Question

Define Cracking and knocking.

Answer 1

a process in which large molecules of a hydrocarbon are broken into smaller molecules is called cracking

Answer 2

Cracking is a term used in petroleum industry and organic chemistry to define the process where complex organic molecules such as long chain hydrocarbons are broken down into simpler molecules by breaking of carbon carbon bonds. Example - Fluid cracking process to produce petrol and LPG.

Knocking is associated with internal combustion engine that works on petrol and a mixture of gasoline vapors and air is used as a fuel. Knocking is a sharp, metallic sound produced due to ignition of air and gasoline mixture in the internal combustion engine.