IGCSE Biology glossary
Acid rain
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Definition
Rain that has a pH lower than normal (below pH 5.6), caused by sulfur dioxide and nitrogen oxides dissolving in atmospheric water. These gases come from burning fossil fuels. Acid rain damages vegetation, acidifies lakes (killing aquatic life), and erodes buildings and statues.
What to include in an exam answer
Know the sources of acid rain gases: sulfur dioxide from burning coal, nitrogen oxides from vehicle exhausts. Effects include: damage to leaves and roots, death of fish in acidified lakes, and corrosion of limestone buildings.
Example in context
Explain how burning fossil fuels can lead to acid rain (3 marks): Burning fossil fuels releases sulfur dioxide and nitrogen oxides into the atmosphere. These gases dissolve in rainwater to form sulfuric acid and nitric acid. This acidified rain falls as acid rain, which damages trees, kills aquatic organisms and corrodes buildings.
Related syllabus topic
Human influences on ecosystems