ABSTRACT
Thermochemistry is a subset of the science of thermodynamics. Heat transfer between matter (system and surroundings) at different temperatures follows the first law of thermodynamics. The heat energy of an object is proportional to the average kinetic energy of all atoms; this includes kinetic energy of translation, kinetic energy of bond vibration, and kinetic energy of molecular rotation. The average kinetic energy of matter is measured by temperature. The specific heat capacity measures the specific response of each compound or element to heat changes; units are Joules/gram-K or Joules/gram-°C. Enthalpy is the change in potential energy of a chemical process measured as heat transfer under conditions of constant pressure; work energy change is not included Enthalpy is a useful measure of energy change for a wide variety of chemical processes and is often a close approximation of total energy change.
