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Chemical Reactions Chemical Reactions UnitUnit
Learning Goal #1: Learning Goal #1: Identify evidence of Identify evidence of chemical reactions and chemical reactions and differentiate between the differentiate between the different types of different types of reactions.reactions.
Evidence for a Chemical Evidence for a Chemical ReactionReaction
PrecipitationPrecipitation– A solid formed from a solution can result A solid formed from a solution can result
from a chemical change.from a chemical change.
Evidence for a Chemical Evidence for a Chemical ReactionReaction
Gas ProductionGas Production– Fizzing, bubblingFizzing, bubbling
Color ChangesColor Changes
Odor ChangesOdor Changes
Evidence for a Chemical Evidence for a Chemical ReactionReaction
Energy ChangesEnergy Changes– ExothermicExothermic
Heat is released (feels hot)Heat is released (feels hot)
– EndothermicEndothermic Heat is absorbed (feels cold)Heat is absorbed (feels cold)
– Light can be absorbed or released also without a Light can be absorbed or released also without a temperature change.temperature change.
Predicting Whether a Reaction Predicting Whether a Reaction Will Occur Will Occur
Most common Driving Forces.Most common Driving Forces.– Formation of a solidFormation of a solid– Formation of waterFormation of water– Transfer of electronsTransfer of electrons– Formation of a gasFormation of a gas
Predicting What Will Be Predicting What Will Be Formed From a ReactionFormed From a Reaction
Solids FormsSolids Forms– PrecipitationPrecipitation
Reaction where a solid is formed.Reaction where a solid is formed.– Ionic CompoundsIonic Compounds
Contains only two types of ions.Contains only two types of ions. Anion and cationAnion and cation Strong Electrolyte: A substance that Strong Electrolyte: A substance that
dissolved in water produces ions.dissolved in water produces ions.
Steps for predicting Steps for predicting precipitatesprecipitates
Step 1 – Write the reactants as they Step 1 – Write the reactants as they actually exist before any reaction actually exist before any reaction occurs.occurs.
Step 2 – Consider the various solids Step 2 – Consider the various solids that could form.that could form.
Step 3 – Use the solubility rules to Step 3 – Use the solubility rules to decide whether a solid forms, and, if decide whether a solid forms, and, if so, to predict the identity of the solid.so, to predict the identity of the solid.
– Soluble SolidSoluble SolidSolid that readily dissolves in Solid that readily dissolves in water.water.
– Insoluble solid and slightly Insoluble solid and slightly soluble solidsoluble solidVery small amount dissolves Very small amount dissolves in water, the majority stays in water, the majority stays solid.solid.
Types of ReactionsTypes of Reactions
Decomposition ReactionsDecomposition Reactions– A compound breaks down into two or A compound breaks down into two or
more simpler substances.more simpler substances.– AB AB A + B A + B
Types of ReactionsTypes of Reactions
Synthesis ReactionsSynthesis Reactions– Two or more substances combine to Two or more substances combine to
form a single product.form a single product.– A + B A + B AB AB
Zn + I ZnI
Types of ReactionsTypes of Reactions
Single-displacement (replacement) Single-displacement (replacement) ReactionsReactions– One element takes the place of another One element takes the place of another
in a compound.in a compound.– A + BC A + BC B + AC B + AC
Acids React with Active Acids React with Active MetalsMetals
Acids react with active metals to form salts and hydrogen gas.
Mg + 2HCl MgCl2 + H2(g)
Zn + 2HCl ZnCl2 + H2(g)
Mg + H2SO4 MgSO4 + H2(g)
Double-displacement (replacement) Double-displacement (replacement) ReactionsReactions– The positive portions of two ionic The positive portions of two ionic
compounds are interchanged.compounds are interchanged.– AB + CD AB + CD CB + AD CB + AD
Types of Reactions
Acid/Base ReactionAcid/Base Reaction– Reaction between an acid and a Reaction between an acid and a
base that produces base that produces waterwater..
Types of Reactions
HCl + NaOH NaCl + H2O
H2SO4 + 2NaOH Na2SO4 + 2H2O
2HNO3 + Mg(OH)2 Mg(NO3)2 + 2H2O
Types of Reactions
CombustionCombustion– The vigorous and The vigorous and
exothermic exothermic oxidation-reduction oxidation-reduction reaction that takes reaction that takes place between place between certain substances certain substances and oxygen.and oxygen.
– Results in a flame.Results in a flame.
Methane
Oxygen
Carbon Dioxide
Water
Combustion ReactionsCombustion Reactions– One in which a substance rapidly One in which a substance rapidly
combines with oxygen to form one or combines with oxygen to form one or more oxides.more oxides.
– A + O A + O AO (oxide) AO (oxide)
Types of Reactions
Types of Reactions
Oxidation-Reduction ReactionOxidation-Reduction Reaction– A reaction that involves a transfer of A reaction that involves a transfer of
electrons.electrons.