1. Chemical Reactions Characterized by a chemical change and it yields one or more products which are different from the reactants

2. Chemical Reactions  A + B  AB Reactants  Products  2H 2 + O 2  2H 2 O  Notice there are the same number of atoms on each side of the arrows

3. Types of Chemical Reactions  Exergonic reaction: energy is released to their surroundings (feel hot) ex. hot pack, light stick  Endergonic reaction: energy is absorbed by the reaction (feel cool) ex. cold pack

4. Some reactions need a kick to get started…  Activation energy: amount of energy needed to start a reaction  Catalyst: reduces the amount of energy needed to start a reaction example: enzymes

5.  Chemical reactions encompass changes that strictly involve the motion of electrons in the forming and breaking of chemical bondselectronschemical bonds  Redox reactions: electrons are transferred between atoms oxidation: reactants lose electrons reduction: reactant gain electrons Why do reactions occur?