Catalyst Get paper out for notes! 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?

Today’s Agenda 5 min Catalyst 20 min Balancing Equations 25 min Practice 5 min Exit Slip

Balancing Equations  WHY do scientists do it?  HOW will I be able to do it?  WHY do I need to be able to do it?

Balancing Equations  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!

Balancing Equations  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.

Balancing Equations Steps to balance a chemical equation: 1. Make a T-chart and check if the equation is balanced 2. Balance one element at a time by changing coefficients in the equation 3. Update your T-chart each time you change a coefficient!!!!! *Leave Oxygen and Hydrogen atoms for last.

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!

Example List out the t-charts for each side of the chemical equation …HgO  …Hg + …O 2 Reactants:Products: 1Hg 1 1O 2

Example  Determine if the equation is balanced or not …HgO  …Hg + …O 2 Reactants:Products: 1Hg 1 1O 2 NOT BALANCED!

Example  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 HgO ---> Hg + O 2 Reactants:Products: 2Hg 1 2O 2 STILL NOT BALANCED! 2

Example 2 HgO ---> Hg + O 2 Reactants:Products: 2Hg 2 2O 2  Let’s see another example 2

Example 2 …N 2 + …H 2  …NH 3

Example 3 __CH 4 + __O 2 --> __CO 2 + __H 2 O

__ NaCl + __ BeF 2  __ NaF + __ BeCl 2

Today’s Agenda 5 min Catalyst 20 min Balancing Equations 25 min Practice 5 min Exit Slip

Today’s Agenda 5 min Catalyst 20 min Balancing Equations 25 min Practice 5 min Exit Slip

1. In the chemical formula, 6 C 2 H 4, what does the 6 mean? a. there are 6 atoms of hydrogen (H) b. there are 6 atoms of carbon (C) c. there are 6 molecules of dicarbon tetrahydride d. there are 6 inches of dicarbon tetrahydride 2. Which law tells us that there must be the same amount of products and reactants? 3. Balance the equation HgO  Hg + O 2

Exit Slip 4. When the equation _3 _ C + __ H 2  __ C 3 H 8 is completely balanced, what is the coefficient of H 2 ? a. 1 b. 2 c. 4 d True or false: You can change the subscripts of a chemical equation to balance it.