1. Introduction to Chemical Reactions

2. Learning Targets Be able to interpret Chemical Equations. Be able to interpret Chemical Equations. Be able to balance Chemical Equations. Be able to balance Chemical Equations. Prove The Law of Conservation of Mass showing that matter is never created or destroyed in a chemical reaction. Prove The Law of Conservation of Mass showing that matter is never created or destroyed in a chemical reaction.

3. Representing Chemical Reactions Chem rxns are a way to represent or model what is happening in a chemical equation Chem rxns are a way to represent or model what is happening in a chemical equation Solid Sodium combines with Chlorine gas to make solid Sodium Chloride: Solid Sodium combines with Chlorine gas to make solid Sodium Chloride: 2Na (s) + Cl 2 (g)  2NaCl (s)

4. SymbolPurpose +Separates more than one reactant or product  Separates reactants from products. Indicates direction of reaction (s)Identifies a solid state (aq)Identifies that something is dissolved in water (l)Identifies liquid state (g)Identifies gaseous state ∆  Heat is needed for rxn Pt  A catalyst is needed

5. Law of Conservation of Mass In a chemical reaction, matter is neither created nor destroyed. In a chemical reaction, matter is neither created nor destroyed. Atoms won’t change their identity (e.g. a Carbon atom can’t become an Iron atom) Atoms won’t change their identity (e.g. a Carbon atom can’t become an Iron atom) Must have the same number of each type of atom on both sides of the chemical equation. Must have the same number of each type of atom on both sides of the chemical equation. Conservation of Mass Video Conservation of Mass Video Conservation of Mass Video Conservation of Mass Video

6. Steps to Balancing a Chemical Equation 6. Check your work 5. Write the Coefficients in their lowest possible ratio 4. Change to Coefficients to make the number of atoms of each element equal on both sides of arrow 2Li(s) + 2 H2O  H2(g) + 2LiOH(aq) 3. Count the atoms of the elements in the products 1 atom Li, 3 atoms H, 1 atom O 2. Count the atoms of the elements in the reactants 1 atom Li, 2 atoms H, 1 atom O 1. Write the Skeleton Equation Li(s) + H2O(l)  H2 (g) + LiOH (aq)

7. Don’t change the polyatomic ions – put a square around them if it helps – Think of it as ONE unit. Don’t change subscripts. They tell you how many atoms are in a molecule C 6 H 22 O 11 C 6 H 22 O 11

8. CaCl 2 + AgNO 3  AgCl + Ca(NO 3 ) 2 CaCl 2 + AgNO 3  AgCl + Ca(NO 3 ) 2 Fe 2 O 3 + H 2 SO 4  Fe 2 (SO 4 ) 3 + H 2 O Fe 2 O 3 + H 2 SO 4  Fe 2 (SO 4 ) 3 + H 2 O

9. Chemical Reactions are Everywhere CookingRespiration

10. Dying your hair Driving your car

11. How do you know when a chemical reaction takes place? Color Change Formation of a Precipitate

12. How do you know when a chemical reaction takes place ? Gas Formation Odor

13. How do you know when a chemical reaction takes place? Temperature Change Change in Acidity