1. Balancing Equations- Intro and Notes

2. Think about it Baking a cake
Cake mix
3 eggs
1/3 cup of vegetable oil
When you bake it, do you gain or lose ingredients??

3. Agenda
Drill
Balancing Equations with Pipecleaners and Beads
Notes and Practice
Exit Slip

4. Looking at a chemical equation…

5. Before Moving On…
How many aluminums are in Al(NO3)3?
How many nitrogens are in Al(NO3)3?
How many oxygens are in Al(NO3)3?

6. Instructions You will work on 5 different equations with a partner
To balance equations, you need the same number of each type of atom on the reactants side and products side
Use the beads and coding sheet (explaining which color represents each bead) to diagram each reaction

7. Keep track of the number of atoms on each side of the reaction
Manipulate the reactants and products until you reach the same number of atoms on each side. Add numbers to the blanks that match your work!

8. Example
_____H _____O  _____H2O
Reactants
Products H O

9. Before moving on… 12 Blue Beads 16 Pink Beads 6 Red Beads
12 Green Beads
4 Orange Beads
4 Yellow Beads
4 Purple Beads
14 Pipecleaners

10. What is YOUR Definition of the Law of Conservation of Mass???

11. Law of Conservation of Mass
Mass in an isolated system is neither created nor destroyed by chemical reactions or physical transformations.
AKA: The mass of the products in a chemical reaction must equal the mass of the reactants.

13. How is balancing an equation like baking a cake?
Question
How is balancing an equation like baking a cake?

14. Soo… Why Balance Equations???
Law of Conservation of Mass!!!
In order for the mass to remain the same, the number of atoms of each element must be the same before and after a chemical reaction

15. Try Balancing On Your Own
In your groups…
Balance the equations given
On the whiteboard, write the steps (in words) of how you would balance an equation

16. What are your Steps?

17. Answers
N2 + 3 H2  2 NH3 S8 + 8 O2  8 SO2 2 AlBr3 + 3 Cl2  2 AlCl3 + 3 Br2 4 Cr + 3 O2  2 Cr2O3 BaCl2 + (NH4)2CO3  BaCO3 + 2 NH4Cl

18. Steps for Balancing
Count the number of atoms of each type appearing on both sides
Balance the elements one at a time by adding coefficients
Check to make sure it is balanced

19. Add a subscript to make an equation balanced?
Can I…???
Add a subscript to make an equation balanced?
Think about…
H2 + O2  H2O

20. NEVER!!!!! Change a subscript to balance an equation
If you change the formula you are describing a different reaction
H2O is a different compound than H2O2
Never put a coefficient in the middle of a formula
2 NaCl is okay, Na2Cl is not
Never have a fraction as a coefficient
½ H2 is not okay

21. Helpful Hints
First balance elements that occur in the fewest formulas; oxygen and hydrogen are usually balanced last
Coefficients must be whole numbers and reduced to the lowest ration
If you get 4-2-2, divide all numbers by 2 to get 2-1-1
Polyatomic ions often remain intact during a chemical reaction, so they can be treated as single entities

22. Helpful Hints Continued
Sometimes you will insert a coefficient but later determine it is wrong, so you will have to take it out and reinsert a new coefficient
If it appears there is no possible solution using whole number coefficients, multiply the entire equation by 2

23. What’s Next
Exit Slip
Continue to practice balancing equations

24. Practice
__ H2 + ___ O2  ___ H2O
__ SO2 + ___ O2  ___ SO3

25. Answers
N H2  2 NH3
2 SO2 + O2  2 SO3