A chemical reaction that neither releases nor absorbs heat is known as an "adiabatic" reaction. In an adiabatic reaction, there is no exchange of heat with the surroundings. This means that the reaction occurs without any change in the thermal energy of the system. Adiabatic reactions are relatively rare because most chemical reactions involve some degree of heat exchange, either as an exothermic reaction (releasing heat) or an endothermic reaction (absorbing heat).