Explain the statement "all alkalis are bases, but all bases are not alkalis" and give an example.

A base is a substance that reacts with and neutralizes an acid. The equation for an acid is:
Acid + Base --> Salt + Water.
Most bases will be metal oxides, metal hydroxides, metal carbonates and metal hydrogen carbonates. Bases may either be soluble or insoluble in water. When something is soluble in water it simply means a compound will give off OH- (hydroxyl) ions when it is placed in water. When a base is soluble in water it is called an alkali.  An example of an alkali equation would be:
NaOH --> Na+  +  OH-
Therefore, all alkalis are bases because they will all neutralize acids, but not all bases are alkalis because not all bases will dissolve in water. An example of an alkali is sodium hydroxide.