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Acid Rain Lesson Plan

Definition of Acid Rain

  • Robert Angus Smith, an English chemist, first used the phrase "acid rain" in 1852 when he noted the connection between London's polluted skies and the acidity of its rainfall.
  • Most Scientists agree that "normal" rainfall has a pH of 5.6. Rain in the atmosphere reacts with carbon dioxide (CO2) to form a weak carbonic acid, altering the rain pH to 5.6.
  • Acid rain is defined as any form of wet precipitation which has a pH less than 5.6 (on a scale of 0 to 14, with 7 being neutral). The "rain" becomes acidic when water molecules (H2O) react with gases in the air.
  • These gases are primarily sulfur dioxide (SO2) and various nitrogen oxides (NOx). This combination of gases and water molecules takes place when the water captures (attracts) hydrogen ions (H+) from the gases (ions are electrically charged particles in molecules).

updated on 04/24/2006  I   http://nature.nps.gov/air/edu/Lessons/DefiOfAcidRain.cfm   I  Email: Webmaster