Chapter 9
Chemical Reactions
National Standards for Chapter 9
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UCP.3 – Change, constancy, and measurement
UCP.5 – Form and function
A.1 –Abilities necessary to do scientific inquiry
A.2 – Understandings about scientific inquiry
B-2 – Structure and properties of matter
B-3 – Chemical reactions
B-6 – Interactions of energy and matter
Vocabulary/Study Guide
• Define each term using the Glossary
• Either write on the handout, or use your own
paper
• This is due on Test Day (tentatively, Thursday,
March 6)
Section 1: Reactions and Equations
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National Standards:
UCP.3 – Change, constancy, and measurement
UCP.5 – Form and function
A.1 –Abilities necessary to do scientific inquiry
B-2 – Structure and properties of matter
B-3 – Chemical reactions
B-6 – Interactions of energy and matter
Objectives – Section 1
• Recognize evidence of chemical change.
• Represent chemical reactions with equations.
• Balance chemical equations.
REVIEW VOCABULARY:
chemical change: a process involving one or more
substances changing into a new substance
New Vocabulary
chemical reaction
reactant
product
chemical equation
coefficient
Chemical reactions are represented by balanced
chemical equations.
Launch Lab
Title: How do you know when a chemical
change has occurred? (page 280)
Math Skills Transparency 11
Chemical Reactions
• The process by which one or more substances
are rearranged to form different substances is
called a chemical reaction.
Chemical Reactions
• Evidence that a chemical reaction may have
occurred:
– Change in temperature
– Change in color
– Odor
– Gas bubbles
– Appearance of a solid (precipitate)
Representing Chemical Reactions
• Chemists use statements
called equations to represent
chemical reactions.
• Reactants are the starting
substances.
• Products are the substances
formed in the reaction.
• This table summarizes the
symbols used in chemical
equations.
Representing Chemical Reactions
• In word equations, aluminum(s) +
bromine(l) → aluminum bromide(s) reads as
“aluminum and bromine react to produce
aluminum bromide”.
• Skeleton equations use symbols and formulas to
represent the reactants and products.
Al(s) + Br(l) → AlBr3(s)
• Both word and skeleton equations lack
information about how many atoms are involved
in the reaction.
Representing Chemical Reactions
• A chemical equation is a statement that uses
chemical formulas to show the identities and
relative amounts of the substances involved in
a chemical reaction.
Representing Chemical Reactions
• Practice Problems #1-3, page 284
Balancing Chemical Equations
• This figure shows the balanced equation for
the reaction between aluminum and bromine.
Balancing Chemical Equations
• A coefficient in a chemical equation is the
number written in front of a reactant or
product, describing the lowest whole-number
ratio of the amounts of all the reactants and
products.
Balancing Chemical Equations
Balancing Chemical Equations
Balancing Chemical Equations
Transparency 29: Parts of a Balanced
Chemical Equation
Representing Chemical Reactions
• Practice Problems #4-6, page 287
Transparency 30: Balancing Chemical
Equations
Balancing Chemical Equations
• The most fundamental law in chemistry is the
law of conservation of mass.
• Balanced equations show this law.
Balancing Chemical Equations
Homework, Section 1
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SECTION 1 REVIEW, Page 288
Questions #7-13
Answer with complete sentences
Due tomorrow
Section 2: Classifying Chemical
Reactions
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National Standards:
UCP.3 – Change, constancy, and measurement
UCP.5 – Form and function
A.1 –Abilities necessary to do scientific inquiry
B-2 – Structure and properties of matter
B-3 – Chemical reactions
Objectives – Section 2
• Classify chemical reactions.
• Identify the characteristics of different
classes of chemical reactions.
Review Vocabulary:
metal: an element that is a solid at room temperature,
a good conductor of heat and electricity, and is
generally shiny
New Vocabulary
synthesis reaction
combustion reaction
decomposition reaction
single-replacement reaction
double-replacement reaction
precipitate
There are four types of chemical reactions:
synthesis, combustion, decomposition, and
replacement reactions.
Types of Chemical Reactions
• Chemists classify reactions in order to
organize the many types.
Synthesis Reactions
• A synthesis reaction is a reaction in which two
or more substances react to produce a single
product.
• When two elements react, the reaction is
always a synthesis reaction.
Combustion Reactions
• In a combustion reaction, oxygen combines
with a substance and releases energy in the
form of heat and light.
• Heated hydrogen reacts with oxygen to
produce heat and water in a combustion
reaction. This is also a synthesis reaction.
Combustion Reactions
• Practice Problems #14-17, page 291
Decomposition Reactions
• A decomposition reaction is one in which a
single compound breaks down into two or
more elements or new compounds.
• Decomposition reactions often require an
energy source, such as heat, light, or
electricity, to occur.
Decomposition Reactions
• Practice Problems #18-20, page 292
Replacement Reactions
• A reaction in which the atoms of one element
replace the atoms of another element in a
compound is called a single replacement
reaction.
A + BX → AX + B
Replacement Reactions
• A metal will not always
replace a metal in a
compound dissolved in water
because of differing
reactivities.
• An activity series can be used
to predict if reactions will
occur.
Replacement Reactions
• Halogens frequently replace other halogens in
replacement reactions.
• Halogens also have different reactivities and
do not always replace each other.
Transparency 31: The Activity Series
Replacement Reactions
Title:
Analyze Trends, page 294
Replacement Reactions
• Practice Problems #21-24, page 295
Replacement Reactions
• Double replacement reactions occur when
ions exchange between two compounds.
• This figure shows a generic double
replacement equation.
Replacement Reactions
• The solid product produced during a chemical
reaction in a solution is called a precipitate.
• All double replacement reactions produce
either water, a precipitate, or a gas.
Replacement Reactions
• This table shows the steps to write double
replacement reactions.
Replacement Reactions
• Practice Problems #25-28, page 297
Replacement Reactions
• This table summarizes different ways to
predict the products of a chemical reaction.
Transparency 32: Summary of
Reaction Types
Lab: Develop an Activity Series, page
310
Lab: Single-Replacement Reactions
Lab: Double-Replacement Reactions
Homework, Section 2
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SECTION 2 REVIEW, Page 298
Questions #29-34
Answer with complete sentences
Due tomorrow
Section 3: Reactions in Aqueous
Solutions
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National Standards:
UCP.3 – Change, constancy, and measurement
UCP.5 – Form and function
A.1 –Abilities necessary to do scientific inquiry
A.2 – Understandings about scientific inquiry
B-2 – Structure and properties of matter
B-3 – Chemical reactions
B-6 – Interactions of energy and matter
Objectives – Section 3
• Describe aqueous solutions.
• Write complete ionic and net ionic equations
for chemical reactions in aqueous solutions.
• Predict whether reactions in aqueous
solutions will produce a precipitate, water, or
a gas.
Review Vocabulary:
solution: a uniform mixture that might contain solids,
liquids, or gases
New Vocabulary
aqueous solution
solute
solvent
complete ionic equation
spectator ion
net ionic equation
Double-replacement reactions occur between
substances in aqueous solutions and produce
precipitates, water, or gases.
Aqueous Solutions
• An aqueous solution contains one or more
dissolved substances (called solutes) in water.
• The solvent is the most plentiful substance in
a solution.
Aqueous Solutions
• Water is always the solvent in an aqueous
solution.
• There are many possible solutes—sugar and
alcohol are molecular compounds that exist as
molecules in aqueous solutions.
• Compounds that produce hydrogen ions in
aqueous solutions are acids.
Aqueous Solutions
• Ionic compounds can also be solutes in
aqueous solutions.
• When ionic compounds dissolve in water, their
ions separate in a process called dissociation.
Type of Reactions in Aqueous
Solutions
• When two solutions that contain ions as
solutes are combined, the ions might react.
• If they react, it is always a double replacement
reaction.
• Three products can form: precipitates, water,
or gases.
Type of Reactions in Aqueous
Solutions
Title: Observe a Precipitate-Forming Reaction,
page 301
Type of Reactions in Aqueous
Solutions
• Aqueous solutions of sodium hydroxide and
copper(II) chloride react to form the
precipitate copper(II) hydroxide.
2NaOH(aq) + CuCl2(aq) → 2NaCl(aq) + Cu(OH)2(s)
• Ionic equations that show all of the particles
in a solution as they actually exist are called
complete ionic equations.
2Na+(aq) + 2OH–(aq) + Cu2+ (aq)+ 2Cl–(aq) →
2Na+(aq) + 2Cl–(aq) + Cu(OH)2(s)
Type of Reactions in Aqueous
Solutions
• Ions that do not participate in a reaction are
called spectator ions and are not usually
written in ionic equations.
• Formulas that include only the particles that
participate in reactions are called net ionic
equations.
2OH–(aq) + Cu2+(aq) → Cu(OH)2(s)
Type of Reactions in Aqueous
Solutions
• Practice Problems #35-39, page 302
Type of Reactions in Aqueous
Solutions
• Some reactions produce more water
molecules.
• No evidence of a chemical reaction is
observable.
HBr(aq) + NaOH(aq) → H2O(l) + NaBr(aq)
• Without spectator ions
H+(aq) + OH–(aq) → H2O(l).
Type of Reactions in Aqueous
Solutions
• Practice Problems #40-44, page 304
Type of Reactions in Aqueous
Solutions
• Gases that are commonly produced are
carbon dioxide, hydrogen cyanide, and
hydrogen sulfide.
2HI(aq) + Li2S(aq) → H2S(g) + 2LiI(aq)
Type of Reactions in Aqueous
Solutions
• Another example is mixing vinegar and baking
soda, which produces carbon dioxide gas.
HCl(aq) + NaHCO3(aq) → H2CO3(aq) + NaCl(aq)
• H2CO3(aq) decomposes immediately.
H2CO3(aq) → H2O(l) + CO2(g)
Type of Reactions in Aqueous
Solutions
• Practice Problems #45-49, page 306
Type of Reactions in Aqueous
Solutions
• Two reactions can be combined and
represented by a single chemical reaction.
Type of Reactions in Aqueous
Solutions
Reaction 1
HCl(aq) + NaHCO3(aq) → H2CO3(aq) + NaCl(aq)
Reaction 2
H2CO3(aq) → H2O(l) + CO2(g)
Combined equation
HCl(aq) + NaHCO3(aq) + H2CO3(aq) → H2CO3(aq)
+ NaCl(aq) + H2O(l) + CO2(g)
Overall equation
HCl(aq) + NaHCO3(aq) → H2O(l) + CO2(g) +
NaCl(aq)
Transparency 33: Types of Equations
Math Skills Transparency 12: Simplifying Equations
Homework, Section 3
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SECTION 3 REVIEW, Page 308
Questions #50-56
Answer with complete sentences
Due tomorrow
SECTION
Reactions and Equations
9.
1
Study Guide
Key Concepts
Some physical changes are evidence that indicate a chemical
reaction has occurred.
Word equations and skeleton equations provide important
information about a chemical reaction.
A chemical equation gives the identities and relative amounts of
the reactants and products that are involved in a chemical
reaction.
Balancing an equation involves adjusting the coefficients until the
number of atoms of each element is equal on both sides of the
equation.
SECTION
Classifying Chemical Reactions
9.
2
Study Guide
Key Concepts
Classifying chemical reactions makes them easier to understand,
remember, and recognize.
Activity series of metals and halogens can be used to predict if
single-replacement reactions will occur.
SECTION
Reactions in Aqueous Solutions
9.
3
Study Guide
Key Concepts
In aqueous solutions, the solvent is always water. There are many
possible solutes.
Many molecular compounds form ions when they dissolve in
water. When some ionic compounds dissolve in water, their
ions separate.
When two aqueous solutions that contain ions as solutes are
combined, the ions might react with one another. The solvent
molecules do not usually react.
Reactions that occur in aqueous solutions are double-replacement
reactions.