What reaction involves two or more substances combining to form a single compound?

A synthesis reaction involves two or more substances combining to form a single compound

Explanation:

A synthesis reaction occurs when two different atoms or molecules interact to form a different molecule or compound. In most cases, energy is released, the reaction being exothermic. However, there are cases in which an endothermic result can be obtained. They are also known as addition reactions.

The general form for this type of reactions is:

A + B __ AB

As it is possible to observe, A and B are two different chemical substances that combine to form a new product (AB). In a synthesis reaction the chemical bonds between the reagents are broken and new bonds are formed, giving rise to a different compound.

An example of this type of reaction is:

4 Al (s) + 3 O₂ (g) ⇒ 2 Al₂O₃ (s)