋₂) bond. The NCERT chapter on carbon and its compounds class 10 focuses on ethene (C₂H₄, common name ethylene) and ethyne (C₂H₂, common name acetylene). IUPAC nomenclature: Replace the '-ane' of the corresponding alkane with '-ene' for alkenes or '-yne' for alkynes. Unsaturated hydrocarbons are more reactive than alkanes because the π bond in C=C or C≡C is weaker and more exposed. They undergo addition reactions where atoms or groups add across the multiple bond, converting it to a single bond. Key tests: Bromine water test—when ethene or ethyne is passed through bromine water (reddish-brown), the colour is discharged (decolourised) because Br₂ adds across the double/triple bond. Equation for ethene: C₂H₄ + Br₂ → C₂H₄Br₂ (1,2-dibromoethane, colourless). Equation for ethyne: C₂H₂ + 2Br₂ → C₂H₂Br₄ (1,1,2,2-tetrabromoethane). Alkaline KMnO₄ (Baeyer's reagent) is another test: pink/purple colour fades when an unsaturated hydrocarbon is present. Hydrogenation (addition of H₂ in presence of Ni/Pt/Pd catalyst at high temperature) converts alkenes/alkynes to alkanes, used industrially to harden vegetable oils (liquid unsaturated fats) into solid fats (margarine).

A homologous series is a family of organic compounds that have the same functional group, similar chemical properties, and differ from one member to the next by a constant unit of –CH₂– (methylene group, molecular mass 14 u). The NCERT textbook for carbon and its compounds class 10 defines homologous series and lists alkanes (–CH₂– difference between methane, ethane, propane, etc.) as the standard example. Characteristics: (i) All members can be represented by the same general formula (e.g. CₙH₂ₙ₊₂ for alkanes). (ii) Successive members differ by 14 u in molecular mass. (iii) All members show similar chemical reactions because the functional group is identical. (iv) Physical properties (melting point, boiling point, density) vary gradually—usually increase with increasing molecular mass due to stronger van der Waals forces. (v) All members can be prepared by similar methods. Examples beyond alkanes: alcohols (CₙH₂ₙ₊₁OH: methanol CH₃OH, ethanol C₂H₅OH, propanol C₃H₇OH), carboxylic acids (CₙH₂ₙ₊₁COOH: methanoic HCOOH, ethanoic CH₃COOH, propanoic C₂H₅COOH). Homologous series simplifies the study of organic chemistry—instead of memorising millions of compounds individually, students learn the behaviour of one functional group and apply it across the entire series.

A functional group is an atom or group of atoms that defines the chemical properties of an organic compound. In carbon and its compounds class 10, students encounter six major functional groups: (1) Haloalkanes (–X where X = F, Cl, Br, I), (2) Alcohols (–OH), (3) Aldehydes (–CHO), (4) Ketones (–CO–), (5) Carboxylic acids (–COOH), and (6) Esters (–COO–). The NCERT textbook provides a table correlating each functional group with its IUPAC suffix. IUPAC nomenclature for Class 10 (simplified): (i) Identify the longest carbon chain containing the functional group. (ii) Number the chain so the functional group gets the lowest possible locant. (iii) Replace the '-e' of the parent alkane name with the appropriate suffix: '-ol' for alcohol, '-al' for aldehyde, '-one' for ketone, '-oic acid' for carboxylic acid. (iv) For haloalkanes, treat halogen as a prefix (chloro-, bromo-). Examples: CH₃OH = methanol, C₂H₅OH = ethanol, CH₃CHO = ethanal, CH₃COCH₃ = propanone, CH₃COOH = ethanoic acid, CH₃CH₂COOH = propanoic acid. Students often confuse aldehyde (–CHO, terminal group) with ketone (–CO–, internal group); remember aldehyde must be at the end of the chain, ketone in the middle.

Ethanol (ethyl alcohol, C₂H₅OH) is the most important alcohol in carbon and its compounds class 10. It is a colourless, volatile liquid with a characteristic pleasant smell, b.p. 78°C, and is miscible with water in all proportions due to hydrogen bonding. Commercial preparation: (1) Fermentation of sugars (glucose, sucrose) by the enzyme zymase in yeast under anaerobic conditions: C₆H₁₂O₆ (zymase, absence of air) → 2C₂H₅OH + 2CO₂. The maximum alcohol concentration by fermentation is about 10–15%; distillation can raise it to 95%. (2) Industrial hydration of ethene: C₂H₄ + H₂O (300°C, 60 atm, phosphoric acid catalyst) → C₂H₅OH. Chemical reactions tested in CBSE board exams: (a) Reaction with sodium metal: 2C₂H₅OH + 2Na → 2C₂H₅ONa (sodium ethoxide) + H₂↑. This reaction is similar to water but slower; it confirms the presence of the –OH group. (b) Oxidation with alkaline KMnO₄ or acidified K₂Cr₂O₇: C₂H₅OH + [O] (oxidising agent) → CH₃CHO (ethanal, aldehyde) + [O] → CH₃COOH (ethanoic acid). Controlled oxidation stops at aldehyde, vigorous oxidation yields acid. (c) Dehydration by conc. H₂SO₄ at 170°C: C₂H₅OH (conc. H₂SO₄, 170°C) → C₂H₄ (ethene) + H₂O. At 140°C, two ethanol molecules condense to give diethyl ether (C₂H₅–O–C₂H₅), but this is not in the NCERT syllabus. Uses: Alcoholic beverages, solvent, antiseptic (hand sanitisers), fuel (blended with petrol as ethanol-petrol mix).

Ethanoic acid (acetic acid, CH₃COOH) is the simplest and most studied carboxylic acid in carbon and its compounds class 10. Pure ethanoic acid is called glacial acetic acid because it freezes at 17°C into ice-like crystals. It is a colourless liquid with a pungent, vinegar-like smell (vinegar is 5–8% aqueous ethanoic acid). Preparation: (1) Oxidation of ethanol: C₂H₅OH + [O] (alk. KMnO₄ or acidified K₂Cr₂O₇) → CH₃COOH. (2) Industrial oxidation of acetaldehyde (ethanal): 2CH₃CHO + O₂ (catalyst) → 2CH₃COOH. (3) Bacterial oxidation (fermentation) of dilute ethanol: C₂H₅OH + O₂ (Acetobacter bacteria) → CH₃COOH + H₂O. This is how vinegar is traditionally made. Chemical properties: (a) Acidic nature: Ethanoic acid is a weak acid (only partially ionises in water), turning blue litmus red. CH₃COOH ⇌ CH₃COO⁻ + H⁺. (b) Reaction with sodium carbonate/bicarbonate: 2CH₃COOH + Na₂CO₃ → 2CH₃COONa (sodium ethanoate) + H₂O + CO₂↑. Brisk effervescence confirms presence of –COOH group. (c) Reaction with NaOH (neutralisation): CH₃COOH + NaOH → CH₃COONa + H₂O. (d) Esterification: Reaction with alcohol in presence of conc. H₂SO₄ (catalyst and dehydrating agent) forms an ester with a fruity smell. CH₃COOH + C₂H₅OH (conc. H₂SO₄, heat) ⇌ CH₃COOC₂H₅ (ethyl ethanoate, sweet smell) + H₂O. This reaction is slow and reversible. Uses: Manufacture of vinegar, preservative, making cellulose acetate (rayon), ethyl ethanoate (solvent in nail polish remover).

Esterification is the reversible reaction between a carboxylic acid and an alcohol in the presence of a small amount of concentrated sulphuric acid (which acts as both catalyst and dehydrating agent) to form an ester and water. General equation: R–COOH + R'–OH (conc. H₂SO₄) ⇌ R–COO–R' + H₂O. For Class 10, the key example is: CH₃COOH + C₂H₅OH ⇌ CH₃COOC₂H₅ (ethyl ethanoate) + H₂O. The reaction is slow and reaches equilibrium; to shift equilibrium toward ester formation, either excess alcohol is used or water is removed continuously. Esters are characterised by pleasant, fruity smells: ethyl ethanoate (nail polish remover, sweet apple-like), amyl acetate (banana smell), octyl acetate (orange smell). Mechanism (simplified for Class 10): The –OH group of the acid and the H of the alcohol's –OH combine to form water, and the remaining parts (acyl group from acid + alkyl group from alcohol) join to form the ester. CBSE board exam questions often ask students to identify the ester formed, write the equation, or name the reactants given the ester. Reverse reaction (hydrolysis of ester): Heating an ester with dilute acid or alkali breaks it back into alcohol and acid (or salt of acid). Saponification is the alkaline hydrolysis of an ester of a long-chain fatty acid, yielding soap.

Soaps are sodium or potassium salts of long-chain fatty acids (carboxylic acids with 12–18 carbon atoms), such as sodium stearate (C₁₇H₃₅COONa) or sodium palmitate (C₁₅H₃₁COONa). Preparation of soap (saponification): Heating animal fats or vegetable oils (esters of glycerol and fatty acids, triglycerides) with concentrated sodium hydroxide solution. Example: C₃H₅(C₁₇H₃₅COO)₃ (tristearin, fat) + 3NaOH → 3C₁₇H₃₅COONa (sodium stearate, soap) + C₃H₅(OH)₃ (glycerol). Glycerol is a by-product used in cosmetics. Structure of soap molecule: A soap molecule has two distinct parts—a long hydrophobic tail (non-polar hydrocarbon chain that is water-repelling but oil/grease-attracting) and a hydrophilic head (ionic –COONa⁺ group that is water-attracting). Cleansing action: When soap is added to water containing dirt/grease, the hydrophobic tails attach to oil droplets while the hydrophilic heads remain in water, forming spherical clusters called micelles. The oil is trapped in the centre of the micelle and is rinsed away with water. Limitation of soaps: In hard water (containing Ca²⁺, Mg²⁺ ions), soap reacts to form insoluble calcium or magnesium salts (scum): 2C₁₇H₃₅COONa + Ca²⁺ → (C₁₇H₃₅COO)₂Ca↓ (white precipitate) + 2Na⁺. This wastes soap and leaves a greasy layer. Detergents are synthetic cleaning agents (usually sodium salts of sulphonic acids, e.g. sodium dodecyl benzene sulphonate) that do not form scum with hard water because their calcium/magnesium salts are soluble. Detergents work in both hard and soft water, making them more versatile than soaps, but many are non-biodegradable and cause water pollution.

CBSE Class 10 board exams award 2–3 marks for writing balanced chemical equations with state symbols and conditions. Below is a consolidated list of all key equations students must memorise for carbon and its compounds class 10. (1) Combustion of methane (complete): CH₄ + 2O₂ → CO₂ + 2H₂O + heat. (2) Combustion of ethane: 2C₂H₆ + 7O₂ → 4CO₂ + 6H₂O. (3) Chlorination of methane (substitution): CH₄ + Cl₂ (sunlight) → CH₃Cl + HCl. (4) Addition of bromine to ethene: C₂H₄ + Br₂ → C₂H₄Br₂ (1,2-dibromoethane, colour of Br₂ disappears). (5) Hydrogenation of ethene: C₂H₄ + H₂ (Ni catalyst, heat) → C₂H₆. (6) Fermentation of glucose: C₆H₁₂O₆ (zymase, no air) → 2C₂H₅OH + 2CO₂. (7) Oxidation of ethanol to ethanoic acid: C₂H₅OH + [O] (alk. KMnO₄) → CH₃COOH + H₂O. (8) Dehydration of ethanol: C₂H₅OH (conc. H₂SO₄, 170°C) → C₂H₄ + H₂O. (9) Reaction of ethanol with sodium: 2C₂H₅OH + 2Na → 2C₂H₅ONa + H₂↑. (10) Reaction of ethanoic acid with sodium carbonate: 2CH₃COOH + Na₂CO₃ → 2CH₃COONa + H₂O + CO₂↑. (11) Neutralisation of ethanoic acid: CH₃COOH + NaOH → CH₃COONa + H₂O. (12) Esterification: CH₃COOH + C₂H₅OH (conc. H₂SO₄, heat) ⇌ CH₃COOC₂H₅ + H₂O. (13) Saponification: Fat/oil + 3NaOH → 3(soap) + glycerol. Students should practise writing these equations with correct formulas, balancing, and conditions every day for two weeks before the board exam.

Isomers are compounds with the same molecular formula but different structural formulas (arrangement of atoms). Carbon and its compounds class 10 introduces only structural isomerism (also called chain isomerism). The simplest example is butane (C₄H₁₀), which has two isomers: (1) n-butane (normal butane): straight chain CH₃–CH₂–CH₂–CH₃. (2) Isobutane (2-methylpropane): branched chain CH₃–CH(CH₃)–CH₃. Both have the same molecular formula C₄H₁₀ and molecular mass 58 u, but different structural arrangements lead to different physical properties (b.p. of n-butane = −0.5°C, b.p. of isobutane = −11.7°C). As the number of carbon atoms increases, the number of possible isomers increases rapidly: C₅H₁₂ (pentane) has 3 isomers, C₆H₁₄ (hexane) has 5 isomers, C₁₀H₂₂ has 75 isomers. CBSE exams may ask students to draw and name the structural isomers of a given alkane (typically butane or pentane). Remember, isomers have identical molecular formulas and hence the same molecular mass, but they are different compounds with different boiling points, melting points, and densities. Other types of isomerism (positional, functional, geometrical, optical) are beyond Class 10 syllabus and are taught in Class 11-12.

Understanding carbon and its compounds class 10 is not just for scoring marks; carbon chemistry is everywhere in daily life. Fuels we use—LPG (liquefied petroleum gas, mixture of propane C₃H₈ and butane C₄H₁₀), CNG (compressed natural gas, mainly methane CH₄), petrol (mixture of hydrocarbons C₅ to C₁₂)—are all alkanes or their mixtures. The process of cooking food involves combustion of these hydrocarbons releasing heat. Ethanol is in hand sanitisers (60–70% solution kills bacteria by denaturing proteins), alcoholic drinks, and is blended with petrol (E10 fuel = 10% ethanol, cleaner burning, reduces import of crude oil). Ethanoic acid as vinegar is a preservative (pickles, chutneys) and antimicrobial agent. Esters provide the flavour in candies, ice creams, and perfumes; isoamyl acetate gives banana flavour, octyl acetate gives orange smell, ethyl butanoate gives pineapple flavour. Soaps clean our clothes and body by emulsifying oils and grease. Detergents are in washing powders, dishwashers, and shampoos. Plastics (polyethylene, polypropylene, PVC) are polymers of unsaturated hydrocarbons (ethene, propene, vinyl chloride). Synthetic fibres like polyester and nylon are also carbon-based polymers. Medicines like aspirin (acetylsalicylic acid), paracetamol, and antibiotics are complex organic molecules. Even the food we eat—carbohydrates (sugars, starch), proteins (amino acids), and fats (triglycerides)—are carbon compounds. The NCERT chapter lays the conceptual foundation for biochemistry, pharmacology, petrochemistry, and materials science.

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