A reaction occurs when two substances combine to from one substance. An example of this kind of reaction is rusting, in which iron reacts with oxygen

*replacement
*synthesis

A ___synthesis _ reaction occurs when two substances combine to from one substance. An example of this kind of reaction is rusting, in which iron reacts with oxygen

Explanation:

Synthesis reactions are characterized by being exothermic, where two compounds react to generate a new one. In the case of iron and oxygen, the following reaction occurs:

2Fe + 02 ---> 2Fe0 (iron oxide)

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.