In chemistry, you generally are trying to make a complicated molecule. This takes many different chemical reactions. At the start, you don’t know if any of the reactions will work. Sometimes you try them and they work very well (success!), sometimes you try them and they partially work (Good but needs further work to make it better) and sometimes they just don’t work at all (Fail, try a different reaction).
Most of my failed experiments are chemical reactions which don’t do what I expect or don’t do what I want or just don’t do anything!