1. Chemical Reactions

2. Chemical reactions occur when bonds between the outermost parts of atoms are formed or broken

3. Chemical reactions involve changes in matter, the making of new materials with new properties, and energy changes.
                                       

4. Symbols represent elements, formulas describe compounds, chemical equations describe a chemical reaction

5. Items to the LEFT of the arrow in a chemical equation are called
REACTANTS.
2Na + Cl NaCl

6. Ex: 2Na + Cl2 2NaCl PRODUCTS. Items to the right of the
arrow are called
PRODUCTS.
Ex: 2Na + Cl2 2NaCl

7. Important NOTE:
No matter how many reactants and products are involved, all atoms present at the start of a reaction are present at the end.

8. Conservation
of Mass
THE TOTAL MASS OF THE REACTANTS MUST EQUAL THE TOTAL MASS OF PRODUCTS.
MATTER IS NEVER CREATED OR DESTROYED.

9. A coefficient of 1 is not written.
A number that tells how many molecules of a substance are involved in a
chemical reaction.
A coefficient of 1 is not written.

10. Subscripts
A subscript indicates how many atoms of an element are in a compound
Ex. H2SO4
H= S = O = 4

11. Subscripts vs. Coefficients

12. + -- used to separate two reactants or products.
Symbols
+ -- used to separate two reactants or products.
(yields) Separates reactants and products.

13. Reactions that release heat.
Exothermic
Reactions that release heat.

14. Reactions that absorb heat.
Endothermic
Reactions that absorb heat.

15. A substance that speeds up chemical reactions.
Catalyst
A substance that speeds up chemical reactions.

16. A substance that slows down a chemical reaction.
Inhibitor
A substance that slows down a chemical reaction.

17. Types of Reactions

18. Combustion
Reactions that have hydrocarbons (CH4) and oxygen as reactants, and carbon dioxide and water as products.

19. Example:
C3H O2  3CO H2O

20. Synthesis Reactions

21. Examples
2Na + Cl NaCl
Na2O + CO Na2CO3

22. Decomposition Reactions
Starts with one reactant and ends with 2 or more products.

23. Examples
2KClO KCl + 3O2
2NaCl Na + Cl2

24. Single Replacement
Reactions
One compound and a free element that recombine to yield a new compound and new free element.

25. Examples
Fe + CuSO Cu + FeSO4
2Na HCl H NaCl

26. Double Replacement
Reactions
Starts with 2 compounds as reactants. These recombine to form 2 new compounds as products.

27. Examples
NaCl + AgNO NaNO3 + AgCl
KOH + HNO HOH + KNO3

28. Let's Practice!

29. C O  CO2

30. 2NaCl  2Na + Cl2

31. FeCl2 + K2S  FeS KCl

32. C2H O2  2CO H2O

33. 2AlCl3 + 3Na2CO3  Al2(CO3)3 + 6NaCl

34. CS O2  CO2 + 2SO2

35. 3Fe + 4H2O  Fe3O H2

36. 2AlCl3  2Al + 3Cl2

37. 2Na + H2SO4 ---> Na2SO4 + H2

38. 2Cr O2  2CrO3