1. Chapter 7 Notes
Chemical Changes – when a substance is changed at the molecular level and can not be changed back.
Evidence
Light produced
Change in color
Smoke
New substance appear

2. Chapter 7 Chemical reactions can be either Endothermic or exothermic
Endothermic reactions absorb energy (feel colder)
Exothermic reactions give off energy (feel hot)

3. Chapter 7
Endothermic Reaction

4. Chapter 7
Exothermic Reactions

5. Chapter 7 Collision Theory (particle theory)
In order for a reaction to occur the reactants must collide or come in contact with each other.
Most collisions occur with gases
Second with liquids
Last with solids

6. Chapter 7 Writing chemical reactions
Chemical formulas vs Chemical reactions
Chemical Formula is when you have the formulas of the reactants and what products are produced. (Not Balanced) H2, O2, H2O
Chemical Reaction is when the chemical formula is balanced 2H2 + O2  2H2O

7. Chapter 7 Types of Chemical Reactions
Synthesis (Multiple things combine to make a more complex product) H2 + O2  H20
Decomposition (One thing breaking down into smaller parts) H20  H2 + O2
Single Replacement (A single substance replaces a bonded substance) 2Na + Zn(OH)2 Zn + 2NaOH
Double Replacement (The positive ions on two bonded compounds switch places) FeO + 2HCl  H2O + FeCl2
Combustion (Burning of a hydrocarbon with O2) C3H8 + 5O2  4H2O + 3CO2 (Always get H2O and CO2)

8. Chapter 7
All Chemical Rxns are dependant on the activity series. Some things just don’t react with each other so mixing them won’t yield a reaction. Pg 259
Na(s) + HOH(l)  NaOH (aq) + H2(g)
Mg (s) + H2O (l) No RXN

9. Chapter 7
The coefficients in a balanced reaction are representing the number of moles of each part needed to react to completion.
2H2 + O2  2H2O
2 moles of Hydrogen are required to react with 1 mole oxygen to make 2 moles water
If you don’t have 2 moles of hydrogen but do have 1 mole of oxygen the reaction will stop once the hydrogen is used up and you will have extra oxygen that didn’t react.