Chapter 11
Matter and Change
11.1 Describing Chemical
Reactions
11.2 Types of Chemical Reactions
11.3 Reactions in Aqueous Solution
Reaction(explosion of alkali
metals)
http://www.youtube.com/watch?v=HvVUtpdK7xw
11.1 Chemical Reactions
Examples of Chemical Reactions
 Rusting of iron
 Burning (combustion) of wood
 Cooking
o Vinegar + Baking soda ->
 Photosynthesis
o 6CO2 + 6H2O + Energy --> C6H12O6 + 6O2
Chemical reactions are like sentences.
Symbols  elements
Formula  compound
Equations  chemical reactions
Chemical reaction
 a reaction that occurs when the atoms of one
of more substances are rearranged to form
different substances
 a chemical change
Evidence of a chemical reaction
- Temperature change
- Color change
- Odor produced
- Formation of bubbles
- Appearance of a solid
Chemical Equations
2H2(g) + O2(g)
2H2O (l)
 Reactants: elements or compounds to the left of the arrow that
combine together in a chemical reaction
 Products: elements or compounds to the right of the arrow
that are produced in a chemical reaction
 Coefficient: whole number before a chemical formula
 Subscript: small lowered number after a chemical symbol
+
: represents “and”
: direction reaction progresses, yields or produces
C(s) + O2(g)
CO2 (g)
physical states of reactants and products are indicated by:
(s)
= solid: C(s)
(g)
= gas:
(l)
= liquid: H2O(l)
(aq)
= aqueous, dissolved in water,
NaCl(aq) is a salt water solution
(cr)
= crystalline
CO2(g)
= precipitate forms
Chemical Equations
2H2(g) + O2(g)
Identify the following and label
 Reactants:
 Products:
 Coefficient:
 Subscript:
 + define

define
2H2O (l)
Covalent Bonding
• A molecule is a neutral group of atoms
joined together by covalent bonds.
• Diatomic molecules – molecules made up
of the same element
Examples: O2 , H2 , N2, F2 , Cl2 , Br2 , I2
GEN-U-INE
Word and Formula Equations
 Skeleton equation represents the reactants and products
of a chemical reaction by their formulas.
Example: Na(s) + Cl2(g)
NaCl(s)
Balancing Chemical Equations
balanced chemical equation – shows that each side of the
equation has the same number of atoms of each element
and mass is conserved
2 Na(s) +
Cl2(g)
2 NaCl(s)
Law of conservation - in a chemical reaction matter is
neither created nor destroyed
 Chemical equations must be balanced using coefficients
Balancing Equations
1) ____ K + ____ Cl2  ____ KCl
2) ____ Ag + ____ O2  ____ Ag2O
3) ____ H2 + ____ O2  ____ H2O
4) ____ Na + ____ MgF2  ____ NaF + ____ Mg
5) ____ N2 + ____ H2  ____ NH3
Balance the following equations
Mg +
O2
KClO3 ---->
Na
---->
MgO
KCl + O2
+ MgCl2 ---->
NaCl
+
Mg
Word and Formula Equations
 A word equation is an equation represented by words.
Example: solid sodium plus chlorine gas reacts to produce
sodium chloride
Steps for Balancing Equations
1) Write skeleton equation: assemble the correct formulas
2) Count the number of atoms of elements in reactants
3) Count the number of atoms of elements in products
4) Balance the elements one at a time by adding
coefficients in front of a formula to make number of atoms
equal on both sides of equation
5) Check to make sure equation is balanced and
coefficients are in lowest possible ratio
Sample problems – Balancing Equations
Word Equation
Hydrogen plus oxygen yields water
Skeleton Equation
Balanced Equation
Sample problems – Balancing Equations
Word Equation
Fluorine plus calcium bromide yields calcium fluoride and bromine
Skeleton Equation
Balanced Equation
Water and iron react to form iron III oxide and hydrogen
Propane (C3H8) burns in oxygen to form carbon dioxide and water
Do-Now
 Identify and write the polyatomic ion using your ion
chart. Include charge!
1. sulfate –
3. hydroxide –
2. nitrate –
4. phosphate –
 Write the formulas for the following compounds. Must
show charge and crisscross!
1. Potassium oxide 3. Iron (III) hydroxide
2. Calcium chloride 4. Barium sulfate
Chapter 11
Chemical Reactions
11.1 Describing Chemical Reactions
11.2 Types of Chemical Reactions
11.3 Reactions in Aqueous
Solution
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
CHEMISTRY
& YOU
What happens to the wax when you burn
a candle?
When you burn a
candle, a chemical
reaction called
combustion takes
place.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
Classifying Reactions
What are the five general types of
reactions?
1.
2.
3.
4.
5.
Synthesis (or combination)
Decomposition
Singe-replacement
Double-replacement
Combustion
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
1. Synthesis Reactions (Combination)
Two (or more) reactants combine to form one product
general form:
A
+
B
AB
Fe
+
S
Fe+2S-2
specific types:
a) 2 elements
b) 2 compounds
c) 1 element, 1 compound
Ca+2O-2 + H2O
2SO2 + O2
Ca+2(OH)-12
2SO3
2. Decomposition Reactions
one reactant breaks down into two or more products
general form:
AB
Examples:
2Na+1N-3
3
Ca+2(CO3)-2
*decomposition reactions require energy
heat
--->
electricity --->
catalyst
--->
A
+ B
6Na +
N2
Ca+2O-2 + CO2
Classify each reaction as Synthesis or
Decomposition
1. _________________
2 Na + Cl2 ---> 2NaCl
2. _________________
CaCO3 ---> CaO + CO2
3. _________________
2H2O ---> 2H2 + O2
4. _________________
2CO +
O2
---> 2CO2
3. Single-Replacement
 A single-replacement reaction is one in which one element
replaces a second element in a compound
general form:
Ao
Example:
Zn + Cu+2(NO3)-1
general form:
B+C- +
Example:
2Na+Cl- + Br2
+
B+C-
Do
Bo +
2
A+C-
Cu + Zn+2(NO3)-1
B+D- +
Co
2Na+Br- + Cl2
2
2
4. Double-Replacement
3
general form: A+B- + C+D- ---> A+D- +
Ex.:
C+B-
Na+(2CO )3-2 + Ba+2Cl-1 ---> 2Na+Cl-1 + Ba+2(CO )-2
2
Specific type: Neutralization
Ca(OH)2 + 2HCl --->
base
+
acid
yields
CaCl2
salt
+
+
2H2O
water
3
Classify each reaction as Single Replacement or
Double Replacement
1. __________ Mg + Ag2SO4 --->
MgSO4 + 2Ag
2. __________ 2NaF + CaCO3 ---> Na2CO3 + CaF2
3. __________ SrBr2 + 2KOH
---> Ca(OH)2 + 2KBr
4. __________ 2LiCl +
--->
Br2
Cl2
+
2LiBr
Combustion Rxns
-a reactant (hydrocarbon) and oxygen, O2
react and release energy, heat, and/or light, and
products formed are CO2 and H2O
Ex:
CH4
+
2 O2
CO2 + 2 H2O
Endothermic and Exothermic
Reactions

We can indicate if energy was present in the reaction
 Reactions that have energy as a reactant are called
endothermic
- They require energy for the reaction to occur
- Also sometimes represented as → or →
heat
 Reactions that have energy as a product are called
exothermic
- Energy happens as a result of the reaction
Do Now Quiz on Balancing and Word Equations
Practice problems
1. Aluminum bromide + chlorine yield aluminum
chloride and bromine
2. Zinc nitrate + lead yield lead (II) nitrate + zinc
3. Potassium chlorate when heated yields potassium
chloride + oxygen gas