Explain why catalytic cracking is preferred for producing gasoline and diesel, whereas steam cracking is mainly used to produce ethylene and propylene.

Catalytic cracking is preferred for gasoline and diesel because the catalyst allows the reaction to occur at lower temperatures, producing a range of medium‑sized hydrocarbons that are suitable for these fuels. Steam cracking is used for ethylene and propylene because the very high temperatures break long chains into small, unsaturated molecules that are the precursors for many petrochemical products.

The answer demonstrates knowledge of the product profiles of each cracking method and links the reaction conditions to the desired end products, showing application of the learning objective.