Chemical Reactions & Chemical Equations

Chemical Reactions A process involving a substance or substances changing into a new substance or substances Chemical Change

Chemical Reactions Evidence of a chemical reaction

Chemical Reactions Evidence of a chemical reaction 1) A permanent color change 2) A gas is produced 3) Energy is exchanged 4) A precipitate is produced

Chemical Equations A statement using chemical formulas to describe the identities and relative amounts of reactants and products involved in the chemical reaction

Reactant(s)  Product(s)

MgCO 3  MgO + CO 2

MgCO 3  CO 2 + MgO

MgCO 3 (s)  MgO (s) + CO 2(g) Phases of Components (s) = solid (l) = liquid (g) = gas (aq) = aqueous

Physical Change Vs. Chemical Change

Physical ChangeChemical Change

Physical ChangeChemical Change Phase Changes Dissolving Mixing Breaking Separating Filtering Rearrange Atoms New Substances form

Did a chemical change occur? 1.Permanent Color Change Occurs 2.Precipitate Formed 3.Gas is Released 4.Energy is Exchanged – Temperature

Chemical Reaction Demonstration 1.Permanent Color Change CuSO 4 (Aq) + Zn (s)  ZnSO 4 (Aq) + Cu (s) Blue Gray Clear Black The Zn and Cu are Switching, this is known as a single replacement Reaction. 2.Gas is Produced HCl (l) + Zn (s)  ZnCl (Aq) + H 2 (g) 3.Energy is Exchanged Mg (s) + O 2 (g)  MgO (s) Rapid Oxidation 4.Precipitate is Formed Pb(NO 3 ) 2 (Aq) + K 2 CrO 4 (Aq)  KNO 3 (Aq) + PbCrO 4 (s) Clear Bright Yellow

Practice Exercise #1 1.Define Chemical Reaction 2.How do we know a chemical reaction has taken place? 3.What is a Chemical Equation and Why do we use them? 4.What are the initial constituents of a chemical reaction? What are the end products called? 5.What do the following symbols stand for? slgaq

Types of Chemical Equations

Synthesis Putting things together Also known as Direct Combination. 2 Na + Cl 2 = 2 NaCl 4 Al + 3 O 2 = 2 Al 2 O 3

Decomposition Breaking things down/Taking apart AKA Analysis 2 KClO 3 = 2 KCl + 3 O 2 3 MnO 2 = Mn 3 O 4 + O 2

Single Replacement Replacing one element in a compound with another element. 2 Al + 6 HCl = 2 AlCl H 2 2 NaBr + Cl 2 = 2 NaCl + Br 2

Double Replacement Switching one element from a compound with another element from a different compound. 2 AgNO 3 + MgCl 2 = 2 AgCl + Mg(NO 3 ) 2 HCl + NaOH = NaCl + H 2 O

Others Combustion –Rapid Oxidation –XXXX + O 2 CO 2 + H 2 O Oxidation –Add Oxygen (Combustion) Reduction Acid – Base Neutralization Etc……

HW Due Monday Read & outline page

Exothermic Reactions Release or give off heat. Heat is a byproduct of the reaction. Temperature increases as the bonds between products are formed. Examples –Combustion, Respiration, Oxidation

Endothermic Reactions Take in or absorb Heat from the surroundings. Temperature decreases as the reaction progresses. Heat is used to break bonds of reactants. –Decomposition or Analysis Reactions

Oxidation Removing Electrons

Reduction Adding Electrons

Rate of Reaction Reactions occur at different speeds. The time it takes for reactants to become products.

Catalysts They speed up reactions without being affected themselves. –They stay the same –Enzymes in living organisms. Lowers activation energy –The amount of energy needed to start a reaction.

Speeding Up Reactions Temperature, Energy, Pressure, Surface Area, Concentration, Collisions, Catalyst.

Measuring Rates of Reactions Measure Reactants Measure Products

Balancing Chemical Equations

Reactant(s)Product(s)

MgCO 3 (s)  MgO (s) + CO 2(g) Phases of Components (s) = (l) = (g) = (aq) =

1 MgCO 3 (s)  1 MgO (s) + 1 CO 2(g)

Reactants Products

1 MgCO 3 (s)  1 MgO (s) + 1 CO 2(g) 5 atoms

H 2 + O 2  H 2 O

2 H O 2  2 H 2 O H 2 + H 2 + O 2  H 2 O + H 2 O

2 H O 2  2 H 2 O H 2 + H 2 + O 2  H 2 O + H 2 O

Ca + Cl 2  CaCl 2

Na + Cl 2  NaCl

Fe 2 O 3  Fe + O 2

AgNO 3 + NaCl  NaNO 3 + AgCl

FeS 2 + O 2  Fe 2 O 3 + SO 2

4 FeS O 2  2 Fe 2 O SO 2

NH 4 OH + Ni(NO 3 ) 2  NH 4 NO 3 + Ni(OH) 2

NH 4 OH + Ni(NO 3 ) 2  NH 4 NO 3 + Ni(OH) 2

Na 2 CO 3 + Fe(NO 3 ) 3  Fe 2 (CO 3 ) 3 + NaNO 3

Na 2 CO 3 + Fe(NO 3 ) 3  Fe 2 (CO 3 ) 3 + NaNO 3 3 Na 2 CO Fe(NO 3 ) 3  Fe 2 (CO 3 ) NaNO 3 Balanced!!!

H 3 PO 4 + Ca(OH) 2  Ca 3 (PO 4 ) 2 + H 2 O

NH 4 OH + H 3 PO 4  (NH 4 ) 3 PO 4 + H 2 O

Al(OH) 3 + H 2 SO 4  Al 2 (SO 4 ) 3 + H 2 O

C 6 H 6 + O 2  CO 2 + H 2 O