Entropy

Entropy is a driving force that affect spontaneous process either it is exothermic or endothermic. It is a thermodynamic state quantity for measuring the randomness of the molecules. In early it was believed that in an exothermic process internal energy changes spontaneously. But after a period of time it have been prove that in endothermic process spontaneously internal energy may changes. Just for example, melting of ice is an endothermic process.. Ice melts spontaneously. Entropy is expressed as S. The change in entropy is found by the subtraction of initial entropy from final entropy. There have a limitation in the physical definition of entropy in classical thermodynamic. To overcome this limitation there need a numerical definition of entropy. In 1850 Clausius gives a numerical definition of entrop y. According to Clausius, entropy is a constant value of a system if there have no role of heat. Hence, it is clear that heat have an impacts on entropy. If heat flows into a system, entropy changes of this system. The changes of entropy is  expressed as heat divided by temperature. The absolute entropy of a substance at standard temperature and pressure is called standard entropy. It is also called absolute entropy. The unit of entropy is expressed as eu that is calories per degree per mole.