1. Science Starter
Write a letter (at least 4 sentences) to a student who was absent Friday. What did we learn? Make sure to include the following words:
Products Reactants
Synthesis Decomposition
Single Replacement -Double Replacement
Combustion -Oxidation
Reduction
Take out your HW!

2. Objective
SWBAT count atoms in chemical reactions and balance them, as per the Law of Conservation of Mass.

3. Agenda Science Starter Balancing Equations Exit Ticket/Homework
Law of Conservation of Mass
Counting Atoms
What is oxidized and reduced?
Exit Ticket/Homework
Lab Wednesday
Test Friday
Midterm Tues/Wed
*No tutorial today*

4. What’s up with the apples?

5. How ‘Bout Them Apples

6. Chemical Reactions  Br Br Br Br Li Li Li Li

7. For the rest of today, we will be balancing chemical equations.
This will seem like a bunch of rules a chemist made up unless you understand the following concepts.

8. Unit 4: Chemical Reactions Counting Atoms Balancing Equations

9. Chemical Reaction Notes
1. Law of Conservation of Mass: in a chemical reaction, the mass of the products equals the mass of the reactants.
What is the Law of Conservation of Matter?
2. Chemical reactions MUST BE BALANCED
The number of atoms on the reactant side and the product side must be EQUAL
But how do we count the number of atoms?

10. Counting Atoms Rules 3P6Cl3
1. Subscripts apply ONLY to the element before
Ex) MgCl2 #Mg ____ #Cl_____
2. Coefficients multiply the entire molecule
Ex) 2C6H2 #C___ #H____

11. Counting Atoms Rules
3. If there are parentheses, the subscript multiples everything inside the parentheses
Ex) 3Be(NO3)2 #Be___ #N____ #O____

12. Counting Atoms 1. H2SO4 2. Ca(OH)2 3. 4NaCl 4. 2(NH3)3PO4 5. 3H2O
How many atoms of each element are in the following molecules?
1. H2SO4
2. Ca(OH)2
3. 4NaCl
4. 2(NH3)3PO4
5. 3H2O

13. To decide if an equation is balanced, compare the number of atoms of each element that appear on each side of the equation. If the number of atoms is equal then the equation is balanced, if not equal than the equation is not balanced
Ex) N2 + 3 H2  2 NH3
Is it balanced?

14. You Try!
C3H8 + 5 O2  3 CO2 + 4 H2O
Is is balanced?

15. Ok, cool.
BUT HOW DO WE BALANCE THESE BAD BOYS????!!!

16. (never change subscripts!)
When balancing…
Step 1: Draw a line between products and reactants
Step 2: Tally up atoms of each element on each side
Step 3: Change coefficients to start balancing
(never change subscripts!)
Step 4: Recalibrate each time you change a coefficient
Step 5: CHECK YOUR WORK!

17. Balancing Chemical Reactions
Notes
Balancing Chemical Reactions
Ex 1: ____N2 + ____H2  ___NH3
What is oxidized?
What is reduced?

18. Balancing Chemical Reactions
Notes
Balancing Chemical Reactions
Ex 2: ____FeO  ____Fe ____O2
What is oxidized?
What is reduced?

19. ____Fe + ____Cl2  ___FeCl3 4. ____CH4 + ____O2  ___CO2 + ___H2O
The best way to learn this is to practice.
With a partner, balance the following equations:
____NO + ____O2  ___NO2
____H2 + ____Cl2  ___HCl
____Fe + ____Cl2  ___FeCl3
4. ____CH4 + ____O2  ___CO2 + ___H2O
What is oxidized?
What is reduced?

21. Partner Practice
1. ____NO + ____O2  ___NO2

22. Partner Practice
2. ____H2 + ____Cl2  ___HCl

23. 3. ____Fe + ____Cl2  ___FeCl3
Partner Practice
3. ____Fe + ____Cl2  ___FeCl3

24. 4. ___CH4 + ___O2  ___CO2 +___H2O
Partner Practice
4. ___CH4 + ___O2  ___CO2 +___H2O

25. Independent Practice
For the rest of class, work on (and complete, if possible) Worksheet 4.2 If you get done: come and see me. If you are done, I will have you check your answers against my answer key. If you get any wrong, you must go back and fix them. If you get done with that: You may help a neighbor