Endothermic reactions absorb heat, while exothermic reactions release heat. The cycle is a combination of endothermic and exothermic neutronic reactions involving lithium and deuterium/tritium. These have segregated compartments where exothermic or endothermic reactions provide the desired effect. This is the physical understanding of exothermic and endothermic reactions. Polymerization of ethylene oxide is an exothermic process. The is a positive change in endothermic reactions, and negative in heat-releasing exothermic processes. In NVT, the energy of endothermic and exothermic processes is exchanged with a thermostat. SOEC module can operate in three different modes which are thermoneutral, exothermic and endothermic. Another redox reaction is the extremely exothermic thermite reaction with aluminium. Smaller quantities can be prepared by the partial oxidation of ethanol in an exothermic reaction. Monopropellants are propellants consisting of chemicals that release energy through exothermic chemical decomposition. Calcium chloride is highly hygroscopic and its hydration is an exothermic reaction. Such behavior is a result of an exothermic enthalpy of solution. The water gas shift reaction is a moderately exothermic reversible reaction. The first reaction represents the chlorination of a sulfide ore involving an exothermic reaction.