Thermodynamics can predict the spontaneity of a given process, but to understand how, we need to learn a little bit more about this idea of the inter conversion of different forms of energy. Heat of Reaction - the quantity of heat required to return a system to its original temperature, after completion of the chemical reaction. Exothermic Reaction - q is negative. Chemical potential energy is converted into kinetic energy. Endothermic Reaction - q is positive.
Kinetic energy is converted into chemical potential energy as the reaction proceeds.
Heat must then be added to the system to return it to its original temperature. State Functions - A property of a system that depends only on its present state, as defined by variables such as, temperature and pressure, and is independent of the previous history of the system. Enthalpy -A state function which can be considered to be the amount of energy within a substance that can be converted to heat. Expressed as, H rxn . Entropy Symbolized as S - the measure of the randomness or disorder in a system.