1. Turn in Section 11.1 to your class tray.
Chemical Reactions
Intro to Reactions
Turn in Section 11.1 to your class tray.
Get out paper for notes.

2. Why are Chemical Reactions Important?
Chemical reactions occur everywhere.
Your body is a chemical machine, if chemical reactions did not occur, we would not be alive.

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

4. 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

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

6. C. Chemical Equations

7. 2H2(g) + O2(g)  2H2O(g) D. Writing Equations
Identify the substances involved.
Use symbols to show:
How many? - coefficient
Of what? - chemical formula
In what state? - physical state
Remember the diatomic elements.

8. D. Writing Equations 2 Al (s) + 3 CuCl2 (aq)  3 Cu (s) + 2 AlCl3 (aq)
Two atoms of aluminum react with three units of aqueous copper(II) chloride to produce three atoms of copper and two units of aqueous aluminum chloride.
How many?
Of what?
In what state? 2 Al
(s)
+ 3
CuCl2
(aq)
 3 Cu
(s)
+ 2
AlCl3
(aq)

9. E. Describing Equations
Zn(s) + 2HCl(aq)  ZnCl2(aq) + H2(g)
How many?
Of what?
In what state?
One atom of solid zinc
reacts with
two molecules of aqueous hydrochloric acid
to produce
one unit
of aqueous zinc chloride
and one
molecule of hydrogen gas.

10. II. Balancing Equations
Ch. 11 – Chemical Reactions
II. Balancing Equations
Get out your notes from yesterday and your practice sheet

11. Counting Atoms 1. H2SO4 2. Ca(OH)2 3. NaCl 4. (NH3)3P04 5. 3H2O
How many atoms of each element are in the following molecules?
1. H2SO4
2. Ca(OH)2
3. NaCl
4. (NH3)3P04
5. 3H2O
6. 4Al2(CO3)3

12. B. Helpful Tips Balance one element at a time.
Update ALL atom counts after adding a coefficient.
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”

13. 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