$11.$ Polymerization, which is crucial for producing substances like $\_\_\_\_\_\_\_\_,$ involves the chemical reaction of lighter olefins under controlled $\_\_\_\_\_\_$ and $\_\_\_\_\_\_\_\_$ to form heavier hydrocarbon chains.

$12.$ Isomerization changes straight$-$chain hydrocarbons into their $\_\_\_\_\_\_\_\_$ isomers, enhancing fuel $\_\_\_\_\_\_$ and increasing $\_\_\_\_\_\_\_\_,$ which are essential for cold$-$start performance in vehicles.

$13.$ Naphtha is a critical petroleum product used primarily in the $\_\_\_\_\_\_\_\_$ industry; it is produced through distillation of crude oil and is a key feedstock for $\_\_\_\_\_\_$ and $\_\_\_\_\_\_\_\_$ synthesis.

$14.$ Aviation gasoline, specifically formulated for $\_\_\_\_\_\_\_\_$ engines, requires high $\_\_\_\_\_\_$ stability and $\_\_\_\_\_\_\_\_$ volatility to ensure efficient combustion and performance at high altitudes.