1. Unit: Chemical Reactions
Balancing chemical equations
Upper left: Thermite reaction, Fe2O3 + Al => 2Fe +2Al2O3 + HEAT!!!
Upper right: potassium in water, K + H2O => KOH + H2 + HEAT
Bottom right: potassium chlorate and sugar, C12H22O11 + 8KClO3 => 12CO2 + 11H2O + 8KCl + HEAT!!!
Bottom left: magnesium reacting with oxygen, Mg + O2 => MgO

2. After today you will be able to…
Explain the Law of Conservation of Atoms
Differentiate between endothermic and exothermic reactions
Balance equations using the “tally method”
heat Pt

3. Chemical Reaction: When substances undergo chemical changes to form new substances.

4. Chemical Energy: The energy released when a chemical compound reacts to produce new compounds.

5. Exothermic Reaction: A chemical reaction in which heat is released to the surroundings.

6. Endothermic Reaction: A chemical reaction that requires heat, or pulls heat from the surroundings.

7. Law of Conservation of Atoms: There must be the same number of each type of atom before the reaction as after the reaction.

8. Coefficients: Numbers that go in front of each substance to indicate the number of atoms or molecules that are reacting or being produced.

9. Subscripts: Numbers that go after a substance to indicate the number of atoms or molecules immediately before the subscript.

10. Reactants: What is being “mixed” together in a reaction and are located on the left side of the equation

11. Products: What is produced from the chemical reaction and are located on the right side of the equation

12. Balancing Rule #1: Balance all METALS first

13. Balancing Rule #2: Balance all NONMETALS second

14. Balancing Rule #3: Balance all CARBON third

15. Balancing Rule #4: Balance all HYDROGEN fourth

16. Balancing Rule #5: Balance all OXYGEN last

17. Balancing Rule Add-on: Any time you have a polyatomic ion that is the same on both sides of the equation, balance it as one “thing”

18. Let’s try some examples! 
We will be using the “tally method” to balance equations in this class.

19. If the numbers match on either side… You’re balanced!
Examples: Balance the following equation:
___ Al + ___S  ___Al2S3
Products
Reactants 2 3 2 1 Al 2 3 1 S 3
If the numbers match on either side… You’re balanced!

20. ___ Li + ___O2  ___Li2O Examples: Balance the following equation: 4 21 Li 2 4 2 O 1 2

21. ___Fe2(SO4)3 + ___Na3(PO4)  ___Fe(PO4) + ___Na2(SO4)

22. ___C2H6 + ___O2  ___CO2 + ___H2O