Chapter #6 Chemical Reactions Chapter 6 Chemical Reactions • A chemical reactions is an abbreviated way to show a chemical change • A chemical change alters the physical and chemical properties of a substance • Factors that indicate a chemical change – – – – Change in color Temperature change Change in odor Change in taste (we do not taste chemicals) • Reactions always contain an arrow that separates the reactants from the products Reactants Products Chapter 6 Chemical Change Evidence Chapter 6 Chemical Change Evidence What is a clue that a chemical reaction has occurred? a) b) c) d) The color changes. A solid forms. Bubbles are present. A flame is produced. Chapter 6 Chemical Change Evidence What is a clue that a chemical reaction has occurred? “Colorless hydrochloric acid is added to a red solution of cobalt(II) nitrate, turning the solution blue.” a) b) c) d) The color changes. A solid forms. Bubbles are present. A flame is produced. Chapter 6 Chemical Change Evidence What is a clue that a chemical reaction has occurred? “A solid forms when a solution of sodium dichromate is added to a solution of lead nitrate.” a) b) c) d) A gas forms. A solid forms. Bubbles are present. A flame is produced. Chapter 6 Types of Chemical Reactions • Combination reaction (synthesis) – Elements for reactants – Examples: H2 + O2 N2 + H2 Al + O2 H2O NH3 Al2O3 The Law of Conservation of matter, states matter cannot be created nor destroyed, the means equations must be balanced. Chapter 6 Types of Chemical Reactions Balance the first equation H2 + O2 H2O Note two oxygen atoms on the reactant side and only one on the product side, therefore place a two in front of water Chapter 6 Types of Chemical Reactions Balance the first equation H2 + O2 2H2O Note two oxygen atoms on the reactant side and only one on the product side, therefore place a two in front of water The two now doubles everything in water, thus 4 hydrogen and 2 oxygen. Now place a 2 in front of hydrogen. Chapter 6 Types of Chemical Reactions Balance the first equation 2H2 + O2 2H2O Note two oxygen atoms on the reactant side and only one on the product side, therefore place a two in front of water The two now doubles everything in water, thus 4 hydrogen and 2 oxygen. Now place a 2 in front of hydrogen. Chapter 6 Types of Chemical Reactions Now balance the second equation N2 + H2 NH3 Note two nitrogen atoms on the reactant side and only one on the product side. Place a 2 in front of ammonia Chapter 6 Types of Chemical Reactions Now balance the second equation N2 + H2 2NH3 Note two nitrogen atoms on the reactant side and only one on the product side. Place a 2 in front of ammonia. This makes 2 nitrogen atoms and 6 hydrogen atoms. Now place a 3 in front of hydrogen to balance hydrogen atoms. Chapter 6 Types of Chemical Reactions Now balance the second equation N2 + 3 H2 2NH3 Note two nitrogen atoms on the reactant side and only one on the product side. Place a 2 in front of ammonia. This makes 2 nitrogen atoms and 6 hydrogen atoms. Now place a 3 in front of hydrogen to balance hydrogen atoms. Chapter 6 Types of Chemical Reactions • Decomposition Reaction – Compounds form simpler compounds or elements. – Examples H2O H2 + O2 Chapter 6 Types of Chemical Reactions • Decomposition Reaction – Compounds form simpler compounds or elements. – Examples 2H2O H2 + O2 Chapter 6 Types of Chemical Reactions • Decomposition Reaction – Compounds form simpler compounds or elements. – Examples 2H2O 2 H2 + O2 • Notice decomposition reactions are the opposite of combination reactions Chapter 6 Types of Chemical Reactions • Single Replacement Reactions Single Replacement reactions have an element and a compound for reactants. Example: Zn + HCl How do we predict the products? Trade places with the metal or nonmetal with the metal or nonmetal in the compound Chapter 6 Types of Chemical Reactions Single Replacement reactions have an element and a compound for reactants. Example: Zn + HCl How do we predict the products? Trade places with the metal or nonmetal with the metal or nonmetal in the compound Chapter 6 Types of Chemical Reactions Single Replacement reactions have an element and a compound for reactants. Example: Zn + HCl ZnCl + H Now make the products stable. Slide with Clyde Chapter 6 Types of Chemical Reactions Single Replacement reactions have an element and a compound for reactants. Example: Zn + HCl ZnCl2 + H2 Now make the products stable. Slide with Clyde Chapter 6 Types of Chemical Reactions Single Replacement reactions have an element and a compound for reactants. Example: Zn + HCl ZnCl2 + H2 Now make the products stable. Slide with Clyde Now Balance Chapter 6 Types of Chemical Reactions Single Replacement reactions have an element and a compound for reactants. Example: Zn + 2HCl ZnCl2 + H2 Now make the products stable. Slide with Clyde Now Balance Chapter 6 Types of Chemical Reactions Single Replacement reactions have an element and a compound for reactants. Another Example: Cl2 + MgBr2 How do we predict the products? Trade places with the metal or nonmetal with the metal or nonmetal in the compound. In this case we are trading nonmetals Chapter 6 Types of Chemical Reactions Single Replacement reactions have an element and a compound for reactants. Another Example: Cl2 + MgBr2 Br + MgCl How do we predict the products? Trade places with the metal or nonmetal with the metal or nonmetal in the compound. In this case we are trading nonmetals Chapter 6 Types of Chemical Reactions Single Replacement reactions have an element and a compound for reactants. Another Example: Cl2 + MgBr2 Br2 + MgCl2 How do we predict the products? Trade places with the metal or nonmetal with the metal or nonmetal in the compound. In this case we are trading nonmetals Chapter 6 Types of Chemical Reactions • Double Replacement Reactions Double Replacement reactions contain compounds as reactants. HCl + Ca(OH)2 CaCl + HOH Check formulas, and slide with Clyde when necessary Chapter 6 Types of Chemical Reactions Double Replacement reactions contain compounds as reactants. HCl + Ca(OH)2 CaCl 2 + HOH Check formulas, and slide with Clyde when necessary Chapter 6 Types of Chemical Reactions Double Replacement reactions contain compounds as reactants. 2HCl + Ca(OH)2 CaCl 2 + 2HOH Check formulas, and slide with Clyde when necessary Now Balance! Chapter 6 Types of Chemical Reactions Combustion Reactions occur when an element or compound combine with oxygen to produce oxides of each element. H2 + O2 CH4 + O2 What is the oxide of hydrogen? Chapter 6 Types of Chemical Reactions Combustion Reactions occur when an element or compound combine with oxygen to produce oxides of each element. H2 + O2 CH4 + O2 What is the oxide of hydrogen? Water Chapter 6 Types of Chemical Reactions Combustion Reactions occur when an element or compound combine with oxygen to produce oxides of each element. H2 + O2 H2O CH4 + O2 What is the oxide of hydrogen? Water And the oxide of carbon? Chapter 6 Types of Chemical Reactions Combustion Reactions occur when an element or compound combine with oxygen to produce oxides of each element. H2 + O2 H2O CH4 + O2 CO2 + H2O What is the oxide of hydrogen? Water And the oxide of carbon? Carbon dioxide Chapter 6 Types of Chemical Reactions Combustion Reactions occur when an element or compound combine with oxygen to produce oxides of each element. 2H2 + O2 2H2O CH4 + O2 CO2 + H2O Now balance Chapter 6 Types of Chemical Reactions Combustion Reactions occur when an element or compound combine with oxygen to produce oxides of each element. 2H2 + O2 2H2O CH4 + O2 CO2 + 2H2O Now balance Chapter 6 Types of Chemical Reactions Combustion Reactions occur when an element or compound combine with oxygen to produce oxides of each element. 2H2 + O2 2H2O CH4 + 2O2 CO2 + 2H2O Now balance Chapter 6 The End