enthalpy 2

The steam engine works on the priciple of First law of thermodynamics

 The energy supplied to a system is utilized in two different ways i.e first the given energy increases the the internal energy of the system, the it does work by increasing its volume

                                   This will be carried at constant temperature

work = PΔV  (ΔV is change in volume)

or work = ΔnRT ( where Δn is the change in no. of moles, R is the universal gas constant T is the temperature)