1. Reactions and Equations

2. Evidence of Chemical Reactions How can you tell a chemical reaction has taken place? – Temperature change – Color change – Odor – Gas/bubbles – Appearance of a solid (precipitate)

3. Chemical Reaction A chemical reaction is the process by which atoms of one or more substances are rearranged to form different substances.

4. Reactant(s) and Product(s) Reactant(s) are the starting substance(s) of a reaction Product(s) are the substance(s) formed during the reaction  means “react to produce” or “yield” Reactant(s) are on the left Product(s) are on the right

5. Representing Chemical Reactions reactant A+ reactant B  product C + product D The plus sign separates each reactant or product (s) Identifies solid state (l) Identifies liquid state (g) Identifies gaseous state (aq) Identifies water solution (aqueous)  Heat is applied to the reaction Example NH 4 NO 3 (s)  N 2 O(g) + 2H 2 O(g) 

6. Word Equation Uses words not chemical symbols to indicate the reactant(s) and product(s) of a chemical reaction. Example: iron(s) + chlorine(g)  iron(III)chloride(s)

7. Skeleton Equation Skeleton equation uses formulas rather than words to identify the reactant(s) and product(s) Example Fe(s) + Cl 2 (g)  FeCl 3 (s)

8. Balanced Chemical Equation The equation that shows the number of atoms of each reactant and each product is equal on both sides of the arrow is a balanced chemical equation Example 2Fe(s) + 3Cl 2 (g)  2FeCl 3 (s)