1. Classifying Chemical Reactions

2. Types of Reactions There are literally millions of chemical reactions that occur every day. Chemists have defined five main categories of chemical reactions: combustion, synthesis, decomposition, single displacement, and double displacement.

3. Combustion Reactions If you have ever observed something burning, you have observed a combustion reaction. Our definition states that a combustion reaction occurs when a substance reacts with oxygen to produce energy in the form of heat and light.

4. C x H y +O 2  CO 2 +H 2 O Combustion CH 4 + 2O 2  CO 2 + 2H 2 O The burning of a substance in O 2 to produce heat Hydrocarbons (C x H y ) always form CO 2 and H 2 O

5. Synthesis the combination of 2 or more substances to form a compound only one product forms Basic form: A + B  AB 2P + 3Br 2  2PBr 3

6. Decomposition Reactions A decomposition reaction is just the reverse of a synthesis Instead of two substances coming together to form a third, a decomposition reaction occurs when one substance breaks down, or decomposes, into two or more substances Most decomposition reactions require the use of heat, light, or electricity.

7. Decomposition a compound breaks down into 2 or more simpler substances only one reactant Basic form: AB  A + BAB  A + B 2H 2 O 2  2H 2 O + O 2

8. The Activity Series We can predict which metal will replace another using the diagram shown which lists metals according to how reactive they are A metal will replace any less active metal.

9. Single Replacement one element replaces another in a compound metal replaces metal (+) nonmetal replaces nonmetal (-) Basic form: A + BC  AC + B Zn + 2HCl  ZnCl 2 + H 2

10. Double Replacement ions in two compounds “change partners” cation(+) of one compound combines with anion(-) of the other Basic form: AB + CD  AD + CB 2KOH + CuSO 4  K 2 SO 4 + Cu(OH) 2

11. Double Replacement A double replacement reaction takes place if a precipitate, water, or a gas forms when two ionic compounds in solution are combined. A precipitate is an insoluble compound that comes out of solution during this type of reaction.