nuts'''Acid rain''' is [[rain]] that is more [[acid]]ic than in its natural state, and is usually considered to have a pH of less than 5 (Natural rain water is slightly acidic due to the presence of dissolved [[carbon dioxide]]). Acid rain forms when [[sulfur dioxide]] dissolves in [[water]] to make [[sulfurous acid]]. The [[sulfur dioxide]] can also be oxidized to [[sulfur trioxide]] and form [[sulfuric acid]] upon reaction with [[water]]. Acid rain can cause damage to structures and statues, and also plant life. (For example, the [[Black forest]] of [[Germany]] has been heavily damaged by acid rain.) [[Category:Environment]][[Category:Acids]]