What is unit operation ? - Chemical Engineering

In unit operations their is only physical change is occur but no chemical change take place or we can say no chemical reaction take place.
Evaporation, Distillation, Liquid liquid extraction, Drying, Size reduction, Crystallization are the example of unit operations.
In these operations thier is only physical change take place like phase will be change or two or more substances are separated each other or particle size will reduce.
Unit operations are processes related to physical changes of the materials involved:
- Mixing (Solid-Solid, Solid-Liquid, Solid-Gas, Liquid-Liquid, Liquid-Gas, Gas-Gas)
- Separating (Sieving, Filtration, Distillation, Fractional crystallization, Fractional freezing, Centrifugation)
- Heating / Cooling of materials
- Transporting (Solids, Granulates, Liquids, Slurries, Pastes, Gases)
- Measuring (Weighing, Volumetrizing, Counting)

unit operation