1 Introduction to Chemical Reactions

2 Products-___________Chemical Reaction-process that changes one set of chemicals into another set of chemicals. A. Components 1. Reactants-substances that change 2. Products-new substance formed -Example #1 CO2 + H20-->H2CO3 Reactants-__________ Products-___________ (Carbon dioxide reacts with water to produce carbonic acid. This keeps the body in homeostasis.)

3 Examples Continued Reactant- Product- # 2.Mg + 2 H2O ---> 2 Mg(OH)2 +H2 What are the parts of the equation? Reactant- Magnesium (Mg), Hydrogen (H) and Oxygen (O) Product- Magnesium Hydroxide (MgOH2) and Hydrogen gas (H2) What is the evidence for the reaction? Formation of a gas!

4 Examples Continued Products- Reactants- # 3.2 Mg + O2  2 MgO What are the parts of the equation? Products- Magnesium (Mg) and Oxygen (O) Reactants- Magnesium Oxide (MgO) What is the evidence for the reaction? Formation of a precipitate!

5 B. Energy in Reactions-energy is released or absorbed any time chemical bonds are broken.Types A. Endothermic-energy is absorbed (The energy required to break bonds is greater than the energy released when the new bonds are formed; additional energy needed is absorbed from the surroundings, thus causing the reaction to cool). Example: CH3COOH + NaHCO3 + thermal energyH2O + CO2 +CH3COONa Vinegar+ Baking Soda Water +Carbon dioxide + Sodium Acetate Evidence: loss of heat

6 B. Exothermic-energy is released (the energy required to break bonds is less than the energy required to form new bonds, thus causing the reaction to produce heat). Example: 2 Mg + O2  2 MgO Magnesium + Oxygen  Magnesium Oxide Evidence: Light is produced