Chemical engineering students study changes in the composition, energy content or state of aggregation of materials and take into consideration the fundamentals of the nature of matter and its properties (chemistry); the forces that act on matter (physics); and the relationships between them (mathematics). Chemical engineering differs from chemistry in its emphasis on commercial applications of chemical reactions and separations and techniques for designing, operating and controlling processes. Chemistry, on the other hand, emphasizes development of new compounds that may become useful products and the determination of their structures and properties.