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.
Acetic acid and sodium bicarbonate -> sodium acetate, water and CO2

4. Reactant(s) Reactant(s) are the starting substance(s) of a reaction
Reactant(s) are on the left

5. Product(s) Product(s) are the substance(s) formed during the reaction
Product(s) are on the right

6. Representing Chemical Reactions
Reactants  Products
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
NH4NO3(s)  N2O(g) + 2H2O(g) 

7. Example Fe(s) + Cl2(g)  FeCl3(s)
Have students circle reactants, put a square around products, label the states of matter

8. Word Equation
Uses words not chemical symbols to indicate the reactant(s) and product(s) of a chemical reaction.
 means “react to produce” or “yield”
+ means and

9. Solid iron plus chlorine gas react to produce solid iron(III) chloride
Example
Fe(s) + Cl2(g)  FeCl3(s)
Solid iron plus chlorine gas react to produce solid iron(III) chloride

10. Example
Acetic acid and sodium bicarbonate react to produce sodium acetate and water and carbon dioxide

11. Skeleton Equation
Skeleton equation uses formulas rather than words to identify the reactant(s) and product(s)
Example
Fe(s) + Cl2(g)  FeCl3(s)

12. 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) + 3Cl2(g)  2FeCl3(s)
Why do chemical reactions need to be balanced? what scientific law tells us that they have to be balanced?
DEMO if time: mass baking soda in a balloon and vinegar in a beaker, combine the two and re-mass the entre apparatus.
Lighting a match: At ignition, phosphorus is oxidized. 4P + 3O2 --> 2P2O3 and 4P + 5O2 --> 2P2O5. That reaction is exothermic and gives off enough heat for the sulfur to ignite. S + O2 --> SO2. Air doesn't have enough oxygen for this to burn too well. However, the heat from the phosphorus burning allows the potassium chlorate to decompose. 2KClO3 --> 2KCl + 3O2. That supplies the oxygen for the sulfur to burn sufficiently. (found online)

13. Example Lighting an outdoor gas grill—Combustion of propane
C3H8 + 5O2 → 3CO2 + 4H20
Using a disposable lighter—Combustion of butane
2C4H O2 → 8CO2 + 10H2O