<P> `` Acid rain '' is a popular term referring to the deposition of a mixture from wet ( rain , snow , sleet , fog , cloudwater , and dew ) and dry ( acidifying particles and gases ) acidic components . Distilled water , once carbon dioxide is removed , has a neutral pH of 7 . Liquids with a pH less than 7 are acidic , and those with a pH greater than 7 are alkaline . `` Clean '' or unpolluted rain has an acidic pH , but usually no lower than 5.7 , because carbon dioxide and water in the air react together to form carbonic acid , a weak acid according to the following reaction : </P>
rain sleet or snow that contains a high concentration of acids is called
`` Acid rain ''