1. Balancing Equations
a. Add coefficients to make atoms the same on both sides b. Must balance Metals first, then Non-metals, followed by Hydrogen, and Oxygen last (“met nine hairy oxen”) c. Adjust totals to account for the addition of your coefficient d. Continue to add coefficients and make adjustments until all elements are balanced

2. Balancing Hydrocarbons
Divide H subscript by 2. IF it is odd or a fraction, then multiply the hydrocarbon by 2.
IF it is not odd, do not multiply by 2, but go to step 3.
Then balance in the order C, H, O, and lastly O2
C18H34O2 + O2  H2O(g) + CO2(g)
C3H6O2 + O2  H2O(g) + CO2(g)
Oleic Acid 2 52 34 36
Propionic Acid 2 7 6 6

3. Chemical Reactions

4. Chemical Reaction
a process in which a substance(s) is changed into one or more new substances

5. Chemical Equation
uses chemical symbols to show what happens during a chemical reaction; standard way of representing chemical reactions;
chemists shorthand description of a reaction

6. Chemical Symbols
1. + = reacts with, and, can combine 2.  = to produce, yield, to form; the reaction is assumed to proceed from left to right as the arrow indicates 3. = heat 4. Subscript = tells how many atoms of an element are present (smaller and to the right of the number) 5. Coefficient = multiplier (larger number to the left of the number)

7. Chemical Symbols 6. Physical states a. (s) solid b. (l) liquid
c. (g) gas
d. (aq) aqueous - (dissolved in water)

8. Balanced Chemical Equations
After writing a skeleton equation:
to conform with the law of conservation of mass, there must be the same number of each type of atom on both sides of the arrow
we must have as many atoms after the reactions ends as we did before it started
to balance a chemical equation place coefficients in front of reactants and/or products

9. “to produce” or “yield”
Chemical Equations
2 H2 (g) + O2 (g) H2O (l)
coefficient
Product(s)
Reactants
“Reactants with”
“to produce” or “yield”
State of matter

10. Interpretation 2 H2 + O2 → 2 H2O Two molecules One molecule 2 moles
2(2.02 g)
32.00 g
2 (18.02 g)
36.04 g reactants
36.04 g product

11. Reactants and Products
Reactants—starting materials in a chemical reaction; written on the left of the arrow
2. Products—substance formed as a result of a chemical reaction; written on the right of the arrow

12. Evidence Temperature change Color change Odor Gas/bubbles
Appearance of a solid (precipitate)
**difference in composition before and after

13. Types of Reactions Synthesis (or Combination)
Two or more substances react to produce a single product

14. Decomposition
A single compound breaks down into two or more new elements or compounds  +

15. + Single-replacement (or single-displacement)
atoms of one element replace the atoms of another element in a compound + 
Like a “girlfriend thief”

16. Double-replacement (or double-displacement)
When there is an exchange of ions between compounds 
Like “Wife Swap”

17. -a substance combines with oxygen (O2) and releases energy
Combustion
-a substance combines with oxygen (O2) and releases energy
-Oxygen is always a reactant!
2H2(g) + O2(g)  2H2O(g)
Hydro carbon
+ O2(g)  CO2(g) + H2O(g)
Wax is made of carbon and hydrogen atoms bonded together in long chains. The chains are tangled, intertwined and packed together to make the wax.

18. Use S, D, SR, DR or C for abbreviations Al2O3 → Al + O2
Mg + O → MgO
Al2O → Al O2
CuCl H2S → CuS HCl
Cl NaBr → NaCl Br2
CH O2 → CO2 + H20 C S D DR SR
Wax is made of carbon and hydrogen atoms bonded together in long chains. The chains are tangled, intertwined and packed together to make the wax. C

19.  Reactions Key H2O = liquid (l) unless told other state of matter
solution = aqueous = (aq)
gas or vapor = (g)
metal, powder, particles or solid = (s)
heat, burned =  ∆

20. Skeleton equations are not balanced using coefficients
It is a translation from words to formulas only
Most times states of matter are given in the words stated

21. Skeleton Equation (not balanced)
Sodium metal = Na(s)
Reacts with = +
Water = H2O(l)
(use l for water unless you know it forms a gas or solid)
Forming = 
Sodium hydroxide solution = NaOH (aq)
(aq because it said solution)
Hydrogen gas = H2(g)
Na(s) + H2O(l)  NaOH (aq)+ H2(g)