Science 10 with CSS teacher

For a reaction to occur, reactant particles must collide, creating an opportunity for old bonds to break and new bonds to form. Any one collision may be successful or unsuccessful depending on two factors. These factors are the geometry of the collision (head on versus side swipes for example) and the energy of the collision (faster moving molecules with more kinetic energy are more likely to react).

Each chemical reaction has an activation energy or minimum energy required for the reaction to occur. If the colliding atoms or molecules generate sufficient activation energy (kinetic energy is converted to potential energy in the collision) then bonds in reactant molecules will break and atoms can re-arrange and form new bonds in the products that are formed. If collisions that do not generate this activation energy the reactant atoms and molecules will repel each other with no reaction taking place.

The bonds within a chemical compound are a source of potential energy. The process of breaking bonds initially requires energy and then releases energy. If more energy is absorbed than released, the reaction is endothermic. If less energy is absorbed than released it is exothermic. The process of forming bonds absorbs energy. An analogy for a bond is a partly stretched elastic band (PE is present). Energy must be applied to break the bond, but once broken, a different amount of energy is released.

The changes that occur in a chemical reaction typically involve breaking of the bonds that exist in the reactant molecules. This process requires energy. New bonds are formed, as new chemical substances are formed as the products in the reaction. This process releases energy.