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.

Chemical reaction

Chemical reaction is a process by which two or more chemical compounds reacts with each other or a single chemical compound restructures os dissociates and finaly produce a new compound. The new product is called product of the chemical reaction and the substance that take place in reaction is called reactant. For example, let Hydrochloric acid and sodium hydroxide is are reactants of a chemical reaction. After a reaction these reactant produces sodiam chloride and water. It is an example of neutralization reaction.Reaction can be classified into following class. These are addition reaction, substitution reaction, redox reaction, dissociation reaction etc.

Spontaneous process

Spontaneous process can be defined as things happening naturally without any external force concerning. Spontaneously process in physical chemistry is very important to know. In an opposite view, the process that is not concerned with naturally happening, but occurs by an external force is a non spontaneous process. The heat will flow higher temperature to lower temerature., it is a natural process. There need an external force to flow heat from lower temperature to higher temperature.Rolling of a ball from top of the hill to botom is a naturalprocess. But picking ball from botom to top is not natural.

Thermochemistry

Thermochemistry is a study of thermal and heat change in chemical reaction. The including topics of thermochemistry is internal energy of a substance, exothermic chemical reaction and endothermic chemical reaction. Internal energy is the processed energy by any substance. It can not measure for a substance. But in a chemical reaction the changes in internal energy can be measure. The change of internal energy of a chemical reaction determines that the reaction will be exothermic or endothermic reaction. If in a chemical reaction, the changing of internal energy is positive then the reaction is exothermic. But, the change of internal energy if negative then chemical reaction is termed as endothermic chemical reaction. Positive value of internal energy indicates the reaction will will absorb energy from surrounding. Because, in this case products internal energy is higher than reactant internal energy.

Chemical kinetics

Chemical kinetics is the important part of chemistry that deals with the rate of a chemical reaction. It is a study of chemical reaction rates, rate law, factors affacting on chemical reaction, such as temperature, concentration and pressure. Mechanism of the reaction is also a topics of chemical kinetics. In a reaction converting reactant into product happens spontaneously. In such spontaneous process reactant starts to convert into product. This conversion of reactant into product happens in a different rate for different reactant and product. Some reactions are slow and others are fast. The example of a slow chemical reaction is rusting of iron. It takes years of time. On the other hand reaction of water with sulfuric acid is a fast reaction. In different temperature same reactant shows different reaction rate. Same things happens in different