In chemistry terms, cracking is a process by which complicated organic molecules (such as kerogens or heavy hydrocarbons) are broken down into simpler molecules (e.g. light hydrocarbons) by breaking their carbon-carbon bonds. How fast the cracking process is and how long it takes for the end products to form are very dependent on the temperature and any existing catalysts. Cracking, also referred to as pyrolysis, is the breakdown of a large alkane into smaller, more useful alkanes and an alkene.
It usually produces a short chain alkane and a long chain alkene.