In chemical engineering, theories serve as the foundation for understanding and predicting the behavior of various processes and systems. These theories encompass principles from physics, chemistry, mathematics, and other disciplines, providing a framework for designing, optimizing, and troubleshooting chemical processes. From thermodynamics and fluid dynamics to reaction kinetics and transport phenomena, theories in chemical engineering elucidate the fundamental mechanisms governing phenomena like mass and energy transfer, phase equilibria, and reaction kinetics, facilitating the development of innovative technologies and sustainable practices in various industries.