In this episode, the five main types of chemical reactions are explained as a way to predict chemical behavior. A synthesis reaction combines two or more reactants into one product, while decomposition is the reverse, breaking one reactant into multiple products. Single replacement involves one element replacing another in a compound, whereas double replacement is where two compounds trade ions. Lastly, a combustion reaction typically involves a hydrocarbon reacting with oxygen to produce carbon dioxide and water. The key to identifying these reactions is recognizing their unique patterns.