2013-3-1 Heat vs.Work Properties are point functions/have exact differentials(d). (2 V=-V=△V J Path functions(Heat and work)have inexact differentials(8) 2m 2 Properties are point functions; 8W=W12 (not△W） but heat and work are path functions(their magnitudes depend on the path followed). 2.19 Illustrations of Work When a spring is compressed, energy is transferred to the spring by work. When a gas in a closed vessel is stirred,energy is transferred to the gas by work. When a battery is charged electrically,energy is transferred to the battery contents by work. The first two examples of work are encompassed by mechanics.The third example is an example of the broader interpretation of work encountered in thermodynamics. 2-20 10 2013-3-1 10 Heat vs. Work 2-19 Properties are point functions; but heat and work are path functions (their magnitudes depend on the path followed). Properties are point functions / have exact differentials (d ). Path functions (Heat and work) have inexact differentials (δ ) ►When a spring is compressed, energy is transferred to the spring by work. ►When a gas in a closed vessel is stirred, energy is transferred to the gas by work. ►When a battery is charged electrically, energy is transferred to the battery contents by work. Illustrations of Work ►The first two examples of work are encompassed by mechanics. The third example is an example of the broader interpretation of work encountered in thermodynamics. 2-20