In chemical engineering and related fields, a unit operation is a basic step in a process that involves physical change or chemical transformation . Examples of unit operations include separation, crystallization, evaporation, filtration, polymerization, isomerization, and other reactions . Unit operations only deal with physical changes of the materials involved in the process. They are equipments which cause the materials to undergo physical changes .
A unit process, on the other hand, is a process in which chemical changes take place to the material present in the reaction and result in the chemical reaction . This basically consists of a reaction between two or more chemicals which results in another chemical and can also be defined as a unit process .
Large processes are broken into unit operations in order to make them easier to analyze. The conservation laws apply not only to the process as a whole but also to each individual unit operation .