Reversible processes

• Reversible processes can be fully reverted in time, following the same path and exactly reversing the quantities of heat transferred and work done
• Isothermal process: Taking place at a constant temperature

  (The heat added/removed from the system must be = to the work done on/by)

  A gas can only be changed isothermally if:

  1)It's in a well-conducted, thin-walled container

  2)Surrounded by a constant temperature reservoir

  3)The change occurs very slowly

  
  

  If temperature is constant, the ideal gas equation is reduced to:

  P1 x V1 = P2 x V2

  
  

  The first law is reduced to:

  0 = Q +/- W
• Adiabatic process: Zero heat transfer, all work done must be friction-free and not create any extra thermal energy


  A gas can only be changed adiabatically if:

  1)It's in a thick-walled, badly-conducting vessel

  2)The change occurs rapidly

  • If the gas expands and does work, the temperature of the gas falls