A combustion reaction is when all substances in a compound are combined with oxygen, which then produces carbon dioxide and water. Combustion is commonly called burning. It is an exothermic reaction, which means heat is produced and is easily distinguished. Combustion occurs predominantly in automobiles, homes, and in factories. An example of a combustion reaction is as follows:

A synthesis reaction is when there is a combination of two or more substances and a compound results. An example of a synthesis reaction is as follows:

Decomposition is the opposite of synthesis. It is when a compound is broken down into simpler substances, usually through electrolysis. An example of decomposition is as follows:

Dissociation is commonly mistaken as decomposition, but there is a difference. When the compound is broken down, it is broken down into ions rather than atoms, so there will be a charge on the product side of the equation. An example of dissociation is as follows:

In a single replacement reaction, there is a rule that is always followed. A metal replaces a metal, or a nonmetal replaces a nonmetal. An example of a single replacement reaction is as follows:

In a double replacement reaction, this rule is always followed. A metal replaces a metal, and a nonmetal replaces a nonmetal. An example of a double replacement reaction is as follows: