Categorize each of the following classes as either 'hard', 'medium', 'easy': english writing, math, history, chemistry, physics.
English writing in general is considered as easy, however to master the skills of writing is actually pretty hard. 

Math is in general considered as hard in school, since it's less intuitive and requires multiple step thinking process to solve problems.

History is considered easy at school while chemistry is considered as medium.

Physics is considered as hard. It combines math and science. It has lots of concepts to learn, and it's cumulative: one new concept is built on top of many previous concepts, one physics concept may depends on concepts from math, science, etc.