1. Chemical Reactions This will be posted on the website.

2. Equations Thermite (single displacement)
Aluminum + iron(III) oxide  Iron + aluminum oxide
Al Fe2O  Fe Al2O HOT
Nitrogen Triiodide Decomposition
NI3  I N Boom

3. When a chemical reaction occurs, there is ALWAYS
Chemical Reactions
When a chemical reaction
occurs, there is ALWAYS
a change in properties
AND energy

4. Color change Heat change Gas produced Precipitate formed
Chemical Reactions
Color change
Heat change
Gas produced
Precipitate
formed
indicators

5. Chemical Reactions
There are 5 basic
types of chemical
reactions:

6. Two simple substances combine to form a more complex one.
Synthesis
Two simple substances combine
to form a more complex one.
element + element compound 1

7. Synthesis
Examples:
2H2 + O H2O
6CO H2O C6H12O6 + 6O2 1

8. A complex substance breaks into simple substances.
Decomposition
A complex substance breaks
into simple substances.
compound element + element 2

9. Decomposition
Examples:
2H2O H2 + O2
2KClO KCl + 3O2 2

10. A single element replaces an element in a compound. element + compound
Single Displacement
A single element replaces
an element in a compound.
element + compound 3

11. Single Displacement
Example:
Zn + 2HCl H2 + ZnCl2 3

12. Two different elements in two different compounds switch places.
Double Displacement
Two different elements in two
different compounds switch places.
compound + compound 4

13. Double Displacement
Example:
H2SO4 + 2NaOH Na2SO4 + 2HOH 4

14. A hydrocarbon reacts with oxygen to form carbon dioxide and water.
Combustion
A hydrocarbon reacts with oxygen
to form carbon dioxide and water. 5

15. Combustion
Example:
CH4 + O CO2 + H2O 5

16. Chemical Reactions
can be classified
in other ways as well

17. An acid and base react to form a salt and water
Neutralization
An acid and base react
to form a salt and water
acid + base salt + water

18. Neutralization
Example:
2HCl + Mg(OH) MgCl2 + 2H2O

19. Any reaction in which elements change oxidation number.
Oxidation - Reduction
Any reaction in which
elements change
oxidation number.

20. Oxidation - Reduction
Example:
S + O SO2 -2

21. Oxidation - Reduction
Example:
S + O SO2 +4 -2

22. Aqueous reactions that involve the formation of a precipitate,
Precipitation
Aqueous reactions that
involve the formation
of a precipitate,
an insoluble
substance.

23. Physical State Symbols: (aq) = aqueous (g) = gas
Precipitation
Example:
2KI(aq) + Pb(NO3)2(aq) 2KNO3(aq) + PbI2(s)
Physical State Symbols:
(aq) = aqueous (g) = gas
(s) = solid (cr) = crystal
(l) = liquid

24. Predicting Reaction
Products (handout)

25. Balancing
Equations

26. Atoms can be neither
created nor destroyed
in ordinary chemical
reactions...

27. so there must be the
same number of atoms
on both sides of
the equation.

28. Subscripts represent the number of atoms in each molecule.
2H2O H2 + O2
Subscripts represent the
number of atoms in
each molecule.

29. Coefficients represent the number of molecules.
2H2O H2 + O2
Coefficients represent the
number of molecules.

30. multiply the coefficient by the subscript.
2H2O H2 + O2
To determine the total
number of atoms,
multiply the coefficient
by the subscript.

31. H2SO4
There are ___
atoms of hydrogen.

32. H2SO4 2
There are ___
atoms of hydrogen.

33. H2SO4
There are ___
atoms of oxygen.

34. H2SO4 4
There are ___
atoms of oxygen.

35. Al2(SO4)3
There are ___
atoms of oxygen.

36. Al2(SO4)3 12
There are ___
atoms of oxygen.

37. 2 Na2O2
There are ___
atoms of sodium.

38. 2 Na2O2 4
There are ___
atoms of sodium.

39. 2 Ca3(PO4)2
There are ___
atoms of phosphorus.

40. 2 Ca3(PO4)2 4
There are ___
atoms of phosphorus.

41. 2 Ca3(PO4)2
There are ___
atoms of oxygen.

42. 2 Ca3(PO4)2 16
There are ___
atoms of oxygen.

43. 6 CaSiO3
There are ___
atoms of calcium.

44. 6 CaSiO3 6
There are ___
atoms of calcium.

45. Balancing equations
by inspection

46. The order in which
these seven steps are
performed is important.

47. While there ARE
shortcuts, and you will
learn about one, ...

48. following these steps in
order is the best way to
be sure you are correct.

49. Check for diatomic molecules. H2 - N2 - O2 - F2 - Cl2 - Br2 - I2
Step 1
Check for
diatomic molecules.
H2 - N2 - O2 - F2 -
Cl2 - Br2 - I2

50. Step 2
Balance the Metals
DO NOT
include H

51. Step 3
Balance the Nonmetals
DO NOT
include O

52. Step 4
Balance Oxygen

53. Step 5
Balance Hydrogen

54. balanced at this point, BUT...
Step 5
Balance Hydrogen
The equation should be
balanced at this point, BUT...

55. This is done to find any counting mistakes!
Step 6
Recount All Atoms
This is done to find
any counting mistakes!

56. Recount All Atoms Step 6 If the atoms are NOT balanced, there is a
problem somewhere. Work your way
back up the steps, from bottom to top,
until you find the problem and fix it.

57. If every coefficient in the equation will reduce,
Step 7
If every coefficient in the
equation will reduce,
rewrite the equation with
reduced coefficients.

58. If there is a coefficient of 1 - the equation cannot be reduced.
Step 7
If there is a coefficient
of 1 - the equation
cannot be reduced.

59. Practice!!

60. End
Equations