2. When a chemical reaction occurs, there is ALWAYS a change in properties AND energy

3. Color change Heat change Gas produced Precipitate formed

4. Chemical Reactions - 3 min

5. There are 5 basic types of chemical reactions:

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

7. Examples: 2H 2 + O 2 2H 2 O 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2

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

9. Examples: 2H 2 O 2H 2 + O 2 2KClO 3 2KCl + 3O 2

10. A single element replaces an element in a compound. element + compound

11. Example: Zn + 2HCl H 2 + ZnCl 2

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

13. Example: H 2 SO 4 + 2NaOH Na 2 SO 4 + 2HOH

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

15. Example: CH 4 + O 2 CO 2 + H 2 O

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

18. Example: 2HCl + Mg(OH) 2 MgCl 2 + 2H 2 O

19. Any reaction in which elements change oxidation number.

20. Example: S + O 2 SO 2 0 0 -2

21. Example: S + O 2 SO 2 0 0 -2 +4

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

23. Example: 2KI (aq) + Pb(NO 3 ) 2(aq) 2KNO 3(aq) + PbI 2(s) Physical State Symbols: (aq) = aqueous (g) = gas (s) = solid (cr) = crystal (l) = liquid

24. Predicting Reaction Products

25. Predicting Reaction Products

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

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

29. Subscripts represent the number of atoms in each molecule. 2H 2 O 2H 2 + O 2

30. Coefficients represent the number of molecules. 2H 2 O 2H 2 + O 2

31. To determine the total number of atoms, multiply the coefficient by the subscript. 2H 2 O 2H 2 + O 2

32. H 2 SO 4 There are ___ atoms of hydrogen.

33. H 2 SO 4 There are ___ atoms of hydrogen. 2

34. H 2 SO 4 There are ___ atoms of oxygen.

35. H 2 SO 4 There are ___ atoms of oxygen. 4

36. Al 2 (SO 4 ) 3 There are ___ atoms of oxygen.

37. There are ___ atoms of oxygen. 12 Al 2 (SO 4 ) 3

38. 2 Na 2 O 2 There are ___ atoms of sodium.

39. There are ___ atoms of sodium. 4 2 Na 2 O 2

40. 2 Ca 3 (PO 4 ) 2 There are ___ atoms of phosphorus.

41. 4 2 Ca 3 (PO 4 ) 2 There are ___ atoms of phosphorus.

42. 2 Ca 3 (PO 4 ) 2 There are ___ atoms of oxygen.

43. 16 2 Ca 3 (PO 4 ) 2 There are ___ atoms of oxygen.

44. 6 CaSiO 3 There are ___ atoms of calcium.

45. 6 There are ___ atoms of calcium. 6 CaSiO 3

46. Balancing equations by inspection

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

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

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

50. Check for diatomic molecules. H 2 - N 2 - O 2 - F 2 - Cl 2 - Br 2 - I 2

51. Balance the Metals DO NOT include H x

52. Balance the Nonmetals DO NOT include O x

53. Balance Oxygen

54. Balance Hydrogen

56. Recount All Atoms This is done to find any counting mistakes!

57. Recount All Atoms 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.

58. If every coefficient in the equation will reduce, rewrite the equation with reduced coefficients.

59. If there is a coefficient of 1 - the equation cannot be reduced.

61. Balancing Equations