Activated carbon is an extremely porous form of carbon and thus with a very large surface area available for adsorption or chemical reactions. Due to its high degree of microporosity, just 1 gram of activated carbon may have a surface area in excess of 500 m2 (about one tenth the size of a football field), as determined typically by nitrogen gas absorption. Sufficient activation for useful applications may come solely from the high surface area, though further chemical treatment often enhances the adsorbing properties of the material. Activated carbon is usually derived from charcoal.