Chemical ractions are actually caused by a wide variety of factors and issues. The most common cause for a chemical reaction however, the application of heat being added to various chemicals causes a reaction. This is witnessed firsthand when cooking dinner. The process of cooking is a chemical reaction! Another cause for a chemical reaction is the adding of an acid to a base. A chemical reaction also occurrs when chemical levels are totally balanced within each other. When this happens, chemists say that there is a neutral Ph level.