There are plenty of awesome science apps for iPhone that can teach you a thing or two about chemistry, physics, and other topics. Many of them have an Apple Watch interface too. Take Molar for instance: it is a neat little app that brings the periodic table of elements to your wrist.
This periodic table Apple Watch app lets you view elements and detailed info on your wrist, including atomic number, symbol, name, and mass. You can perform search by name, symbol, and mass on your phone. This app is available as a free download.[where to get it]