Chemistry is the study of the physical science of atoms within compounds and molecules including both the synthesis and physical properties of the compounds. Chemical Engineering is the study of applying chemical and physical processes to perform real-world tasks. For example, the Haber Bosch process for making ammonia was invented by two chemists. However, a practical ammonia manufacturing factory is designed in concert with a chemical engineer. The engineer determines the efficiency, waste products procedure and techniques against the cost of the process and its sustainability and reliability as well as other objective measures. In a sense, the engineer takes a raw process or reaction and proceeds to make a practical application from it. (Chemical engineers, not chemists design batteries... although chemists typically find new anode/cathode reactants for potential storage battery systems. This is necessarily a bit a generalization, chemists and chemical engineers overlap in several areas.