The origin of replication (also called the replication origin) is a particular sequence in a genome at which replication is initiated.
It is the interaction of two or more substances, resulting in chemical changes in them. Chemical reactions take place when some kind of energy is supplied to them. The supplied energy may be in the form of heat, light or mechanical shaking for proper contact between the reactant molecules or electricity.
When a process releases energy into the surroundings it's called exothermic (from the Greek thermo meaning heat, and exo meaning outside). The most obvious effect of an exothermic chemical reaction is a rise in the temperature of the reaction mixture.