Chapter 4 — Carbon and its Compounds

Chapter 4 of the Class 10 Science NCERT textbook, "Carbon and its Compounds", explains how carbon's tetravalency and catenation enable it to form millions of compounds through covalent bonding, and covers key carbon compounds including hydrocarbons, ethanol, ethanoic acid, soaps, and detergents.

• Why carbon forms so many compounds — Two properties make carbon unique: tetravalency lets it bond with four other atoms, and catenation lets it link with more carbon atoms into chains, branches, and rings. Together these produce millions of stable covalent compounds.
• Hydrocarbons and functional groups — Carbon compounds range from saturated alkanes with single bonds to more reactive unsaturated alkenes and alkynes. Attaching functional groups such as alcohol or carboxylic acid groups gives families of compounds with shared, predictable behaviour.
• How soaps and detergents clean — Soap molecules form micelles whose water-hating tails trap oily dirt while their water-loving ends face outward, letting grime rinse away. Detergents work by the same principle but stay effective even in hard water.

1. 01Carbon has a valency of four (tetravalent) and forms covalent bonds by sharing electrons with carbon or other elements such as hydrogen, oxygen, nitrogen, sulphur, and chlorine.
2. 02Catenation — carbon's ability to bond with other carbon atoms — gives rise to long chains, branched chains, and ring structures, resulting in millions of stable carbon compounds.
3. 03Saturated hydrocarbons (alkanes) contain only single bonds and are relatively unreactive; unsaturated hydrocarbons (alkenes, alkynes) contain double or triple bonds and are more reactive.
4. 04A homologous series is a family of compounds sharing the same functional group and differing by a –CH2– unit; successive members differ by 14 u in molecular mass.
5. 05Ethanol reacts with sodium to produce hydrogen gas and is dehydrated by hot concentrated H2SO4 to form ethene; ethanoic acid (acetic acid) undergoes esterification with ethanol to give sweet-smelling esters.
6. 06Soap molecules form micelles in water — the hydrophobic carbon chain points inward toward oily dirt while the ionic hydrophilic end faces outward — allowing oily dirt to be rinsed away; detergents work similarly but are effective even in hard water.