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GOALS
1. Relate how the Law of Conservation of Matter is used to determine
chemical composition in chemical reactions.
2. Experimentally determine indicators of a chemical reaction specifically
precipitation, gas evolution, water production, and changes in
energy to the system.
3. Identify and balance the following types of chemical equations:
• Synthesis
• Decomposition
• Single Replacement
• Double Replacement
• Combustion
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Chemical Reactions
• A chemical reaction is a change in which
one or more substances are converted into
new substances.
– Rearrangement of bonds in compounds and
molecules.
• Chemical Equations make it possible to see
clearly what is happening during a chemical
reaction
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Visualizing Chemical Reactions
• Chemical
Reactions are
simply the
rearrangement
of bonds
between
molecules.
Chemical equations are a shorthand
way to show chemical reactions.
Reactants
Products
H2 + O2
H2O
This is a skeleton equation. It does
not show the amounts
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Chemical Equations
(more details)
• Physical States can be shown by subscripts in
parentheses.
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Write the skeleton equations for the following:
1) Hydrogen peroxide  Water + Oxygen
2) Methane + Oxygen  carbon dioxide + water
3) Aluminum and iodine react to form aluminum iodide
4) Hydrogen iodide gas breaks down into hydrogen gas and
iodine gas.
During a chemical reaction, mass is
conserved.
Law of Conservation
of Mass
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The mass of the
products always
equals the mass of
the reactants
Antoine
Lavoisier
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Law of Conservation of Mass
The mass of the products always equals the
mass of the reactants
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Showing Conservation of Mass in Chemical Formulas
H2 + O2
H2O
Does this meet the
Conservation
of
Mass
2 Hydrogen
2 Oxygen atoms
2 Hydrogen atoms & one Oxygen
atoms
atom
Law?
Must Balance the Equation to show Conservation
of Mass.
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Can add coefficients to Balance equations.
2 H2 + O2
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Steps:
2 H2O
2
42
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Balanced!!
1. Count Atoms on both sides
2. If not Balanced, add coefficients to balance.
3. Recount atoms after adding each coefficient.
4. Keep adding coefficients until balanced.
5. Check coefficients to make sure they are the
SMALLEST whole number..
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Balancing Equations Practice
____ K + ____ Cl2  ____ KCl
____ N2 + ____ H2  ____ NH3
____ N2 + ____ F2  ____ NF3
____ P4 + ____ Br2  ____ PBr3
____ GaF3 + ____ Cs  ____ CsF + ____ Ga
____ Al + ____ HCl  ____ H2 + ____ AlCl3
____ SO2 + ____ Li2Se  ____ SSe2 + ____ Li2O
____ Na3P + ____ CaF2  ____ NaF + ____ Ca3P2
____ AgNO3 + ____ Li  ____ LiNO3 + ____ Ag
____ CH4 + ____ O2  ____ CO2 + ____ H2O
____ BaS + ____ PtF2  ____ BaF2 + ____ PtS
____ Pb(OH)2 + ____ HCl  ____ H2O + ____ PbCl2
____ AlBr3 + ____ K2SO4  ____ KBr + ____ Al2(SO4)3
____ Na3PO4 + ____ CaCl2  ____ NaCl + ____ Ca3(PO4)
____ LiNO3 + ____ ____ CaBr2  ____ Ca(NO3)2 + ____ LiBr
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Writing and Balancing Formulas
For Reactions
Steps
• EX: Solid carbon and
1.Determine correct
oxygen gas react to
formulas for all
form carbon dioxide
reactants and
gas.
products.
2.Write the
• EX: Aluminum sulfate
Skeleton equation.
reacts with calcium
3.Use coefficients
hydroxide to produce
to balance the
aluminum hydroxide
equation.
and calcium sulfate.
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Writing Formulas Practice
• Aluminum metal dissolves in an aqueous
solution of sulfuric acid to form hydrogen
gas bubbles and a solution of aluminum
sulfate. (don’t forget states of matter)
Al (s) + H2SO4 (aq)  H2 (g) + Al2 (SO4)3 (aq)
Balanced: 2Al (s) + 3H2SO4 (aq)  3H2 (g) + Al2(SO4)3 (aq)
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More Practice
• Potassium metal and chlorine gas combine to
form potassium chloride.
– 2 K + Cl2  2 KCl
• Aluminum and hydrochloric acid react to
form aluminum chloride and hydrogen gas.
– 2 Al + 6 HCl  3 H2 + 2 AlCl3
• Zinc and lead (II) nitrate react to form zinc
nitrate and lead.
– Zn + Pb(NO3)2  Zn(NO3)2 + Pb
• Aluminum bromide and chlorine gas react to
form aluminum chloride and bromine gas.
– 2 AlBr3 + 3 Cl2  2 AlCl3 + 3 Br2
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Chemical Reactions
• You start with one or more
compounds and turn it into
different compounds.
• Indicators of a chemical
Reaction
–
–
–
–
Bubbling (evolution of a gas)
Color Change
Emission of heat and/or light
Formation of new substance
• Precipitate
– Temperature change
Vapors of hydrogen
chloride in a beaker and
ammonia in a test tube
meet to form a cloud of
a new substance,
ammonium chloride.
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5 Types of Chemical Reactions
1.Synthesis (combination)
2.Decomposition
3. Single Replacement
4. Double Replacement
5. Combustion
Synthesis
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“to make”
A + B
Cu + O
2H + O2
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2 or more smaller
chemical substances
combine into a new,
larger compound.
AB
CuO
2H O
2
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Decomposition
One larger chemical
compound breaking up
into 2 or more
smaller substances.
“to breakdown”
Usually
require
energy
AB
A + B
2H O
2H + O
NaOH
Na+ OH
2
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Animation
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Single Replacement
When one element replaces another element in a compound
The more reactive metal will always replace the less reactive metal.
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A + BC
Cu+AgNO3
AC + B
Cu(NO3)2+ 2Ag
Mg(s) +2HCl(aq) MgCl2(aq) +H2 (g)
-The Mg bumps out the H+1 & forms Mg+2 ion in solution
Single Replacement
The more reactive metal will always replace
the less reactive metal.
• Metal replaces hydrogen or another
metal
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– use the activity series to predict
whether or not certain reactions will
occur.
– specific metal can replace any metal
listed below it
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Single-Replacement Reactions
Predict the products that will result when
these reactants combine, and write a balanced
chemical equation for each reaction.
a. Fe(s) + CuSO4 (aq) →
b. Br2 (l) + MgC l2 (aq) →
c. Mg(s) + AlCl3 (aq) →
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Predict the outcome of the reaction
2Fe (s) + 3NiCl2 (aq)  2FeCl3 (aq) + Ni (s)
2Fe (s) + 3CoCl2 (aq)  2FeCl3 (aq) + 3Co (s)
2Fe (s) + 3Pb(NO3)2 (aq)  2Fe(NO3)3 (aq) + 3Pb (s)
2Fe (s) + AlCl3 (aq)  No reaction
2Fe (s) + FeCl3 (aq) No reaction
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Single Replacement
• Clip
Animation
Double Replacement
Positive Ion of One compound replaces the positive ion of
another compound and a Precipitate is formed.
AB + CD
Ba(NO3)2+KSO4
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AD + CB
2KNO3 + BaSO4
**start with 2 AQUEOUS SOLUTIONS,
the cations switch anions with each other.
Clip
Double Replacement
• Generally takes place in an aqueous solution
1 of the following
is usually true:
1.Precipitate forms
2.One of the
products is a gas
3.One of the
products is a
molecular compound
such as water.
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Clip
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Animation
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Combustion
• Chemical change
in which an
element or
compound reacts
with oxygen,
often producing
energy in the
form of heat or
light
• Always involves
oxygen as a
reactant.
CH4(g) + 2O2(g)  CO2(g) + 2H2O(g)
2C4H10 (g) +18O (g) 8CO (g) +10H2O(g)
Combustion reactions are almost always
exothermic (i.e., they give off heat).
Review
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Identification of Reactions Practice
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2 C6H14 + 19 O2 --> 12 CO2 + 14 H2O C
2 C2H2 + 5 O2 --> 4 CO2 + 2 H2O C
8 Cu + S8 --> 8 CuS S
P4 + 5 O2 --> 2 P2O5 S
H2CO3 --> H2O + CO2 D
2 NaClO3 --> 2 NaCl + 3 O2 D
2 AgNO3 + Ni --> Ni(NO3)2 + 2 Ag SD
Ca + 2 HCl --> CaCl2 + H2 SD
Ca(C2H3O2)2 + Na2CO3 --> CaCO3 + 2 NaC2H3O2 DD
BaCO3 --> BaO + CO2 D
4 Cr + 3 O2 --> 2 Cr2O3 S
Cu(OH)2 + 2 HC2H3O2 --> Cu(C2H3O2)2 + 2 H2O DD
C3H8 + 5 O2 --> 3 CO2 + 4 H2O C
3 AgNO3 + K3PO4 --> Ag3PO4 + 3 KNO3 DD
2 K + 2 H2O --> 2 KOH + H2 SD
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