Transcript Balancing Chemical Equations

BALANCING CHEMICAL
EQUATIONS
DAILY OBJECTIVE
• The students will apply the law of
conservation of mass to balance a
chemical reaction.
KEY TERMS
1. Chemical Equation: A representation of a
chemical reaction that uses symbols to
show relationships between reactants and
products.
2. Reactants: A substance or molecule that
participates in a chemical reaction.
-What you start with
-Left side of arrow
3. Products: A substance that is formed in a
chemical reaction.
-What you end with
-Right side of arrow
LABEL THE PARTS
+
+
Methane + Oxygen
CH4
+
O2
Carbon
Dioxide + Water
CO2
+
H 2O
LAWS OF SCIENCE
• Law of Conservation of Mass: Mass cannot be
created or destroyed, it can only change forms.
• Mass has to be the same on both sides of the
reaction
• The number of atoms has to be the same for the
products and reactants.
• What you start with, you must end with
VIOLATION OF THE LAW OF
CONSERVATION OF MASS
CH4
+
Reactants
C=
H=
O=
O2
CO2
+
H2 O
Check the Number of Atoms:
Products
C=
H=
O=
HOW TO BALANCE EQUATIONS
1. You MUST have the SAME number of
atoms of each element on the right and
left hand side of the arrow.
2. You CANNOT change the chemical
formulas.
3. LEAVE THE SUBSCRIPTS ALONE!!
4. To balance an equation we have to use
coefficients (numbers placed in front of
the compounds or elements).
COEFFICIENTS
• Coefficients go in front of a compound
4H2O
-All atoms in a compound are multiplied by
the coefficient
Number of atoms:
HydrogenOxygen-
PRACTICE WITH COEFFICIENTS
*List the amount of each atom in the 6 substances below:
4CH4
2O2
3Ni(NO3)2
3NH3
6HF
4Ca3(PO4)2
STEPS TO FOLLOW TO BALANCE
EQUATIONS
1. Determine the number of atoms for each
element.
2. Pick an element that is not equal on both
sides of the equation.
3. Add a coefficient in front of the formula
with that element and adjust your counts.
4. Continue adding coefficients to get the
same number of atoms of each element
on each side.
LET’S PRACTICE
Mg +
O2
MgO
Mg =
Mg =
O=
O=
MORE PRACTICE
CH4 +
O2
CO2 +
C=
C=
H=
H=
O=
O=
H2O
LET’S TRY ONE MORE 
Na2S +
AgNO3
NaNO3 +
Na =
Na =
S=
S=
Ag =
Ag =
N=
N=
O=
O=
Ag2S