Hydrocarbon

Summary: A compound containing only carbon and hydrogen atoms. Tags: igcse chemistry definition organic-chem Created: 2026-07-14 Last Updated: 2026-07-14

A hydrocarbon is an organic compound composed exclusively of carbon and hydrogen atoms, making it the simplest class of organic molecules. Hydrocarbons are divided into two fundamental categories: saturated hydrocarbons (alkanes), which contain only single C—C bonds and have the general formula CₙH₂ₙ₊₂, and unsaturated hydrocarbons (alkenes), which contain at least one C=C double bond and follow the formula CₙH₂ₙ. The primary natural source of hydrocarbons is crude oil, a complex mixture from which fractions such as petrol, diesel, and naphtha are obtained through fractional distillation. The combustion of hydrocarbons is a central IGCSE topic — complete combustion in excess oxygen produces carbon dioxide and water, while incomplete combustion yields carbon monoxide or carbon particulates. Unsaturated hydrocarbons can be distinguished from saturated ones in the laboratory using bromine water, which turns from orange-brown to colourless in the presence of a C=C bond.

Key term — IGCSE Chemistry (0620/0971) glossary.