1. Today’s Objective The student will be able to recognize if a chemical equation is balanced by counting atoms on reactant and product side.

2. Chemical Equations A chemical equation is a shorthand description of a chemical reaction Uses chemical formulas and symbols.

3. Chemical Reactions Reactants - substances being mixed Products – new substances that are made after chemical reaction

4. Chemical Equations C + O 2 = CO 2 C + O 2 are reactants CO 2 is the product

5. Coefficients A number placed in front of a chemical symbol or formula. Example 2NaCl The “2” is the coefficient

6. Purpose of Coefficients Used to balance equations Must have equal # of atoms of each element on both sides of the equation

7. Subscripts Can’t be changed when balancing equations It would change the mass ratio of the compound and be a different compound Example H 2 O The 2 is the subscript. It shows that there are 2 hydrogen for every one oxygen.

8. Law of Conservation of Mass During a chemical reaction, atoms are neither created nor destroyed. The number of atoms doesn’t change The mass or weight doesn’t change.

9. Conservation of Mass and Balancing Equations There should be the same number of atoms on the reactant side as on the product side.