1. Unit 6 – Lesson 1
Chemical Reactions

2. A chemical reaction is when the bonds between atoms of a substance are broken and the atoms rearrange and form new bonds to make substances.

3. How do you know when a chemical reaction occurs? What is your evidence?
Temperature change
Light
Color Change

4. Appearance of a solid
(precipitate)
Gas formation
Formation of

5. Reactant(s)  Product(s)  What is used in a reaction
What is produced/made during a reaction

6. calcium + oxygen  calcium oxide
Uses symbols and formulas to show what happens in a chemical reaction
Chemical equation 
Symbol
Purpose +
Separates more than one reactant or product 
Separates reactants from products. Indicates direction of reaction
(s)
solid
(aq)
dissolved in water
(l)
liquid
(g)
gas
Word equation -
calcium + oxygen  calcium oxide
reactants
product
Formula (skeleton) equation -
Ca + O2  CaO
reactants
product

7. Law of Conservation of Mass
In a chemical reaction, matter is not created or destroyed
This means that you have to have the same number of each type of atom on each side of the chemical equation.
After you write a chemical equation you have to balance it to make sure that the same number of atoms of each element are on each side.

8. SO3 = 1 sulfur & 3 oxygen 3SO3 = 3 sulfur & 9 oxygen
Balancing Equations
TIPS
A coefficient is the number placed in FRONT of an element or compound. Coefficients are used to balance the number of atoms on each side.
2H2O - coefficient is 2
When counting atoms you multiply the compound by the coefficient.
SO3 = 1 sulfur & 3 oxygen SO3 = 3 sulfur & 9 oxygen

9. NEVER change subscripts for a compound or polyatomic ion
Make sure all formulas are written correctly before attempting to balance
Balance oxygen LAST

11. Steps 1. Write the skeleton/formula equation. Make sure all the
formulas are written correctly!
CH4 + O2  CO2 + H2O
2. Complete an atom inventory
CH4 + O2  CO2 + H2O C H O

12. ___CH4 + ___O2  ___CO2 + ___H2O
3. Add coefficients to make the atoms balance
___CH4 + ___O2  ___CO2 + ___H2O C H O 2 2 4 4 4

13. Practice
Write a balanced chemical equation for the reaction in which aluminum reacts with oxygen to produce aluminum oxide.
____Al 4
+ ___O2 3
 ___Al2O3 2 4 Al O 4 6 6

14. Write a balanced chemical equation for the reaction in which hydrochloric acid reacts with calcium carbonate to produce calcium chloride, water, and carbon dioxide.
__HCl 2
+ __CaCO3
 __CaCl2
+ __H2O
+ __CO2 H Cl Ca C O

15. __BeF2 + __ Al2O3  __ BeO+ __ AlF3 Be F Al O
__BeF2 + __ Al2O3  __ BeO+ __ AlF3

16. __PbO + __HCl  __H2O + __PbCl2 Pb O H Cl
__PbO + 2HCl  __H2O + __PbCl2