An alkene is a type of hydrocarbon that contains at least one carbon-carbon double bond (C=C). This double bond gives alkenes unique chemical properties, making them more reactive than alkanes, which only have single bonds. Alkenes are commonly found in various natural and synthetic substances, including fuels and plastics. Alkenes can be classified based on the number of carbon atoms they contain. For example, ethylene (C2H4) is the simplest alkene, while propylene (C3H6) is another common example. These compounds play a crucial role in the production of many important chemicals and materials in the industry.