Final answer:
In cracking, small short-chain hydrocarbons are produced from long-chain hydrocarbons found in heavy petroleum fractions. This process involves heating to very high temperatures which causes the larger molecules to break apart and form lighter, more valuable hydrocarbons like those in gasoline.
Step-by-step explanation:
In a controlled process called cracking, small short-chain hydrocarbons are produced from long-chain hydrocarbons. Cracking involves heating larger and heavier molecules in petroleum fractions like kerosene to high temperatures, often as high as 900°C, which initiates reactions that break the carbon-carbon bonds. This results in the conversion of these long-chain hydrocarbons into shorter, more volatile molecules similar to those found in gasoline.
Fossil fuels, such as oil, coal, and natural gas, are formed from prehistoric plants and animals that lived hundreds of millions of years ago. Through a natural process taking millions of years, involving burial, heat, and pressure, these organic materials were converted into hydrocarbons of various lengths that make up the fossil fuels we find in the Earth's crust today.
The refinement of crude oil produces a variety of hydrocarbons including petrochemical feedstock, which is used to create various products, but some of the heavier fractions have lower market value and are therefore cracked to increase the yield of more valuable lighter hydrocarbons like gasoline.