1. Unit: Chemical Reactions
Day 2 - Notes
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
Balance equations using the “tally method”
heat Pt

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

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

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

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

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

8. Do not separate polyatomic ions!
Examples: Balance the following equation:
___Fe2(SO4)3 + ___Na3(PO4)  ___Fe(PO4) + ___Na2(SO4) 2 3
Helpful tip:
Do not separate polyatomic ions! 2 2 Fe 1 2 3
(SO4) 1 3 6 3 Na 2 6 1
(PO4) 2 1 2
YES!!!!
Are we balanced?

9. Do now: Complete “Exit Ticket”
Then: Begin WS 2 (Homework)