Question

with an activity differentiate good quality coal and bad quality coal

Answer 1

Coal is a naturally occurring combustible material consisting primarily of the element carbon. It also contains low percentages of solid, liquid, and gaseous hydrocarbons and/or other materials, such as compounds of nitrogen and sulfur.
Types of coal are
Anthracite: Hard coal; a form of coal with high heat content and a high concentration of pure carbon.
Bituminous: Soft coal; a form of coal with less heat content and pure carbon content than anthracite, but more than lignite
Lignite: Brown coal; a form of coal with less heat content and pure carbon content than either anthracite or bituminous coal.