What is always produced when an alkane undergoes cracking?

When an alkane undergoes cracking, the process involves breaking larger alkane molecules into smaller hydrocarbons. This reaction typically produces smaller alkane molecules, but it also produces alkenes, which are unsaturated hydrocarbons containing at least one double bond.

The cracking process usually occurs in the presence of heat and a catalyst, such as aluminum oxide or silica. During this process, the long-chain hydrocarbons are broken down into both smaller alkanes and alkenes. The presence of alkenes is significant because they are used in various chemical syntheses and are more reactive than alkanes.

Thus, the correct answer indicates that both smaller alkane molecules and alkenes are produced during the cracking of alkanes, reflecting the typical nature of this chemical reaction in producing a mixture of products.