1. Types of Reactions Types of Reactions
Synthesis reactions occur when two or more substances react to form a single substance.
A + B  AB
2Na + Cl2  2NaCl

2. Types of Reactions
Decomposition reactions are the opposite of synthesis reactions. It is when a single substance is broken down into two or more substances.
AB  A + B
2NaCl  2Na + Cl2

3. Types of Reactions
A single replacement reaction occurs when one element takes the place of another element in a compound.
A + BC  B + AC
Cu + 2AgNO3  2Ag + Cu(NO3)2

4. Types of Reactions
A double replacement reaction is one which two different compounds exchange cations to form two new compounds.
AB + CD  AD + CB
HCl + NaOH  H(OH) + NaCl

5. Types of Reactions
A combustion reaction is one in which a substance reacts rapidly with oxygen, often producing heat and light.
Note in a combustion reaction the reactants are always C and H in the presence of O2 and the products are always water and CO2.

6. Types of Reactions
Sometimes, reactions occur due to electron transfer.
Oxidation is the losing of electrons.
Reduction is the gaining of electrons.
OIL RIG!
Look at a synthesis reaction between calcium and oxygen.

7. Types of Reactions
Chemical energy is the energy stored in the chemical bonds of a substance.
When bonds are broken or formed, energy is given off or taken in.
When energy is released (lost), the reaction is exothermic.
When energy is absorbed (gained), the reaction is endothermic.