A strong acid is any chemical compound that completely dissociates once it comes into contact with water. The dissociation must be full in order for the compound to be considered a strong acid. Conversely, weak acids do not completely dissociate when they come into contact with water.
Another term for the dissociation of strong acids is ionization. Since strong acids completely ionize in water, it is possible to determine the pH of a strong acid. The pH of a strong acid is defined as the negative logarithm of the dissociated hydrogen atom after the strong acid has completely dissociated. In terms of bases, strong bases can also be defined by their ability to completely dissociation in water. Strong acids can be differentiated from weak acids by analysing the atoms that are a part of the compound.