Internal Energy (E,also denoted by U): Every system having some quantity of matter is associated with a definite amount of energy, called internal energy. E=E_("Transiational")+E_("Rotational")+E_("Vibrational")+E_("bonding")+.... DeltaE=E_("Final")-E_("initial") DeltaE=q_v, heat supplied to a gas at constant volume, since all the heat supplied goes to increase the internal energy to the gas. It is an extensive property & a state function.It is exclusively a function of temperature. If DeltaT=0 , DeltaE=0 as well. The internal energy of a certain substance is given by the following equation : U=3 PV+84 where U is given in kJ/kg, P is in kPa, and V is in m^3//kg A system composed of 3 kg of this substance expands from an initial pressure of 400 kPa and a volume of A 0.2 m^3 to a final pressure 100 kPa in a process in which pressure and volume are related by PV^2=constant. Explain the difference in work transfer in question (6.25) and (6.26).