System and surroundings:
A system is defined as a matter or region on which analysis is done. The system is separated from the surroundings by the boundary. Everything external to the system is surrounding.
Specific heat function:
The amount of heat that must be added to one unit of mass of the substance in order to cause an increase of one unit in temperature.
Enthalpy changes:
We could say that it is equal to the difference between the energy used to break bonds in a chemical reaction and the energy gained by the formation of new chemical bonds in the reaction.
Standard enthalpy of formation:
It is a measure of the energy released or consumed when one mole of a substance is created under conditions from its pure elements.