Chapter 4 — Carbon and its Compounds

NCERT Class 10 Science Chapter 4, 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.

Carbon forms covalent bonds by sharing valence electrons, giving compounds low melting/boiling points and poor electrical conductivity. Carbon's two unique properties — tetravalency (valency of four) and catenation (ability to bond with other carbon atoms) — result in millions of organic compounds. These include saturated hydrocarbons (alkanes), unsaturated hydrocarbons with double or triple bonds (alkenes, alkynes), and compounds with functional groups like alcohols, aldehydes, ketones, and carboxylic acids. Important reactions include combustion, oxidation, addition, and substitution. Ethanol and ethanoic acid are commercially significant compounds, and soaps/detergents clean by forming micelles that emulsify oily dirt.

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.