PX154 - D1 - introduction

some concepts

• ideal gases are considered
• systems:
  • consider a specific system in a closed container
    • no particles enter/leave $⟹n$ is constant
  • volume, $V$, must be changeable
    
  • a piston that moves without friction and with a perfect seal is used
    • diathermal wall: perfect heat transmission through wall via conduction
    • adiabatic wall: perfectly insulating, no heat transmission, often depicted as double wall
  • states:
    • the state of a system is given by the state variables at any given time
      • $p$ - intensive variable
      • $V$ - extensive variable
      • $T$ - intensive variable
      • $m$ - extensive variable
      • $S$ (entropy) - extensive variable
    • intensive and extensive correspond to whether the variable changes with a change in the size of the system. so, if a system has twice the volume, it has twice the mass, but the temperature is the same.