1. Do Now – 5 minutes Do your Do Now on the back of your worksheet (on front desk) 1. According to the law of conservation of mass, the number of atoms on the reactants side and the products side must be __________________. 2. Make a T-chart for the reactants and the products in this equation: 2 H 2 + O 2  H 2 O According to your t-chart, is the equation balanced or not?

2. Announcements Not a passing grade on your progress report?  See me right after class or one at a time during independent practice

3. Balancing Equations WHY do scientists do it? HOW will I be able to do it?

4. Balancing Equations KP #1: A balanced chemical equation obeys the law of conservation of mass – there must be the same number of atoms of each element on each side of the equation!

5. Balancing Equations KP #2: When balancing a chemical equation, never, never, NEVER change the subscripts. Only change coefficients! Remember – subscripts are the small numbers and coefficients are the big numbers. You multiply the coefficient by the subscript to get the number of atoms on each side of an equation.

6. Balancing Equations Steps to balance a chemical equation: 1. List out the t-charts for each side of the chemical equation 2. Determine if the equation is balanced or not 3. Change coefficients in the equation to make the number of atoms on each side of the equation match – balance one element at a time! 4. Leave Oxygen and Hydrogen atoms for last. 5. Make sure to update your t-charts each time you change a coefficient.

7. Balancing Equations Don’t get discouraged – balancing equations is a game of trial and error. It might not work the first time, but you have to keep trying to get it right!

8. List out the t-charts for each side of the chemical equation HgO ---> Hg + O 2 Reactants:Products: Hg - 1Hg - 1 O – 1O - 2

9. Determine if the equation is balanced or not HgO ---> Hg + O 2 Reactants:Products: Hg - 1Hg - 1 O – 1O - 2 NOT BALANCED!

10. Change coefficients in the equation to make the number of atoms on each side of the equation match – balance one element at a time! Update your T-chart 2 HgO ---> Hg + O 2 Reactants:Products: Hg - 2Hg - 1 O – 2O - 2 STILL NOT BALANCED!

11. 2 HgO ---> 2 Hg + O 2 Reactants:Products: Hg - 2Hg - 2 O – 2O - 2 Let’s see another example

12. Worksheet time! ___ C 2 H 6 + ____ O 2  ____ H 2 O + ____ CO 2 ____KOH + ____ H 3 PO 4  ___K 3 PO 4 + ___H 2 O ____SnO 2 + ____ H 2  ___Sn + ____H 2 O ____NH 3 + ____O 2  ____NO + ____ H 2 O