Take out your Homework.
 Identify the reactants and products in
the following chemical reaction
equations:

› 2 Mg (s) + O2 (g)
› CH4 (g) +


2 MgO (s)
2 O2 (g)  CO2 (g) + 2 H2O (l)
Write the chemical reaction equation for the
following description:
› Hydrogen gas and oxygen gas combine to form
liquid water.
Take out your Homework.
 Identify the reactants and products in the
following chemical reaction equations:

› 2 Mg (s) + O2 (g)
2 MgO (s)
› CH4 (g) + 2 O2 (g)  CO2 (g) + 2 H2O (l)
› Reactants are on the left and products on the
right of the arrow.

Write the chemical reaction equation for the
following description:
› Hydrogen gas and oxygen gas combine to form liquid
water.
› 2 H2 (g) + O2 (g)  2 H2O (l)

I can compare and contrast different
types of chemical reactions.

I can define and identify a balanced
chemical equation.

I can balance simple chemical
equations.
Catalyst (10)
 Balancing Notes & HW Review (20)
 Group Work: Balancing Chemical
Equations. (40)
 Types of Chemical Equations Reading
Activity (40)

› Group Work (20)
› Presentations & Debrief (20)

Exit Slip (10)

Matter cannot be created or destroyed in a
chemical reaction

The number of atoms on the reactant side must
equal the atoms of the products
H2 (g) +
H H
O2 (g) 
H2O (l)
O O
H O H
H H
Unbalanced!
H O H
Balanced!

A chemical equation is “balanced” when
there are the same number of atoms of each
element on both sides of the arrow.
NaHCO3 (s) + HC2H3O2 (aq) NaC2H3O2 (aq) +
CO2 (g) + H2O (l)
Is it balanced?
Reactants
Products
Na = 1
Na = 1
H=5
H=5
C=3
C=3
O=5
O=5
Determine the number of atoms of each
element in the reactants and products.
Then, state whether the equation is
balanced.
1. P4 + O2 → P2O5
Not balanced.
2. C3H8 + O2 → CO2 + H2O Not balanced.
3. Ca2Si + Cl2 → CaCl2 + SiCl4 Not balanced.
4. Si + CO2 → SiC + SiO2 Not balanced.

coefficient
2 H (g) +
2
H= 2
O= 2

4
O2 (g)  2 H2O (l)
H= 2
4
O= 1
2
Only the coefficients can be
changed!
Always balance non-Oxygen’s &
Hydrogen’s first (ex. Chlorine)
 Then balance Hydrogens
 Balance Oxygens Last

1.
P4 + O2 → P2O5
P4 + 5 O2 → 2 P2O5
C3H8 + O2 → CO2 + H2O
C3H8 + 5 O2 → 3 CO2 + 4 H2O
3. Ca2Si + Cl2 → CaCl2 + SiCl4
2.
Ca2Si + 4 Cl2 → 2 CaCl2 + SiCl4
4.
Si + CO2 → SiC + SiO2
2 Si + CO2 → SiC + SiO2

Instructions:
› Work with the person next to you.
› You have two worksheets to work on.
 1. “Is it balanced?” Determine whether the
chemical equation is balanced by counting
atoms in the reactants and products.
 2. “Balancing Act” Practice balancing equations.
› What you do not finish is homework.
› Ms. Boon will stamp your work when you are
done.
› Once you have a stamp, you may check your
answers on the posted answer sheet.
Atoms are not created or destroyed
during a chemical reaction.
 Scientists know that there must be the
same number of atoms on each side of
the equation.
 To balance the chemical equation, you
must add coefficients to the different
parts of the equation.




You will work in groups of four or five at your
table.
Fold a sheet of paper into four squares.
Label each square:
1.
2.
3.
4.





Synthesis reaction
Decomposition reaction
Single Replacement Reaction
Double Replacement Reaction
You will be assigned one reaction.
Read the section on that reaction, define it,
give an example, and draw a picture in your
chart. (7 min)
Take turns sharing with your group. (8 min)
Take notes on the other 3 reactions.
If you finish early, read the entire article.
Two substances combine to make one
 Synthesis means “to make”

H2 (g)+ O2(g) 
H H
H H
O O
H O O
H
H
H
H2O(l)
SYNTHESIS
Na + Cl2  NaCl
One substance breaks down into 2
 Decomposition means “to break down” or
“decay”

NH3 (l)  N2 (g) + H2 (g)
H
N
H
H
H
N
H
H
Decomposition
NaCl  Na + Cl2
3. SINGLE
REPLACEMENT
AB + C  AC + B
Single Replacement
NaBr + Cl2  NaCl + Br2
Both elements in two
compounds switch places
AB + CD  AD + CB
Double Replacement
NaBr + Pb2S3  Na2S +
PbBr3
K2SO4 + Ba(OH)2 KOH + BaSO4
A hydrocarbon reacts with oxygen gas to
produce carbon dioxide and water vapor
 Combustion means to “burn in oxygen”

CH4 + O2  CO2 + H2O
C2H4 + O2  CO2 + H2O
C6H12O6+ O2  CO2 + H2O
1.
Mg
+
O2 
MgO
2.
C3H8
+
O2 
3.
Na
+
Cl2 
4.
C6H6  C + H2
5.
FeO
CO2
+ H2 O
NaCl
+ CO2  FeCO3
Read pp. 271-274
 Do problems pp. 271 #1-3, pp. 298 #1, 2,
3, 5, 6, 7
