Chemical Reactions Notes Chemical Reaction= In a chemical reaction __ with different properties Most reactions happen when reactants are in __ ) Existing bonds must be broken ( __ and new bonds must be formed __

A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and breaking of chemical bonds between atoms, with no change to the nuclei (no change to the elements present), and can often be described by a chemical equation. In a chemical reaction, the substances that interact are called reactants, and the substances formed are called products. The properties of the reactants and products are different. Most chemical reactions require an input of energy to start, known as the activation energy. This energy is used to break the existing bonds in the reactants. Once the bonds are broken, new bonds can be formed to create the products. The energy released when the new bonds are formed is often what drives the reaction forward. The process of breaking old bonds and forming new ones is what leads to the change in properties between the reactants and products.