Chemical Reactions and Equations Exothermic Iron-Oxide and Aluminum Reaction Exothermic Iron-Oxide and Aluminum Reaction Elementary Productions: Endothermic reaction Elementary Productions: Endothermic reaction

Two Main Types of Reactions  Exothermic – energy is released by the reaction (feels hot). The products are lower in energy than the reactants.  Endothermic – energy is absorbed by the reaction (feels cold) the products are higher in energy than the reactants.

Exo/Endothermic Reactions

Chemical Equations  During a chemical reaction existing bonds are broken and new bonds are formed. –Reactants are written on the left side of the equation –Products are written to the right –Phase is indicated with a symbol  (s) = solid(g) = gas(l) = liquid (aq) = aqueous, dissolved in water.

Balancing Chemical Equations  Law of conservation of mass – the number and type of atoms must be the same before and after a chemical reaction.  Coefficients – whole numbers written before the formulas are used to balance the reactants and products. Example: 2 H 2 + O 2  2 H 2 O

Balancing Chemical Equations  When balancing equations never change the formulas. Use coefficients to balance the reactants and products. Example: Zn + AlCl 3  ZnCl 2 + Al Is this equation balanced? No, the Chlorines are not the same on both sides. 3 Zn + 2 AlCl 3  3 ZnCl Al Practice Balancing Equations Practice Balancing Equations