section_path: Energy transfer/Open systems
section_name: Open systems
paragraph_text: Open systems
  
  Beyond the constraints of closed systems, open systems can gain or lose energy in association with matter transfer (this process is illustrated by injection of an air-fuel mixture into a car engine, a system which gains in energy thereby, without addition of either work or heat). Denoting this energy by E matter {\displaystyle E_{\text{matter}}}, one may write