Under normal pressure, the work done by gas to the environment is W, and W=p△V (generally speaking, dW=-pdV means the work done by the environment to the gas). For an ideal gas, at atmospheric pressure, P △ V = NR △ T. The thermodynamic energy changes of the whole process △U=nCv, m△T, because it is a newly awakened diatomic molecule, Cv, m=5/2 R, R.