Date:
Questions
EQ: What are the parts of chemical equation? What is equal about equations?
Why and How are the equations balanced?
ENGAGE – Lego (or Skittles) activity
A Chemical equations are NOT accurate in terms of QUANTITY (how much)
of each reactant and product. The Law of Conservation of Mass must be
met: matter can NOT be created nor destroyed in a chemical reaction.
B
Parts of a chemical equation:
What is a “balanced”
chemical equation?
to yield = form=produce
4Al + 3O2  2Al2O3 (s)
coefficient
subscripts
states of matter
(# of molecules) (# of atoms) (s, l, g, aq – aqueous solution)
REACTANTS
What is the evidence
that chemical reaction
took place?
When a chemical
reaction is called
“balanced”?
PRODUCT
C
How have the atoms of the reactants been rearranged in the products of
the reaction below?
C + O2  CO2
C + O=O  O=C=O
BREAK FORM
-Bonds between the oxygen atoms have been BROKEN
-NEW BONDS have formed between the carbon atom and two O atoms.
D
Count the number of atoms of each element below:
O2: O=2 atoms
H2O: H = 2 atoms, O=1 atom
Mg(NO3)2: Mg = 1, N=2, O=6
Count the number of molecules below:
O2 = 1 molecule of oxygen gas
2H2O= 2 molecules of water
17HCl = 17 molecules of HCl
E
A balanced chemical equation is one in which each side of the equation
has the same number of atoms of the same kind on both sides.
Example: C (s) + O2 (g) → CO2 (g)
(balanced)
1 C
2 O
H2 (g) +
O2 (g) → H2O (l)
2 H
2 O
What are the only
numbers that you can
manipulate when
balancing equations?
F
1 C
2 O
(not balanced)
2 H
1 O
To balance chemical equation, you must add COEFFICIENTS (big
numbers) in front of the chemical formulas in the equation. You cannot
add or change subscripts!!! Why? B/c it will alter the identity of the
substance otherwise.
When is oxygen
balanced?
G Rule: Balance oxygen – O, last. If hydrogen present instead – same rule.
H Balancing with shapes:
_____H2 + ____O2  ____H2O
You try!
____ Al2O3  ___Al + ____O2
Coefficient ratio:
Balancing using T-chart:
_____H2 + ____O2  ____H2O
Coefficient ratio:
You try!
____ Al2O3  ___Al + ____O2
R
P
Coefficient ratio: ___________
R
P
Coefficient ratio: _________
You try! (Use shapes of T-chart)
___Fe + ____O2  ____Fe2O3
R
P
Coefficient ratio: __________
I
WE (with teacher)
a. ___P4 + ____O2 _____ P4O6
Coefficient ratio: _______
b. ____AgNO3(aq) + ___Cu(s)  ___Cu(NO3)2(aq) + ____Ag(s)
(Hint: treat “NO3” as one element )
Coefficient ratio: _______
YOU (with a partner)
c. ____C + ______H2  ____CH4
Coefficient ratio: _______
d. ____Cu2O + ____C _____ Cu +_____ CO2 Coefficient ratio: _____
I (independent practice)
e. ___H2O2 ___H2 + ___ O2
f.
____Cl2 + ____KI  ____KCl + ____I2
Challenge (choose your method to balance):
CH4 + O2  CO2 + H2O
Summary
Coefficient ratio: _______
Coefficient ratio: _______