Constant agitation increases the action of the developer and will cause overdevelopment if the developing time isn't cut. Chemicals and jugs. Powder vs. liquid concentrate. Darkroom chemicals usually come packaged either as a powder or a concentrated liquid. They also dissolve more slowly in water.
Many chemicals come in liquid form.
They mix easily and don't cloud the air the way powders do. Darkroom chemicals have to be stored in bottles or jugs when they're not in use. I recommend plastic over glass, as plastic won't shatter if it's dropped. All chemical s have shelf-lives, but developers are particularly short. There are a variety of ways to slow down this process.