1. Classifying Chemical Reactions
Chapter 10.2

2. Categories There are 5 major categories of chemical reactions.
Each has a specific way that the atoms rearrange themselves during the reaction.
You must be able to recognize each general pattern.

3. Synthesis Reaction
Two or more substances combine to form one new substance
A + B  AB
2 H O2  2 H2O

4. Synthesis Reactions (Marriage)
two elements can combine to form a compound
two compounds can combine to form a larger compound
monomers can combine to form polymers
glucose + glucose = cellulose
polystyrene (foam cups)
polyvinyl acetate (chewing gum)

5. Decomposition
A substance breaks down into two or more simpler substances
AB  A + B
2 H2O  2H2 + O2

6. Decomposition (Divorce)
Decomposition is the reverse of Addition
If the only reactant is a compound, it is most likely a decomposition reaction
Most decomposition reactions require heat, light or electricity to provide energy to break the bonds
Airbags work through a decomposition reaction. 2 NaN3  2 Na N2

7. Single Replacement
a more active element replaces a less active element
A BC  AC B
Fe(s) CuSO4(aq)  FeSO4(aq) Cu(s)

8. Single Replacement (Homewrecker)
Usually a more active metal replaces a less active metal in a salt.
An activity series will be used to determine whether an element is more active.
A more active halogen can replace a less active halogen.
Reactivity of halogens can be read directly from the periodic table.

10. Double Replacement
Two elements from two different compounds swap places
AB + CD  CB + AD
AgNO3 + NaCl  AgCl + NaNO3

11. Double Replacement (Wife Swap)
Double replacement reactions usually occur in aqueous solutions
Double replacement reactions usually produce a precipitate, a gas or water
A cation can only replace another cation

12. Combustion
A hydrocarbon (fuel) in the presence of oxygen breaks down into carbon dioxide and water.
Combustion reactions release large amounts of heat and light
C3H8(g) O2(g)  3 CO2(g) H2O(g)
Other materials, such as metals, will form different products