Final answer:
A combustion reaction, which is spontaneous and self-sustaining after ignition, occurs and continues on its own after an initial spark. These reactions release energy and proceed until reactants are exhausted.
Step-by-step explanation:
The type of reaction that occurs and continues on its own after an initial spark is a combustion reaction. A combustion reaction is considered a spontaneous reaction because it releases free energy and tends toward a more stable state. Once started, the combustion process is self-sustaining until reactants such as fuel or oxygen are exhausted.
It is important to note that spontaneous reactions are those in which product formation is favored, despite the possibility of a slow rate; the term does not necessarily imply rapid occurrence. For a combustion reaction to begin, an initial input of energy, also known as activation energy, is required to reach the point where the reaction can proceed spontaneously.