AC is a black, solid substance resembling granular or powdered charcoal. It is extremely porous with a very large surface area. Certain contaminants accumulate on the surface of the AC. This is called adsorption. The two main reasons that chemicals adsorb onto AC is 1 a "dislike" of the water and 2 attraction to the AC. Adsorption of most contaminants results from a combination of 1 and 2. Many organic compounds, such as chlorinated and non-chlorinated solvents, gasoline, pesticides and trihalomethanes can be adsorbed by AC. AC is also effective for removal of chlorine and moderately effective for removal of some heavy metals. Metals that are bound to organic molecules will also be removed by AC. Fluoride, chloride, nitrate, hardness (calcium and magnesium) and most metal ions are not removed by AC to any significant degree. It is important to note that carbon is not necessarily the same as AC. AC removes vastly more contaminants from water than does ordinary carbon.