1. Chemical Reactions
Intro to Reactions

2. A.Signs of a Chemical Reaction
Evolution of heat and light
Formation of a gas
Formation of a precipitate
Color change

3. B.Law of Conservation of Mass
mass is neither created nor destroyed in a chemical reaction
total mass stays the same
atoms can only rearrange
4 H
2 O
4 H
2 O
36 g
4 g
32 g

4. C. Chemical Equations
A+B  C+D
REACTANTS
PRODUCTS

5. (substance dissolved in water)
C. Chemical Equations
(substance dissolved in water) Pt
a catalyst is present (in this case, platinum)

6. Diatomic Elements
H2, N2, O2, F2, Cl2, Br2, and I2

7. II. Balancing Equations

8. Coefficient  subscript = # of atoms
A. Balancing Steps
1. Write the unbalanced equation.
2. Count atoms on each side.
3. Add coefficients to make #s equal.
Note: you may not change a subscript
Coefficient  subscript = # of atoms
4. Reduce coefficients to lowest possible ratio, if necessary.

9. B. Helpful Tips Balance one element at a time.
If an element appears more than once per side, balance it last.
Balance polyatomic ions as single units.
“1 SO4” instead of “1 S” and “4 O”

10. C. Balancing Example 2 Al + CuCl2  Cu + AlCl3 Al Cu Cl 3 3 2 2  1 1
Aluminum and copper(II) chloride react to form copper and aluminum chloride. 2
Al CuCl2  Cu AlCl3 Al Cu Cl 3 3 2
2 
 2
 6
3 
6 
 3

11. Balancing Equations C3H8(g) + O2(g) ----> CO2(g) + H2O(g)
B4H10(g) + O2(g) > B2O3(g) + H2O(g)

12. Balancing Equations Na3PO4 + Fe2O3 ----> Na2O + FePO4
Sodium phosphate and iron (III) oxide react to form sodium oxide and iron (III) phosphate
Na3PO4 + Fe2O > Na2O + FePO4