1. Rules for balancing equations
Bell Ringer
(Copy in your notebook on NEXT CLEAN PAGE (in notes section).
Rules for balancing equations
You can’t change or add a subscript.
You can only add coefficients (numbers at the beginning of the formula, after plus sign, or after arrow).
There should be the same atoms on both sides.
Both sides should be equal (balanced).

2. ALCOS Objectives:
#1- Identify the steps of the scientific method
#4 State the law of conservation of matter (Balancing Chemical Equations)

3. Chapter 6 Section 2 : Describing Chemical Reactions

4. Chemical Equations
Use chemical formulas and other symbols instead of words to summarize a reaction.

6. Conservation of Mass
The principle of conservation of mass states that in a chemical reaction, the total mass of the reactants must be equal to the total mass of the
product.

7. A Balanced Chemical Equation
Same numbers of each type of atom on each side of the equation.
Al S Al2S Not Balanced
2Al S Al2S Balanced

8. Balance Equations with Coefficients
Coefficients in front of formulas balance each type of atom.
4NH O NO + 6H2O
4 N = 4 N
12 H = 12 H
10 O = 10 O

9. Steps in Balancing An Equation
Fe3O H Fe H2O
Fe: Fe3O H Fe H2O
O: Fe3O H Fe H2O
H: Fe3O H Fe H2O

10. Exothermic energy – heat energy is being released.
Endothermic energy – heat energy being absorbed.
Ex. Baking something
Exothermic energy – heat energy is being released.
Ex. Burning something

11. Let’s Try These… Balance these equations
Fe + H2O → Fe3O4 + H2
C + H → CH4
Zn + Ag2S → ZnS + Ag
Ag2O → Ag + O2
Cl2 + NaBr → NaCl + Br2
K2CO3 + CaCl2 → CaCO3 + KCl
AgNO3 + NaI → AgI + NaNO3