an acid is a molecule/compound (i.e. hcl, ch3cooh), that when added to a solvent (water) will dissociate donating additional h (protons) to the resulting solution. therefore, an acid is a molecule that increases the hydrogen ion concentration of the solution. the molecule is an acid, whereas the solution containing the acid is acidic. some acids are considered strong and some are considered weak. what is the difference between a strong and weak acid? for an acid to be strong, when it is mixed in water the majority of the molecules will dissociate (very little is left intact), therefore it adds a large number of h into the solution, creating a strong acidic solution (ph