November 14, 2012
Name: ____________________________________ Period: ____
Competency
2a
Identify patterns found in chemical symbols, formulas, reactions, and
equations that apply to the law of conservation of mass. (DOK 1)
8th – Lesson 1.8
I can determine if a simple chemical equation is balanced.
Unit 4 – Chemistry: Balancing Chemical Equations
Daily Question: When two substances react, can atoms disappear?
Quick Review of Chemical Reactions:
1. Process where chemical substances change into new substances = chemical reaction
2. Substances that are started out with before a reaction occurs = reactants
3. Substances that are ended with after a reaction occurs = products
4. A simplified explanation of a reaction using chemical symbols = chemical equation
For the following use the chemical equation Br + NaO  NaBr + H2O
5. Reactants = Br and NaO
6. Products = NaBr and H2O
7. Does this obey the Law of Conservation of Mass = No, H is products but not in the reactants.
Key Points on Balancing Chemical Equations:
1. What: Chemical equations must have the same number of each type of atom in the
reactants as in the products.
a. If there are a total of four oxygen atoms in the reactants, there must be a total
of four oxygen atoms in the products.
b. If each type of atom has the same number on both sides of the reaction, it is
said to be balanced.
2. Why: Matter cannot be created or destroyed so if it exists in the reactants it must also
be in the products.
a. The idea that matter cannot be created or destroyed is the Law of Conservation
of Mass. We can’t violate LAWS!
3. How
a. We can list all of the different types of atoms in the reactants
b. We then list all the different types in the products.
c. We can then compare by counting to see if we have the same number of each
type of atom in the reactants and products.
i. If there are the same type and number, the equation is balanced.
ii. If there are a different number or extra types of atoms, the equation is NOT
balanced.
Balancing Chemical Equations: Guided Practice
1. Is the chemical equation HBr + NaOH  NaBr + H2O balanced?
a. List the different types of atoms and the number of each type in the reactants.
b. List the different types of atoms and the number of each type in the products.
November 14, 2012
Name: ____________________________________ Period: ____
Competency
2a
Identify patterns found in chemical symbols, formulas, reactions, and
equations that apply to the law of conservation of mass. (DOK 1)
8th – Lesson 1.8
I can determine if a simple chemical equation is balanced.
Unit 4 – Chemistry: Balancing Chemical Equations
Daily Question: When two substances react, can atoms disappear?
Quick Review of Chemical Reactions:
1. Process where chemical substances change into new substances =
2. Substances that are started out with before a reaction occurs =
3. Substances that are ended with after a reaction occurs =
4. A simplified explanation of a reaction using chemical symbols =
For the following use the chemical equation Br + NaO  NaBr + H2O
5. Reactants = and
6. Products =
and
7. Does this obey the Law of Conservation of Mass =
Key Points on Balancing Chemical Equations:
1. What: Chemical equations must have the
of
of atom in the
as in the
.
a. If there are a total of
oxygen atoms in the reactants, there must be a total of
oxygen atoms in the products.
b. If each type of atom has the same number on both sides of the reaction, it is said to be
.
2. Why:
cannot be
or
so if it exists in the reactants it
must also be in the products.
a. The idea that matter cannot be created or destroyed is the
of
of
. We can’t violate LAWS!
3. How
a. We can
all of the
of atoms in the
b. We then
all the
in the
.
c. We can then
by
to see if we have the
of each type of atom in the reactants and products.
i. If there are the same type and number, the equation is
.
ii. If there are a different number or extra types of atoms, the equation is
balanced.
Balancing Chemical Equations: Guided Practice
1. Is the chemical equation HBr + NaOH  2NaBr + H2O balanced?
a. List the different types of atoms and the number of each type in the reactants.
b. List the different types of atoms and the number of each type in the products.
2. Is the chemical equation CH4 + O2  CO2 + 2H2O balanced?
a. List the different types of atoms and the number of each type in the reactants.
b. List the different types of atoms and the number of each type in the products.
November 14, 2012
Name: ____________________________________ Period: ____
Balancing Chemical Equations: Independent Practice
Directions: Answer the questions using the picture that is directly to the left of those questions in the
same row. MONEY TALK APPLIES! Write like you are a successful person using professional language
and complete sentences.
1. Key Point #1: Describe how the products and reactants in a chemical reaction must be
similar.
2. Key Point #2: Why can there not be different types of atoms in the reactants and
products?
3. Key Point #3: What are the steps to go through when checking to see if a reaction
equation is balanced?
4. Is the chemical equation Na + Cl 2  NaCl balanced? Why or why not?
5. Is the chemical equation 2H2O2  2H2O + O2 balanced? Why or why not?
6. Is the chemical equation AgNO3 + MgCl2  AgCl + MgNO3 balanced? Why or why not?
7. Is the chemical equation CH4 + 2O2  CO2 + 2H2O balanced? Why or why not?
8. Daily Question: When two substances react, can atoms disappear?