Chemical Reactions Section 7-1 Chemical Changes in Matter

Describing Chemical Reactions Chemical Reaction: A well defined example of a chemical change in which one or more substances are changed to new substances.

Chemical Reaction ReactantsProducts Yields Reactants: The substances that are about to react. Products: The new substances that are produced.

Conservation of Mass The mass of the reactants EQUALS The mass of the products.

Conservation of Mass Mercury(II) Oxide Oxygen + Mercury 2HgO O 2 + 2Hg 10.0g0.7g + 9.3g10.0g

SymbolMeaning Produces or forms +Plus (cr)Crystalline Solid (l)Liquid (g)Gas (aq)Dissolved in water ( Aqueous ) heatReactants are heated lightReactants exposed to Light elec.Electric Current applied to reactants

Reactants And Carbon Oxygen Gas

C Reactants + O2O2

Yields

Products Carbon Dioxide

Chemical Equation C O2O2 + CO 2

Chemical Equation H2H2 O2O2 + H2OH2O22 Coefficients

A number which represents the number of units of each substance taking part in a reaction. Coefficients

Chemical Equations Balanced Chemical Equation The number of atoms of each element is the same on both sides of the equation.

Example Ag + H 2 S Ag 2 S+ H

Writing Balanced Equations Step 1: Write the equation in words. Magnesium plus Oxygen produces Magnesium Oxide Step 2: Write the chemical equation using formulas and symbols. Mg + O 2 MgO

Step 3: Check the equation for atom balance. Mg + O 2 MgO

Step 4: Choose coefficients that balance the equation

MINOH Method M - Metals I – Polyatomic Ions (SO 4 ) Page 173 in the book. N – Non-Metals O – Oxygen H - Hydrogen

MINOH Example Na 2 SO 4 + BaCl 2 → NaCl+ BaSO 4

The Mole The atom is too small a unit for chemist to count with, so the mole is used. Bakers use a dozen. 1 mole = 6.02X10 23 atoms. Avogadro’s number

The Mole The mass of a mole is different for each element. Use the atomic mass for that element. Use the periodic table.

The Mole 1 mole of C 1mole of Na 1mole of O 2

The Mole H20H20 H2H2 O2O moles 1 mole

Homework: #7-1 Section 7-1 Worksheet Due: 01/09/09

Synthesis Reaction Two or more substances combine to form another substance.

Synthesis Reaction A + B AB 2H 2 +O 2 2H 2 O

Decomposition Reaction One substance breaks down, or decomposes, into two or more simpler substances.

Decomposition Reaction AB A + B elec. 2H 2 O 2H 2 + O 2

Single Replacement Reaction One element replaces another element in a compound.

Replacement Reaction A + BC AC + B D + BC BD + C Cu + 2AgNO 3 2Ag + Cu(NO 3 ) 2

Double Replacement Reaction Two elements replace each other in two compound.

Double-replacement Reaction AB + CD AD + CB AgNO 3 +NaCl AgCl+NaNO 3

Double-Replacement Reaction Takes place if a precipitate, water, or a gas forms when two compounds in solution are combined.

Precipitate An insoluble compound formed during a displacement reaction.

Combustion Reaction A substance reacts rapidly with oxygen. CH 4 + 2O 2 CO 2 + 2H 2 0

Electron Transfer Reactions Electrons are transferred from one reactant to another. 2Ca + O 2 2CaO Oxidation-Reduction

Oxidation The atom that loses electrons undergoes oxidation. Ca Ca e - Oxidation

Reduction The atom that gains electrons undergoes reduction e Oxidation

Homework #7-2 Section 7-2 Work sheet Due: 01/09/08

Energy Changes in Reactions C 3 H 8 + O 2 CO 2 + H 2 O345 + Heat

Breaking Bonds C-C-CH HHH H HHH O O2O2 C3H8C3H8

CO 2 H2OH2O Forming Bonds H O COO H Heat

Energy and Chemical Reactions Exothermic Reaction A chemical reaction in which energy is released. Fire Explosions

Mg +2H 2 O ----> Mg(OH) 2 +H 2 +Heat MRE

Energy and Chemical Reactions Endothermic Reaction A chemical reaction in which energy is absorbed. 2Al Al elec.

Ice Pack NH 4 N0 3 + H 2 O NH 4 OH + HN0 3 Heat

Reaction Rates Reaction rates tell you how fast the reaction is going.

Factors Affecting Reaction Rates Temperature Surface Area Stirring Concentration Catalyst

Energy and Chemical Reactions Catalyst A substance that speeds up a chemical reaction without itself being permanently changed.

Catalyst Proteins Enzymes that act as catalysts in a living organism.

Energy and Chemical Reactions Inhibitors Substance used to combine with one of the reactants that will keeps it from reacting.

Inhibitors BHT and BHA Food preservatives.

Catalytic Converter

CO NO 2 Hydro- carbons Catalytic Converter CO 2 N 2 CO 2 + H 2 O

Worksheets 7-3 and 7-4 Due: 1/13/09 Test: 1/15/09 Homework: #7-3

Mid Year Exam Tuesday - Jan 20 th 8 - 9:30am C Period – Room 291 G Period – Room 289 Full Sheet of Notes Pencil Review Sheet (1 Point per Sheet)

Section 7-5 Equilibrium

Forward and Reverse paths of a physical or chemical change take place at the same rate.

Physical Equilibrium A state in which the forward and reverse paths of a physical or chemical change take place at the same rate. H 2 0(l) H 2 0(g)

Chemical Equilibrium Forward and Reverse paths of a chemical change take place at the same rate.

Reversible Reaction Conversion of Reactants into Products and the conversion of Products into Reactants happens at the same time.

2SO SO 3 Reversible Reaction

At the completion of a chemical reaction, a chemical equilibrium is reached

Factors Affecting Chemical Equilibrium Temperature Pressure Concentration

N 2 + 2NH 3 +Heat3H 2

Le Chatelier Principle

Sect: 7-5 Word Wise Math Due: 1/15/09 Test: 1/16/09

Section 7-5 Worksheet Due: 1/10/08 Test: 1/14/08