Each chemical reaction system can be classified as exothermic or endothermic in the course of product development. The term refers to the kind of change in temperature “q” that occurs within the system in relation to its surrounding environment. The surroundings comprise the reaction vessel and the atmosphere surrounding it. The reaction can either use heat during the process of development, and therefore heat energy is a reaction agent or it emits energy when the product is formed which is an end product.