14.1 Chemical Reactions A chemical reaction is the process of breaking of chemical bonds in one or more substances, and the reforming of new bonds to create new substances. Atoms are rearranged, but atoms and mass are conserved Chemical properties of new substances are different than properties of original substances When you make pizza, which changes are physical and which are chemical changes?

Physical vs. Chemical Change The process of making pizza involves some physical changes (like chopping vegetables&rolling out dough). The processes used by yeast in the dough or by the gas stove to bake the pizza are chemical changes. Baking, burning, rusting, rotting, digestion are chemical changes due to forming or breaking chemical bonds.

Observations of a Chemical Change

Reactants and Products In chemical reactions, we start with Reactants that are combined to make Products. The Reactants are the starting substances. The Products are the new substances which result from the chemical reaction. Basic format of chemical equation: yields Reactant + Reactant  Product + Product

Writing word equations and switching to chemical equations When beryllium chloride reacts with sodium bromide, beryllium bromide and sodium chloride are formed. beryllium chloride + sodium bromide beryllium bromide + sodium chloride BeCl2 + NaBr BeBr2 + NaCl

Law of Conservation of Mass The combined mass is any chemical change is conserved. Burning wood and oxygen is converted into carbon dioxide and water. 1000g 100g 500g 600g