Answer:
A synthesis reaction is a reaction that occurs when two or more reactants combine into one product.
Step-by-step explanation:
A reaction that occurs when two or more reactants combine into one product is called a synthesis reaction.
A reaction that occurs when one element within a compound is exchanged with another element is called a single replacement reaction.
A reaction that occurs when a substance combines with molecular oxygen, releasing light and energy is called combustion.
A reaction that occurs when a single substance breaks apart and forms two or more new substances is called decomposition.