adiabatic  process    A  process  in  which  no  heat is transferred  to  or  from  the system. Any work done by the system  is  at  the  expense  of the internal energy of the  system.  Any work done on the system increases its internal  energy.

For  an  ideal gas changing from conditions (p₁,V₁,T₁) to (p₂,V₂,T₂) in an adiabatic process

p₁V_{1 g} =p₂V_2g and

T₁V_{1 g} ^-1 =T₂V_{2 g} ^-1

where  g is the ratio of specific heat at constant pressure to  specific heat at constant volume. For diatomic gases g = 1.4, and for monatomic gases g = 1.67.