Physical & Chemical Changes Physical Changes Substance stays the same Change in shape or form Breaking of glass Molding a shape out of clay

Different substances are formed Change in molecules Cement hardening Chemical Changes Different substances are formed Change in molecules Cement hardening Rust Baking a cake Dynamite exploding

Glucose and oxygen react to form carbon dioxide and water. 6.2 Chemical Reactions Glucose and oxygen react to form carbon dioxide and water.

This reaction is exothermic and released heat energy. Energy of Reactions The activation energy is the minimum amount of energy needed for reactants to form products in a chemical reaction. This reaction is exothermic and released heat energy. This reaction is endothermic and absorbed heat energy.

Energy and Chemical Reactions Problem- Reactions occur too slowly Must speed up reactions with Enzymes Enzymes are protein molecules that act as catalysts to speed up reactions A catalyst speeds up chemical reactions

Enzyme Action – Joining Enzyme attaches to molecules Holds molecules near each other so they can connect together with bonds Bonds form between molecules creating a larger molecule or compound

EX. H2O2 H2O + ½ O2 LIVER CATALASE Hydrogen peroxide is broken apart into water and oxygen. The reverse reaction also occurs