Four factors have marked effects on the rates of chemical reactions:
The nature of reactants refers to the physical states of the reacting substances (gas vs. liquid vs. solid). It can also refer to dry solid versus aqueous solutions where sometimes aqueous solutions can react much more quickly than solids reacting. Finally it can refer to the extent of subdivision of solids or liquids. For example a powdered solid will react much faster than chunks of the solids.
The final three factors will each be described in detail in later sections of this chapter.