Final answer:
Coal, charcoal, and graphite are all forms of carbon with different structures affecting their burnability. Charcoal typically burns better than graphite, owing to its amorphous structure and higher reactivity, not just purity. Anthracite coal is the purest form of coal and burns most efficiently.
Step-by-step explanation:
Coal, charcoal, and graphite are all forms of elemental carbon but have different structures and combustion properties. Coal is a complex material made primarily from plants that have been subjected to high temperatures and pressures over millions of years, and it encompasses types such as bituminous, subbituminous, lignite, and anthracite. Each type of coal has varying amounts of carbon, hydrogen, oxygen, and other elements, which along with their structural differences, influence their enthalpies of combustion and burning properties.
Charcoal is produced from wood by heating it at high temperatures in the absence of air, while graphite is a crystalline form of carbon. The burning behavior differs among them because of differences in purity, structural arrangement of carbon atoms, and the presence of other elements. Charcoal, for example, has a more amorphous structure with a higher surface area that facilitates burning, while graphite has a crystalline structure that makes it less reactive and harder to ignite. The presence of impurities and the physical structure play crucial roles in determining the combustibility of each.
Due to these variations, powdered charcoal generally burns better than powdered graphite, not solely due to purity but because of its better combustion-supporting structure and the presence of other reactive elements. While anthracite coal is the purest and has the highest heat value, facilitating more efficiency in burning, powdered graphite does not burn as well because its crystalline lattice makes it less prone to reaction with oxygen at regular burning conditions.