RESTATEMENT of the law of conservation of energy. It states that energy cannot be created or destroyed in an isolated system; energy can only be transferred or changed from one form to another.When heat energy is supplied to a gas, TWO THINGS may occur:The internal energy of the gas may changeThe gas may do some external work by expanding According to the first law of Thermodynamics:δQ = ΔU + δW When a process is executed by a system, the change in stored energy of the system is NUMERICALLY equal to the NET heat interaction minus the net work interaction during the process:ΔU = δQ – δW where U is the internal energy which is introduced by this law.For the cyclic process: ΔU = 0\(\oint \delta Q = \oint \delta W\)The first law of thermodynamics states that for a cyclic process, the cyclic integral of heat is equal to the cyclic integral of work.